At the end of January, there were reports of new successes in Russian science and technology. It became known from official sources that one of the domestic projects of a promising detonation-type jet engine has already passed the testing stage. This brings the moment of complete completion of all the required work, as a result of which space or military rockets Russian development will be able to get new power plants with improved performance. Moreover, the new principles of engine operation can be applied not only in the field of rockets, but also in other areas.
In the last days of January, Deputy Prime Minister Dmitry Rogozin told the domestic press about the latest successes of research organizations. Among other topics, he touched on the process of creating jet engines using new operating principles. A promising engine with detonation combustion has already been brought to the test. According to the Deputy Prime Minister, the application of new principles of work power plant allows you to get a significant increase in performance. In comparison with the designs of traditional architecture, there is an increase in thrust of about 30%.
Diagram of a detonation rocket engine
Modern rocket engines different classes and types operated in various areas use the so-called. isobaric cycle or deflagration combustion. In their combustion chambers, a constant pressure is maintained, at which the fuel burns slowly. An engine based on deflagration principles does not need particularly strong units, but is limited in maximum performance. Increasing the main characteristics, starting from a certain level, turns out to be unreasonably difficult.
An alternative to an isobaric cycle engine in the context of performance enhancement is a system with a so-called. detonation combustion. In this case, the fuel oxidation reaction occurs behind the shock wave, with high speed moving through the combustion chamber. This places special demands on the design of the engine, but at the same time offers obvious advantages. In terms of fuel combustion efficiency, detonation combustion is 25% better than deflagration combustion. It also differs from combustion with constant pressure by an increased heat release rate per unit surface area of the reaction front. In theory, it is possible to increase this parameter by three to four orders of magnitude. Consequently, the speed of reactive gases can be increased by 20-25 times.
Thus, the detonation engine, characterized by an increased coefficient useful action, capable of developing more thrust with less fuel consumption. Its advantages over traditional designs are obvious, but until recently, progress in this area left much to be desired. The principles of a detonation jet engine were formulated as early as 1940 by the Soviet physicist Ya.B. Zeldovich, but finished products of this kind have not yet reached operation. The main reasons for the lack of real success are problems with creating a sufficiently strong structure, as well as the difficulty of launching and subsequently maintaining a shock wave using existing fuels.
One of the latest domestic projects in the field of detonation rocket engines started in 2014 and is being developed at NPO Energomash im. Academician V.P. Glushko. According to the available data, the purpose of the project with the Ifrit cipher was to study the basic principles new technology with the subsequent creation of a liquid rocket engine using kerosene and gaseous oxygen. The new engine, named after the fire demons from Arab folklore, was based on the principle of spin detonation combustion. Thus, in accordance with the main idea of the project, the shock wave must continuously move in a circle inside the combustion chamber.
The lead developer of the new project was NPO Energomash, or rather, a special laboratory created on its basis. In addition, several other research and design organizations were involved in the work. The program received support from the Advanced Research Foundation. By joint efforts, all participants of the Ifrit project were able to form an optimal image promising engine, as well as to create a model combustion chamber with new principles of operation.
To study the prospects of the whole direction and new ideas, a so-called. a model detonation combustion chamber that meets the requirements of the project. Such an experimental engine with a reduced configuration was supposed to use liquid kerosene as a fuel. Gaseous hydrogen was proposed as the oxidizing agent. In August 2016, testing of the experimental chamber began. Important, that for the first time in history, a project of this kind was brought to the stage of bench tests. Previously, domestic and foreign detonation rocket engines were developed, but not tested.
In the course of testing a model sample, it was possible to obtain very interesting results showing the correctness of the approaches used. So, by using the right materials and technologies turned out to bring the pressure inside the combustion chamber to 40 atmospheres. The thrust of the experimental product reached 2 tons.
Model camera on the test bench
Within the framework of the Ifrit project, certain results were obtained, but the domestic liquid-fuel detonation engine is still far from full-fledged practical application. Before introducing such equipment into new technology projects, designers and scientists will have to decide whole line the most serious tasks. Only after that, the rocket and space industry or the defense industry will be able to start realizing the potential of new technology in practice.
In the middle of January Russian newspaper”published an interview with the chief designer of NPO Energomash, Petr Levochkin, the topic of which was the current state of affairs and the prospects for detonation engines. The representative of the enterprise-developer recalled the main provisions of the project, and also touched upon the topic of the successes achieved. In addition, he spoke about the possible areas of application of Ifrit and similar structures.
Eg, detonation engines can be used in hypersonic aircraft. P. Levochkin recalled that the engines now proposed for use in such equipment use subsonic combustion. At the hypersonic speed of the flight apparatus, the air entering the engine must be slowed down to sound mode. However, the braking energy must lead to additional thermal loads on the airframe. In detonation engines, the fuel burning rate reaches at least M=2.5. This makes it possible to increase the flight speed of the aircraft. Such a machine with a knock-type engine would be able to accelerate to speeds eight times the speed of sound.
However, the real prospects for detonation-type rocket engines are not too great yet. According to P. Levochkin, we "have just opened the door to the area of detonation combustion." Scientists and designers will have to study many issues, and only after that it will be possible to create structures with practical potential. Because of this, the space industry will have to use traditional liquid-propellant engines for a long time, which, however, does not negate the possibility of their further improvement.
An interesting fact is that detonation principle combustion finds application not only in the field of rocket engines. Already exists domestic project aviation system with a detonation-type combustion chamber operating on the impulse principle. A prototype of this kind was brought to the test, and in the future it may give rise to a new direction. New engines with detonation combustion can find application in a variety of fields and partially replace gas turbine or turbojet engines traditional designs.
The domestic project of a detonation aircraft engine is being developed at the OKB. A.M. Cradles. Information about this project was first presented at last year's international military-technical forum "Army-2017". At the stand of the enterprise-developer there were materials on various engines, both serial and under development. Among the latter was a promising detonation sample.
The essence of the new proposal is the use of a non-standard combustion chamber capable of carrying out pulsed detonation combustion of fuel in an air atmosphere. In this case, the frequency of "explosions" inside the engine should reach 15-20 kHz. In the future, an additional increase in this parameter is possible, as a result of which the engine noise will go beyond the range perceived by the human ear. Such features of the engine may be of particular interest.
The first launch of the Ifrit prototype
However, the main advantages of the new power plant are associated with improved performance. Bench tests of experimental products showed that they are about 30% superior to traditional gas turbine engines in terms of specific performance. By the time of the first public demonstration of materials on the OKB engine. A.M. Cradles could get and quite high performance characteristics. An experimental engine of a new type was able to work for 10 minutes without interruption. The total operating time of this product at the stand at that time exceeded 100 hours.
Representatives of the developer indicated that it is already possible to create a new detonation engine with a thrust of 2-2.5 tons, suitable for installation on light aircraft or unmanned aerial vehicles. aircrafts. In the design of such an engine, it is proposed to use the so-called. resonators responsible for right move fuel combustion. An important advantage new project is the fundamental possibility of installing such devices anywhere in the airframe.
Specialists of OKB im. A.M. The cradles are working on aircraft engines with pulsed detonation combustion for more than three decades, but so far the project has not left the research stage and has no real prospects. main reason– lack of order and necessary financing. If the project receives the necessary support, then in the foreseeable future a sample engine suitable for use on various vehicles can be created.
To date, Russian scientists and designers have managed to show very remarkable results in the field of jet engines using new operating principles. There are several projects at once suitable for use in the rocket-space and hypersonic fields. In addition, new engines can be used in "traditional" aviation. Some projects are still in their early stages and not yet ready for inspections and other work, while in other areas the most remarkable results have already been obtained.
Exploring the subject of jet engines with detonation combustion, Russian specialists were able to create a bench model of a combustion chamber with the desired characteristics. The experimental product "Ifrit" has already passed the tests, during which it was assembled a large number of varied information. With the help of the received data, the development of the direction will continue.
Mastering a new direction and translating ideas into a practically applicable form will take a lot of time, and for this reason, in the foreseeable future, space and army rockets in the foreseeable future will be equipped only with traditional liquid engines. Nevertheless, the work has already left the purely theoretical stage, and now each test run of an experimental engine brings closer the moment of building full-fledged missiles with new power plants.
According to the websites:
http://engine.space/
http://fpi.gov.ru/
https://rg.ru/
https://utro.ru/
http://tass.ru/
http://svpressa.ru/
Detonation engines will replace the core of gas turbines / Photo: finobzor.ru
In reality, instead of a constant frontal flame in the combustion zone, a detonation wave is formed, rushing at supersonic speed. In such a compression wave, fuel and oxidizer are detonated, this process, from the point of view of thermodynamics, increases Engine efficiency by an order of magnitude, due to the compactness of the combustion zone.
Interestingly, back in 1940, the Soviet physicist Ya.B. Zel'dovich proposed the idea of a detonation engine in the article "On the energy use detonation combustion". Since then, many scientists from different countries, then the United States, then Germany, then our compatriots came forward.
In the summer, in August 2016, Russian scientists managed to create the world's first full-size liquid-propellant jet engine operating on the principle of detonation combustion of fuel. Our country has finally established a world priority in the development of the latest technology for many post-perestroika years.
Why is it so good new engine? A jet engine uses the energy released by burning a mixture at constant pressure and a constant flame front. During combustion, the gas mixture of fuel and oxidizer sharply increases the temperature and the flame column escaping from the nozzle creates jet thrust.
Detonation engine / Photo: sdelanounas.ru
During detonation combustion, the reaction products do not have time to collapse, because this process is 100 times faster than deflagration and the pressure increases rapidly, while the volume remains unchanged. The release of such a large amount of energy can actually destroy a car engine, which is why such a process is often associated with an explosion.
In reality, instead of a constant frontal flame in the combustion zone, a detonation wave is formed, rushing at supersonic speed. In such a compression wave, fuel and oxidizer are detonated, this process, from the point of view of thermodynamics, increases the efficiency of the engine by an order of magnitude, due to the compactness of the combustion zone. Therefore, experts so zealously set about developing this idea. In a conventional rocket engine, which is essentially a large burner, the main thing is not the combustion chamber and nozzle, but the fuel turbopump unit (TNA), which creates such pressure that fuel penetrates into the chamber. For example, in the Russian RD-170 rocket engine for Energia launch vehicles, the pressure in the combustion chamber is 250 atm and the pump that supplies the oxidizer to the combustion zone has to create a pressure of 600 atm.
In a detonation engine, pressure is created by detonation itself, which represents a traveling compression wave in the fuel mixture, in which the pressure without any TNA is already 20 times greater and turbopump units are superfluous. To make it clear, the American Shuttle has a pressure in the combustion chamber of 200 atm, and the detonation engine in such conditions needs only 10 atm to supply the mixture - this is like a bicycle pump and the Sayano-Shushenskaya hydroelectric power station.
In this case, a detonation-based engine is not only simpler and cheaper by an order of magnitude, but much more powerful and economical than a conventional rocket engine. The problem of co-control with a detonation wave arose on the way to implementing the detonation engine project. This phenomenon is not just a blast wave, which has the speed of sound, but a detonation wave propagating at a speed of 2500 m / s, there is no stabilization of the flame front in it, for each pulsation the mixture is updated and the wave starts again.
Previously, Russian and French engineers developed and built pulsating jet engines, but not on the principle of detonation, but on the basis of ordinary combustion pulsation. The characteristics of such PUVRDs were low, and when engine builders developed pumps, turbines and compressors, the age of jet engines and LREs came, and pulsating ones remained on the sidelines of progress. The bright heads of science tried to combine detonation combustion with a PUVRD, but the frequency of pulsations of a conventional combustion front is no more than 250 per second, and the detonation front has a speed of up to 2500 m/s and its pulsation frequency reaches several thousand per second. It seemed impossible to put into practice such a rate of mixture renewal and at the same time initiate detonation.
In the USA, it was possible to build such a detonation pulsating engine and test it in the air, however, it worked for only 10 seconds, but the priority remained with the American designers. But already in the 60s of the last century, the Soviet scientist B.V. Voitsekhovsky and, almost at the same time, an American from the University of Michigan, J. Nichols, came up with the idea to loop a detonation wave in the combustion chamber.
Image: sdelanounas.ru
How a detonation rocket engine works
Such a rotary engine consisted of an annular combustion chamber with nozzles placed along its radius to supply fuel. The detonation wave runs like a squirrel in a wheel around the circumference, the fuel mixture is compressed and burned out, pushing the combustion products through the nozzle. In a spin engine, we obtain a wave rotation frequency of several thousand per second, its operation is similar to the working process in a rocket engine, only more efficiently, due to the detonation of the fuel mixture.
In the USSR and the USA, and later in Russia, work is underway to create a rotary detonation engine with a continuous wave, to understand the processes occurring inside, for which a whole science of physical and chemical kinetics was created. To calculate the conditions of an undamped wave, powerful computers were needed, which were created only recently.
In Russia, many research institutes and design bureaus are working on the project of such a spin engine, including the engine building company of the space industry. The Advanced Research Foundation came to help in the development of such an engine, because it is impossible to obtain funding from the Ministry of Defense - they only need a guaranteed result.
Nevertheless, during tests in Khimki at Energomash, a steady state of continuous spin detonation was recorded - 8 thousand revolutions per second on an oxygen-kerosene mixture. At the same time, detonation waves balanced vibration waves, and heat-shielding coatings withstood high temperatures.
But do not flatter yourself, because this is only a demonstrator engine that has worked for a very short time and nothing has yet been said about its characteristics. But the main thing is that the possibility of creating detonation combustion has been proven and a full-size spin engine it is in Russia that will remain in the history of science forever.
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12
In reality, instead of a constant frontal flame in the combustion zone, a detonation wave is formed, rushing at supersonic speed. In such a compression wave, fuel and oxidizer are detonated, this process, from the point of view of thermodynamics, increases the efficiency of the engine by an order of magnitude, due to the compactness of the combustion zone.
Interestingly, back in 1940, the Soviet physicist Ya.B. Zel'dovich proposed the idea of a detonation engine in the article "On the Energy Use of Detonation Combustion". Since then, many scientists from different countries have been working on a promising idea, either the United States, then Germany, or our compatriots came forward.
In the summer, in August 2016, Russian scientists managed to create the world's first full-size liquid-propellant jet engine operating on the principle of detonation combustion of fuel. Our country has finally established a world priority in the development of the latest technology for many post-perestroika years.
Why is the new engine so good? A jet engine uses the energy released by burning a mixture at constant pressure and a constant flame front. During combustion, the gas mixture of fuel and oxidizer sharply increases the temperature and the flame column escaping from the nozzle creates jet thrust.
During detonation combustion, the reaction products do not have time to collapse, because this process is 100 times faster than deflagration and the pressure increases rapidly, while the volume remains unchanged. The release of such a large amount of energy can actually destroy a car engine, which is why such a process is often associated with an explosion.
In reality, instead of a constant frontal flame in the combustion zone, a detonation wave is formed, rushing at supersonic speed. In such a compression wave, fuel and oxidizer are detonated, this process, from the point of view of thermodynamics increases engine efficiency by an order of magnitude, due to the compactness of the combustion zone. Therefore, experts so zealously set about developing this idea. In a conventional rocket engine, which is essentially a large burner, the main thing is not the combustion chamber and nozzle, but the fuel turbopump unit (TNA), which creates such pressure that fuel penetrates into the chamber. For example, in the Russian RD-170 rocket engine for Energia launch vehicles, the pressure in the combustion chamber is 250 atm and the pump that supplies the oxidizer to the combustion zone has to create a pressure of 600 atm.
In a detonation engine, pressure is created by detonation itself, which represents a traveling compression wave in the fuel mixture, in which the pressure without any TNA is already 20 times greater and turbopump units are superfluous. To make it clear, the American Shuttle has a pressure in the combustion chamber of 200 atm, and the detonation engine in such conditions needs only 10 atm to supply the mixture - this is like a bicycle pump and the Sayano-Shushenskaya hydroelectric power station.
In this case, a detonation-based engine is not only simpler and cheaper by an order of magnitude, but much more powerful and economical than a conventional rocket engine. The problem of co-control with a detonation wave arose on the way to implementing the detonation engine project. This phenomenon is not just a blast wave, which has the speed of sound, but a detonation wave propagating at a speed of 2500 m / s, there is no stabilization of the flame front in it, for each pulsation the mixture is updated and the wave starts again.
Previously, Russian and French engineers developed and built pulsating jet engines, but not on the principle of detonation, but on the basis of ordinary combustion pulsation. The characteristics of such PUVRDs were low, and when engine builders developed pumps, turbines and compressors, the age of jet engines and LREs came, and pulsating ones remained on the sidelines of progress. The bright heads of science tried to combine detonation combustion with a PUVRD, but the frequency of pulsations of a conventional combustion front is no more than 250 per second, and the detonation front has a speed of up to 2500 m/s and its pulsation frequency reaches several thousand per second. It seemed impossible to put into practice such a rate of mixture renewal and at the same time initiate detonation.
In the USA, it was possible to build such a detonation pulsating engine and test it in the air, however, it worked for only 10 seconds, but the priority remained with the American designers. But already in the 60s of the last century, the Soviet scientist B.V. Voitsekhovsky and, almost at the same time, an American from the University of Michigan, J. Nichols, came up with the idea to loop a detonation wave in the combustion chamber.
How a detonation rocket engine works
Such a rotary engine consisted of an annular combustion chamber with nozzles placed along its radius to supply fuel. The detonation wave runs like a squirrel in a wheel around the circumference, the fuel mixture is compressed and burned out, pushing the combustion products through the nozzle. In a spin engine, we obtain a wave rotation frequency of several thousand per second, its operation is similar to the working process in a rocket engine, only more efficiently, due to the detonation of the fuel mixture.
In the USSR and the USA, and later in Russia, work is underway to create a rotary detonation engine with a continuous wave, to understand the processes occurring inside, for which a whole science of physical and chemical kinetics was created. To calculate the conditions of an undamped wave, powerful computers were needed, which were created only recently.
In Russia, many research institutes and design bureaus are working on the project of such a spin engine, including the engine-building company of the space industry NPO Energomash. The Advanced Research Foundation came to help in the development of such an engine, because it is impossible to obtain funding from the Ministry of Defense - they only need a guaranteed result.
Nevertheless, during tests in Khimki at Energomash, a steady state of continuous spin detonation was recorded - 8 thousand revolutions per second on an oxygen-kerosene mixture. At the same time, detonation waves balanced vibration waves, and heat-shielding coatings withstood high temperatures.
But do not flatter yourself, because this is only a demonstrator engine that has worked for a very short time and nothing has yet been said about its characteristics. But the main thing is that the possibility of creating detonation combustion has been proven and a full-sized spin engine has been created in Russia, which will remain in the history of science forever.
1The problem of development of rotary detonation engines is considered. The main types of such engines are presented: the Nichols rotary detonation engine, the Wojciechowski engine. The main directions and trends in the development of the design of detonation engines are considered. It is shown that modern concepts of a rotary detonation engine cannot, in principle, lead to the creation of a workable design that surpasses the existing ones in terms of its characteristics. jet engines. The reason is the desire of designers to combine wave generation, fuel combustion, and fuel and oxidizer ejection into one mechanism. As a result of self-organization of shock-wave structures, detonation combustion is carried out in a minimum rather than maximum volume. The result actually achieved today is detonation combustion in a volume not exceeding 15% of the volume of the combustion chamber. The way out is seen in a different approach - first, an optimal configuration of shock waves is created, and only then fuel components are fed into this system and optimal detonation combustion is organized in a large volume.
detonation engine
rotary detonation engine
Wojciechowski engine
circular detonation
spin detonation
impulse detonation engine
1. B. V. Voitsekhovsky, V. V. Mitrofanov, and M. E. Topchiyan, Structure of the detonation front in gases. - Novosibirsk: Publishing House of the USSR Academy of Sciences, 1963.
2. Uskov V.N., Bulat P.V. On the problem of designing an ideal diffuser for compressing a supersonic flow // Basic Research. - 2012. - No. 6 (part 1). - S. 178-184.
3. Uskov V.N., Bulat P.V., Prodan N.V. The history of the study of irregular reflection of the shock wave from the symmetry axis of a supersonic jet with the formation of a Mach disk // Fundamental research. - 2012. - No. 9 (part 2). - S. 414-420.
4. Uskov V.N., Bulat P.V., Prodan N.V. Justification of the application of the stationary Mach configuration model to the calculation of the Mach disk in a supersonic jet // Fundamental research. - 2012. - No. 11 (part 1). – S. 168–175.
5. Shchelkin K.I. Instability of combustion and detonation of gases // Uspekhi fizicheskikh nauk. - 1965. - T. 87, no. 2.– S. 273–302.
6. Nichols J.A., Wilkmson H.R., Morrison R.B. Intermittent Detonation as a Trust-Producing Mechanism // Jet Propulsion. - 1957. - No. 21. - P. 534–541.
Rotary detonation engines
All types of rotary detonation engines (RDE) have in common that the fuel supply system is combined with the fuel combustion system in the detonation wave, but then everything works like in a conventional jet engine - a flame tube and a nozzle. It was this fact that initiated such activity in the field of modernization of gas turbine engines (GTE). It seems attractive to replace only the mixing head and the mixture ignition system in the gas turbine engine. To do this, it is necessary to ensure the continuity of detonation combustion, for example, by launching a detonation wave in a circle. Nichols was one of the first to propose such a scheme in 1957, and then developed it and conducted a series of experiments with a rotating detonation wave in the mid-1960s (Fig. 1).
By adjusting the chamber diameter and the thickness of the annular gap, for each type fuel mixture you can choose such a geometry that the detonation will be stable. In practice, the relationship between the gap and the diameter of the engine turns out to be unacceptable, and it is necessary to control the speed of wave propagation by controlling the fuel supply, as discussed below.
As with pulse detonation engines, the circular detonation wave is capable of ejecting oxidizer, allowing RDE to be used at zero speeds. This fact led to a flurry of experimental and computational studies of RDE with an annular combustion chamber and spontaneous ejection. fuel-air mixture, to list here which does not make any sense. All of them are built approximately according to the same scheme (Fig. 2), reminiscent of the Nichols engine scheme (Fig. 1).
Rice. 1. Scheme of organization of continuous circular detonation in the annular gap: 1 - detonation wave; 2 - a layer of "fresh" fuel mixture; 3 - contact gap; 4 - an oblique shock wave propagating downstream; D is the direction of the detonation wave
Rice. 2. Typical Circuit RDE: V - free flow velocity; V4 - flow rate at the outlet of the nozzle; a - fresh fuel assemblies, b - detonation wave front; c - attached oblique shock wave; d - combustion products; p(r) - pressure distribution on the channel wall
A reasonable alternative to the Nichols scheme could be the installation of a plurality of fuel-oxidation injectors that would inject a fuel-air mixture into the region immediately before the detonation wave according to a certain law with a given pressure (Fig. 3). By adjusting the pressure and the rate of fuel supply to the combustion region behind the detonation wave, it is possible to influence the rate of its propagation upstream. This direction is promising, but the main problem in the design of such RDEs is that the widely used simplified model of the flow in the detonation combustion front does not correspond to reality at all.
Rice. 3. RDE with controlled fuel supply to the combustion area. Wojciechowski rotary engine
The main hopes in the world are associated with detonation engines operating according to the scheme rotary engine Voitsekhovsky. In 1963 B.V. Voitsekhovsky, by analogy with spin detonation, developed a scheme for continuous combustion of gas behind a triple configuration of shock waves circulating in an annular channel (Fig. 4).
Rice. Fig. 4. Scheme of the Wojciechowski continuous combustion of gas behind a triple configuration of shock waves circulating in the annular channel: 1 - fresh mixture; 2 - doubly compressed mixture behind a triple configuration of shock waves, detonation area
IN this case the stationary hydrodynamic process with gas combustion behind the shock wave differs from the detonation scheme of Chapman-Jouguet and Zel'dovich-Neumann. Such a process is quite stable, its duration is determined by the reserve of the fuel mixture and, in well-known experiments, is several tens of seconds.
The scheme of Wojciechowski's detonation engine served as a prototype for numerous studies of rotational and spin detonation engines̆ initiated in the last 5 years. This scheme accounts for more than 85% of all studies. All of them have one organic drawback - the detonation zone occupies too little of the total combustion zone, usually no more than 15%. As a result, the specific performance of engines is worse than that of engines of traditional design.
On the causes of failures with the implementation of the Wojciechowski scheme
Most work on engines with continuous detonation associated with the development of Wojciechowski's concept. Despite the more than 40-year history of research, the results actually remained at the level of 1964. The share of detonation combustion does not exceed 15% of the volume of the combustion chamber. The rest is slow combustion under conditions that are far from optimal.
One of the reasons for this state of affairs is the lack of a workable calculation methodology. Since the flow is three-dimensional, and the calculation takes into account only the laws of conservation of momentum on the shock wave in the direction perpendicular to the model detonation front, the results of calculating the inclination of shock waves to the flow of combustion products differ from those observed experimentally by more than 30%. The result is that, despite many years of research various systems fuel supply and experiments on changing the ratio of fuel components, all that has been done is to create models in which detonation combustion occurs and is maintained for 10-15 s. There is no talk of increasing efficiency, or of advantages over existing liquid-propellant and gas-turbine engines.
The analysis of the available RDE schemes carried out by the authors of the project showed that all the RDE schemes offered today are inoperative in principle. Detonation combustion occurs and is successfully maintained, but only to a limited extent. In the rest of the volume, we are dealing with the usual slow combustion, moreover, behind a non-optimal system of shock waves, which leads to significant losses full pressure. In addition, the pressure is also several times lower than necessary for ideal combustion conditions with a stoichiometric ratio of the fuel mixture components. As a result specific consumption fuel per unit of thrust is 30-40% higher than that of conventional engines.
But most main problem is the very principle of organizing continuous detonation. As shown by studies of continuous circular detonation, carried out back in the 60s, the detonation combustion front is a complex shock wave structure consisting of at least two triple configurations (about triple configurations of shock waves. Such a structure with an attached detonation zone, like any thermodynamic system with feedback, left alone, tends to take a position corresponding to the minimum level of energy. As a result, the triple configurations and the area of detonation combustion are adjusted to each other so that the detonation front moves along the annular gap with the minimum possible volume of detonation combustion for this. This is directly opposite to the goal that engine designers set for detonation combustion.
For creating efficient engine RDE needs to solve the problem of creating an optimal triple configuration of shock waves and organizing a detonation combustion zone in it. Optimal shock-wave structures must be able to create in a variety of technical devices, for example, in optimal diffusers of supersonic air intakes. The main task is the maximum possible increase in the share of detonation combustion in the volume of the combustion chamber from today's unacceptable 15% to at least 85%. Existing engine designs based on the schemes of Nichols and Wojciechowski cannot provide this task.
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. ROTARY DETONATING ENGINES // Fundamental Research. - 2013. - No. 10-8. - S. 1672-1675;URL: http://fundamental-research.ru/ru/article/view?id=32642 (date of access: 20.02.2019). We bring to your attention the journals published by the publishing house "Academy of Natural History"
At the end of January, there were reports of new successes in Russian science and technology. From official sources it became known that one of the domestic projects of a promising detonation-type jet engine has already passed the testing stage. This brings the moment of complete completion of all the required work, as a result of which Russian-made space or military rockets will be able to receive new power plants with improved performance. Moreover, the new principles of engine operation can be applied not only in the field of rockets, but also in other areas.
In the last days of January, Deputy Prime Minister Dmitry Rogozin told the domestic press about the latest successes of research organizations. Among other topics, he touched upon the process of creating jet engines using new operating principles. A promising engine with detonation combustion has already been brought to the test. According to the Deputy Prime Minister, the use of new principles of operation of the power plant makes it possible to obtain a significant increase in performance. In comparison with the designs of traditional architecture, there is an increase in thrust of about 30%.
Diagram of a detonation rocket engine
Modern rocket engines of different classes and types, operated in various fields, use the so-called. isobaric cycle or deflagration combustion. In their combustion chambers, a constant pressure is maintained, at which the fuel burns slowly. An engine based on deflagration principles does not need particularly strong units, but is limited in maximum performance. Increasing the main characteristics, starting from a certain level, turns out to be unreasonably difficult.
An alternative to an isobaric cycle engine in the context of performance enhancement is a system with a so-called. detonation combustion. In this case, the fuel oxidation reaction occurs behind the shock wave moving at high speed through the combustion chamber. This places special demands on the design of the engine, but at the same time offers obvious advantages. In terms of fuel combustion efficiency, detonation combustion is 25% better than deflagration combustion. It also differs from combustion with constant pressure by an increased heat release rate per unit surface area of the reaction front. In theory, it is possible to increase this parameter by three to four orders of magnitude. As a result, the speed of reactive gases can be increased by 20-25 times.
Thus, a detonation engine, characterized by an increased efficiency, is able to develop more thrust with less fuel consumption. Its advantages over traditional designs are obvious, but until recently, progress in this area left much to be desired. The principles of a detonation jet engine were formulated as early as 1940 by the Soviet physicist Ya.B. Zeldovich, but finished products of this kind have not yet reached operation. The main reasons for the lack of real success are problems with creating a sufficiently strong structure, as well as the difficulty of launching and subsequently maintaining a shock wave using existing fuels.
One of the latest domestic projects in the field of detonation rocket engines was launched in 2014 and is being developed at NPO Energomash named after V.I. Academician V.P. Glushko. According to the available data, the goal of the Ifrit project was to study the basic principles of new technology with the subsequent creation of a liquid rocket engine using kerosene and gaseous oxygen. The new engine, named after the fire demons from Arab folklore, was based on the principle of spin detonation combustion. Thus, in accordance with the main idea of the project, the shock wave must continuously move in a circle inside the combustion chamber.
The lead developer of the new project was NPO Energomash, or rather, a special laboratory created on its basis. In addition, several other research and design organizations were involved in the work. The program received support from the Advanced Research Foundation. By joint efforts, all participants in the Ifrit project were able to form the optimal look of a promising engine, as well as create a model combustion chamber with new operating principles.
To study the prospects of the whole direction and new ideas, a so-called. a model detonation combustion chamber that meets the requirements of the project. Such an experimental engine with a reduced configuration was supposed to use liquid kerosene as a fuel. Gaseous oxygen was proposed as the oxidizing agent. In August 2016, testing of the experimental chamber began. It is important that for the first time in history a project of this kind was brought to the stage of bench tests. Previously, domestic and foreign detonation rocket engines were developed, but not tested.
In the course of testing a model sample, it was possible to obtain very interesting results showing the correctness of the approaches used. So, through the use of the right materials and technologies, it was possible to bring the pressure inside the combustion chamber to 40 atmospheres. The thrust of the experimental product reached 2 tons.
Model camera on the test bench
Within the framework of the Ifrit project, certain results were obtained, but the domestic liquid-fuel detonation engine is still far from full-fledged practical application. Before the introduction of such equipment into new technology projects, designers and scientists have to solve a number of the most serious tasks. Only after that, the rocket and space industry or the defense industry will be able to start realizing the potential of new technology in practice.
In mid-January, Rossiyskaya Gazeta published an interview with the chief designer of NPO Energomash, Petr Levochkin, whose topic was the current state of affairs and the prospects for detonation engines. The representative of the enterprise-developer recalled the main provisions of the project, and also touched upon the topic of the successes achieved. In addition, he spoke about the possible areas of application of Ifrit and similar structures.
For example, detonation engines can be used in hypersonic aircraft. P. Levochkin recalled that the engines now proposed for use in such equipment use subsonic combustion. At hypersonic speed of the flight apparatus, the air entering the engine must be slowed down to the sound mode. However, the braking energy must lead to additional thermal loads on the airframe. In detonation engines, the fuel burning rate reaches at least M=2.5. This makes it possible to increase the flight speed of the aircraft. Such a machine with a detonation-type engine would be able to accelerate to speeds eight times the speed of sound.
However, the real prospects for detonation-type rocket engines are not too great yet. According to P. Levochkin, we "have just opened the door to the area of detonation combustion." Scientists and designers will have to study many issues, and only after that it will be possible to create structures with practical potential. Because of this, the space industry will have to use traditional liquid-propellant engines for a long time, which, however, does not negate the possibility of their further improvement.
An interesting fact is that the detonation principle of combustion is used not only in the field of rocket engines. There is already a domestic project for an aviation system with a detonation-type combustion chamber operating on the impulse principle. A prototype of this kind was brought to the test, and in the future it may give rise to a new direction. New engines with detonation combustion can find application in a variety of areas and partially replace gas turbine or turbojet engines of traditional designs.
The domestic project of a detonation aircraft engine is being developed at the OKB. A.M. Cradles. Information about this project was first presented at last year's international military-technical forum "Army-2017". At the stand of the enterprise-developer, there were materials on various engines, both serial and those under development. Among the latter was a promising detonation sample.
The essence of the new proposal is the use of a non-standard combustion chamber capable of carrying out pulsed detonation combustion of fuel in an air atmosphere. In this case, the frequency of "explosions" inside the engine should reach 15-20 kHz. In the future, an additional increase in this parameter is possible, as a result of which the engine noise will go beyond the range perceived by the human ear. Such features of the engine may be of particular interest.
The first launch of an experimental product "Ifrit"
However, the main advantages of the new power plant are associated with improved performance. Bench tests of experimental products showed that they are about 30% superior to traditional gas turbine engines in terms of specific performance. By the time of the first public demonstration of materials on the OKB engine. A.M. The cradles could also obtain sufficiently high performance characteristics. An experimental engine of a new type was able to work for 10 minutes without interruption. The total operating time of this product at the stand at that time exceeded 100 hours.
Representatives of the developer indicated that it is already possible to create a new detonation engine with a thrust of 2-2.5 tons, suitable for installation on light aircraft or unmanned aerial vehicles. In the design of such an engine, it is proposed to use the so-called. resonator devices responsible for the correct course of fuel combustion. An important advantage of the new project is the fundamental possibility of installing such devices anywhere in the airframe.
Specialists of OKB im. A.M. Lyulki have been working on aircraft engines with pulsed detonation combustion for more than three decades, but so far the project has not left the research stage and has no real prospects. The main reason is the lack of an order and the necessary funding. If the project receives the necessary support, then in the foreseeable future a sample engine suitable for use on various vehicles can be created.
To date, Russian scientists and designers have managed to show very remarkable results in the field of jet engines using new operating principles. There are several projects at once suitable for use in the rocket-space and hypersonic fields. In addition, new engines can be used in "traditional" aviation. Some projects are still in their early stages and not yet ready for inspections and other work, while in other areas the most remarkable results have already been obtained.
Exploring the subject of jet engines with detonation combustion, Russian specialists were able to create a bench model of a combustion chamber with the desired characteristics. The Ifrit prototype has already been tested, during which a large amount of various information was collected. With the help of the received data, the development of the direction will continue.
Mastering a new direction and translating ideas into a practically applicable form will take a lot of time, and for this reason, in the foreseeable future, space and army rockets in the foreseeable future will be equipped only with traditional liquid engines. Nevertheless, the work has already left the purely theoretical stage, and now each test run of an experimental engine brings closer the moment of building full-fledged missiles with new power plants.
According to the websites:
http://engine.space/
http://fpi.gov.ru/
https://rg.ru/
https://utro.ru/
http://tass.ru/
http://svpressa.ru/
