Basic research. Detonation engine: myths and reality Detonation spin engine

Basic research. Detonation engine: myths and reality Detonation spin engine

What is really behind the reports of the world's first detonation rocket engine being tested in Russia?

At the end of August 2016, the news spread around the world news agencies: at one of the stands of NPO Energomash in Khimki near Moscow, the world's first full-size liquid rocket engine (LPRE) using detonation combustion of fuel was launched -. Domestic science and technology has been going to this event for 70 years. The idea of ​​a detonation engine was proposed by the Soviet physicist Ya. B. Zeldovich in the article “On the Energy Use of Detonation Combustion”, published in the Journal of Technical Physics back in 1940. Since then, research and experiments on the practical implementation of promising technology have been going on all over the world. In this race of minds, Germany, then the USA, then the USSR pulled ahead. And now Russia secured an important priority in the world history of technology. IN last years something like our country can not boast often.

On the crest of a wave

Detonation liquid-propellant rocket engine test


What are the advantages of a detonation engine? In traditional rocket engines, as, indeed, in conventional piston or turbojet aircraft engines uses the energy that is released when the fuel is burned. In this case, a stationary flame front is formed in the LRE combustion chamber, combustion in which occurs at a constant pressure. This process of normal combustion is called deflagration. As a result of the interaction of the fuel and the oxidizer, the temperature of the gas mixture rises sharply and a fiery column of combustion products escapes from the nozzle, which form the jet thrust.

Detonation is also combustion, but it occurs 100 times faster than with conventional fuel combustion. This process goes so fast that detonation is often confused with an explosion, especially since so much energy is released at the same time that, for example, an automobile engine, when this phenomenon occurs in its cylinders, can actually collapse. However, detonation is not an explosion, but a type of burning so rapid that the reaction products do not even have time to expand, so this process, unlike deflagration, takes place at a constant volume and a sharply increasing pressure.

In practice, it looks like this: instead of a stationary flame front in fuel mixture a detonation wave is formed inside the combustion chamber, which moves at supersonic speed. In this compression wave, the detonation of the mixture of fuel and oxidizer occurs, and from a thermodynamic point of view, this process is much more efficient than conventional fuel combustion. The efficiency of detonation combustion is 25–30% higher, i.e., when the same amount of fuel is burned, more thrust is obtained, and due to the compactness of the combustion zone, the detonation engine in terms of power removed per unit volume theoretically exceeds conventional rocket engines by an order of magnitude.

This alone was enough to draw the closest attention of specialists to this idea. After all, the stagnation that has now arisen in the development of world cosmonautics, which has been stuck in near-Earth orbit for half a century, is primarily associated with the crisis of rocket engine building. By the way, aviation is also in crisis, unable to cross the threshold of three speeds of sound. This crisis can be compared to the situation in piston aviation in the late 1930s. Screw and motor internal combustion have exhausted their potential, and only the advent of jet engines made it possible to reach a qualitatively new level altitude, speed and range.

Detonation rocket engine

The designs of classical rocket engines over the past decades have been licked to perfection and have practically come to the limit of their capabilities. It is possible to increase their specific characteristics in the future only within very small limits - by a few percent. Therefore, world cosmonautics is forced to follow an extensive path of development: for manned flights to the Moon, giant launch vehicles have to be built, and this is very difficult and insanely expensive, at least for Russia. An attempt to overcome the crisis with nuclear engines ran into environmental problems. It may be too early to compare the appearance of detonation rocket engines with the transition of aviation to jet propulsion, but they are quite capable of accelerating the process of space exploration. Moreover, this type of jet engines has another very important advantage.

GRES in miniature

An ordinary LRE is, in principle, a large burner. To increase its thrust and specific characteristics, it is necessary to raise the pressure in the combustion chamber. In this case, the fuel that is injected into the chamber through the nozzles must be supplied at a higher pressure than is realized during the combustion process, otherwise the fuel jet simply cannot penetrate into the chamber. Therefore, the most difficult and expensive unit in the LRE is not a chamber with a nozzle, which is in plain sight, but a fuel turbopump unit (TNA), hidden in the depths of the rocket among the intricacies of pipelines.

For example, the most powerful RD-170 liquid-propellant rocket engine in the world, created for the first stage of the Soviet super-heavy launch vehicle Energia by the same NPO Energia, has a pressure in the combustion chamber of 250 atmospheres. This is a lot. But the pressure at the outlet of the oxygen pump pumping the oxidizer into the combustion chamber reaches 600 atm. This pump is powered by a 189 MW turbine! Just imagine this: a turbine wheel with a diameter of 0.4 m develops four times more power than the nuclear icebreaker Arktika with two nuclear reactors! At the same time, TNA is a complex mechanical device, the shaft of which makes 230 revolutions per second, and he has to work in an environment of liquid oxygen, where the slightest spark, not even a grain of sand in the pipeline, leads to an explosion. The technology for creating such a TNA is the main know-how of Energomash, the possession of which allows Russian company and today to sell their engines for installation on American launch vehicles Atlas V and Antares. There are no alternatives to Russian engines in the USA yet.

For a detonation engine, such difficulties are not needed, since detonation itself provides pressure for more efficient combustion, which is a compression wave running in the fuel mixture. During detonation, the pressure increases by 18–20 times without any TNA.

In order to obtain conditions in the combustion chamber of a detonation engine equivalent, for example, to the conditions in the combustion chamber of an LRE of the American Shuttle (200 atm), it is enough to supply fuel at a pressure of ... 10 atm. The unit required for this, in comparison with the TNA of a classic rocket engine, is like a bicycle pump near the Sayano-Shushenskaya State District Power Plant.

That is, a detonation engine will not only be more powerful and more economical than a conventional rocket engine, but also an order of magnitude simpler and cheaper. So why was this simplicity not given to designers for 70 years?

Pulse of progress

the main problem, which faced the engineers - how to cope with the detonation wave. The point is not only to make the engine stronger so that it can withstand increased loads. Detonation is not just a blast wave, but something more subtle. The blast wave propagates at the speed of sound, and the detonation wave propagates at supersonic speed - up to 2500 m/s. It does not form a stable flame front, so the operation of such an engine is pulsating: after each detonation, it is necessary to renew the fuel mixture, and then start a new wave in it.

Attempts to create a pulsating jet engine were made long before the idea of ​​\u200b\u200bdetonation. It was in the application of pulsating jet engines that they tried to find an alternative to piston engines in the 1930s. Simplicity again attracted: in contrast to aviation turbine for pulsating air jet engine(PuVRD) did not need a compressor rotating at a speed of 40,000 revolutions per minute to force air into the insatiable womb of the combustion chamber, nor a turbine operating at a gas temperature of over 1000 ° C. In the PuVRD, the pressure in the combustion chamber created pulsations in the combustion of the fuel.

The first patents for a pulsating jet engine were obtained independently in 1865 by Charles de Louvrier (France) and in 1867 by Nikolai Afanasyevich Teleshov (Russia). The first workable design of the PuVRD was patented in 1906 by the Russian engineer V.V. Karavodin, who built a model plant a year later. Due to a number of shortcomings, the Karavodin installation has not found application in practice. The first PUVRD to operate on a real aircraft was the German Argus As 014, based on a 1931 patent by the Munich inventor Paul Schmidt. Argus was created for the "weapon of retaliation" - the V-1 winged bomb. A similar development was created in 1942 by the Soviet designer Vladimir Chelomey for the first Soviet 10X cruise missile.

Of course, these engines were not yet detonation engines, since they used conventional combustion pulses. The frequency of these pulsations was low, which gave rise to a characteristic machine-gun sound during operation. Specific characteristics of PUVRD due to intermittent mode work on average was low, and after designers coped with the difficulties of creating compressors, pumps and turbines by the end of the 1940s, turbojet engines and rocket engines became the kings of the sky, and PUVRD remained on the periphery of technical progress.

It is curious that the German and Soviet designers created the first PuVRD independently of each other. By the way, the idea of ​​a detonation engine in 1940 came to mind not only to Zeldovich. At the same time, the same thoughts were expressed by Von Neumann (USA) and Werner Döring (Germany), so that in international science The model for using detonation combustion was called ZND.

The idea to combine a PUVRD with detonation combustion was very tempting. But the front of an ordinary flame propagates at a speed of 60–100 m/s, and the frequency of its pulsations in a PUVRD does not exceed 250 per second. And the detonation front moves at a speed of 1500‒2500 m/s, so the frequency of pulsations should be thousands per second. It was difficult to implement such a rate of mixture renewal and detonation initiation in practice.

Nevertheless, attempts to create workable pulsating detonation engines continued. The work of the US Air Force specialists in this direction culminated in the creation of a demonstrator engine, which on January 31, 2008 for the first time took to the skies on an experimental Long-EZ aircraft. In a historic flight, the engine worked for ... 10 seconds at a height of 30 meters. Nevertheless, the priority in this case remained with the United States, and the aircraft rightfully took its place in the National Museum of the US Air Force.

Meanwhile, another, much more promising scheme for a detonation engine was invented long ago.

Like a squirrel in a wheel

The idea to loop the detonation wave and make it run in the combustion chamber like a squirrel in a wheel was born by scientists in the early 1960s. The phenomenon of spin (rotating) detonation was theoretically predicted by the Soviet physicist from Novosibirsk B. V. Voitsekhovsky in 1960. Almost simultaneously with him, in 1961, the same idea was expressed by the American J. Nicholls from the University of Michigan.

Rotary, or spin, detonation engine is structurally an annular combustion chamber, fuel is supplied to which by means of radially arranged nozzles. The detonation wave inside the chamber does not move in an axial direction, as in a PuVRD, but in a circle, compressing and burning the fuel mixture in front of it and, in the end, pushing the combustion products out of the nozzle in the same way as a meat grinder screw pushes minced meat out. Instead of the pulsation frequency, we get the frequency of rotation of the detonation wave, which can reach several thousand per second, that is, in practice, the engine does not operate as a pulsating engine, but as a conventional liquid-propellant rocket engine with stationary combustion, but much more efficiently, since in fact it detonates the fuel mixture .

In the USSR, as well as in the USA, work on a rotary detonation engine has been going on since the beginning of the 1960s, but again, despite the seeming simplicity of the idea, its implementation required the solution of puzzling theoretical issues. How to organize the process so that the wave does not die out? It was necessary to understand the most complex physical and chemical processes occurring in a gaseous medium. Here, the calculation was no longer carried out at the molecular, but at the atomic level, at the junction of chemistry and quantum physics. These processes are more complex than those that occur during the generation of a laser beam. That is why the laser has been working for a long time, but the detonation engine has not. To understand these processes, it was necessary to create a new fundamental science - physicochemical kinetics, which did not exist 50 years ago. And for the practical calculation of the conditions under which the detonation wave will not fade, but will become self-sustaining, powerful computers were required, which appeared only in recent years. This is the foundation that had to be laid in the basis of practical success in taming detonation.

Active work in this direction is being carried out in the United States. These studies are carried out by Pratt & Whitney, General Electric, NASA. For example, the US Naval Research Laboratory is developing spin detonation gas turbines for the fleet. The US Navy uses 430 gas turbine units on 129 ships, consuming $3 billion worth of fuel a year. The introduction of more economical detonation gas turbine engines (GTE) will save huge amounts of money.

In Russia, dozens of research institutes and design bureaus have worked and continue to work on detonation engines. Among them is NPO Energomash, the leading engine-building company in the Russian space industry, with many of whose enterprises VTB Bank cooperates. The development of a detonation rocket engine was carried out for more than one year, but in order for the tip of the iceberg of this work to sparkle under the sun in the form of a successful test, it took the organizational and financial participation of the notorious Advanced Research Foundation (FPI). It was the FPI that allocated necessary funds to create in 2014 a specialized laboratory "Detonation rocket engines". After all, despite 70 years of research, this technology is still “too promising” in Russia to be funded by customers like the Ministry of Defense, who, as a rule, need a guaranteed practical result. And it's still very far away.

The Taming of the Shrew

I would like to believe that after all that has been said above, the titanic work that peeps between the lines of a brief message about the tests that took place at Energomash in Khimki in July - August 2016 becomes clear: “For the first time in the world, a steady state mode of continuous spin detonation of transverse detonation waves with a frequency of about 20 kHz (wave rotation frequency - 8 thousand revolutions per second) on the fuel pair "oxygen - kerosene". It was possible to obtain several detonation waves that balanced the vibration and shock loads of each other. Heat-shielding coatings specially developed at the Keldysh Center helped to cope with high temperature loads. The engine withstood several starts under extreme vibration loads and over high temperatures in the absence of wall layer cooling. A special role in this success was played by the creation of mathematical models and fuel injectors, which made it possible to obtain a mixture of the consistency necessary for the occurrence of detonation.

Of course, the significance of the success achieved should not be exaggerated. Only a demonstrator engine was created, which worked for a relatively short time, and about it real characteristics nothing is reported. According to NPO Energomash, a detonation rocket engine will increase thrust by 10% while burning the same amount of fuel as in conventional engine, and the specific thrust impulse should increase by 10–15%.

The creation of the world's first full-size detonation rocket engine secured for Russia an important priority in the world history of science and technology.

But the main result is that the possibility of organizing detonation combustion in a liquid-propellant rocket engine has been practically confirmed. However, the way to use this technology as part of real aircraft there is still a long way to go. Another important aspect is that another global priority for high technology from now on, it is assigned to our country: for the first time in the world, a full-size detonation rocket engine was launched in Russia, and this fact will remain in the history of science and technology.

For the practical implementation of the idea of ​​a detonation rocket engine, it took 70 years of hard work of scientists and designers.

Photo: Foundation for Advanced Study

Overall rating of the material: 5

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Pulsating detonation engine tested in Russia

The Lyulka Experimental Design Bureau developed, manufactured and tested a prototype of a pulsating resonator detonation engine with a two-stage combustion of a kerosene-air mixture. According to ITAR-TASS, the average measured thrust of the engine was about one hundred kilograms, and the duration continuous work─ more than ten minutes. By the end of this year, the Design Bureau intends to manufacture and test a full-size pulsating detonation engine.

According to Alexander Tarasov, chief designer of the Lyulka Design Bureau, during the tests, the operating modes typical of turbojet and ramjet engines were simulated. Measured values ​​of specific thrust and specific consumption fuels turned out to be 30-50 percent better than conventional jet engines. During the experiments, the new engine was switched on and off repeatedly, as well as traction control.

On the basis of the studies carried out, the data obtained during testing, as well as the circuit design analysis, the Lyulka Design Bureau intends to propose the development of a whole family of pulsed detonation aircraft engines. In particular, engines with a short service life for unmanned aerial vehicles and missiles and aircraft engines with a cruising supersonic flight mode can be created.

In the future, on the basis of new technologies, engines for rocket-space systems and combined propulsion systems of aircraft capable of flying in the atmosphere and beyond it can be created.

According to the design bureau, the new engines will increase the aircraft's thrust-to-weight ratio by 1.5-2 times. In addition, when using such power plants, the flight range or the mass of aircraft weapons can increase by 30-50 percent. At the same time, the specific weight of the new engines will be 1.5-2 times less than that of conventional jet power plants.

The fact that in Russia work is underway to create a pulsating detonation engine was reported in March 2011. This was stated then by Ilya Fedorov, managing director of the Saturn research and production association, which includes the Lyulka Design Bureau. What type of detonation engine was in question, Fedorov did not specify.

Currently, three types of pulsating engines are known - valved, valveless and detonation. The principle of operation of these power plants is to periodically supply fuel and oxidizer to the combustion chamber, where the fuel mixture is ignited and the combustion products flow out of the nozzle with the formation jet thrust. The difference from conventional jet engines lies in the detonation combustion of the fuel mixture, in which the combustion front propagates faster speed sound.

The pulsating jet engine was invented at the end of the 19th century by the Swedish engineer Martin Wiberg. A pulsating engine is considered simple and cheap to manufacture, but due to the characteristics of fuel combustion, it is unreliable. For the first time, a new type of engine was used in series during World War II on German V-1 cruise missiles. They were equipped with the Argus As-014 engine from Argus-Werken.

Currently, several major defense firms in the world are engaged in research in the field of high-efficiency pulsating jet engines. In particular, the work is carried out by the French company SNECMA and the American General Electric and Pratt & Whitney. In 2012, the US Naval Research Laboratory announced its intention to develop a spin detonation engine that would replace conventional gas turbine power plants on ships.

Spin detonation engines differ from pulsating ones in that the detonation combustion of the fuel mixture in them occurs continuously ─ the combustion front moves in the annular combustion chamber, in which the fuel mixture is constantly updated.

Detonation engine tests

Foundation for Advanced Study

The Energomash Research and Production Association tested a model chamber of a liquid detonation rocket engine with a thrust of two tons. About this in an interview Russian newspaper”, said the chief designer of Energomash, Petr Levochkin. According to him, this model ran on kerosene and gaseous oxygen.

Detonation is the combustion of a substance in which the combustion front propagates faster than the speed of sound. In this case, a shock wave propagates through the substance, followed by a chemical reaction with the release of a large amount of heat. Modern rocket engines burn fuel at subsonic speeds; this process is called deflagration.

Detonation engines today are divided into two main types: impulse and rotary. The latter are also called spin. In impulse engines, short explosions occur as small portions of the fuel-air mixture are burned. In rotary, the combustion of the mixture occurs constantly without stopping.

In such power plants, an annular combustion chamber is used in which the fuel mixture is supplied sequentially through radially located valves. In such power plants, detonation does not fade - the detonation wave “runs around” the annular combustion chamber, the fuel mixture behind it has time to be updated. Rotary engine first began to be studied in the USSR in the 1950s.

Detonation engines are capable of operating in a wide range of flight speeds - from zero to five Mach numbers (0-6.2 thousand kilometers per hour). It is believed that such power plants may issue more power, consuming less fuel than conventional jet engines. At the same time, the design of detonation engines is relatively simple: they lack a compressor and many moving parts.

The new Russian liquid detonation engine is being developed jointly by several institutes, including the Moscow Aviation Institute, the Lavrentiev Institute of Hydrodynamics, the Keldysh Center, the Baranov Central Institute of Aviation Motors and the Faculty of Mechanics and Mathematics of Moscow State University. The development is overseen by the Foundation for Advanced Study.

According to Levochkin, during the tests, the pressure in the combustion chamber of the detonation engine was 40 atmospheres. At the same time, the installation worked reliably without complicated cooling systems. One of the objectives of the tests was to confirm the possibility of detonation combustion of an oxygen-kerosene fuel mixture. It was previously reported that the frequency of detonation in the new Russian engine is 20 kilohertz.

The first tests of a liquid detonation rocket engine in the summer of 2016. Whether the engine has been tested again since then is unknown.

At the end of December 2016, the American company Aerojet Rocketdyne contracted the US National Energy Technology Laboratory to develop a new gas turbine power plant based on a rotary detonation engine. Work leading to the creation of a prototype new installation scheduled for completion by mid-2019.

According to a preliminary assessment, gas turbine engine new type will have at least five percent best performance than conventional such installations. In this case, the installations themselves can be made more compact.

Vasily Sychev

detonation engine often seen as an alternative to the standard internal combustion or rocket engine. It is overgrown with many myths and legends. These legends are born and live only because the people spreading them either forgot the school physics course, or even skipped it completely!

Increase in specific power or thrust

The first misconception.

From an increase in the rate of fuel combustion up to 100 times, it will be possible to increase the specific (per unit of working volume) power of an internal combustion engine. For rocket engines operating in detonation modes, thrust per unit mass will increase by a factor of 100.

Note: As always, it is not clear what mass we are talking about - the mass of the working fluid or the entire rocket as a whole.

There is no connection at all between the speed at which fuel burns and specific power.

There is a relationship between compression ratio and power density. For gasoline engines internal combustion, the compression ratio is about 10. In engines using the detonation mode, it can be increased by about 2 times, which is just realized in diesel engines, which have a compression ratio of about 20. Actually they work in detonation mode. That is, of course, the compression ratio can be increased, but after detonation has occurred, no one needs it! About what 100 times there can be no question!! Moreover, the working volume of the internal combustion engine is, say, 2 liters, the volume of the entire engine is 100 or 200 liters. The savings in terms of volume will be 1% !!! But the additional “expenditure” (wall thickness, new materials, etc.) will be measured not in percentages, but in times or tens of times !!

For reference. The work done is proportional, roughly speaking, to V * P (the adiabatic process has coefficients, but it does not change the essence now). If the volume is reduced by 100 times, then the initial pressure must increase by the same 100 times! (to do the same job).

Liter power can be increased if compression is abandoned altogether or left at the same level, but hydrocarbons (in larger quantities) and pure oxygen are supplied in a weight ratio of about 1: 2.6-4, depending on the composition of hydrocarbons, or liquid oxygen in general (where it was already :-)). Then it is possible to increase both the liter capacity and the efficiency (due to the growth of the "degree of expansion" which can reach 6000!). But on the way stands both the ability of the combustion chamber to withstand such pressures and temperatures, and the need to "feed" not on atmospheric oxygen, but on stored pure or even liquid oxygen!

Actually, something similar to this is the use of nitrous oxide. Nitrous oxide is just a way to put an increased amount of oxygen into the combustion chamber.

But these methods have nothing to do with detonation !!

It is possible to propose further development of such exotic ways to increase the liter capacity - to use fluorine instead of oxygen. This is a stronger oxidizing agent, i.e. reactions with it go with a large release of energy.

Increasing jet blast velocity

The second lure.
In rocket engines using detonation modes of operation, as a result of the fact that the combustion mode occurs at speeds above the speed of sound in a given medium (which depends on temperature and pressure), the pressure and temperature parameters in the combustion chamber increase several times, the speed of the outgoing jet jets. This proportionally improves all parameters similar engine, including, reduces its mass and consumption, and hence the required fuel supply.

As noted above, it is impossible to increase the compression ratio by more than 2 times. But again, the rate of outflow of gases depends on the energy supplied and their temperature! (Law of energy conservation). With the same amount of energy (the same amount of fuel), you can increase the speed only by lowering their temperature. But this is already prevented by the laws of thermodynamics.

Detonation rocket engines are the future of interplanetary flight

Misunderstanding the third.

Only rocket engines on detonation technologies make it possible to obtain the speed parameters required for interplanetary flights based on a chemical oxidation reaction.

Well, this is at least a logical fallacy. It follows from the first two.

No technology can already squeeze anything out of the oxidation reaction! At least for known substances. The outflow rate is determined by the energy balance of the reaction. Part of this energy, according to the laws of thermodynamics, can be converted into work (kinetic energy). Those. even if all the energy goes into kinetic energy, then this is a limit based on the law of conservation of energy and it cannot be overcome by any detonations, compression ratios, etc.

Except energy balance Very important parameter- "energy per nucleon". If you make small calculations, you can get that the oxidation reaction of a carbon atom (C) gives 1.5 times more energy than the oxidation reaction of a hydrogen molecule (H2). But due to the fact that the carbon oxidation product (CO2) is 2.5 times heavier than the hydrogen oxidation product (H2O), the rate of outflow of gases from hydrogen engines by 13%. True, we must also take into account the heat capacity of the combustion products, but this gives a very small correction.

1

The problem of development of impulse detonation engines is considered. The main research centers conducting research on new generation engines are listed. The main directions and trends in the development of the design of detonation engines are considered. The main types of such engines are presented: impulse, impulse multitube, impulse with a high-frequency resonator. The difference in the method of creating thrust is shown in comparison with a classic jet engine equipped with a Laval nozzle. The concept of a traction wall and a traction module is described. It is shown that pulse detonation engines are being improved in the direction of increasing the pulse repetition rate, and this direction has its right to life in the field of light and cheap unmanned aerial vehicles, as well as in the development of various ejector thrust amplifiers. The main difficulties of a fundamental nature in modeling a detonation turbulent flow using computational packages based on the use of differential turbulence models and time averaging of the Navier–Stokes equations are shown.

detonation engine

impulse detonation engine

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2. Bulat P.V., Zasukhin O.N., Prodan N.V. Bottom pressure fluctuations // Fundamental research. - 2012. - No. 3. - S. 204–207.

3. Bulat P.V., Zasukhin O.N., Prodan N.V. Peculiarities of application of turbulence models in the calculation of flows in supersonic paths of advanced air-jet engines // Engine. - 2012. - No. 1. - P. 20–23.

4. Bulat P.V., Zasukhin O.N., Uskov V.N. On the classification of flow regimes in a channel with sudden expansion // Thermophysics and Aeromechanics. - 2012. - No. 2. - S. 209–222.

5. Bulat P.V., Prodan N.V. On low-frequency flow oscillations of bottom pressure // Fundamental research. - 2013. - No. 4 (3). – S. 545–549.

6. Larionov S.Yu., Nechaev Yu.N., Mokhov A.A. Research and analysis of "cold" purges of the traction module of a high-frequency pulsating detonation engine // Bulletin of the MAI. - T.14. - No. 4 - M .: Publishing house MAI-Print, 2007. - S. 36–42.

7. Tarasov A.I., Shchipakov V.A. Prospects for the use of pulsed detonation technologies in turbojet engines. OAO NPO Saturn NTC im. A. Lyulki, Moscow, Russia. Moscow Aviation Institute (GTU). - Moscow, Russia. ISSN 1727-7337. Aerospace Engineering and Technology, 2011. - No. 9 (86).

US Detonation Projects Included in Development Program promising engines IHPTET. The cooperation includes almost all research centers working in the field of engine building. NASA alone allocates up to $130 million a year for these purposes. This proves the relevance of research in this direction.

Overview of work in the field of detonation engines

The market strategy of the world's leading manufacturers is aimed not only at the development of new jet detonation engines, but also at the modernization of existing ones by replacing the traditional combustion chamber with a detonation one. In addition, detonation engines can become constituent element combined plants various types, for example, be used as an afterburner of a turbofan engine, as lifting ejector engines in VTOL aircraft (an example in Fig. 1 is a Boeing VTOL transport project).

In the USA, many research centers and universities are developing detonation engines: ASI, NPS, NRL, APRI, MURI, Stanford, USAF RL, NASA Glenn, DARPA-GE C&RD, Combustion Dynamics Ltd, Defense Research Establishments, Suffield and Valcartier, Uniyersite de Poitiers , University of Texas at Arlington, Uniyersite de Poitiers, McGill University, Pennsylvania State University, Princeton University.

The leading position in the development of detonation engines is occupied by specialized center Seattle Aerosciences Center (SAC), acquired in 2001 by Pratt and Whitney from Adroit Systems. Most of the work of the center is funded by the Air Force and NASA from the budget of the interagency program Integrated High Payoff Rocket Propulsion Technology Program (IHPRPTP), aimed at creating new technologies for jet engines of various types.

Rice. 1. Patent US 6,793,174 B2 by Boeing, 2004

In total, since 1992, SAC specialists have carried out more than 500 bench tests of experimental samples. Work on pulsed detonation engines (PDE) with the consumption of atmospheric oxygen is carried out by the SAC Center on the order of the US Navy. Given the complexity of the program, the Navy specialists involved almost all organizations involved in detonation engines in its implementation. Except Pratt and Whitney, the United Technologies Research Center (UTRC) and Boeing Phantom Works are involved in the work.

Currently in our country over this topical issue theoretically, the following universities and institutes of the Russian Academy of Sciences (RAS) operate: Institute of Chemical Physics RAS (ICP), Institute of Mechanical Engineering RAS, Institute for High Temperatures RAS (IVTAN), Novosibirsk Institute of Hydrodynamics. Lavrentiev (ISIL), Institute for Theoretical and applied mechanics them. Khristianovich (ITMP), Physico-Technical Institute. Ioffe, Moscow State University (MGU), Moscow State Aviation Institute (MAI), Novosibirsk State University, Cheboksary State University, Saratov State University, etc.

Directions of work on pulse detonation engines

Direction No. 1 - Classic pulse detonation engine (PDE). The combustion chamber of a typical jet engine consists of nozzles for mixing fuel with an oxidizer, a device for igniting the fuel mixture, and the flame tube itself, in which redox reactions (combustion) take place. The flame tube ends with a nozzle. As a rule, this is a Laval nozzle, which has a tapering part, a minimum critical section in which the velocity of the combustion products is equal to the local speed of sound, an expanding part in which the static pressure of the combustion products is reduced to a pressure of environment, as much as possible. It is very rough to estimate the thrust of the engine as the area of ​​the critical section of the nozzle, multiplied by the pressure difference in the combustion chamber and the environment. Therefore, the thrust is higher, the higher the pressure in the combustion chamber.

The thrust of a pulse detonation engine is determined by other factors - the transfer of an impulse by a detonation wave to the thrust wall. Nozzle in this case is not needed at all. Pulse detonation engines have their own niche - cheap and disposable aircraft. In this niche, they are successfully developing in the direction of increasing the pulse repetition rate.

The classic appearance of the IDD is a cylindrical combustion chamber, which has a flat or specially profiled wall, called the “draft wall” (Fig. 2). The simplicity of the IDD device is its undeniable advantage. As the analysis of available publications shows, despite the variety of proposed schemes of PDE, all of them are characterized by the use of detonation tubes of considerable length as resonant devices and the use of valves that provide periodic supply of the working fluid.

It should be noted that the PDE, created on the basis of traditional detonation tubes, despite the high thermodynamic efficiency in a single pulsation, has the disadvantages characteristic of classical pulsating air-jet engines, namely:

Low frequency (up to 10 Hz) of pulsations, which determines the relatively low level of average traction efficiency;

High thermal and vibration loads.

Rice. 2. circuit diagram pulse detonation engine (PDE)

Direction No. 2 - Multipipe IDD. The main trend in the development of IDD is the transition to a multi-pipe scheme (Fig. 3). In such engines, the frequency of operation of a single tube remains low, but due to the alternation of pulses in different tubes, the developers hope to obtain acceptable specific characteristics. Such a scheme seems to be quite workable if the problem of vibrations and asymmetry of thrust is solved, as well as the problem of bottom pressure, in particular, possible low-frequency oscillations in the bottom region between the pipes.

Rice. 3. Pulse detonation engine (PDE) of the traditional scheme with a package of detonation tubes as resonators

Direction No. 3 - IDD with a high-frequency resonator. There is also an alternative direction - a recently widely advertised scheme with traction modules (Fig. 4) having a specially profiled high-frequency resonator. Work in this direction is being carried out at the NTC im. A. Lyulka and in MAI. The scheme is distinguished by the absence of any mechanical valves and intermittent ignition devices.

The traction module of the IDD of the proposed scheme consists of a reactor and a resonator. The reactor serves to prepare fuel-air mixture To detonation combustion, decomposing molecules combustible mixture into reactive constituents. A schematic diagram of one cycle of operation of such an engine is clearly shown in fig. 5.

Interacting with the bottom surface of the resonator as with an obstacle, the detonation wave in the process of collision transfers to it an impulse from the overpressure forces.

IDD with high-frequency resonators have the right to success. In particular, they can claim to modernize afterburners and refine simple turbojet engines, again designed for cheap UAVs. An example is the attempts of the MAI and CIAM to modernize the MD-120 turbojet engine in this way by replacing the combustion chamber with a fuel mixture activation reactor and installing traction modules with high-frequency resonators behind the turbine. So far, it has not been possible to create a workable design, because. when profiling resonators, the authors use the linear theory of compression waves, i.e. calculations are carried out in the acoustic approximation. The dynamics of detonation waves and compression waves is described by a completely different mathematical apparatus. The use of standard numerical packages for the calculation of high-frequency resonators has a fundamental limitation. All modern models turbulences are based on averaging the Navier-Stokes equations (the basic equations of gas dynamics) over time. In addition, Boussinesq's assumption is introduced that the turbulent friction stress tensor is proportional to the velocity gradient. Both assumptions are not satisfied in turbulent flows with shock waves if the characteristic frequencies are comparable with the frequency of turbulent pulsation. Unfortunately, we are dealing with just such a case, so here it is necessary either to build a model more high level, or direct numerical simulation based on the full Navier-Stokes equations without the use of turbulence models (a task that is unbearable at the present stage).

Rice. 4. Scheme of PDD with a high-frequency resonator

Rice. Fig. 5. Scheme of PDE with a high-frequency resonator: SZS - supersonic jet; SW - shock wave; Ф - resonator focus; DW - detonation wave; VR - rarefaction wave; SHW - reflected shock wave

IDD are being improved in the direction of increasing the pulse repetition rate. This direction has its right to life in the field of light and cheap unmanned aerial vehicles, as well as in the development of various ejector thrust boosters.

Reviewers:

Uskov V.N., Doctor of Technical Sciences, Professor of the Department of Hydroaeromechanics of St. Petersburg State University, Faculty of Mathematics and Mechanics, St. Petersburg;

Emelyanov V.N., Doctor of Technical Sciences, Professor, Head of the Department of Plasma Gas Dynamics and Heat Engineering, BSTU "VOENMEH" named after A.I. D.F. Ustinov, St. Petersburg.

The work was received by the editors on October 14, 2013.

Bibliographic link

Bulat P.V., Prodan N.V. REVIEW OF PROJECTS OF DETONATING ENGINES. PULSE ENGINES // Fundamental research. - 2013. - No. 10-8. - S. 1667-1671;
URL: http://fundamental-research.ru/ru/article/view?id=32641 (date of access: 07/29/2019). We bring to your attention the journals published by the publishing house "Academy of Natural History"

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