The problem of developing rotary detonation engines. The main types of such engines are presented: Nichols rotary detonation engine, 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 is superior in its characteristics to existing air-breathing engines. The reason is the desire of designers to combine wave generation, fuel combustion and ejection of fuel and oxidizer into one mechanism. As a result of the self-organization of shock wave structures, detonation combustion occurs in a minimum rather than a maximum volume. The actual result achieved today is detonation combustion in a volume not exceeding 15 % of the volume of the combustion chamber. The solution is seen in a different approach - first, an optimal configuration of shock waves is created, and only then fuel components are supplied to this system and optimal detonation combustion is organized in a large volume.
detonation engine
rotary detonation engine
Wojciechowski engine
circular detonation
spin detonation
pulse detonation engine
1. Voitsekhovsky B.V., Mitrofanov V.V., Topchiyan M.E., Structure of the detonation front in gases. – Novosibirsk: Publishing House of the Siberian Branch 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 // Fundamental Research. – 2012. – No. 6 (part 1). – pp. 178–184.
3. Uskov V.N., Bulat P.V., Prodan N.V. History of the study of irregular reflection of a shock wave from the symmetry axis of a supersonic jet with the formation of a Mach disk // Fundamental Research. – 2012. – No. 9 (part 2). – pp. 414–420.
4. Uskov V.N., Bulat P.V., Prodan N.V. Justification for 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). – pp. 168–175.
5. Shchelkin K.I. Instability of combustion and detonation of gases // Advances in Physical Sciences. – 1965. – T. 87, issue. 2.– pp. 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 the fact that the fuel supply system is combined with a fuel combustion system in a detonation wave, but then everything works as in a conventional jet engine - a flame tube and a nozzle. It was this fact that initiated such activity in the field of modernization gas turbine engines(GTD). 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 continuity 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 in the mid-60s conducted a series of experiments with a rotating detonation wave (Fig. 1).
By adjusting the diameter of the chamber and the thickness of the annular gap, for each type of fuel mixture it is possible to select such a geometry that the detonation will be stable. In practice, the ratio of the gap size and the engine diameter turns out to be unacceptable and it is necessary to regulate the speed of wave propagation by controlling the fuel supply, as discussed below.
As in pulse detonation engines, the circular detonation wave is capable of ejecting the oxidizer, allowing RDE to be used at zero speeds. This fact entailed a flurry of experimental and computational studies of RDE with an annular combustion chamber and spontaneous ejection fuel-air mixture, which makes no sense to list here. All of them are built according to approximately the same scheme (Fig. 2), reminiscent of the Nichols engine diagram (Fig. 1).
Rice. 1. Scheme of organization of continuous circular detonation in an annular gap: 1 - detonation wave; 2 - layer of “fresh” fuel mixture; 3 - contact break; 4 - oblique shock wave propagating downstream; D - direction of movement of the detonation wave
Rice. 2. Typical scheme RDE: V - free flow velocity; V4 - flow velocity at the nozzle exit; a - fresh fuel assembly, 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 would be to install multiple fuel-oxidation nozzles that would inject a fuel-air mixture into the area immediately before the detonation wave according to a certain law with a given pressure (Fig. 3). By adjusting the pressure and speed of fuel supply to the combustion region behind the detonation wave, it is possible to influence the speed of its propagation upstream. This direction is promising, but the main problem in designing such RDEs is that the commonly used simplified model of 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. Wojciechowski diagram of continuous gas combustion 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 region
IN in this case the stationary hydrodynamic process with gas combustion behind the shock wave differs from the Chapman-Jouguet and Zeldovich-Neumann detonation scheme. This process is quite stable, its duration is determined by the supply of the fuel mixture and in known experiments amounts to several tens of seconds.
The Wojciechowski detonation engine design has served as the prototype for numerous studies of rotary and spin detonation engines initiated in the last 5 years. This design accounts for more than 85% of all studies. All of them have one organic drawback - the detonation zone occupies too small a part of the total combustion zone, usually no more than 15%. As a result specific indicators engines are worse than those of traditionally designed engines.
On the reasons for failures in the implementation of Woitsekhovsky’s scheme
Most of the work on engines with continuous detonation is 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 burning under conditions that are far from optimal.
One of the reasons for this state of affairs is the lack of a workable calculation method. 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 consequence is that, despite many years of research various systems fuel supply and experiments on changing the ratio of fuel components, all that was possible to do was to create models in which detonation combustion occurs and is maintained for 10-15 s. There is no talk of increasing efficiency or advantages over existing liquid propellant engines and gas turbine engines.
An analysis of the existing RDE schemes carried out by the authors of the project showed that all RDE schemes offered today are ineffective 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, and behind a non-optimal system of shock waves, which leads to significant losses of total pressure. In addition, the pressure is also several times lower than necessary for ideal combustion conditions with a stoichiometric ratio of the components of the fuel mixture. As a result, the specific fuel consumption per unit of thrust is 30-40% higher than that of traditional 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 shock wave configurations. Such a structure with an attached detonation zone, like any thermodynamic system with feedback, left alone, tends to take a position corresponding to minimum level energy. As a result, the triple configurations and the detonation combustion region are adjusted to each other so that the detonation front moves along the annular gap with the minimum possible volume of detonation combustion. This is exactly the opposite of 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 created in a variety of technical devices, for example, in optimal diffusers of supersonic air intakes. The main task is to maximize the possible increase in the proportion of detonation combustion in the volume of the combustion chamber from today's unacceptable 15% to at least 85%. Existing engine designs based on Nichols and Wojciechowski designs cannot achieve 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 Thermal Engineering, BSTU "VOENMEH" named after. D.F. Ustinova, St. Petersburg.
The work was received by the editor on October 14, 2013.
Bibliographic link
Bulat P.V., Prodan N.V. REVIEW OF DETONATION ENGINE PROJECTS. ROTARY DETONATION ENGINES // Fundamental Research. – 2013. – No. 10-8. – S. 1672-1675;URL: http://fundamental-research.ru/ru/article/view?id=32642 (date of access: 07/29/2019). We bring to your attention magazines published by the publishing house "Academy of Natural Sciences"
Engines that use detonation combustion of fuel in normal mode are called detonation engines. The engine itself can be (theoretically) anything - internal combustion engine, jet, or even steam. In theory. However, until now, all known commercially acceptable engines of such fuel combustion modes, commonly referred to as “explosion”, have not been used due to their... mmm... commercial unacceptability..
Source:
What does the application give detonation combustion in engines? To greatly simplify and generalize, something like this:
Advantages
1. Replacing conventional combustion with detonation combustion due to the gas dynamics of the shock wave front increases the theoretical maximum achievable completeness of combustion of the mixture, which makes it possible to increase Engine efficiency, and reduce consumption by about 5-20%. This is true for all types of engines, both internal combustion engines and jet engines.
2. The combustion rate of a portion of the fuel mixture increases approximately 10-100 times, which means that it is theoretically possible for an internal combustion engine to increase the liter power (or specific thrust per kilogram of mass for jet engines) approximately the same number of times. This factor is also relevant for all types of engines.
3. The factor is relevant only for jet engines of all types: since combustion processes take place in the combustion chamber at supersonic speeds, and the temperatures and pressures in the combustion chamber increase significantly, there is an excellent theoretical opportunity to repeatedly increase the speed of the jet stream from the nozzle. Which in turn leads to a proportional increase in thrust, specific impulse, efficiency, and/or reduction in engine weight and required fuel.
All these three factors are very important, but they are not revolutionary, but evolutionary, so to speak. The fourth and fifth factors are revolutionary, and they apply only to jet engines:
4. Only the use of detonation technologies makes it possible to create a direct-flow (and therefore, using an atmospheric oxidizer!) universal jet engine of acceptable weight, size and thrust, for practical and large-scale development of the range of sub-, super-, and hypersonic speeds 0-20Max.
5.Only detonation technologies make it possible to squeeze fuel-oxidizer out of chemical rocket engines (steam fuel-oxidizer) speed parameters required for their wide application in interplanetary flights.
P.4 and 5. theoretically reveal to us a) cheap road into near space, and b) a road to manned launches to nearby planets, without the need to make monstrous super-heavy launch vehicles weighing over3500 tons.
The disadvantages of detonation engines arise from their advantages:
Source:
1. The combustion rate is so high that most often these engines can only be made to operate cyclically: intake-combustion-exhaust. Which reduces the maximum achievable liter power and/or thrust by at least three times, sometimes defeating the purpose of the idea itself.
2. Temperatures, pressures, and the rates of their increase in the combustion chamber of detonation engines are such that they exclude the direct use of most materials known to us. All of them are too weak to build a simple, cheap and efficient engine. Either a whole family of fundamentally new materials is required, or the use of yet unproven design tricks. We don’t have the materials, and complicating the design again often makes the whole idea meaningless.
However, there is an area in which detonation engines cannot be avoided. This is an economically feasible atmospheric hypersound with a speed range of 2-20 Max. Therefore, the battle goes on three fronts:
1. Creation of an engine diagram with continuous detonation in the combustion chamber. Which requires supercomputers and non-trivial theoretical approaches to calculate their hemodynamics. In this area, the damned quilted jackets, as always, took the lead, and for the first time in the world they theoretically showed that a continuous delegation is generally possible. Invention, discovery, patent - that's all. And they began to make a practical structure from rusty pipes and kerosene.
2. Creation constructive solutions doing possible applications classic materials. Damn the quilted jackets with the drunken bears, and here they were the first to come up with and make a laboratory multi-chamber engine, which already works indefinitely. The thrust is like that of a Su27 engine, and the weight is such that one (one!) grandfather can hold it in his hands. But since the vodka was scorched, the engine turned out to be pulsating. But the bastard works so cleanly that you can even turn it on in the kitchen (where the quilted jackets actually washed it down in the intervals between vodka and balalaika)
3. Creation of supermaterials for future engines. This area is the tightest and most secretive. I have no information about breakthroughs in it.
Based on the above, let’s consider the prospects for detonation, piston internal combustion engine. As is known, the increase in pressure in the combustion chamber classic sizes, during detonation in the internal combustion engine occurs faster speed sound. Remaining in the same design, there is no way to make a mechanical piston, and even with significant associated masses, move in the cylinder at approximately the same speeds. A timing belt with a classic layout also cannot operate at such speeds. Therefore, direct conversion of a classic internal combustion engine to a detonation one is pointless from a practical point of view. The engine needs to be redesigned. But as soon as we start doing this, it turns out that the piston in this design is simply extra detail. Therefore, IMHO, piston detonation internal combustion engine this is an anachronism.
The Lyulka Experimental Design Bureau developed, manufactured and tested a prototype of a pulsating resonator detonation engine with two-stage combustion of a kerosene-air mixture. As ITAR-TASS reports, the average measured engine thrust was about one hundred kilograms, and the duration of continuous operation was 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 the chief designer of the Lyulka Design Bureau, Alexander Tarasov, during the tests, operating modes characteristic of a turbojet and ramjet engines. Measured values of specific thrust and specific consumption the fuels were 30-50 percent better than conventional air-breathing engines. During the experiments, the new engine was turned on and off repeatedly, as well as traction control.
Based on the research conducted, data obtained from testing, as well as circuit design analysis, the Lyulka Design Bureau intends to propose the development of a whole family of pulsating detonation aircraft engines. In particular, short-life engines for unmanned aerial vehicles and missiles and aircraft engines for supersonic cruising flight can be created.
In the future, based on new technologies, engines for rocket and space systems and combined power plants aircraft capable of flying in the atmosphere and beyond.
According to the design bureau, the new engines will increase the thrust-to-weight ratio of aircraft by 1.5-2 times. In addition, when using such power plants, the flight range or weight of aircraft weapons can increase by 30-50 percent. At the same time, the specific gravity of the new engines will be 1.5-2 times less than that of conventional jet power plants.
It was reported in March 2011 that work was underway in Russia to create a pulsating detonation engine. This was stated then by Ilya Fedorov, managing director of the Saturn research and production association, which includes the Lyulka Design Bureau. Fedorov did not specify what type of detonation engine was being discussed.
Currently, three types of pulsating engines are known: valve, valveless and detonation. The operating principle of these power plants is to periodically supply fuel and oxidizer to the combustion chamber, where the fuel mixture is ignited and combustion products flow out of the nozzle to form jet thrust. The difference from conventional jet engines is the detonation combustion of the fuel mixture, in which the combustion front propagates faster than the speed of sound.
Throbbing 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. First new type The engine was used commercially 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 into the development of highly efficient pulse jet engines. In particular, the work is being carried out by the French company SNECMA and American General Electric and Pratt & Whitney. In 2012, the US Naval Research Laboratory announced its intention to develop a spin detonation engine, which would replace conventional gas turbine power plants on ships.
The US Navy Research Laboratory (NRL) intends to develop a rotational, or spin, detonation engine (Rotating Detonation Engine, RDE), which in the future could replace conventional gas turbine power plants on ships. According to NRL, the new engines will allow the military to reduce fuel consumption while increasing the energy efficiency of power plants.
The US Navy currently operates 430 gas turbine engines (GTEs) on 129 ships. They consume two billion dollars worth of fuel every year. NRL estimates that RDE could save the military up to $400 million a year in fuel costs. RDEs will be able to produce ten percent more energy than conventional gas turbine engines. The RDE prototype has already been created, but it is still unknown when such engines will begin to enter the fleet.
The RDE is based on NRL's developments obtained during the creation of a pulsating detonation engine (Pulse Detonation Engine, PDE). The operation of such power plants is based on stable detonation combustion of the fuel mixture.
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 fuel mixture is constantly updated.
The Military-Industrial Courier publication reports great news from the field of breakthrough missile technologies. A detonation rocket engine has been tested in Russia, Deputy Prime Minister Dmitry Rogozin said on his Facebook page on Friday.
“The so-called detonation rocket engines developed within the framework of the Advanced Research Foundation program have been successfully tested,” Interfax-AVN quotes the Deputy Prime Minister.
It is believed that a detonation rocket engine is one of the ways to implement the concept of so-called motor hypersound, that is, the creation of hypersonic aircraft capable of own engine reach speeds of Mach 4 - 6 (Mach is the speed of sound).
The portal russia-reborn.ru provides an interview with one of the leading specialized engine specialists in Russia regarding detonation rocket engines.
Interview with Petr Levochkin, chief designer of NPO Energomash named after. Academician V.P. Glushko."
Engines are being created for hypersonic missiles of the future
So-called detonation rocket engines have been successfully tested, yielding very interesting results. Development work in this direction will be continued.
Detonation is an explosion. Can it be made manageable? Is it possible to create hypersonic weapons based on such engines? Which rocket engines will they launch uninhabited and manned vehicles into near space? We talked about this with the Deputy General Director - Chief Designer of NPO Energomash named after. Academician V.P. Glushko" by Pyotr Levochkin.
Petr Sergeevich, what opportunities do new engines open up?
Petr Levochkin: If we talk about the near future, today we are working on engines for rockets such as Angara A5V and Soyuz-5, as well as others that are at the pre-design stage and unknown to the general public. In general, our engines are designed to lift a rocket off the surface of a celestial body. And it can be anything - terrestrial, lunar, Martian. So, if lunar or Martian programs are implemented, we will definitely take part in them.
What is the efficiency of modern rocket engines and are there ways to improve them?
Petr Levochkin: If we talk about the energy and thermodynamic parameters of engines, then we can say that ours, as well as the best foreign chemical rocket engines today, have reached a certain perfection. For example, the completeness of fuel combustion reaches 98.5 percent. That is, almost all the chemical energy of the fuel in the engine is converted into thermal energy of the flowing gas stream from the nozzle.
Engines can be improved in different directions. This includes the use of more energy-intensive fuel components, the introduction of new circuit solutions, and an increase in pressure in the combustion chamber. Another direction is the use of new, including additive, technologies in order to reduce labor intensity and, as a consequence, reduce the cost of the rocket engine. All this leads to a reduction in the cost of output payload.
However, upon closer examination, it becomes clear that increasing the energy performance of engines traditional way ineffective.
Using a controlled explosion of propellant can give a rocket speeds eight times the speed of sound
Why?
Petr Levochkin: Increasing the pressure and fuel flow in the combustion chamber will naturally increase engine thrust. But this will require increasing the thickness of the chamber walls and pumps. As a result, the complexity of the structure and its mass increase, the energy gain is not so great. The game won't be worth the candle.
That is, rocket engines have exhausted their development resource?
Petr Levochkin: Not exactly. In technical terms, they can be improved by increasing the efficiency of intramotor processes. There are cycles of thermodynamic conversion of chemical energy into the energy of the outflowing jet, which are much more efficient than the classical combustion of rocket fuel. This is the detonation combustion cycle and the closely related Humphrey cycle.
The effect of fuel detonation itself was discovered by our compatriot, later academician Yakov Borisovich Zeldovich, back in 1940. The implementation of this effect in practice promised very great prospects in rocket science. It is not surprising that in those same years the Germans actively studied the detonation combustion process. But they did not progress beyond the not entirely successful experiments.
Theoretical calculations have shown that detonation combustion is 25 percent more efficient than the isobaric cycle corresponding to the combustion of fuel at constant pressure, which is implemented in the chambers of modern liquid-propellant engines.
What are the advantages of detonation combustion compared to classical combustion?
Petr Levochkin: The classic combustion process is subsonic. Detonation - supersonic. The speed of the reaction in a small volume leads to enormous heat release - it is several thousand times higher than during subsonic combustion, implemented in classical rocket engines with the same mass of burning fuel. And for us, engine engineers, this means that with significantly smaller dimensions of the detonation engine and with a low fuel mass, we can obtain the same thrust as in huge modern liquid rocket engines.
It is no secret that engines with detonation combustion of fuel are also being developed abroad. What are our positions? Are we inferior, are we at their level, or are we leading?
Petr Levochkin: We are not giving in - that’s for sure. But I can’t say that we are in the lead. The topic is quite closed. One of the main technological secrets is how to ensure that the fuel and oxidizer of a rocket engine do not burn, but explode, without destroying the combustion chamber. That is, to actually make a real explosion controlled and manageable. For reference: detonation is the combustion of fuel in the front of a supersonic shock wave. A distinction is made between pulsed detonation, when a shock wave moves along the axis of the chamber and one replaces the other, as well as continuous (spin) detonation, when shock waves in the chamber move in a circle.
As far as we know, experimental studies of detonation combustion have been carried out with the participation of your specialists. What results were obtained?
Petr Levochkin: Work was carried out to create a model chamber of a liquid detonation rocket engine. A large collaboration of leading scientists worked on the project under the patronage of the Foundation for Advanced Research scientific centers Russia. Among them are the Institute of Hydrodynamics named after. M.A. Lavrentyeva, MAI, "Keldysh Center", Central Institute aviation engine building named after. P.I. Baranova, Faculty of Mechanics and Mathematics, Moscow State University. We proposed to use kerosene as a fuel, and gaseous oxygen as an oxidizer. In the process of theoretical and experimental research, the possibility of creating a detonation rocket engine using such components was confirmed. Based on the data obtained, we developed, manufactured and successfully tested a model detonation chamber with a thrust of 2 tons and a pressure in the combustion chamber of about 40 atm.
This problem was solved for the first time not only in Russia, but also in the world. So, of course, there were problems. Firstly, related to ensuring stable detonation of oxygen with kerosene, and secondly, to ensuring reliable cooling of the fire wall of the chamber without curtain cooling and a host of other problems, the essence of which is understandable only to specialists.
The Military-Industrial Courier publication reports great news from the field of breakthrough missile technologies. A detonation rocket engine has been tested in Russia, Deputy Prime Minister Dmitry Rogozin said on his Facebook page on Friday.
“The so-called detonation rocket engines developed within the framework of the Advanced Research Foundation program have been successfully tested,” Interfax-AVN quotes the Deputy Prime Minister.
It is believed that a detonation rocket engine is one of the ways to implement the concept of so-called motor hypersound, that is, the creation of hypersonic aircraft capable of reaching speeds of Mach 4 - 6 (Mach - the speed of sound) using their own engine.
The portal russia-reborn.ru provides an interview with one of the leading specialized engine specialists in Russia regarding detonation rocket engines.
Interview with Pyotr Levochkin, chief designer of NPO Energomash named after Academician V.P. Glushko.
Engines are being created for hypersonic missiles of the future
So-called detonation rocket engines have been successfully tested, yielding very interesting results. Development work in this direction will be continued.
Detonation is an explosion. Can it be made manageable? Is it possible to create hypersonic weapons based on such engines? What rocket engines will launch uninhabited and manned vehicles into near space? Our conversation with the Deputy General Director - Chief Designer of NPO Energomash named after Academician V.P. Glushko, Petr Levochkin, was about this.
Petr Sergeevich, what opportunities do new engines open up?
Petr Levochkin: If we talk about the near future, today we are working on engines for rockets such as Angara A5V and Soyuz-5, as well as others that are at the pre-design stage and unknown to the general public. In general, our engines are designed to lift a rocket off the surface of a celestial body. And it can be anything - terrestrial, lunar, Martian. So, if lunar or Martian programs are implemented, we will definitely take part in them.
What is the efficiency of modern rocket engines and are there ways to improve them?
Petr Levochkin: If we talk about the energy and thermodynamic parameters of engines, then we can say that ours, as well as the best foreign chemical rocket engines today, have reached a certain perfection. For example, the completeness of fuel combustion reaches 98.5 percent. That is, almost all the chemical energy of the fuel in the engine is converted into thermal energy of the flowing gas stream from the nozzle.
Engines can be improved in different directions. This includes the use of more energy-intensive fuel components, the introduction of new circuit solutions, and an increase in pressure in the combustion chamber. Another direction is the use of new, including additive, technologies in order to reduce labor intensity and, as a consequence, reduce the cost of the rocket engine. All this leads to a reduction in the cost of the launched payload.
However, upon closer examination, it becomes clear that increasing the energy characteristics of engines in the traditional way is ineffective.
Using a controlled explosion of propellant can give a rocket speeds eight times the speed of sound
Why?
Petr Levochkin: Increasing the pressure and fuel flow in the combustion chamber will naturally increase engine thrust. But this will require increasing the thickness of the chamber walls and pumps. As a result, the complexity of the structure and its mass increase, the energy gain is not so great. The game won't be worth the candle.
That is, rocket engines have exhausted their development resource?
Petr Levochkin: Not exactly. In technical terms, they can be improved by increasing the efficiency of intramotor processes. There are cycles of thermodynamic conversion of chemical energy into the energy of the outflowing jet, which are much more efficient than the classical combustion of rocket fuel. This is the detonation combustion cycle and the closely related Humphrey cycle.
The effect of fuel detonation itself was discovered by our compatriot - later academician Yakov Borisovich Zeldovich back in 1940. The implementation of this effect in practice promised very great prospects in rocket science. It is not surprising that in those same years the Germans actively studied the detonation combustion process. But they did not progress beyond the not entirely successful experiments.
Theoretical calculations have shown that detonation combustion is 25 percent more efficient than the isobaric cycle corresponding to the combustion of fuel at constant pressure, which is implemented in the chambers of modern liquid-propellant engines.
What are the advantages of detonation combustion compared to classical combustion?
Petr Levochkin: The classical combustion process is subsonic. Detonation - supersonic. The speed of the reaction in a small volume leads to enormous heat release - it is several thousand times higher than during subsonic combustion, implemented in classical rocket engines with the same mass of burning fuel. And for us, engine engineers, this means that with significantly smaller dimensions of the detonation engine and with a low fuel mass, we can obtain the same thrust as in huge modern liquid rocket engines.
It is no secret that engines with detonation combustion of fuel are also being developed abroad. What are our positions? Are we inferior, are we at their level, or are we leading?
Petr Levochkin: We are not giving in - that’s for sure. But I can’t say that we are in the lead. The topic is quite closed. One of the main technological secrets is how to ensure that the fuel and oxidizer of a rocket engine do not burn, but explode, without destroying the combustion chamber. That is, to actually make a real explosion controlled and manageable. For reference: detonation is the combustion of fuel in the front of a supersonic shock wave. A distinction is made between pulsed detonation, when a shock wave moves along the axis of the chamber and one replaces the other, as well as continuous (spin) detonation, when shock waves in the chamber move in a circle.
As far as we know, experimental studies of detonation combustion have been carried out with the participation of your specialists. What results were obtained?
Petr Levochkin: Work was carried out to create a model chamber of a liquid detonation rocket engine. A large collaboration of leading scientific centers in Russia worked on the project under the patronage of the Foundation for Advanced Research. Among them are the Institute of Hydrodynamics named after. M.A. Lavrentyev, MAI, "Keldysh Center", Central Institute of Aviation Engine Engineering named after. P.I. Baranova, Faculty of Mechanics and Mathematics, Moscow State University. We proposed to use kerosene as a fuel, and gaseous oxygen as an oxidizer. In the process of theoretical and experimental research, the possibility of creating a detonation rocket engine using such components was confirmed. Based on the data obtained, we developed, manufactured and successfully tested a model detonation chamber with a thrust of 2 tons and a pressure in the combustion chamber of about 40 atm.
This problem was solved for the first time not only in Russia, but also in the world. So, of course, there were problems. Firstly, related to ensuring stable detonation of oxygen with kerosene, and secondly, to ensuring reliable cooling of the fire wall of the chamber without curtain cooling and a host of other problems, the essence of which is understandable only to specialists.
Can a detonation engine be used in hypersonic missiles?
Petr Levochkin: It’s both possible and necessary. If only because the fuel combustion in it is supersonic. And in those engines on which they are now trying to create controlled hypersonic aircraft, combustion is subsonic. And this creates a lot of problems. After all, if the combustion in the engine is subsonic, and the engine flies, say, at a speed of five machs (one mach equal to speed sound), you need to slow down the oncoming air flow to sound mode. Accordingly, all the energy of this braking is converted into heat, which leads to additional overheating of the structure.
And in a detonation engine, the combustion process occurs at a speed at least two and a half times higher than sound speed. And, accordingly, we can increase the speed of the aircraft by this amount. That is, we are no longer talking about five, but about eight swings. This is the currently achievable speed of aircraft with hypersonic engines, which will use the principle of detonation combustion.
Petr Levochkin: This is complex issue. We have just opened the door to the area of detonation combustion. There is still a lot that remains unexplored beyond the scope of our research. Today, together with RSC Energia, we are trying to determine what the engine as a whole with a detonation chamber might look like in relation to the upper stages in the future.
On what engines will a person fly to distant planets?
Petr Levochkin: In my opinion, we will be flying traditional liquid-propellant rocket engines for a long time, improving them. Although other types of rocket engines are certainly being developed, for example, electric rocket engines (they are much more efficient than liquid rocket engines - their specific impulse is 10 times higher). Alas, today's engines and launch vehicles do not allow us to talk about the reality of mass interplanetary, and even more so intergalactic flights. Everything here is still at the level of science fiction: photon engines, teleportation, levitation, gravitational waves. Although, on the other hand, just a little over a hundred years ago, the works of Jules Verne were perceived as pure fantasy. Perhaps we won’t have long to wait for a revolutionary breakthrough in the area where we work. Including in the region practical creation missiles using explosion energy.
Dossier "RG":
"Research and Production Association Energomash" was founded by Valentin Petrovich Glushko in 1929. Now bears his name. Here they develop and produce liquid rocket engines for the first and, in some cases, second stages of launch vehicles. The NPO has developed more than 60 different liquid jet engines. The first satellite was launched using Energomash engines, the first man flew into space, and the first self-propelled vehicle Lunokhod-1 was launched. Today, more than ninety percent of launch vehicles in Russia take off using engines developed and produced at NPO Energomash.
