Micro turbojet engine. Jet microaviation: Turbo models. Service and motor resources

Piloting aircraft has become a hobby that unites adults and children from all over the world. But with the development of this entertainment, propellers for mini-planes are also developing. The most numerous engine for aircraft of this type is electric. But recently, jet engines (RD) have appeared on the arena of engines for RC aircraft models.

They are constantly supplemented with all sorts of innovations and notions of designers. The task before them is quite difficult, but possible. After the creation of one of the first models of a downsized engine, which became significant for aeromodelling, much changed in the 1990s. The first turbojet engine was 30 cm long, about 10 cm in diameter and weighing 1.8 kg, but over the decades, the designers managed to create a more compact model. If you thoroughly take up the consideration of their structure, then you can reduce the complexity and consider the option of creating your own masterpiece.

RD device

Turbojet engines (TRDs) operate by expanding heated gas. These are the most efficient engines for aviation, even carbon-fueled minis. From the moment the idea of ​​creating an aircraft without a propeller appeared, the idea of ​​a turbine began to develop throughout the society of engineers and designers. TRD consists of the following components:

• Diffuser;
• Turbine wheel;
• The combustion chamber;
• Compressor;
• stator;
• nozzle cone;
• guide apparatus;
• Bearings;
• Air intake nozzle;
• Fuel line and more.

Principle of operation

The structure of a turbocharged engine is based on a shaft that rotates with the help of a compressor thrust and pumps air with rapid rotation, compressing it and directing it from the stator. Once in a freer space, the air immediately begins to expand, trying to find the usual pressure, but in the internal combustion chamber it is heated by fuel, which causes it to expand even more.

The only way for the pressurized air to escape is to exit the impeller. With great speed, he strives for freedom, heading in the opposite direction from the compressor, to the impeller, which spins with a powerful stream, and begins to rotate rapidly, giving traction to the entire engine. Part of the received energy begins to rotate the turbine, driving the compressor with more force, and the residual pressure is released through the engine nozzle with a powerful impulse directed to the tail section.

The more air is heated and compressed, the greater the pressure generated and the temperature inside the chambers. The resulting exhaust gases spin the impeller, rotate the shaft and enable the compressor to constantly receive fresh air flows.

Types of TRD control

There are three types of motor control:

Types of engines for aircraft models

Jet engines on model aircraft come in several basic types and two classes: air-jet and missile. Some of them are outdated, others are too expensive, but gambling lovers of controlled aircraft are trying to test the new engine in action. With an average flight speed of 100 km/h, model aircraft only become more interesting for the viewer and the pilot. The most popular types of engine differ for controlled and bench models, due to different efficiency, weight and thrust. There are few types in aeromodelling:

• Missile;
• Direct-flow air-jet (PRVD);
• Pulsating air-jet (PuRVD);
• Turbojet (TRD);

Missile used only on bench models, and then quite rarely. Its principle of operation is different from air-jet. The main parameter here is the specific impulse. Popular due to the lack of the need to interact with oxygen and the ability to work in zero gravity.

Direct flow burns the air out environment, which is sucked from the inlet diffuser into the combustion chamber. The air intake in this case sends oxygen to the engine, which, thanks to its internal structure, forces it to build up pressure in the fresh air stream. During operation, air approaches the air intake at a flight speed, but in the inlet nozzle it sharply decreases several times. Due to the closed space, pressure is built up, which, when mixed with fuel, splashes out of reverse side exhaust at high speed.

Throbbing works identically to direct-flow, but in its case, the combustion of fuel is intermittent, but periodic. With the help of valves, fuel is supplied only at the necessary moments, when the pressure in the combustion chamber begins to drop. For the most part, a pulse jet engine performs between 180 and 270 fuel injection cycles per second. To stabilize the pressure condition (3.5 kg/cm2), forced air supply is used with the help of pumps.

turbojet engine, the device of which you considered above has the most modest fuel consumption, due to which they are valued. Their only downside is their low weight to thrust ratio. Turbine RD allow you to develop the speed of the model up to 350 km / h, while the engine idle is kept at 35,000 rpm.

Specifications

An important parameter that makes model aircraft fly is thrust. It provides good power, capable of lifting large loads into the air. Thrust differs between old and new engines, but models built from 1960s blueprints, running on modern fuels and upgraded with modern fixtures, efficiency and power increase significantly.

Depending on the type of taxiway, the characteristics, as well as the principle of operation, may differ, but all of them need to create optimal conditions for launch. Engines are started using a starter - other engines, mainly electric ones, which are attached to the engine shaft in front of the inlet diffuser, or the start is made by spinning the shaft using compressed air supplied to the impeller.

engine GR-180

On the example of data from the technical passport of a serial turbojet engine GR-180 you can see the actual characteristics of the working model:
Thrust: 180N at 120,000 rpm, 10N at 25,000 rpm
RPM range: 25,000 - 120,000 rpm
Exhaust gas temperature: up to 750 C°
Jet blast velocity: 1658 km/h
Fuel consumption: 585ml/min (under load), 120ml/min (idle)
Weight: 1.2kg
Diameter: 107mm
length: 240mm

Usage

The main area of ​​application has been and remains aviation orientation. The number and size of different types of turbojet engines for aircraft is staggering, but each of them is special and is used when necessary. Even in aircraft models of radio-controlled aircraft From time to time, new turbojet systems appear, which are presented to the general public at exhibitions and competitions. Attention to its use allows you to significantly develop the capabilities of engines, supplementing the principle of operation with fresh ideas.
In the last decade, skydivers and wingsuit extreme sport athletes have been integrating mini TRD as a source of thrust for flight using a wingsuit wingsuit fabric, in which case the motors are attached to the legs, or rigid wing, worn like a backpack on the back, to which the engines are attached.
Another promising area of ​​use is combat military drones, at the moment they are actively used in the US Army.

The most promising area for the use of mini turbojet engines is drones for transportation goods between cities and around the world.

Installation and connection

Installing a jet engine and connecting it to the system is a complex process. It is necessary to connect the fuel pump, bypass and control valves, tank and temperature sensors to a single circuit. Due to the high temperatures involved, refractory lined connections and fuel lines are commonly used. Everything is fixed with homemade fittings, a soldering iron and seals. Since the tubing may be as large as the head of a needle, the connection must be tight and insulated. Incorrect connection may result in destruction or explosion of the motor. The principle of connecting the chain on bench and flying models is different and must be carried out according to the working drawings.

Advantages and disadvantages of RD

All types of jet engines have many advantages. Each of the types of turbines is used for specific purposes, which are not afraid of its features. In aeromodelling, the use of a jet engine opens the door to overcoming high speeds and the ability to maneuver independently of many external stimuli. Unlike electric and internal combustion engines, jet models are more powerful and allow the aircraft to spend more time in the air.
conclusions
Jet engines for model aircraft can have different thrust, mass, structure and appearance. For aircraft modeling, they will always remain indispensable due to their high performance and the ability to use a turbine using different fuels and operating principles. Choosing certain goals, the designer can adjust the rated power, the principle of traction, etc., by applying different types turbines for different models. The operation of the engine on fuel combustion and oxygen pressurization makes it as efficient and economical as possible from 0.145 kg/l to 0.67 kg/l, which aircraft designers have always achieved.

What to do? Buy or DIY

This question is not simple. Since turbojet engines, whether they are full-scale or scaled-down models, they are technically complex devices. Making it out is not an easy task. On the other hand, mini turbojet engines are produced exclusively in the USA or European countries, which is why their average price is $ 3,000, plus or minus 100 bucks. So buying a ready-made turbojet engine will cost you $ 3,500, including shipping and all related pipes and systems. You can see the price yourself, just google “P180-RX turbojet engine”

Therefore, in modern realities, it is better to approach this matter as follows - what is called do-it-yourself. But this is not an entirely correct interpretation, rather give the work to contractors. The engine consists of mechanical and electronic parts. We buy components for the electronic part of the mover in China, we order the mechanical part from local turners, but for this you need drawings or 3D models and, in principle, the mechanical part is in your pocket.

Electronic part

The controller for maintaining engine modes can be assembled on Arduino. To do this, you need a flashed Arduino chip, sensors - a speed sensor and a temperature sensor and actuators, an electronically controlled fuel supply damper. You can flash the chip yourself if you know programming languages, or go to the Arduino forum for a service.

Mechanical

With mechanics, all the spare parts in theory can be made by turners and millers, the problem is that for this you need to specifically look for them. It's not a problem to find a turner who will make the shaft and shaft sleeve, but everything else. The most difficult part to manufacture is the centrifugal compressor wheel. It is made either by casting. or on 5 coordinate milling machine. The easiest way to get a centrifugal pump impeller is to buy it as a spare part for a car's internal combustion engine turbocharger. And already under it to orient all the other details.

Kholodniy Maxim Vitaliyovych

National Aerospace University named after M. Y. Zhukovsky "Kharkiv Aviation Institute"

Micro-GTE

7.1. Aviation and astronautics

Drawings changed by the administration of the competition, can be given in the original version at the discretion of the expert.

Introduction

Relevance of the research topic. The miniaturization of onboard equipment, the creation of control systems and a target load with a mass of hundreds of grams makes it possible to create unmanned aerial vehicles (UAVs) with a takeoff weight of a few kilograms, equipped with satellite navigation and radio communication systems, with the ability to operate in almost any area of ​​the globe as part of the complex remotely controlled aviation system (DUAS).

One of the most important problems in the creation of all-weather UAVs is the creation of a propulsion system (PS), which, on the one hand, provides a high cruising speed of the UAV, and on the other hand, a sufficient flight duration. The requirements for overcoming wind drift, flight in conditions of surface turbulence, efficiency in obtaining information put forward the need to ensure a cruising flight speed of M = 0.5 and a flight duration of at least 30 minutes.

Given the drop in Reynolds numbers, as well as the increase in the area washed by the flow, in relation to volume and mass, as the physical dimensions of the aircraft decrease, the task of achieving high flight speeds is complicated by a disproportionate increase in the required thrust with a decrease in the dimension of the UAV. The use of an air-jet engine (AJE) as a propulsion system opens up the possibility of providing high speed characteristics, however, the creation of a micro-AJE of traditional schemes with a thrust of up to 50-200 N, suitable for installation on an ultralight UAV, encounters significant difficulties, primarily related to large-scale degeneration of the workflow.

Thus, the task of creating a low-thrust WFD (LTW) seems to be relevant.

The issue of creating private firms are engaged in small-thrust air-jet engines based on turbojet engines: France - Vibraye (JPX-t240 ...), Japan - Sophia-Precision (J-450 ...), Germany - JetCat (P-80 ...), Austria - Schneidtr-Sanchez (FD-3). The engines of the firms listed above are intended for aircraft models, but, apparently, for lack of a better one, they are used in civil and military unmanned aircraft.

Despite the apparent simplicity of micro-GTE designs compared to full-size ones, their manufacture is also associated with production difficulties due to the fact that they contain the same basic structural elements as full-scale counterparts: a compressor, a nozzle apparatus, a turbine (operating at a temperature over 700 degrees Celsius and peripheral circumferential speeds of 500 m/s).

At such high temperatures and circumferential speeds, fracture stresses in the root part of the blade can reach 700 MPa and more. From which we can draw a simple conclusion: for the manufacture of turbines of these WFD samples, heat-resistant steels or alloys were used - analogues of domestic steels: KhN62BMKTYU with a temporary resistance of 520-550 MPa at an operating temperature of 700 degrees Celsius, KhN50VMKTSR -540 MPa at 900 degrees, which determines high final cost of remote control.

In our country, low-thrust gas turbine engines suitable for installation on UAVs with a take-off weight of up to 100 kg are not produced.

Research objective was the development of remote control for UAVs based on micro-turbojet engines.

During development, a serial engine from AMT-Olimpus with a thrust of 230N and a diameter of 130mm was chosen as an analogue.

Table. Characteristics of the author's engine and serial analogue

Characteristics	AMT Olympus	TRD with PPM
DN diameter (mm) DN length (mm) Compressor diameter (mm) Turbine diameter (mm) Speed ​​(rpm) Compression ratio Fuel consumption (ml/min) Mass air flow (kg/s)

Due to the high cost and scarcity of the above steels, it was decided to use available materials and reduce the maximum circumferential speeds from 475m/s (analogue) to 300m/s, which is inevitable with the same midsection of the PS, entailed a decrease in air consumption and, as a result , at the same exhaust velocity from the nozzle - a decrease in frontal thrust.

In an effort to develop an engine with the same frontal thrust, but with lower peripheral speeds at the periphery of the turbine blades and based on the experience of creating full-scale gas turbine engines with a centrifugal compressor, the choice was made on a double-sided centrifugal compressor (PPM), which is an innovation in the micro-GTE class. This design solution doubles the airflow without increasing the diffuser diameter.

novelty - consists in a new constructive and technological solution, which allows the most complex technological assembly of the turbojet engine with the pulp and paper mill - the diffuser - to be technologically advanced, and to completely abandon bolted and welded joints(Fig.3, 6).

Research methods were numerical simulation of work processes in aircraft air-breathing engines based on complex models of the work process and full-scale tests of a working GTE sample.

Rotor assembly: cooker, two-way centrifugal turbo compressor, shaft, turbine.

Turbine – active-reactive axial single-stage with a degree of reactivity of 0.5.

One of the variants of the disk is presented, the strength calculation was carried out using the CosmosWorks package - fig. nine.

A 3D model of the turbine assembly is shown in Figure 10. Individual segments of the blade ring are visible. One of the three segments is highlighted in dark tone. This design of the blade crown allows, in contrast to a solid cast one, to use the necessary steels in various loading zones, which saves material. There are expansion joints in the junction areas of the segmented crown, which reduce prestresses in the disk. When casting a segment, almost complete absence shrinkage cavities, compared with a solid disc, due to the smaller relative thicknesses. Such a design of the turbine in a small-thrust micro-GTE has been developed for the first time.

The technological equipment used in the manufacture of the engine is shown in fig. 10-11. Separate stages of technological processes are shown in fig. 13.

Compressor - single-stage centrifugal double-sided with a semi-open impeller.

Some elements technological process manufacture of turbocharger fig. 15-18.

The combustion chamber - ring type, direct flow. In Fig.19,20.

https://pandia.ru/text/79/124/images/image007_8.jpg" width="624" height="162 src=">

The floating sleeve gear pump is worth a separate description in itself, is not inferior to industrial designs used in the automotive industry, provides a pressure drop of up to 1 MPa at a flow rate of only 20 ml / s, a rotation speed of 12,000 rpm.

Fire tests.

Implementation of design solutions. General form designed micro-GTE and its individual units presented in the figures. All structural elements are made personally by the author of the article.

Conclusions. To date, the use of micro-GTE on vehicles with a takeoff weight of about 100 kg and above seems to be the most reasonable prospect. With a thrust level of 200-300 N, micro-GTEs can provide high subsonic flight speeds for light class UAVs. From the point of view of mass perfection, a propulsion system with a small-sized gas turbine engine is attractive. The low specific gravity of the micro-GTE is especially pronounced with a short flight duration (up to 30 minutes). When the flight duration is limited to 15-20 minutes. Based on the micro-GTE, a highly maneuverable UAV with a thrust-to-weight ratio of more than 0.5 can be created.

List of sources used

one. . Theory of aircraft engines. - Oborongis. –1958

2. . Numerical modeling of thermophysical processes in engine building. -Kharkov, KhAI. –2005

3. , . Radial-axial turbines of low power. – Moscow, Mashgiz. –1963

4. . Air microturbines. - Moscow, Mechanical engineering. –1970

5., Borovsky and calculation of power units for liquid rocket engines. – Moscow, Mechanical engineering. –1986

6. , . Aircraft jet engine testing. – Moscow, Mechanical engineering. –1967

7. Artyomenko N. P. et al. Hydrostatic bearings of rotors of high-speed machines. -Kharkov, Osnova. –1992

8. . Theory, calculation and design of aircraft engines and power plants. – Moscow, Mechanical engineering. –2003

nine. , . Calculation of aircraft engine turbines. – Moscow, Mechanical engineering. –1974

10. Helicopter power plants// ed. . – Oborongiz, Moscow. –1959

11. Harvesting - processing technologies in the production of aerospace aircraft / / Textbook, etc. -Kharkov, KhAI. –1999

12. The design of aircraft gas turbine engines// ed. . – Moscow, Military Publishing. –1961

From the received e-mail (copy of the original):

“Dear Vitaly! Could you tell me a little more

about model turbojet engines, what is it all about and what do they eat with?

Let's start with gastronomy, turbines do not eat with anything, they are admired! Or, to paraphrase Gogol in a modern way: "Well, what kind of aircraft modeler does not dream of building a jet fighter ?!"

Many dream, but do not dare. A lot of new, even more incomprehensible, a lot of questions. You often read in various forums how representatives of reputable LII and research institutes with a smart look are catching up with fear and trying to prove how difficult it all is! Difficult? Yes, maybe, but not impossible! And the proof of this is hundreds of home-made and thousands of industrial models of microturbines for modeling! It is only necessary to approach this issue philosophically: everything ingenious is simple. Therefore, this article was written, in the hope of reducing fears, lifting the veil of uncertainty and giving you more optimism!

What is a turbojet engine?

A turbojet engine (TRD) or gas turbine drive is based on the work of gas expansion. In the mid-thirties, a clever English engineer came up with the idea of ​​creating an aircraft engine without a propeller. At that time, it was just a sign of madness, but all modern turbojet engines still work on this principle.

At one end of the rotating shaft is a compressor that pumps and compresses air. Released from the compressor stator, the air expands, and then, entering the combustion chamber, it is heated by the burning fuel there and expands even more. Since there is nowhere else for this air to go, it tends to leave the confined space with great speed, while squeezing through the turbine impeller located at the other end of the shaft and setting it into rotation. Since the energy of this heated air jet is much greater than the compressor requires for its operation, its remainder is released in the engine nozzle in the form of a powerful backward impulse. And the more air is heated in the combustion chamber, the faster it tends to leave it, accelerating the turbine even more, and hence the compressor located at the other end of the shaft.

All turbochargers for gasoline and diesel engines, both two and four-stroke, are based on the same principle. The exhaust gases accelerate the turbine impeller, rotating the shaft, at the other end of which is the compressor impeller, which supplies the engine with fresh air.

The principle of operation is simpler than you can imagine. But if only it were that easy!

TRD can be clearly divided into three parts.

• BUT. Compressor stage
• B. The combustion chamber
• IN. Turbine stage

The power of the turbine largely depends on the reliability and performance of its compressor. In principle, there are three types of compressors:

• BUT. Axial or linear
• B. Radial or centrifugal
• IN. Diagonal

A. Multistage linear compressors have become widespread only in modern aviation and industrial turbines. The fact is that it is possible to achieve acceptable results with a linear compressor only if you put several compression stages in series one after another, and this greatly complicates the design. In addition, a number of requirements for the arrangement of the diffuser and the walls of the air channel must be met in order to avoid stall and surge. There were attempts to create model turbines on this principle, but due to the complexity of manufacturing, everything remained at the stage of experiments and trials.

B. Radial or centrifugal compressors. In them, the air is accelerated by the impeller and, under the action of centrifugal forces, it is compressed - it is compressed in the stator rectifier system. It was with them that the development of the first operating turbojet engines began.

Simplicity of design, less susceptibility to airflow stalls, and the comparatively greater output of just one stage were the advantages that previously pushed engineers to start their development with this type of compressor. At present, this is the main type of compressor in microturbines, but more on that later.

B. Diagonal, or a mixed type of compressor, usually single-stage, similar in principle to a radial one, but is quite rare, usually in turbochargers of reciprocating internal combustion engines.

Development of turbojet engines in aircraft modeling

There is a lot of controversy among aircraft modelers about which turbine was the first in aircraft modeling. For me, the first aircraft model turbine is the American TJD-76. The first time I saw this apparatus was in 1973, when two half-drunk midshipmen were trying to connect a gas cylinder to a round contraption, about 150 mm in diameter and 400 mm long, tied with ordinary knitting wire to a radio-controlled boat, setting targets for the Marine Corps. To the question: "What is it?" they replied, "It's a mini mom! American ... her mother does not start like that ... ".

Much later I found out that this is a Mini Mamba, weighing 6.5 kg and with a thrust of about 240 N at 96,000 rpm. It was developed back in the 50s as an auxiliary engine for light gliders and military drones. The peculiarity of this turbine is that it used a diagonal compressor. But in aircraft modeling, it has not found wide application.

The first "folk" flying engine was developed by the forefather of all microturbines Kurt Schreckling in Germany. Starting more than twenty years ago to work on the creation of a simple, technologically advanced and cheap to manufacture turbojet engines, he created several samples that were constantly improved. Repeating, supplementing and improving its developments, small-scale manufacturers have formed a modern look and design of a model turbojet engine.

But back to the Kurt Schreckling turbine. Outstanding design with carbon fiber reinforced wooden compressor impeller. An annular combustion chamber with an evaporative injection system, where fuel was supplied through a coil about 1 m long. Homemade turbine wheel from 2.5 mm tin! With a length of only 260 mm and a diameter of 110 mm, the engine weighed 700 grams and produced 30 Newtons of thrust! It is still the quietest turbojet engine in the world. Because the speed of gas leaving the engine nozzle was only 200 m/s.

Based on this engine, several options for self-assembly kits were created. The most famous was the FD-3 of the Austrian company Schneider-Sanchez.

Even 10 years ago, an aircraft modeler faced a serious choice - an impeller or a turbine?

The traction and acceleration characteristics of the first aircraft model turbines left much to be desired, but they had an incomparable superiority over the impeller - they did not lose traction with an increase in the speed of the model. Yes, and the sound of such a drive was already a real “turbine”, which was immediately appreciated by the copyists, and most of all by the public, which was certainly present on all flights. The first Shrekling turbines calmly lifted 5-6 kg of the weight of the model into the air. The launch was the most critical moment, but in the air, all other models faded into the background!

At that time, an aircraft model with a microturbine could be compared with a car constantly moving in fourth gear: it was difficult to disperse it, but then such a model was no longer equal either among impellers or among propellers.

I must say that the theory and development of Kurt Schreckling contributed to the fact that the development of industrial designs, after the publication of his books, went along the path of simplifying the design and technology of engines. Which, in general, led to the fact that this type of engine became available to a large circle of aircraft modelers with an average wallet size and family budget!

The first samples of serial aircraft model turbines were the JPX-T240 of the French company Vibraye and the Japanese J-450 Sophia Precision. They were very similar both in design and in appearance, had a centrifugal compressor stage, an annular combustion chamber and a radial turbine stage. The French JPX-T240 ran on gas and had a built-in gas supply regulator. She developed thrust up to 50 N, at 120,000 rpm, and the weight of the apparatus was 1700 gr. Subsequent samples, T250 and T260, had a thrust of up to 60 N. The Japanese Sophia, unlike the Frenchwoman, worked on liquid fuel. At the end of its combustion chamber was a ring with spray nozzles, it was the first industrial turbine that found a place in my models.

These turbines were very reliable and easy to operate. The only drawback was their overclocking characteristics. The fact is that the radial compressor and the radial turbine are relatively heavy, that is, they have a larger mass and, consequently, a larger moment of inertia compared to axial impellers. Therefore, they accelerated from low gas to full speed slowly, about 3-4 seconds. The model reacted to the gas correspondingly even longer, and this had to be taken into account when flying.

The pleasure was not cheap, one Sofia cost in 1995 6.600 German marks or 5.800 "evergreen presidents". And you had to have very good arguments to prove to your wife that a turbine is much more important for a model than a new kitchen, and that an old family car can last a couple more years, but you can’t wait with a turbine.

A further development of these turbines is the P-15 turbine sold by Thunder Tiger.

Its difference is that the turbine impeller is now axial instead of radial. But the thrust remained within 60 N, since the entire structure, compressor stage and combustion chamber remained at the level of the day before yesterday. Although for its price it is a real alternative to many other samples.

In 1991, two Dutchmen, Benny van de Goor and Han Enniskens, founded AMT and in 1994 produced the first 70N class turbine, the Pegasus. The turbine had a radial compressor stage with a Garret turbocharger impeller, 76 mm in diameter, as well as a very well thought out annular combustion chamber and an axial turbine stage.

After two years of careful study of the work of Kurt Schreckling and numerous experiments, they achieved optimal engine performance, established by trial the dimensions and shape of the combustion chamber, and the optimal design of the turbine wheel. At the end of 1994, at one of the friendly meetings, after the flights, in the evening in a tent for a glass of beer, Benny winked slyly in a conversation and confidentially announced that the next production model of the Pegasus Mk-3 “blowing” already 10 kg, has a maximum speed of 105.000 and a degree compression 3.5 at an air flow rate of 0.28 kg/s and a gas outlet velocity of 360 m/s. The mass of the engine with all units was 2300 g, the turbine was 120 mm in diameter and 270 mm long. Then these figures seemed fantastic.

In essence, all today's samples copy and repeat, to one degree or another, the units incorporated in this turbine.

In 1995, Thomas Kamps' book "Modellstrahltriebwerk" (Model Jet Engine) was published, with calculations (more borrowed in abbreviated form from K. Schreckling's books) and detailed drawings of a turbine for self-production. From that moment on, the monopoly of manufacturing firms on the technology of manufacturing model turbojet engines ended completely. Although many small manufacturers simply mindlessly copy the Kamps turbine units.

Thomas Kamps, through experiments and trials, starting with the Schreckling turbine, created a microturbine in which he combined all the achievements in this area for that period of time and voluntarily or unwittingly introduced a standard for these engines. His turbine, better known as KJ-66 (KampsJetengine-66mm). 66 mm - the diameter of the compressor impeller. Today you can see various names of turbines, which almost always indicate either the size of the compressor impeller 66, 76, 88, 90, etc., or thrust - 70, 80, 90, 100, 120, 160 N.

Somewhere I read a very good interpretation of the value of one Newton: 1 Newton is a bar of chocolate 100 grams plus packaging for it. In practice, the figure in Newtons is often rounded up to 100 grams and the engine thrust is conditionally determined in kilograms.

The design of the model turbojet engine

1. Compressor impeller (radial)
2. Compressor directing system (stator)
3. The combustion chamber
4. Turbine rectifier system
5. Turbine wheel (axial)
6. Bearings
7. shaft tunnel
8. Nozzle
9. nozzle cone
10. Compressor front cover (diffuser)

Where to begin?

Naturally, the modeler immediately has questions: Where to begin? Where to get? What is the price?

1. You can start with kits. Almost all manufacturers today offer a complete range of spare parts and kits for building turbines. The most common are sets repeating KJ-66. Prices of sets, depending on the configuration and workmanship, range from 450 to 1800 Euros.
2. You can buy a ready-made turbine if you can afford it, and you manage to convince your spouse of the importance of such a purchase without bringing the matter to a divorce. Prices for finished engines start from 1500 Euros for turbines without auto start.
3. You can do it yourself. I won’t say that this is the most ideal way, it’s not always the fastest and cheapest, as it might seem at first glance. But for do-it-yourselfers, the most interesting, provided that there is a workshop, a good turning and milling base and a resistance welding device are also available. The most difficult thing in artisanal manufacturing conditions is the alignment of the shaft with the compressor wheel and turbine.

I started with independent construction, but in the early 90s there simply wasn’t such a choice of turbines and kits for their construction as today, and it’s more convenient to understand the operation and subtleties of such a unit when it is made independently.

Here are photos of self-made parts for an aircraft model turbine:

Whoever wants to get acquainted with the device and theory of the Micro-turbine engine, I can only recommend the following books, with drawings and calculations:

• Kurt Schreckling. Strahlturbine fur Flugmodelle im Selbstbau. ISDN 3-88180-120-0
• Kurt Schreckling. Modellturbinen im Eigenbau. ISDN 3-88180-131-6
• Kurt Schreckling. Turboprop Triebwerk. ISDN 3-88180-127-8
• Thomas Kamps Modellstrahltriebwerk ISDN 3-88180-071-9

To date, I know the following companies that produce aircraft model turbines, but there are more and more of them: AMT, Artes Jet, Behotec, Digitech Turbines, Funsonic, FrankTurbinen, Jakadofsky, JetCat, Jet-Central, A.Kittelberger, K.Koch, PST-Jets, RAM, Raketeturbine, Trefz, SimJet, Simon Packham, F. Walluschnig, Wren-Turbines. All their addresses can be found on the Internet.

The practice of use in aircraft modeling

Let's start with the fact that you already have a turbine, the simplest one, how can you manage it now?

There are several ways to get your gas turbine engine running in the model, but the best way is to build a small test rig like this one first:

Manual startstart) - the easiest way to control the turbine.

1. The turbine is accelerated by compressed air, a hair dryer, an electric starter to a minimum working 3000 rpm.
2. Gas is supplied to the combustion chamber, and voltage is applied to the glow plug, the gas ignites and the turbine enters the regime within 5000-6000 rpm. Previously, we simply ignited the air-gas mixture at the nozzle and the flame “shooted through” into the combustion chamber.
3. At operating speed, the stroke regulator is activated, which controls the speed of the fuel pump, which in turn supplies fuel to the combustion chamber - kerosene, diesel fuel or heating oil.
4. When stable operation occurs, the gas supply stops and the turbine runs on liquid fuel only!

Bearings are usually lubricated with fuel to which turbine oil has been added, approximately 5%. If the bearing lubrication system is separate (with an oil pump), then it is better to turn on the pump power before supplying gas. It's best to turn it off last, but DON'T FORGET to turn it off! If you think that women are the weaker sex, then look at what they turn into at the sight of a jet of oil flowing onto the upholstery of the rear seat of a family car from the nozzle of a model.

The disadvantage of this easy way control - the almost complete absence of information about the operation of the engine. To measure temperature and speed, separate instruments are needed, at least an electronic thermometer and a tachometer. Purely visually, one can only approximately determine the temperature by the color of the heat of the turbine impeller. Centering, as with all rotating mechanisms, is checked on the surface of the casing with a coin or fingernail. Applying a fingernail to the surface of the turbine, you can feel even the smallest vibrations.

In the passport data of engines, their maximum speed is always given, for example, 120,000 rpm. This is the maximum permissible value during operation, which should not be neglected! After in 1996 my self-made unit shattered right on the stand and the turbine wheel, tearing the engine casing, pierced through the 15 mm plywood wall of the container standing three meters from the stand, I concluded for myself that without control devices to disperse self-made turbines are life-threatening! Strength calculations later showed that the shaft speed should have been within 150,000. So it was better to limit the operating speed at full throttle to 110.000 - 115.000 rpm.

Another important point. To the fuel management system NECESSARILY an emergency shut-off valve controlled via a separate channel must be switched on! This is done in order to stop the fuel supply to the engine in case of an emergency landing, unscheduled landing and other troubles in order to avoid a fire.

Start ccontrol(Semi-automatic start).

So that the troubles described above do not happen on the field, where (God forbid!) There are also spectators around, they use a fairly well-proven start control. Here, the start control - the opening of gas and the supply of kerosene, the monitoring of engine temperature and speed is carried out by an electronic unit ECU (E electronic- U nit- C control) . The gas tank, for convenience, can already be placed inside the model.

For this, a temperature sensor and a speed sensor, usually optical or magnetic, are connected to the ECU. In addition, the ECU can give fuel consumption readings, save last start parameters, fuel pump supply voltage readings, battery voltage readings, etc. All this can then be viewed on a computer. To program the ECU and remove the accumulated data, use the Manual Terminal (control terminal).

To date, the two competing products in this area, Jet-tronics and ProJet, have received the widest distribution. Which one to prefer - everyone decides for himself, since it's hard to argue about which is better: Mercedes or BMW?

It all works like this:

1. When the turbine shaft (compressed air / hair dryer / electric starter) is untwisted to operating speed, the ECU automatically controls the gas supply to the combustion chamber, ignition and kerosene supply.
2. When you move the throttle on your remote control, the turbine is first automatically brought to operating mode, followed by monitoring the most important parameters of the entire system, from battery voltage to engine temperature and speed.

Autostart(Auto start)

For especially lazy start procedure is simplified to the limit. The turbine is started from the control panel, also through ECU one switch. No compressed air, no starter, no hair dryer needed here!

1. You flip a toggle switch on your radio remote control.
2. The electric starter spins the turbine shaft up to operating speed.
3. ECU controls the start, ignition and output of the turbine to the operating mode, followed by monitoring of all indicators.
4. After turning off the turbine ECU a few more times automatically scrolls the turbine shaft with an electric starter to reduce engine temperature!

The most recent achievement in the field of automatic start was Kerostart. Start on kerosene, without preheating on gas. Having put a different type of glow plug (larger and more powerful) and minimally changing the fuel supply in the system, we managed to completely abandon gas! Such a system works on the principle of an automobile heater, as on Zaporozhets. In Europe, so far only one company is converting turbines from gas to kerosene start, regardless of the manufacturer.

As you have already noticed, in my drawings, two more units are included in the circuit, this is a brake control valve and a landing gear control valve. These are not mandatory options, but very useful. The fact is that for “ordinary” models, when landing, the propeller at low speeds is a kind of brake, while jet models do not have such a brake. In addition, the turbine always has residual thrust even at “idle” revolutions, and landing speeds for jet models can be much higher than for “propeller” ones. Therefore, to reduce the run of the model, especially on short sites, the brakes of the main wheels help a lot.

Fuel system

The second strange attribute in the drawings is the fuel tank. Reminds me of a Coca-Cola bottle, doesn't it? The way it is!

This is the cheapest and most reliable tank, provided that reusable, thick bottles are used, and not wrinkled disposable ones. The second important point is the filter at the end of the suction pipe. Required item! The filter does not serve to filter the fuel, but to avoid air entering the fuel system! More than one model has already been lost due to the spontaneous shutdown of the turbine in the air! Filters from chainsaws of the Stihl brand or the like made of porous bronze have proven themselves best here. But ordinary felt ones are also suitable.

Since we are talking about fuel, we can immediately add that the turbines are very thirsty, and fuel consumption is on average at the level of 150-250 grams per minute. Of course, the biggest expense is at the start, but then the throttle lever rarely goes beyond 1/3 of its position forward. From experience, we can say that with a moderate flight style, three liters of fuel is enough for 15 minutes. flight time, while there is still a margin in the tanks for a couple of landing approaches.

The fuel itself is usually aviation kerosene, known in the west as Jet A-1.

You can of course use diesel fuel or lamp oil, but some turbines, such as those from the JetCat family, do not tolerate it well. Also, turbojet engines do not like poorly refined fuel. The disadvantage of kerosene substitutes is the large formation of soot. Engines have to be taken apart more often for cleaning and inspection. There are cases of operation of turbines on methanol, but I know only two such enthusiasts, they produce methanol themselves, so they can afford such a luxury. The use of gasoline, in any form, should be categorically abandoned, no matter how attractive the price and availability of this fuel may seem! This is literally playing with fire!

Service and motor resources

So the next question has matured by itself - service and resource.

Maintenance is more about keeping the engine clean, visually inspecting and checking for vibration at start up. Most aeromodellers equip the turbines with some sort of air filter. Ordinary metal sieve in front of the suction diffuser. In my opinion - an integral part of the turbine.

Engines kept clean, with a good bearing lubrication system, can operate without fail for 100 or more operating hours. Although many manufacturers advise sending turbines for control maintenance after 50 working hours, this is more to clear one's conscience.

First reactive model

More briefly about the first model. It is best that it be a "coach"! There are many turbine trainers on the market today, most of them deltoid wing models.

Why delta? Because these are very stable models in themselves, and if the so-called S-shaped profile is used in the wing, then both the landing speed and the stall speed are minimal. The coach must, so to speak, fly himself. And you should focus on a new type of engine and control features for you.

The coach must be of decent size. Since speeds of 180-200 km/h on jet models are a matter of course, your model will very quickly move away for decent distances. Therefore, a good visual control must be provided for the model. It is better if the turbine on the trainer is mounted openly and sits not very high in relation to the wing.

A good example of what a trainer SHOULD NOT be is the most common trainer, Kangaroo. When FiberClassics (today Composite-ARF) ordered this model, the concept was based primarily on the sale of Sofia turbines, and as an important argument for modellers, that by removing the wings from the model, it can be used as a test bench. So, in general, it is, but the manufacturer wanted to show the turbine, as in a shop window, and therefore the turbine is mounted on a kind of "podium". But since the thrust vector turned out to be applied much higher than the CG of the model, the turbine nozzle had to be lifted up. The load-bearing qualities of the fuselage were almost completely eaten up by this, plus the small wingspan, which gave a large load on the wing. The customer refused other layout solutions proposed at that time. Only the use of the TsAGI-8 Profile, reduced to 5%, gave more or less acceptable results. Those who have already flown the Kangaroo know that this model is for very experienced pilots.

Given the shortcomings of the Kangaroo, a sports trainer was created for more dynamic flights "HotSpot". This model is distinguished by more thoughtful aerodynamics, and the Ogonyok flies much better.

A further development of these models was "BlackShark". It was designed for quiet flights, with a large turning radius. With the possibility of a wide range of aerobatics, and at the same time, with good soaring qualities. If the turbine fails, this model can be landed like a glider, without nerves.

As you can see, the development of trainers has taken the path of increasing the size (within reasonable limits) and reducing the load on the wing!

An Austrian set of balsa and foam, Super Reaper, can also serve as an excellent trainer. It costs 398 Euros. In the air, the model looks very good. Here is my favorite video from the Super Reaper series: http://www.paf-flugmodelle.de/spunki.wmv

But the low-price champ to date is Spunkaroo. 249 Euro! Very simple balsa construction covered with fiberglass. Only two servos are enough to control the model in the air!

Since we are talking about servos, we must immediately say that standard three-kilogram servos have nothing to do in such models! They have huge loads on the steering wheels, so you need to put cars with a force of at least 8 kg!

Summarize

Naturally, everyone has their own priorities, for some it is the price, for someone it is a finished product and saving time.

by the most fast way take possession of the turbine, it's easy to buy it! Prices for finished turbines of the 8 kg thrust class with electronics today start from 1525 Euros. Considering that such an engine can be immediately put into operation without any problems, this is not a bad result at all.

Sets, Kits. Depending on the configuration, usually a set of compressor directing system, compressor impeller, undrilled turbine wheel and turbine directing stage costs 400-450 Euros on average. To this it must be added that everything else must either be bought or made by yourself. Plus electronics. The final price can be even higher than the finished turbine!

What you need to pay attention to when buying a turbine or kits - it is better if it is a type of KJ-66. Such turbines have proven to be very reliable, and the possibilities for increasing power have not yet been exhausted. So, often replacing the combustion chamber with a more modern one, or changing the bearings and installing a different type of directing systems, you can achieve an increase in power from several hundred grams to 2 kg, and the acceleration characteristics often improve much. In addition, this type of turbine is very easy to operate and repair.

To summarize, what size pocket is needed to build a modern jet model at the lowest European prices:

• Turbine assembly with electronics and small things - 1525 Euro
• Trainer with good flying qualities - 222 Euro
• 2 servos 8/12 kg - 80 Euro
• Receiver 6 channels - 80 Euro

In summary, your dream: about 1900 Euro or about 2500 green presidents!

Recently, a number of popular science publications have published information about rapidly developing turbojet microengines for aircraft models in the West, as well as about world championships held by the International Jet Model Committee (IJMC). So, the Russian RUSJET team at the World Championship, held from July 3 to 15, 2007 in Northern Ireland, scored the most points on the bench evaluation of copy models with a turbojet power plant, and according to the flight results, took second place in the world! Finally, what we aspired to, dreamed of and fantasized about in the 60s and 70s of the last century has come true!

My modeling experience began somewhere in 1959 under the all-shaking roar of jet aircraft and its previously unthinkable records. Mysterious supersonic champions E-33, E-66, E-166, etc. excited the brain and soul, forcing them to recreate drawings from newspaper and magazine clippings, according to which flying models-copies of subsonic and supersonic jet aircraft with powder rocket engines were subsequently designed and built. The flights of such models aroused the admiration and delight of the young part of the population and the significant disapproval of more mature neighbors and passers-by. And rightly so: often jet flights were accompanied by fires and even explosions.
I did not have a chance to master the generally recognized aircraft modeling technologies in well-to-do circles under the guidance of an adult mentor. However, my “self-training” in a communal apartment ensured independence and freedom to translate the flow of ideas into real designs, accustoming me to follow little-known paths from a young age. The passion for aviation in those years gave rise to curiosity, diligence, intuition and ingenuity, which, in addition to making aircraft models according to drawings made by one's own hands and developed technologies, forced one to rummage diligently on the shelves of libraries and find such books on aviation and rocket and space topics that are dear to a young heart. "With bated breath" was read everything from the magazine "Young Technician" and not always ending with the publications of Oborongiz. Aerodynamics, the design of aircraft, the theory and design of air-jet and rocket engines, aviation materials science and even the design of aviation instruments and the basics of electronics, carried away beyond their age, revealing to the young soul not always clear, but such an unusual and interesting world of technology, the world of aviation.
The remnants of the information processed and assimilated by the student, already in the 7th grade, in the lessons of physics, while studying Newton's 3rd law, allowed the teacher to completely entrust the conduct of the lesson to study jet propulsion, principles and design of air-jet and rocket engines to a young aircraft modeller, i.e. to me.
Later, while serving in the Armed Forces, the basic knowledge of electronics acquired at school age, as well as the ability to assemble your own radios, allowed me to graduate with honors from the Military Aviation School of Mechanics, to become a first-class specialist guidance operator, commander of a radar station and later an officer.
In 1969, I developed the Rubicon program, in accordance with which flying models with jet power plants and the engines themselves were designed and built. Motor-compressor SU: in the bow of the model - an impeller, in the tail - a combustion chamber with forced fuel injection; SU with a rocket-ramjet engine: takeoff on a powder rocket engine (RDTT), fixed along the axis of a ramjet engine, which, after acceleration of the ramjet engine, was supposed to provide thrust to such an apparatus, etc. These experiments did not always end successfully, and the young design thought continued to look for more efficient and reliable ways to introduce jet propulsion into aircraft modeling.
My friend and like-minded person Alexander Selin - “AS” took an active part in the implementation of the Rubicon program, who, having irrepressible energy and rich imagination, always understood me and inspired me to new “jet feats”. Not without the influence of ASa, as it seemed to us then, a new highly efficient fuel composition was used for the next repeatedly flown jet model. However, the burning rate of this fuel was so high and uncontrollable that the very first flight ended in an explosion, and the face of the pale-faced AS was born instantly with the Negroid race. But even after such failures, we did not lose heart, but thought, analyzed and “flyed” again. AS not only spawned ideas and created designs, but also superbly piloted the vehicles we tested. In 1970, AS went to his home in the Donetsk region, became a miner, and aviation ceased to excite him ... My creative impulses died out without a friend.
Soon the time came to fulfill the sacred duty of protecting the Motherland. Upon returning from the Army, in 1973, my area of ​​interest covered ekranoplans, which I was “sick” of until 1976, as well as my studies at the Taganrog Radio Engineering Institute (TRTI), where I was sent after serving in the Armed Forces. However, in 1976, my "reactive syndrome" began to progress again with the implementation of new technical ideas.
By that time, on a subconscious level, for many years I had been analyzing the creation of an American aircraft modeling company, which in 1966 informed the world about the creation and sale of the Turbocraft-22 microturbo engine.
This information, which led to an exacerbation of my "reactive syndrome", a diploma of a mechanical technician in "Aircraft", subsequent studies at the branch of the Moscow Aviation Institute (MAI) named after. S. Ordzhonikidze and work as an engineer in the production and dispatch department of the Taganrog Machine-Building Plant (now JSC TANTK named after G.M. Beriev) did their job: finally, I managed to develop and build a turbojet microengine TD-01 with a centrifugal compressor, an annular combustion chamber, centrifugal fuel injection and an axial turbine with a diameter of 68 mm, which was also provided for by the Rubicon program. Micro-turbojet engine, after repeated attempts to manufacture it back in school years, managed to be built in the factory, semi-legally, only at the age of 24 years.
Necessary for the construction of the engine are heat-resistant, heat-resistant, etc. materials were selected according to reference books and, fortunately, they could be found in production waste, and at that time the plant did not experience a shortage of them. They were then able to be processed by highly qualified specialists, always ready to assist in my creative research, who, at the same time, knew how to "keep their mouths firmly shut."
All locksmith and simple turning operations I performed with my own hands. Milling, welding, spinning operations ordered, but in my presence. Fitting, assembly, balancing, etc. did it himself.
In the meantime, three versions of the PuVRD (pulsating air-jet engine) were developed and built, about which I read a lot in my childhood, and the work of which for the first time in my life happened to be seen when testing my PuVRD. A white-hot combustion chamber and a cherry-red resonant pipe, against the background of a cutting and deafening sound of a PUVRD, quickly cooled my fuse to create a reactive model-copy with a PUVRD, forcing me to give more and more preference to the turbojet engine. Around the same time, I developed a project for a turbojet microengine TD-02 with a centrifugal compressor, a centripetal turbine and a pumped fuel supply through a manifold with injectors. But this microengine was no longer destined to be embodied in metal.
Having started testing my micro-turbojet engine in the factory laboratory for testing real aircraft engines, due to the huge difference in the dimensions of the test objects, I had to either fall under the crossfire of statements by highly qualified authoritative critics about the uselessness and impossibility of creating such an engine, or plunge into the waves of the ocean of recommendations for a radical alteration of units TRD, so that they are similar to the units of engines known at that time at the plant: AL-7PB, RD-45F, Vk-1A, AI-20, TS-20, etc.
One leading engineer, who sympathizes with my creative research, came up with the idea to spin up the engine shaft not by supplying air to the compressor impeller, but by tangential air supply to the axial turbine. Such a solution was dangerous in that it could disable the turbine due to its insufficient strength. And so it happened. Without my consent, a fitting was soldered into the turbine housing, through which air was supplied tangentially to the turbine at a pressure of about 10 atmospheres, which, when the turbine was spinning up, mercilessly “laid” all of its blades onto the hub. And there are many such examples.
And yet the engine worked, albeit unstable. Its idle speed was approximately 40,000 rpm. The whistle of the turbine as the speed increased went beyond the threshold of audibility. Sometimes there was a flame failure in the combustion chamber (CC), and then a jet of air with finely dispersed kerosene escaped from the nozzle. The fuel supply system through centrifugal injectors worked flawlessly. The issues of organizing the combustion of kerosene in a small-volume CS were solved by installing swirlers and flame stabilizers, the effectiveness of which was observed in a rather narrow range of fuel-air mixture flow rates. Expanding the range of stable combustion rates required a better preliminary preparation of the fuel for combustion and an increase in the volume of the combustion chamber. Such an increase in the volume of the combustion chamber, in turn, entailed the manufacture of a new hollow shaft of the engine with centrifugal nozzles, the replacement of the combustion chamber flame hood and the engine housing. The details, for those times, are simple, but I no longer had the means to continue the work and the mood to fight the skeptics. Stable combustion in the combustion chamber could probably be ensured by an automatic fuel supply regulator based on the readings of miniature temperature sensors and air pressure sensors at the compressor outlet, but such equipment with suitable parameters was not available at the plant at that time. The development and manufacture of such a device required financial resources, additional research and experiments. Unfortunately, it was not possible to find interest and support from the leadership of the aviation design bureau in fine-tuning, this development ahead of its time.
When the information about my micro-turbojet engine reached the Chief Designer, he said: “We (Machine-Building Plant. - Yu.V.) are not an engine-building company, and it does not suit us to engage in such nonsense ... "
The experience of creating micro-turbojet engines, as well as the experience of working on the implementation of later projects of miniature low-cost aircraft with electronic equipment and UAV capabilities, born of the work and initiative of engineers and inventors of the city of Taganrog, is also not in demand and is not supported. These developments are now presented only in some patents for inventions with the rights and obligations of authors-patent holders, for their ability to enter the innovation environment and participate in competitions for innovative projects.
Today, such "nonsense" as a micro-turbine engine can be purchased at specialized model stores of some Western countries at a price of 3000 to 6000 $, i.e. at the price of a new imported kitchen or a used foreign car, in order to be used not only for jet flying models, but also for unmanned aerial vehicles, small-sized autonomous power plants, and even for new types of manned aircraft with distributed jet thrust.
It should be recalled that the creator of the micro-turbojet engine, generally recognized in the West, is Kurt Schreckling from Germany, who, allegedly in the 80s of the last century, was the first to develop and build an aircraft model turbojet engine. However, according to the magazine "Modelist-Konstruktor" No. 3 of 1966, the championship in the development of such a microengine belongs to an American aircraft modeling company (the Turbocraft-22 engine, which was not a prototype in the development of my TD-01, but was a "catalyst" and confirmation of the fundamental possibility and the reality of the creation of micro-turbojet engines in the 60s - 70s).
Since 1976, part-time, I led aircraft modeling circles and laboratories, where my “turbojet creation” lay unclaimed for a long time, waiting for support and Russian implementation ...

Chairman of the Coordinating
Council of the Charitable Society for Scientific and Technical Creativity and Ecology "Juvenal", Taganrog, engineer, inventor

An engine of this type is not listed in the current classification list of aircraft power plants and is not used in actual operation. Many people have never even heard of him. However, he, in fact, the same age as the first airplanes, has an interesting history. practical application and may be of interest to aviation enthusiasts.

Motor-compressor power plant of the I-250 aircraft.

In transport engineering, for a long time there has been such a concept as combined power plant . Usually this term means the combination in one constructive component of engines (or principles of their operation) of various types, most often two or more.

For ground vehicles good example can serve relatively actively used now cars, buses and trolleybuses, capable of operating with the use of piston internal combustion engines and electric motors in one, so to speak, set. For them, the term "hybrid engines" is most often used.

Aviation also did not escape this fate. Combined power plants of various designs and principles of operation were designed and used on aircraft quite intensively almost from the first steps of aircraft construction.

All this was done not from a good life, but from a mismatch between the desired and the available opportunities. After all, even now, the existing and developed highly advanced aircraft engines cannot make the aircraft absolutely universal, both in terms of high traction characteristics, mass and aerodynamic perfection, and in terms of high fuel efficiency. Each of the existing propulsion schemes, for example, screw and jet-powered schemes (RJD), has its most advantageous field of application for it.

And at the first stages of the development of aviation there was not yet a special choice of power plants, but there was a wide field for innovative activity. The principle of jet propulsion, known, by the way, long before the appearance of the first airplanes, seemed to be one of the most tempting possibilities for solving problems.

And in the future, with an increase in the speed of aircraft (especially in the 40s), and a corresponding drop in the traction capabilities of the propeller, as well as the power capabilities of the piston engine (without increasing mass), it simply became the only possible one.

jet rocket engines, both liquid and solid propellant, could not become the main engines of the aircraft due to the short duration of their operation, some features that complicate operation (concerns LRE) and the complexity of control (RDTT). Therefore, they were used mainly on experimental aircraft and as boosters. This is especially true for solid fuel engines. This is written ().

Pretty soon it became clear that the air-jet engine is the most suitable for the main power plant of the aircraft, or rather, this engine must be exactly a turbojet to be able to start from zero speed, that is, from the parking lot.

Here is just an acceptable embodiment of this fact in a concrete technical device, which could be fruitfully used as a power plant for an atmospheric aircraft, was late for known reasons, both scientific and technical. That is, there was not enough knowledge, there were no specific theoretical developments and practical experience, there were no special productions and materials.

What do you have and what do you want...

But once the development process started, it was already unstoppable. The first purely jet aircraft powered by a turbojet engine made its historic flight on August 27, 1939. It was a German aircraft Heinkel He 178, equipped with a Heinkel HeS 3 engine, which had a maximum thrust of 498 kgf.

Turbojet engine NeS-3B

Aircraft Not 178.

Aircraft Not 178.

This engine was completed by early 1939 and tested in flight in July on a Heinkel He 118 piston dive bomber used as a flying laboratory. HeS 3 hung under its fuselage and turned on in flight (with the exception of takeoff and landing).

For the first time practically used for a full-fledged jet flight, the turbojet engine was, of course, relatively primitive, however, it had all the nodes characteristic of its type, incl. compressor (centrifugal with a retaining axial stage), turbine (radial), outlet device. And he worked already as a full-fledged air-jet engine. However, its performance left much to be desired.

These, however, were all early turbojet engines, both projects and those built in metal. Low thrust, low efficiency, meager resource, low reliability... It is clear, because these were only the first steps, and all the achievements on this path were still ahead. However, one can say so now, but at that time absolutely clear prospects were not yet clear.

Perhaps it is the existence of initial stage some uncertainty in the further development of turbojet engines and the desire to quickly find a simpler, but at the same time complete, and most importantly, a much-needed alternative that would improve the performance of aircraft, forced engineers to consider other options for jet engines.

In one of these options, the principle of combination (or hybridity) was used. This is about motor-compressor air-jet engine (MKVRD). In the USSR, this type of engine in the first half of the 40s received another name - VRDK(air-jet engine with compressor).

Abroad, it has several names. The most commonly used is motorjet (for comparison, turbojet - turbojet), less commonly used (and also used in German) - termojet. There are a few more little-used names - hybrid jets, piston-jets, compound engines, reaction motor, as well as afterburning ducted fan (duct fan with afterburning), bypass ducted fan.

In a turbojet engine, the most loaded and complex unit is the turbine. For the most part, it determines the limiting temperature of the gas in the combustion chamber for the structure, since it itself is not only under its influence, but also under the load of huge centrifugal forces (impellers). Gas temperature, in turn, directly affects traction.

But at the same time, the turbine is in some way secondary and the thrust itself, so to speak, “does not do”. Its main purpose is to create power to rotate the compressor. That is, not only is it complicated and you cannot do without it in a turbojet engine, but if it itself also has low characteristics, then the engine will not have high parameters either. Solid problems...

To get rid of them, the “easiest way” is to get rid of the turbine itself. And this is precisely the case of a motor-compressor engine. It is very convenient in the sense that in the 1930s and early 1940s there was no experience in creating high-quality aircraft turbines with relatively high parameters.

The traditionally classic motor-compressor power plant consists of three main parts: a piston internal combustion engine (PD), a compressor and, if I may say so, simplified air jet engine. In this case, the compressor is driven by a piston engine (usually through a special transmission or shaft) and can be of various types (most often centrifugal or axial).

The compressor is usually low-pressure (by design). Instead, a high-pressure fan or, in fact, a propeller (or several) in an annular shell can also be used.

The WJE in this kit is indeed very simplified compared to the TJD. It has neither its own compressor nor, accordingly, a turbine, and has only fuel injectors (or their manifold), through which fuel is supplied to heat the incoming air, an improvised combustion chamber and an outlet device for gas outlet (nozzle). Moreover, with the use and presence of a combustion chamber, options are also possible (more on this below).

Thus, outside air through a special channel enters an external compressor, which is rotated by a reciprocating engine. Next, compressed air enters the combustion chamber where it is heated by burning fuel, and then power-armed the gas mixture passes in to accelerate and create jet thrust.

In the classic version motor-compressor engine simplified WFD with its device and principle of operation resembles a ramjet engine or even more afterburner combustion chamber for turbojet and turbofan engines. It was during the creation of motor-compressor engines that the first experience was obtained, which was useful later in the development of the FCS.

According to various sources, the contribution of the combustion chamber of the MKVRD to the creation of thrust (in addition to air compression by the compressor) is estimated from one third to one half of the total value, depending on the perfection of the design. Some contribution, depending on the design option, can also be made by the exhaust gases of the PD and the heat of its body.

General aircraft thrust from such combined power plant can be obtained not only due to the jet stream of gases from the WFD, but also with the help of a propeller driven by a piston engine (the same one that rotates the compressor). There are various examples of the design and construction of aircraft with MKVRD both with and without a propeller.

When using both types of propulsion on an aircraft, both propeller and jet thrust, a certain versatility can be traced. At low speeds (heights) it is more advantageous to work with a propeller, and at high speeds (heights) - with the use of jet thrust. The altitude and speed capabilities of the aircraft are increasing.

It is worth saying that there were other, already much more advanced layout options for motor-compressor engines, for example, in the late 30s, in the 40s (mainly in Germany), when they were created in parallel with turbojet engines and evaluation activities were in full swing, to understand which of the two principles is more acceptable. In this version, all the traditionally separate elements of a classic motorjet were combined into a single unit, outwardly very reminiscent of a turbojet engine (see examples below). However, despite the similarity, the principle of operation remained unchanged.

As an interesting addition...

Speaking of general principle MKVRD devices, one curious fact cannot be ignored. Regardless of whether people know what motor-compressor engine, or not, almost every one of them has, one might say, his miniature model at home. Low-powered and not intended for movement, but still ...

This is a normal household hair dryer. It, albeit in a primitive form, has all the necessary elements: a fan (mini-compressor), a heater (combustion chamber) and even a tapering nozzle that blows quite intensely and hotly :-) ...

Directions…

Attempts to introduce “hybridity”, which ultimately led to the construction of actually working models of motor-compressor-type engines, took place almost from the first steps in the development of aviation, when “flying whatnots” were more or less firmly established in the air.

At the same time, it can be said that within the framework of the type itself, there were several directions and options for design developments that changed the design (and sometimes the operating parameters), but did not change the fundamental principle of the engine.

An example is the somewhat unusual engine project of the French engineer René Lorin, which he completed in 1908. From the simplified WFD, which seems to be present in a motorjet, only the output device, that is, the nozzle, remained in Lorin's engine.

Engine Rene Lorin.

The engine, as such, did not have its own combustion chamber, as well as a separate compressor. Combustion products were sent to the nozzle after ignition of the fuel-air mixture in the piston engine cylinder.

That is, it was, in fact, each cylinder of which had its own nozzle for the exit of exhaust gases and, accordingly, the generation of jet thrust. It is clear that the thrust was formed by impulses, although, of course, this fact has nothing to do with the PuVRD. It was understood that such engines were to be installed directly on the wing of the aircraft.

The next in chronology is perhaps worth mentioning the famous experimental aircraft Coandă 1910, designed by the Romanian aerodynamic engineer and inventor Henri Coandă, the famous discoverer of the Coandă effect.

Aircraft Coanda 1910 at the Paris Air Show in 1910.

Schematic of the Coande engine. The fuel supply and ignition system, as well as additional CSs, are not shown. The proposed supply of PD exhaust gases to the flow is shown.

The power plant was located in the forward fuselage. It had the form of an annular canal-hood, the front part of which was equipped with a compressing incoming air, the flow rate of which through the front air intake was regulated using a petal device (Coanda called it an obturator).

The compressor had a rotation speed of about 4000 rpm and was driven by a Clerget in-line piston engine (50 hp) installed in the upper part of the fuselage immediately behind the air channel, through a special transmission.

The inventor himself at first called such a power plant “turbo-propulseur” (the word “turbo” here refers specifically to the compressor), and later, when air-jet engines had already confidently taken a leading place in aircraft engine building, he declared it to be air-jet motor-compressor engine.

Around the same time, it was said that the Coandă 1910 was the first jet-powered aircraft to fly, the maximum value of which (about 220 kgf) was about half the thrust of the aforementioned Heinkel He 178.

It was assumed that the air compressed after the compressor was mixed with fuel, which burned, giving the aircraft increased jet thrust. Fuel was injected in the rear side parts of the air channel and burned there. Later, some sources also mentioned some additional combustion chambers on the sides of the fuselage.

Compressor elements of the Coande engine.

A replica of the Coanda 1910 aircraft. The installed PD does not match the original.

Another possible scheme for the propulsion system of the Coanda 1910 aircraft.

In addition, patent applications stipulated the supply of exhaust gases from a piston engine to the inlet to the air channel, which could increase the air flow through the engine and the flow temperature.

However, statements about combustion chambers actually appeared already in the post-war period. The design of the aircraft, extremely unfortunate in this regard, would hardly allow such a scheme to be used without the risk of fire, which would damage the wooden structure and the completely unprotected pilot.

The aircraft was presented at the 2nd Paris Air Exhibition (October 1910) without additional combustion chambers and the claimed piston engine exhaust system. Many researchers and aviation specialists, both at that time and in recent years, have seriously questioned the very existence of the in-stream fuel combustion system on Coandă 1910.

Even the fact single flight this aircraft. He took place December 16, 1910 and ended unsuccessfully due to damage to the control system (or inattention of the pilot).

According to some Romanian sources (and allegedly from the words of Coande himself), the flight took place by accident. The engineer was not going to take off and was just testing the engine. Carelessly shifted levers increased the speed of the compressor and opened the obturator. The plane began to take off and took off.

Surprise, a large exhaust flame from under the hood and a lack of experience in piloting led to a loss of control over speed and altitude. The plane landed on the ground and caught fire. The engineer himself received some injuries. In the future, due to lack of funds, the aircraft was not restored.

Possible spread of hot gases from the engine on a Coanda 1910 aircraft.

It is curious that this incident is sometimes associated with the discovery later by Henri Coanda of a phenomenon named after him - the Coanda effect. The jet of air coming out of the annular nozzle of the propulsion system of his aircraft, together with hot gases after the combustion of the fuel, seemed to “stuck” to the fuselage and damaged the tail unit. This allegedly prompted the engineer to certain thoughts. However, whether it was really so, we, it seems, will never know ....

There is another interesting point in this case. At the same time, by the beginning of December 1910 in Paris, by order of Grand Duke Kirill Vladimirovich ( cousin Emperor Nicholas II) were built snowmobiles, equipped with a Coande engine (he was directly involved in this), similar in design to an aircraft. So, on this device there was no additional combustion of fuel, except in the piston engine itself.

Snowmobile of Grand Duke Kirill (Koande project).

And yet ... Now, apparently, it is not so important whether the fuel combustion system in the air flow was present on the Coandă 1910 engine. If it was, then it was, although quite primitive, but still a typical motorjet with a full set of characteristic structural units. If not, then all the same, this project was close enough to this type of engine, or rather to their specific version, which creates the so-called "cold thrust".

Motor compressor engine with a combustion chamber, heating the air, creates "mountain thrust". But if there is no additional combustion chamber, then the draft is just cold. In this case, some heating can be carried out only by compressing the air in the compressor (a little, but still ...), diverting the hot exhaust gases of the piston engine into the stream, and also by cooling the PD body (if both of the latter methods are provided for by the design).

The engine of the Coandă 1910 aircraft could be quite close to this "cold" version (assuming that it did not have a fuel combustion system in the stream, or it was not used). The very principle of the arrangement of units, when the compressor is located in front of the piston engine and blows air over it, is sometimes also called the “Coanda scheme”.

It is interesting that in the very next year, 1911, a research project of the Russian engineer A. Gorokhov was announced. It was a classic version of a motor-compressor engine with 2 combustion chambers and a compressor driven by a piston engine. That is, the engine generated just hot thrust. At the same time, the compressor itself was also a piston unit that compresses air in the cylinders and directs it to the combustion chambers.

A. Gorokhov's project. 1 - air intake; 2 - compressor; 3 - combustion chambers; 4 - nozzles; 5 - piston engine.

Options…

However, later, in the 30s and the very beginning of the 40s, there were quite advanced projects of motorjets that worked precisely on cold traction.

An example is the German HeS 60 engine, designed by the combined company Heinkel-Hirth in 1941, as the final model in a whole line of similar engines. This unit did not have a combustion chamber.

The air was compressed (with some increase in temperature) in its own three-stage axial compressor. A 32-cylinder diesel engine (power 2000 hp) was also arranged to enter the exhaust gas flow, which rotated the compressor and heat removal from this PD. Next, the compressed air was directed to a controlled flap nozzle. Estimated thrust reached 1250 kgf.

Schematic of the HeS-60 engine.

This model provided for the selection, if necessary, of a part of the flow energy for intra-engine needs through a special radial turbine.

The piston engine itself was “embedded” inside the HeS 60. Such a scheme was typical for German projects and was later also used for MKVRD projects using hot thrust (mentioned below).

The principle of creating cold thrust was tried to be used, as one of the modes of operation of a motor-compressor engine, on various experimental aircraft, such as, for example, the Focke-Wulf Fw 44.

Diagram of the BMW Flugmotorenbau engine for the Focke-Wulf Fw 44 aircraft.

Scheme of a Focke-Wulf Fw 44 aircraft with a cold-powered motorjet engine.

Focke-Wulf Fw 44 aircraft.

On it, specialists from BMW Flugmotorenbau in 1938, instead of a standard engine and a two-bladed propeller, installed another engine (Bramo 325, later 329), a four-blade fan and a guide vane with an annular shell (according to the impeller principle). The air left the engine through the converging channels of the annular nozzle.

Motorjet engineer Harris. 1917

Later, "cold thrust" found its application in various jet engine designs, mainly in turbojet engines, especially engines.

And the very concept of “motorjet” was first mentioned back in 1917 in the patented project of the British engineer Harris (H.S. Harris of Esher). This project was a classic motor-compressor engine. In it, the centrifugal compressor (A) was driven by a two-cylinder piston engine (C).

Compressed air was sent to two side combustion chambers (D), where fuel (B) was injected and burned, after which the gas stream was sent to the nozzles to create thrust. Here E is the additional ejected air.

The variety of design developments of motorjets is illustrated by an interesting project of the famous British designer Frank Whittle, created by him in 1936. He called his scheme " dual thermal cycle"(Figure). It had two compressors. One, axial, main (B) at the beginning of the air path, and the second, centrifugal (F), at its end. The axial one was driven by a turbine (C), which in turn rotated from the air flow (H) created by the rear centrifugal compressor.

And this CB compressor, in turn, was driven by a piston engine (E), which received air (J) for its work from the same CB compressor, and sent exhaust gases (K) to the turbine for its additional spin. Exhaust air from the turbine (L) was sent to the nozzle channel to obtain additional thrust.

Scheme of Whittle's "dual thermal cycle" motor-compressor engine.

Until the early 1940s, German engineers experimented quite a lot on the topic of a motor-compressor engine. There was even the concept of the possible use of such engines in long-range bombers capable of reaching the coast of America.

Junkers "jet reaction plant" engine project.

Junkers has developed its own large engine project, called " jet reaction plant». In it, a 4-stage axial compressor was driven by a diesel engine with a block of 16 cylinders. At the same time, the air cooled the body of the piston engine (thereby heating up), and in rear camera combustion, fuel was mixed with it and ignited, increasing the final thrust.

The first one to actually fly...

The development of motor-compressor engines at that time was carried out by engineers from various countries. A year after the flight of the Heinkel He 178, in August 1940, another of the first jet aircraft took off. It was an Italian Caproni Campini N.1/CC2.

But despite the “reactivity”, it was not a turbojet engine that was installed on it, but a classic motorjet. The propeller was the WFD itself, that is, the aircraft was set in motion only by jet thrust, without the use of a propeller.

Aircraft Caproni Campini №1/SS2.

The motorjet was equipped with an Isotta Fraschini L.121/RC in-line piston engine (air-cooled version, 900 hp), which drove a three-stage axial compressor located in the forward fuselage. The compressor blades could change the installation angle using hydraulics 1 .

————————

1 Note. Unfortunately, I could not find unambiguous information about the fundamental design of the compressor. According to some sources (Italian), in addition to the three stages of the rotor, there were also three stages of the stator. That is, almost a full-fledged axial compressor. According to others, there was no stator, but there were three stages of a variable-pitch high-pressure propeller (fan) in an annular shell.

At the same time, the first two stages (of this screw) increased the dynamic pressure, and the third served for the most part to “correct” the flow, that is, to give it an axial direction in order to possibly reduce losses during turbulence. After all, the flow still had to get to the exit device through the entire fuselage.

But for our topic as a whole, the essence of this construction, in general, does not play a big role. The principle of operation in any case remains the same. Only the output parameters change.

———————

Atmospheric air entered the air intake (diffuser type), where it was decelerated with an increase in static pressure. Then the pressure (full or dynamic) increased in the compressor (fan), after which the air flowed around the body of the piston engine, heating itself and cooling the PD at the same time. At the same time, the flow absorbed its exhaust gases, also with an elevated temperature, and entered through the fuselage into its tail section.

Structural diagram of the aircraft Caproni Campini No. 1 / SS2. It is recommended to view in an enlarged form (clickable twice).

Flame stabilizers and fuel manifolds in the afterburner of the motor-compressor power plant of Caproni Campini No. 1/CC2 aircraft.

Here, already heated and compressed, it entered the combustion chamber, where its temperature rose even more and then went out into the atmosphere through a nozzle, creating jet thrust. The nozzle was controlled by moving the central body using hydraulics.

The nozzle of the motor-compressor power plant of the aircraft Caproni Campini No. 1 / CC2. A controlled cone (central body) is visible.

The first (inner) circuit sent air for heating by cooling the FP. Further, the air was mixed with hot exhaust gases and then with evaporating (due to the temperature of these gases) fuel (gasoline), after which the mixture was ignited by candles. This was the so-called primary combustion chamber.

The heated primary gas, moving along the axis of the engine, evaporated and ignited the secondary (or main) portion of fuel supplied further (secondary or main CS), while mixing with air supplied through the second (external) circuit. Further, the total flow was sent to the jet nozzle to create thrust.

Nasa Jake's Jeep aircraft project (Clickable).

It was envisaged to use both combustion chambers simultaneously, use only the primary one, or work without a combustion chamber at all, on the already mentioned cold thrust. This made it possible to increase the time the aircraft was in the air, and use hot thrust only for forced acceleration.

This project suffered the same fate as the bulk of others from the motorjet field. Even at the stage of initial development of the combustion chambers, he had problems. But their decision did not affect the final results of the work carried out. Yes, apparently, it could not have affected, because there were already working and promising turbojet engines. In March 1943, the program was closed for this very reason.

"Flying" VRDK ...

By the mid-40s, real practical competition (albeit formally) to many existing in the West aircraft projects with the MKVRD was Soviet aircraft from combined power plant the same principle. In the USSR, the type being developed received another name - VRDK.

By that time, the turbojet engine was asserting itself more and more confidently. More and more perfect and profitable samples were created. If in the 1930s, German aviation firms were engaged in motor-compressor engines in their various versions in parallel with other VRDs, by 1941 this work was almost completely stopped and the designers switched to working with turbojet engines, having finally set goals for themselves in jet engine building. Quite intensively this kind of work was also carried out in America and England.

In the USSR, work on motor-compressor engines (VRDK) has been carried out since 1941. Around this time at CIAM ( Central Institute aircraft engine building) a design bureau was organized to work out the most advantageous scheme VRDK. The bureau was headed by the famous design engineer K. V. Kholshchevnikov.

However, design activity without prioritization was carried out quite slowly (as well as in relation to other types of jet engines). And only in 1944, when German jet aircraft "suddenly" began to appear in real combat operations, all work in this area was intensified. Then, in the system of the people's commissariat of the aviation industry, a research institute was even formed to work on the problems of jet engine building - NII-1.

Fighter I-250 with VRDK.

Structural scheme of the I-250 aircraft. The location of the VRDK is shown.

At the end of May 1944, the design bureau of P.O. Sukhoi, as well as A.I. Mikoyan and M.I. Gurevich, was given the task of designing experimental aircraft "with a piston engine and an additional jet engine with a compressor." These additional "airjet engines with a compressor" just got the name VRDK. They were developed at CIAM by the Kholshchevnikov group.

The result was two flying aircraft: I-250 (according to some sources MiG-13) and Su-5. They had a fundamentally similar design of power plants. The main engine was a piston VK-107A (for the Su-5, the M-107 engine was originally planned), from which an axial compressor was driven through a special shaft. Air entered it through a channel from the forward fuselage.

The combustion chamber was, in fact, and was not intended for permanent operation. The heat of the piston engine and its exhaust gases were not used in the formation of jet thrust.

In this way VRDK turned on only temporarily, if necessary, a sharp increase in thrust, that is, it served as an accelerator (or auxiliary engine). For example, for the I-250, its continuous operation time was no more than 10 minutes. The fuel used is aviation gasoline.

The initial design of the Su-5VRDK.

Late project of the Su-5VRDK.

At the same time, the maximum speed was planned at an altitude of about 7500 m for the I-250 - 825 km / h, for the Su-5 - 795 km / h.

The Su-5 program was closed in 1946, among others recognized as unpromising. Work on the I-250 continued, so to speak, no matter what. And in the summer of 1945, it was even decided to build an experimental series of 10 aircraft. However, there was just something to “look at”…

Combustion chamber (afterburner) VRDK of the Su-5 aircraft.

The jet nozzle of the motor-compressor engine of the Su-5 aircraft.

The I-250, for various reasons, was extremely difficult to introduce into production and turned out to be very inconvenient in operation due to the large number of flaws and breakdowns related specifically to VRDK. By that time, jet MiG-9 and Yak-15 with turbojet engines were already in operation. By the end of the state tests of the I-250, the MiG-15, which later became famous, was being tested at full speed.

Thus, the fate of the I-250 was sealed. Even an experienced serial ten, released, by the way, with difficulty and adventures, did not enter (according to some sources) into the combat strength of the Navy aviation, for which it was intended. In 1950, the aircraft was officially taken out of service.

TsAGI projects…

In the early 1940s (before the formation of NII-1), TsAGI, on its own initiative, also developed several projects for aircraft with VRDK (unfortunately, not implemented). The purpose of these projects was the task of working out ways to radically increase the speed of aircraft. Its importance especially increased with the beginning of the Great Patriotic War.

Some of them…

The project of the S-1VRDK-1 aircraft. Equipped with M-82 piston engine with VRDK: axial compressor, combustion chamber (or afterburner), adjustable nozzle with a central body. Thrust was created only due to the jet stream. The propeller was not provided. Gasoline was used as fuel.

Project S-1VRDK-1. 3 - compressor; 5 - PD; 7 - fuel supply to the combustion chamber; 11 - the central body of the adjustable nozzle.

According to calculations, at an altitude of 4500 m, the speed should have reached 800 km / h, at 7500 m - 820 km / h. Compared to propeller-driven fighters, the aircraft had an increased rate of climb, better acceleration characteristics and could maintain a stable top speed over the entire range of heights.

A cold thrust variant was used to increase flight duration. In this case, no fuel was supplied to the combustion chamber. The air was heated by heat removal from the piston engine and the direction of its exhaust gases into the general flow through the channels of the fuselage and further into the nozzle.

As a result, when using the combustion chamber for no more than 15-20 minutes per flight (and thereby saving fuel), the time spent in the air could be increased to 3.5 hours, that is, such an aircraft could be used as a high-altitude loitering fighter-interceptor. A variant of a twin-engine aircraft with VRDK.

Another project…. On the basis of the Yak-9 fighter (M-105f engine), a project was developed for a fighter with an accelerator of the VDRK type. A combustion chamber and a three-stage axial compressor were installed in the tail section, which was driven through the drive shafts and intermediate gearboxes from the previously developed M-105REN piston engine (with a system of additional gearboxes).

Project Yak-9VRDK.

However, the aircraft was overweight due to the installation of additional equipment. The power of the new M-105REN engine turned out to be lower than the original M-105f. The estimated speed compared to the Yak-9 increased by only 80 km / h, while the combat capabilities decreased due to the required dismantling of part of the weapons. The project was considered unsuccessful, although the very fact of its existence is interesting in terms of gaining practical experience.

Somewhat later (by the end of 1943), another, more advanced project appeared with the VRDK based on the Yak-9. It was supposed to be equipped with an AM-39f high-altitude piston engine, which drove a two-stage VRDK compressor, which directed compressed air into the combustion chamber. According to calculations, the aircraft could reach a speed of 830 km / h at an altitude of about 8100. The flight time with the combined use of cold and hot modes was about 2.5 hours, that is, the aircraft could be used as a loitering fighter-interceptor.

Aircraft (from Yak-9) with VRDK. Piston engine AM-39F

There was also a project providing for the installation of the VRDK on the La-5 aircraft. Here, a single-stage fan installed in front of the engine was used as a compressor (as on the German BMW-801 piston engine) with a guide vane added to it, which made it possible to form an almost full-fledged axial compressor stage. The project scheme is shown in the figure.

Scheme of the aircraft La-5VRDK.

There were others interesting projects in various specialized Soviet design bureaus ...

For example, the development of engines was carried out, structurally somewhat different from traditional VRDK. These were engines in which the piston motor was integrated into the VRD, equipped with its own compressor, and there was no long drive shaft. Units of this design were designed in the first half of the 40s by German designers (the aforementioned HeS 60 cold thrust engine, as well as the Junkers jet reaction plant). After the end of the war, their experience and developments were used in the USSR.

In 1947, the already quite advanced engine "032" was developed under the guidance of design engineer A. Shaibe at the so-called pilot plant No. 2 in OKB-1 (Kuibyshev region). It was one of the "German" factories, formed in 1946 and engaged in gas turbine engines (particularly TVD), using equipment and specialists exported from Germany.

Engine diagram "032".

The engine was equipped with a 10-cylinder star-shaped double-row built-in PD and an adjustable nozzle. Estimated maximum thrust - 2000 kgf, nominal - 1800 kgf. Overall dimensions: length 4.0 m, diameter - 1.0 m. Fuel - kerosene or gas oil. Work on the engine was discontinued in the same 1947 due to lack of prospects due to clear advantage TRD.

Japanese contribution to the "common cause" ...

However, there was another country whose aeronautical engineers paid some attention to the implementation motor compressor engines into operation. This is Japan. Here everything was done for reasons of extreme necessity and, in general, with a significant shortage of time. The motorjet was chosen due to its simplicity and sufficient traction efficiency for the existing conditions.

In the final period of the 2nd World War, Japan created and began to use a projectile aircraft controlled by a kamikaze pilot to fight the warships of the Soviet allied navies (mainly the United States). It was a model Yokosuka MXY7 Ohka (“Oka” is a sakura flower).

Ohka 22 projectile with Tsu 11 engine (Aerospace Museum in Washington).

However, this aircraft (more precisely, its originally existing version Ohka 11) was equipped with rocket engines that had a large initial momentum, but a short operating time. Therefore, the range of the aircraft was low - about 36 km.

Such a short range was a big drawback, because the carriers of the projectiles, the Mitsubishi G4M2 torpedo bombers, were forced to approach the ship carrier groups at short distances to launch the Ohka 11, thereby exposing themselves and their cargo to the risk of being shot down by enemy fighters.

This often happened, and not only the projectile was killed, but also the bomber with the entire crew. Because of these repeated incidents, Ohka 11 even received the nickname Waka from American sailors, which means "fool", "idiot" in Japanese.

To correct this shortcoming and increase the range, a different engine was required. Since there was clearly not enough time or special resources for its development, Japanese engineers turned their attention to the principle of a motor-compressor engine.

The combustion chamber of the Tsu-11 engine of the Ohka-22 aircraft.

View from the side of the nozzle. Aircraft Ohka 22 (museum).

Piston engine from the Tsu-11 and compressor air intakes.

Motorjet piston engine Tsu-11. Compressor air intake.

The result was the Ishikawajima Tsu-11 MKVRD. Its air-jet part consisted of a single-stage axial compressor and a combustion chamber with an outlet fixed nozzle. The compressor was driven by a 4-cylinder inverted in-line piston engine Hitachi Hatsukaze HA-11 (HA-47, licensed by the German Hirth HM 504). Air inlet was carried out through two side air intakes in the rear fuselage.

WFD was very simple, one might say primitive. Its thrust was about 180 kgf, while, according to the American engineers who produced a sample of this engine, the contribution of the combustion chamber to the total thrust was small. Most of the thrust was formed by the compressor. Nevertheless, the flight range compared to the 11th model has increased by more than three times. The aircraft was named Ohka 22.

A fairly small number of Tsu-11 engines were produced. It was also planned to be installed on the Yokosuka MXY9 aircraft. Shuka , which was going to be used as a training interceptor aircraft for pilots with a Mitsubishi J8M rocket engine (marine version, Ki-200 - army version).

However, none of these planes flew - the war ended. Ohka 22 managed to build about 50 pieces (11th model - 755 pieces). One of the Tsu-11 engines is located in Washington at the National Aerospace Museum (NASM). It is mounted on a refurbished Ohka 22.

By the end of the forties, interest in motor-compressor engines had practically waned, and they disappeared from the practical field of vision of aeronautical engineers. In the future, there were separate cases of using his or his principle of operation, most often little-known, isolated and no longer connected with large aviation.

An experimental model of the aircraft (B-208T) with a motor-compressor engine (clickable).

An engine of this type was experimentally used (and is still being used) in aeromodelling (imitation of turbojet engines) or in the development of small unmanned aerial vehicles. An example is the so-called Rubicon program (1968-1978) in the USSR, dedicated to the development of jet-powered micro-engines and the model of the B-208T aircraft created at that time.

This model was equipped with a fan (1) with a guide vane (2) driven by a conventional model piston compression engine (3) and a combustion chamber (4).

Or completely non-aviation developments. For example, the use of an outlet gas jet motor-compressor engine for high-speed cleaning of surfaces, and more specifically, railway tracks from ice and snow. This is the so-called "Hornet Project" of a small Canadian company Nye Thermodynamics Corporation (1998).

In this device, a flame tube from a serial KS and a third-party diesel compressor are used.

Propulsion systems based on the motorjet principle are now sometimes used for exotic vehicles in various auto shows and for record races. As a compressor, usually automobile turbochargers or units similar to them are used.

Practically already in our time there were ideas of using cold-drawn motor-compressor engines with integrated diesel engines for small-sized air taxis. The main thing in these ideas was the use of the latest achievements in aircraft engine building, which would make it possible to make operation profitable and cheap for ordinary passengers.

And still…

And yet, in fact, for aviation, the era of motorjets was finally over by the 50th year ... The motor-compressor engine initially appeared, as it were, at the turn of two eras in the development of aircraft engine building, at the turn where new technologies replace the old ones. This was both his strength and his weakness at the same time, and all seemingly newly created projects became obsolete very quickly.

In the same period of time (30s), work on the creation of turbochargers (turbojet) was also on the rise, but still the existing level of scientific knowledge, technology and the development of metallurgy did not make it possible to simultaneously create a perfect, durable, powerful and reliable gas turbine ( as in modern turbojet engines).

At the same time, the idea of ​​a motorjet, as an engine that forms an air-jet thrust, turned out to be quite revolutionary and had obvious benefits. With a good choice of piston engine power, sufficient compressor performance (in terms of air consumption and compression ratio), proper selection and well-coordinated joint operation of the combustion chamber and nozzle, the thrust of a motor-compressor engine could well be more than the thrust of a propeller of a single piston engine.

Plus, we must not forget about the fact that the propeller thrust drops at a speed that is not characteristic of the WJ (and hence the MKVRD).

In addition, in accordance with all this, the first turbojet engines had a very small operational resource. Motorjet could also have an advantage in this regard. After all, its reliability and durability (in comparison with the turbojet engine) for the most part depended on a well-developed PD and a fairly simple combustion chamber. Therefore, interest in such an engine was quite natural.

However, the aforementioned portability of the engine also determined its significant shortcomings, which ultimately (and especially after the rapid introduction of the turbojet engine) made its further use simply impractical.

Working processes in a combined power plant operating on the principle motor-compressor engine, are described by two thermodynamic cycles at once. The piston engine is the Otto cycle, and for the VRDK it is the Brayton cycle.

As you know, the higher the pressure in the cycle, the higher its work, and hence the resulting power. At high pressure, thermal processes in the combustion chamber proceed more qualitatively, the completeness of combustion increases, which means that the need for fuel decreases and efficiency increases.

completeness beneficial use the heat obtained from the combustion of fuel characterizes thermal cycle efficiency. It directly depends on the degree of compression of the air entering the combustion chamber. The higher the compression ratio, the higher the efficiency.

For a piston engine, the compression ratio is characterized by such a value as "compression", and for an air-jet engine with a compressor, it is π to, that is, the degree of pressure increase in the compressor.

And that's just getting a high π to with the help of a compressor VRDK turned out to be difficult. One of the reasons for this is the imperfection of the compressors used. The complexity of technologies, the insufficient level (compared to the present time) of engineering and design knowledge in the field of creating axial compressors forced the use of mainly centrifugal compressors, in some cases even fans (propellers) in annular shells.

Axial compressors began to appear more often only in German projects of the late 30s, the first half of the 40s. But even such units, in order to create greater compression, must have a greater number of stages, which means larger sizes and masses, which is not always permissible (another reason for the low π to).

One stage of a good CB compressor, in principle, can provide a relatively high degree of pressure increase, however, its throughput is 2.5-3 times less than that of an axial compressor (ceteris paribus). And the throughput is the air consumption, one of the main parameters of any WFD. It is directly proportional to thrust.

Moreover, compression is hard work. The greater the degree of compression we want to obtain and provide a greater air flow, the more work must be done by the unit that drives the compressor.

For the case VRDK is a piston engine, and for it, more power directly means more mass. Mass is one of the main disadvantages of a motor-compressor power plant, in which a completely separate massive unit (PD) is used to drive a generally low-power compressor. It is doubly worse if the compressor drive is its only function, i.e. the propeller is not used.

In this plan gas turbine turbojet engines (especially modern ones) are in a much better position. With a relatively small weight and dimensions (compact), being part of a single unit, it does a very great job of driving the compressor (and often a massive fan in), compressing and passing large masses of air through the engine.

As a result, with all the possible pluses, we have: a low compression ratio, low efficiency, low efficiency (as with any afterburner), a fairly low air consumption and a large mass. It is quite clear that competition with a turbojet engine would be beyond the power of a motor-compressor engine. However, it was practically non-existent.

None of the motorjet-equipped aircraft were actually in "serious" service. All of them, even reaching the small I-250 series, so, in general, remained experienced, a kind of demonstrator of other, unfortunately, not entirely successful technologies.

History, as you know, is written by the winners...

In this case, the turbojet engine became a kind of winner, however, quite deservedly. At the same time, the motor-compressor engine turned out to be in some shadow, so, as already mentioned, not even everyone (especially inexperienced people in the aviation sense) knows about it.

However, in fact, he became an important link in the history of the development of aviation. This is a fact whose importance cannot be underestimated. The practice of using modern turbofan engines (turbojet engines) originates, in fact, from the first motorjet-s. Suffice it to recall the combustion chamber of the Caproni Campini N.1 aircraft engine.

The second circuit of modern turbofan engines, thanks to which they are highly economical and quiet, is a kind of embodiment motor compressor engines with the so-called cold draft.

Thus, contrary to the opinion of some aviation historians regarding the primitiveness and irrelevance of motorjet-s, which are a dead-end branch of the development of the WFD, they still deserve respect and occupy a prominent place among world aviation achievements.

—————-

In conclusion, another video from the Hornet Project and illustrations on the topic that were not included in the main narrative.

Until we meet again…

The layout of the power plant of the aircraft Caproni Campini No. 1 / CC2.

Checking the operation of the afterburner of the Caproni Campini No. 1/CC2 aircraft engine. The fuselage is undocked.

Demonstration of the afterburner on the Caproni Campini No. 1 / CC2 aircraft with the fuselage undocked.

Aircraft Caproni Campini No. 1 / CC2 in the museum exposition.

Turbojet engine HeS-3.

Scheme of the motor-compressor power plant of the I-250 aircraft.

Aircraft I-250 (MiG-13).

An Ohka 22 projectile at the Aerospace Museum.

The process of mounting the Tsu-11 engine on the Ohka-22 aircraft (aerospace museum).

Tsu-11 engine air intake. Compressor visible.

Su-5 aircraft with VRDK.

Another project of an aircraft with a motor-compressor engine of the Sukhoi Design Bureau.

Snowmobile with Coande engine.

The internal structure of a snowmobile with a Koande engine.

Combustion chamber operating as a component of a motor-compressor engine (Hornet project).

Diagram of the "032" engine, view of the piston engine.

 

It might be useful to read:

• From the revolutionary market to the realm of counterfeit: which one will be remembered for "Gorbushka";
• Usmanov awarded the winners of the meme contest about the dispute with Navalny Usmanov presented the iPhone to four winners of the meme contest;
• Thrush bird: description with photo and video, listen to bird singing, black and white (Siberian) thrush Show bird thrush;
• In Sweden, a criminal case was opened against the "daughter" of Bombardier Promised, but did not sell;
• Vargas Properties Inc.;
• Why roosters fight How to make roosters not fight;
• The behavior of planktonic organisms What does it consist of;
• Dodo or dodo bird: description and interesting facts Report on the reasons for the extinction of dodo bird species;