After the Wings of the Motherland magazine (it was a long time ago) appeared the drawings of the PUVRD of the design of the world champion in high-speed models with such an Ivannikov engine, I had a passionate desire to make one. True, I did not have sheet heat-resistant iron. I decided to make it out of a tin can. I wound a welding transformer for spot welding, made the appropriate electrodes and set to work. He was trained in turning and plumbing from his youth. The valve lattice was made of duralumin, the tank was glued from fiberglass, the valves and "springs" for them were made of sheet spring steel with a thickness of 0.15 mm. To cool the valves, I decided to make a tank for methanol or water with its own spray pipe and dosing needle. We started (with friends) the engine in the locksmith's area. The roar was such that one of the guys noticed how the glass on the windows buckled. The engine ran for less than a minute, because. a pipe made from a tin can burned out. But the adrenaline was there. Now I can only imagine in the photo the "head" of the PUVRD: a tank and a valve grid assembled with valves.
After a certain time, I got a small sheet of heat-resistant steel with a thickness of 0.15 mm. I decided to weld a small PUVRD out of it. It started several times. It was not used on models, although with a weight of 90g. gave traction 600g. Once it made a "splash" when, during a break in the regional meeting of the chairmen of the DOSAAF committees, to distract from the boredom of the meeting, it was launched with the help of a bicycle pump and a homemade high-voltage unit on the office desk. It was funny to watch as the crowd of chairmen, having thrown a smoke break, rushed to the table to look at the "curiosity". The spark plug is homemade. The high-voltage unit was powered by a KBS battery. The power supply was interrupted by a bell-type breaker. The unit uses a motorcycle ignition coil
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I also have one more PUVRD, though not completed yet, there is no diffuser. Maybe I'll finish it. The peculiarity of this engine is that there are transverse rings on the exhaust pipe. This is done so that the pipe does not swell, because. metal thickness 0.15mm. Here are some photos:

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Now this technique reminds me of the good old days. Generally, nostalgia.

Piloting airplanes has become a hobby that has united adults and children from all over the world. But with the development of this entertainment, propulsion systems for mini planes are also developing. The most numerous engine for this type of aircraft is electric. But more recently, jet engines (RD) have appeared in the arena of engines for RC model aircraft.

They are constantly supplemented by all kinds of innovations and notions of designers. The task before them is rather difficult, but possible. After the creation of one of the first scaled-down engine models, which became significant for aeromodelling, a lot changed in the 1990s. The first turbojet engine was 30 cm long, about 10 cm in diameter and weighing 1.8 kg, but over 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 difficulties and consider the option of creating your own masterpiece.

Taxiway device

Turbojet engines (turbojet engines) work by expanding the heated gas. These are the most efficient engines for aviation, even mini carbon-fueled engines. Since the inception of the idea of ​​creating an aircraft without a propeller, the idea of ​​a turbine began to develop throughout the society of engineers and designers. The turbojet engine consists of the following components:

• Diffuser;
• Turbine wheel;
• The combustion chamber;
• Compressor;
• Stator;
• Nozzle cone;
• Guiding apparatus;
• Bearings;
• Air intake nozzle;
• Fuel pipe 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 a fast rotation, compressing it and directing it from the stator. Once in a freer space, the air immediately begins to expand, trying to gain the usual pressure, but in the internal combustion chamber it is heated by fuel, which makes it expand even more.

The only way the pressurized air can escape is through the impeller. With great speed, it strives for freedom, heading in the opposite direction from the compressor, to the impeller, which is spun by a powerful stream, and begins to rotate rapidly, giving traction force to the entire engine. A part of the received energy begins to rotate the turbine, driving the compressor with greater force, and the residual pressure is released through the engine nozzle with a powerful pulse directed to the tail section.

The more air is heated and compressed, the stronger the built-in pressure and temperature inside the chambers. The generated exhaust gases spin the impeller, rotate the shaft and enable the compressor to constantly receive fresh air streams.

Types of turbojet control

There are three types of motor control:

Types of engines for aircraft models

Jet engines on model aircraft are of several main types and two classes: air-jet and missile... Some of them are outdated, others are too expensive, but gambling fans of controlled aircraft models 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 engine types differ for driven and bench models, due to different efficiency, weight and thrust. There are few types in aircraft modeling:

• Missile;
• Direct-flow air-jet (PRVD);
• Pulsating air-jet (PURVD);
• Turbojet (turbojet engine);

Missile it is used only on bench models, and that is quite rare. Its principle of operation differs from the 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.

Straight-through burns ambient air that is drawn from the inlet diffuser into the combustion chamber. In this case, the air intake directs oxygen to the engine, which, thanks to its internal structure, makes it necessary to build up pressure in the fresh air stream. During operation, the 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 generated, which, when mixed with fuel, spills out the exhaust from the back side at a tremendous speed.

Throbbing it works identically to the direct-flow one, but in its case the fuel combustion is not constant, but periodic. With the help of valves, fuel is supplied only at the necessary moments when pressure begins to drop in the combustion chamber. For the most part, a pulsating jet engine performs from 180 to 270 fuel injection cycles per second. In order to stabilize the state of pressure (3.5 kg / cm2), forced air supply is used by means of pumps.

Turbojet engine, the device which you considered above has the most modest fuel consumption, due to which it is valued. Their only drawback is their low weight-to-traction ratio. Turbine taxiways allow the model to reach speeds of up to 350 km / h, while the idle speed of the engine 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. The thrust of the old and new engines is different, but the models created according to the drawings of the 1960s, running on modern fuel, and modernized with modern devices, have a significant increase in efficiency and power.

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. The motors are started with the help of a starter - other motors, mainly electric, which are attached to the motor shaft in front of the inlet diffuser, or they are started by untwisting 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:
Traction: 180N @ 120,000rpm, 10N @ 25,000rpm
RPM range: 25,000 - 120,000 rpm
Exhaust gas temperature: up to 750 C °
Jet stream flow rate: 1658 km / h
Fuel consumption: 585ml / min (under load), 120ml / min (idle)
Weight: 1.2kg
Diameter: 107mm
length: 240mm

Usage

The main field of application was and remains aviation focus... The number and size of different types of turbojet engines for aircraft is staggering, but each one is special and applied when needed. Even in model aircraft of radio-controlled aircraft from time to time, new turbojet systems appear, which are presented for general review to spectators of exhibitions and competitions. Attention to its use allows you to significantly develop the capabilities of engines, complementing the principle of operation with fresh ideas.
In the last decade, parachutists and extreme wingsuit athletes have been integrating mini Turbojet engine as a source of thrust for flight with wing suit wingsuit fabric, in which case the motors are attached to the legs, or hard wing, worn as a backpack on the back, to which the motors are attached.
Another promising area of ​​use is combat drones for military, at the moment they are actively used in the US Army.

The most promising direction for using 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 into a single circuit. Due to the high temperatures, fire-resistant lined joints and fuel pipes are commonly used. All is fixed with homemade fittings, a soldering iron and seals. Since the tube can be as large as the head of a needle, the connection must be tight and insulated. Incorrect connection can lead to destruction or explosion of the motor. The principle of connecting the chain on bench and flying models is different and must be carried out in accordance with the working drawings.

Advantages and disadvantages of the taxiway

The advantages of all types of jet engines are many. Each of the types of turbines is used for specific purposes, which are not afraid of its features. In aircraft modeling, 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 aircraft models 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. By choosing certain goals, the designer can adjust the rated power, the principle of thrust formation, etc., applying different types of turbines to different models. The operation of the engine on the combustion of fuel and the injection of oxygen pressure 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 do it yourself

This question is not easy. Since turbojets, whether they are full-scale or scaled-down models, they are technically complex devices. Making from is not an easy task. On the other hand, mini turbojet engines are produced exclusively in the USA or European countries, therefore, their price is on average $ 3,000, plus or minus 100 bucks. So the purchase of a finished turbojet engine will cost you $ 3,500, including shipping and all associated pipes and systems. See the price for yourself, just google "P180-RX turbojet engine"

Therefore, in modern realities, it is better to approach this matter as follows - what is called doing it yourself. But this is not entirely correct interpretation, rather to give the work to contractors. The engine consists of a mechanical and an electronic part. We buy components for the electronic part of the propulsion unit in China, order the mechanical part from local turners, but this requires 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 an Arduino. To do this, you need a chip flashed with Arduino, sensors - a speed sensor and a temperature sensor and actuators, an electronically controlled fuel supply flap. You can flash the chip yourself if you know programming languages, or contact the forum for arduino players for a service.

Mechanical part

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

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

"Dear Vitaly! Neither Magli would you tell us a little more

about model turbojet engines, what is it all about and with what they are eaten? "

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

Many dream, but do not dare. There are many new, even more incomprehensible, many questions. You often read in various forums how representatives of respectable research institutes and research institutes with a clever look are catching up with fear and trying to prove how difficult it is! Hard? Yes, maybe, but not impossible! And proof of this - hundreds of home-made and thousands of industrial samples of microturbines for modeling! You just need 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 (TJE) or gas turbine drive is based on the work of expanding gas. In the mid-thirties, an intelligent 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 according to this principle.

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

The principle of work - you can not imagine any easier. But if only it were that simple!

The turbojet engine can be clearly divided into three parts.

• A. Compressor stage
• B. The combustion chamber
• V. Turbine stage

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

• A. Axial or Linear
• B. Radial or centrifugal
• V. Diagonal

A. Multistage linear compressors became widespread only in modern aircraft and industrial turbines. The fact is that it is possible to achieve acceptable results with a linear compressor only if several compression stages are put in series one after the other, and this greatly complicates the design. In addition, a number of requirements for the design of the diffuser and the walls of the air duct must be met in order to avoid stalling and surging. 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, is compressed - compressed in a rectifier system-stator. It was with them that the development of the first operating turbojet engines began.

Simplicity of design, less susceptibility to air stalls and the relatively high efficiency of just one stage were the advantages that previously pushed engineers to start their development with this type of compressor. It is currently the main type of compressor in microturbines, but more on that later.

B. Diagonal, or a mixed type of compressor, usually a single-stage, in principle of operation is similar to a radial, but is rather rare, usually in turbocharging devices of piston internal combustion engines.

Development of turbojet engine 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 model aircraft turbine is the American TJD-76. The first time I saw this apparatus was in 1973, when two half-drunk midshipmen tried to connect a gas cylinder to a round thing, about 150 mm in diameter and 400 mm long, tied with ordinary knitting wire to a radio-controlled boat, a target set for the Marine Corps. To the question: "What is it?" they replied, “This is a mini mom! American ... her mother does not start ... ".

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 it has not found wide application in aircraft modeling.

The first "popular" flying engine was developed by the forefather of all microturbines Kurt Schreckling in Germany. Having begun more than twenty years ago to work on the creation of a simple, technologically advanced and cheap turbojet engine in production, he created several samples that were constantly being improved. By repeating, supplementing and improving its developments, small-scale manufacturers have formed the modern look and design of the 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 approximately 1 m long. Homemade turbine wheel made of 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 leaving the gas in the engine nozzle was only 200 m / s.

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

10 years ago, the model aircraft designer faced a serious choice - an impeller or a turbine?

The traction and acceleration characteristics of the first model aircraft turbines left much to be desired, but they had an incomparable superiority over the impeller - they did not lose thrust with increasing model speed. And the sound of such a drive was already a real "turbine" one, which was immediately appreciated by the copyists, and most of all by the audience, which is by all means present on all flights. The first Schreckling turbines quietly lifted 5-6 kg of the model's weight into the air. The start was the most critical moment, but in the air all other models fade into the background!

An aircraft model with a microturbine could then be compared to a car constantly moving in fourth gear: it was difficult to accelerate, but then such a model was no longer equal either among the impellers or among the 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, followed 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 and family budget!

The first examples of serial model aircraft turbines were the JPX-T240 of the French company Vibraye and the Japanese J-450 Sophia Precision. They were very similar in design and appearance, with a centrifugal compressor stage, an annular combustion chamber and a radial turbine stage. The French JPX-T240 was gas powered and had a built-in gas regulator. She developed a thrust of up to 50 N, at 120,000 rpm, and the weight of the apparatus was 1700 grams. Subsequent samples, T250 and T260, had a thrust of up to 60 N. The Japanese Sofia worked, in contrast to the Frenchwoman, on liquid fuel. At the end of its combustion chamber there 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 a radial compressor and a radial turbine are relatively heavy, that is, they have a large mass in comparison with axial impellers and, therefore, a larger moment of inertia. Therefore, they accelerated from idle to full 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, Sofia alone cost in 1995 6,600 German marks or 5,800 “forever green presidents”. And you had to have very good arguments to prove to your wife that the turbine is much more important for the model than the new kitchen, and that the old family car can last a couple more years, but you can't wait with the 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 Hahn Enniskens, founded AMT and in 1994 produced the first 70N turbine, the Pegasus. The turbine had a Garret turbocharged radial compressor stage, 76 mm in diameter, as well as a very well thought out annular combustion chamber and axial turbine stage.

After two years of careful study of Kurt Schreckling's work and numerous experiments, they achieved optimal engine performance, experimentally established the size 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 over a glass of beer, Benny sly winked in conversation and confidentially said that the next production model of the Pegasus Mk-3 "blows" already 10 kg, has a maximum speed of 105,000 and a degree compression 3.5 with 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 in length. Then these figures seemed fantastic.

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

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

Thomas Camps, through experiments and trials, starting with the Schreckling turbine, created a microturbine, in which he combined all the achievements in this area at that time and, willingly or unwittingly, introduced a standard for these engines. Its turbine, better known as KJ-66 (KampsJetеngine-66mm). 66 mm - compressor impeller diameter. 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 the thrust - 70, 80, 90, 100, 120, 160 N.

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

The design of the model turbojet engine

1. Compressor impeller (radial)
2. Compressor rectifier 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 full range of spare parts and kits for the construction of turbines. The most common are KJ-66 repetition sets. The prices of the sets, depending on the configuration and quality of workmanship, range from 450 to 1800 Euro.
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 autostart.
3. You can do it yourself. I will not say that this is the most ideal way, it is not always the fastest and cheapest, as it might seem at first glance. But for home-builders, the most interesting, provided that there is a workshop, a good turning and milling base and a device for resistance welding 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 self-construction, but in the early 90s there was simply no such choice of turbines and kits for their construction as today, and it is more convenient to understand the operation and subtleties of such a unit when making it yourself.

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

Whoever wants to get acquainted with the device and theory of the Micro-TRD, I can only advise 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

Today I know the following firms that produce model aircraft 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 of their addresses can be found on the Internet.

Practice of use in aircraft modeling

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

There are several ways to make your turbine engine work in a model, but it is best to build a small test bench like this first:

Manual start (Manualstart) - the easiest way to control a turbine.

1. The turbine is accelerated by compressed air, hairdryer, electric starter to a minimum operating speed of 3000 rpm.
2. Gas is supplied to the combustion chamber, and voltage is supplied to the glow plug, gas is ignited and the turbine enters a mode within 5000-6000 rpm. Previously, we simply set fire to the air-gas mixture at the nozzle and the flame "shot through" into the combustion chamber.
3. At the operating speed, the travel regulator is switched on, 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 is added, about 5%. If the bearing lubrication system is separate (with an oil pump), then it is better to turn on the pump power before gas supply. It is better to turn it off last, but DO NOT FORGET to turn it off! If you think women are the weaker sex, then look at what they turn into when they see the jet of oil flowing out of the model nozzle onto the upholstery of the rear seat of a family car.

The disadvantage of this simplest control method is the almost complete lack 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, you can only approximately determine the temperature, by the color of the heating of the turbine impeller. The alignment, as with all rotating mechanisms, is checked on the surface of the casing with a coin or fingernail. By placing your fingernail on the surface of the turbine, even the smallest vibrations can be felt.

In the passport data of motors, 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 homemade unit flew right on the stand and the turbine wheel, tearing the engine casing, punched through the 15-millimeter plywood wall of the container, standing three meters from the stand, I made a conclusion for myself that without control devices to accelerate 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 full throttle operating speed to 110,000 - 115,000 rpm.

Another important point. To the fuel control circuit NECESSARILY the emergency shut-off valve must be switched on, controlled via a separate channel! This is done so that in the event of a forced landing, carrot-unscheduled landing and other troubles, stop the fuel supply to the engine in order to avoid a fire.

Start control(Semi-automatic start).

Whatever the troubles described above happen on the field, where (God forbid!) Even the audience around, they use a fairly well-proven Start control... Here, the start control is the opening of gas and the supply of kerosene, the electronic unit monitors the engine temperature and rpm ECU (E lectronic- U nit- C ontrol) . The container for gas, for convenience, can already be placed inside the model.

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

To date, the two competing products in this area, Jet-tronics and ProJet, are the most widely used. Which of them to give preference - everyone decides for himself, since it is hard to argue about which is better: Mercedes or BMW?

It all works as follows:

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

Autostart(Automatic start)

For especially lazy people, the startup 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 are 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 control 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 the engine temperature!

The most recent advancement in automatic start-up is Kerostart. Start on kerosene, without preheating on gas. By installing a different type of glow plug (larger and more powerful) and minimally changing the fuel supply in the system, it was possible to completely abandon gas! Such a system works on the principle of an automobile heater, as in the 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 diagram, these are the brake control valve and the landing gear retraction control valve. These options are optional, but very useful. The fact is that in "normal" 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 a residual thrust even at "idle" speed and the landing speed of jet models can be much higher than that of "propeller" models. Therefore, the brakes of the main wheels help a lot to reduce the model's mileage, especially on short grounds.

Fuel system

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

This is the cheapest and most reliable tank provided that reusable, thick bottles are used, and not crinkling disposable ones. The second important point is the filter at the end of the suction pipe. Required element! The filter does not serve to filter the fuel, but to prevent air from entering the fuel system! More than one model has already been lost due to the spontaneous shutdown of the turbine in the air! Best of all, filters from Stihl chainsaws or the like made of porous bronze have proven themselves here. But ordinary felt ones will do as well.

Speaking of fuel, you can immediately add that the turbines are thirsty, and the fuel consumption is on average at the level of 150-250 grams per minute. The largest consumption, of course, falls on the start, but then the throttle lever rarely goes forward beyond 1/3 of its position. From experience we can say that with a moderate style of flight, 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 or lamp oil, but some turbines, such as the JetCat family, do not tolerate it well. Also turbojet engines do not like poorly purified fuel. The disadvantage of kerosene substitutes is the high formation of soot. Engines have to be disassembled more often for cleaning and inspection. There are cases of turbines operating 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 a game with fire!

Service and motor life

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

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

Motors that are kept clean, with a good bearing lubrication system, serve 100 or more working hours without failure. Although many manufacturers advise sending turbines for inspection maintenance after 50 working hours, this is more to clear your conscience.

First reactive model

More shortly about the first model. Best of all, it should be a "trainer"! There are many turbine trainers on the market today, most of them are delta 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 concentrate on a new type of engine and control features for you.

The coach must be of decent size. Since speeds on jet models of 180-200 km / h are a matter of course, your model will very quickly move away at 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 which 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 the Sofia turbines, and as an important argument for modelers 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 showcase, and therefore the turbine is mounted on a kind of "podium". But since the thrust vector was applied much higher than the CG of the model, the turbine nozzle had to be lifted up. The bearing qualities of the fuselage were almost completely eaten away 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 a Kangaroo know that this model is for very experienced pilots.

Taking into account the shortcomings of the Kangaroo, a sports trainer for the more dynamic HotSpot flights was created. This model is distinguished by more thought-out aerodynamics, and "Ogonyok" flies much better.

The further development of these models was the "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 steaming qualities. If the turbine fails, this model can be planted like a glider, without nerves.

As you can see, the development of trainers has gone along the path of increasing sizes (within reasonable limits) and decreasing 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. The model looks very good in the air. Here is my all-time favorite Super Reaper video: http://www.paf-flugmodelle.de/spunki.wmv

But the champion at a low price today is "Spunkaroo". 249 Euro! A very simple construction in balsa covered with fiberglass. Only two servos are enough to control the model in the air!

Since we are talking about servos, I must say right away that there is nothing to do with standard three-kilogram servos in such models! The loads on the steering wheels are huge, so they need to put cars with an effort of at least 8 kg!

Summarize

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

The fastest way to get hold of a turbine is simply to buy it! Today prices for ready-made turbines of the 8 kg thrust class with electronics start from 1525 Euro. Considering that such an engine can be taken into operation immediately without any problems, then this is not a bad result at all.

Sets, Kits. Depending on the configuration, usually a set of a compressor straightening system, a compressor impeller, a non-drilled turbine wheel and a turbine straightening stage costs an average of 400-450 Euro. To this we must add that everything else must either be bought or made by yourself. Plus electronics. The final price may 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 version of the KJ-66. Such turbines have proven to be very reliable, and their capacity to increase power has not yet been exhausted. So, often replacing the combustion chamber with a more modern one, or changing bearings and installing straightening systems of a different type, it is possible to achieve an increase in power from several hundred grams to 2 kg, and the acceleration characteristics are often much improved. In addition, this type of turbine is very easy to operate and repair.

Let's summarize what size pocket is needed to build a modern jet model at the lowest European prices:

• Turbine complete with electronics and small items - 1525 Euro
• A trainer with good flying qualities - 222 Euro
• 2 servos 8/12 kg - 80 Euro
• Receiver 6 channels - 80 Euro

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

Definition and technical description.

* - automatic translation of a part of the book.

It is a curiolls fact that you will not find the term "turbine" in most physics books.

The turbine's jet stream produces axial pressure, accelerating the air mass. When air masses are accelerated in a stream, they create thrust. Forces are measured in Newtons, not kilograms and grams! The force of 1 Newton (denoted by the letter N) acts when a mass of 1 kg is accelerated or decelerated by 1 m / s. The change in speed over a period of time is defined as acceleration and is measured in m / s.

In the encyclopedia in the "turbine" section it is written: "A POWERFUL ENGINE, in which the energy of a moving medium
(water, steam, gas) is converted into useful energy. Another name is turbojet.
The forerunners were windmills and waterwheels, Specialist technical books on the topic explain the various tourist escapes in some detail under the main heading of a jet engine jet.

In Dubbel Engineering you will find the definition: "a gas turbine is a machine that uses heat to transfer mechanical energy (shaft power) or thrust (eg aircraft engines)", respectively, the term gas turbines is a general term for all types of Turbo Jet engines.
Jet turbines as well as turboprop motors. They are all considered “gas turbines; from aircraft modeling systems such as JPX. FD. micro-turbines.
Turbomin and Pegasus as well as KJ-66, .1-66 and TK-50 turbo engines feawred in this book, and including
ING is any such type of engine that either currently exists or has not yet been invented. They are all "gas turbines" for generating thrust!

Indeed, an alternative and more appropriate name for such devices is model aircraft engines with a turbocharged air jet. I prefer a term that is often used by specialists: “jet turbines, some people call them jet engines.
As you can see, we already have more than enough definition at our disposal. There is no need to come up with any new definitions. Unfortunately. technical experts do not always speak a language that is logically correct and clear. Of course, in order to help the understanding of readers who do not have special knowledge, it is necessary to always indicate what exactly is meant by the word wrbines. it turbojet engine drawings.

Not a great example, the engine draws in air at a speed of 0.25 kg / second and accelerates it at the same time to a speed of 400 m / s static axial pressure - 100 N *

Download the drawings of the model aircraft turbojet engine.

Sample page with drawings.