The problem of development of impulse detonation engines is considered. The main scientific centers leading research on new generation engines. 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 impulse 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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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 the specialized center Seattle Aerosciences Center (SAC), bought out 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. In addition to Pratt and Whitney, the United Technologies Research Center (UTRC) and Boeing Phantom Works are participating in the work.
At present, the following universities and institutes of the Russian Academy of Sciences (RAS) are theoretically working on this topical problem in our country: the Institute of Chemical Physics of the Russian Academy of Sciences (ICP), the Institute of Mechanical Engineering of the Russian Academy of Sciences, the Institute of High Temperatures of the Russian Academy of Sciences (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). typical combustion chamber jet engine consists of nozzles for mixing fuel with an oxidizer, an ignition device 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 aircrafts. 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 of a higher level, or direct numerical simulation based on the full Navier-Stokes equations without using 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: 03/14/2019). We bring to your attention the journals published by the publishing house "Academy of Natural History"
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(LRE) using detonation combustion of fuel -. 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 jet thrust.
Detonation is also combustion, but it occurs 100 times faster than with conventional fuel combustion. This process is so fast that detonation is often confused with an explosion, especially since so much energy is released in this case that, for example, car motor when this phenomenon occurs in its cylinders, it 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 the fuel mixture inside the combustion chamber, a detonation wave is formed, 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. The propeller and the internal combustion engine 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. Alternatives Russian engines not yet in the US.
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 a pulse jet engine (PUJE) neither a compressor rotating at a speed of 40,000 revolutions per minute was needed to force air into the insatiable belly 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. However, the priority 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 plants on 129 ships, they consume fuel worth three billion dollars a year. The introduction of more economical detonation gas turbine engines(GTE) will save huge funds.
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 the necessary funds for the creation in 2014 of a specialized laboratory "Detonation LRE". 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 conditions of extreme vibration loads and ultra-high temperatures in the absence of cooling of the near-wall layer. 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, there is still a long way to go before using this technology in real aircraft. 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
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Detonation engine tests
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The specialized laboratory "Detonation LRE" of the Energomash Research and Production Association tested the world's first full-size detonation liquid-propellant rocket engine technology demonstrators. According to TASS, the new power plants run on an oxygen-kerosene fuel pair.
The new engine, unlike other power plants operating on the principle of internal combustion, operates due to fuel detonation. Detonation is the supersonic combustion of a substance, in this case a fuel mixture. In this case, a shock wave propagates through the mixture, followed by a chemical reaction with the release of a large amount of heat.
The study of the principles of operation and the development of detonation engines has been carried out in some countries of the world for more than 70 years. The first such work began in Germany in the 1940s. True, the researchers failed to create a working prototype of a detonation engine at that time, but pulsating jet engines were developed and mass-produced. They were placed on V-1 rockets.
In pulsating jet engines, fuel burned at subsonic speeds. This combustion is called deflagration. The engine is called pulsating because fuel and oxidizer were fed into its combustion chamber in small portions at regular intervals.
Pressure map in the combustion chamber of a rotary detonation engine. A - detonation wave; B - trailing front of the shock wave; C - mixing zone of fresh and old combustion products; D - fuel mixture filling area; E is the region of the non-knocking burnt fuel mixture; F - expansion zone with detonated burnt fuel mixture
Detonation engines today are divided into two main types: impulse and rotary. The latter are also called spin. Principle of operation pulse engines similar to that of pulse jet engines. The main difference lies in the detonation combustion of the fuel mixture in the combustion chamber.
Rotary detonation engines use an annular combustion chamber in which the fuel mixture is fed sequentially through radial 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 can produce 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.
All detonation engines tested so far have been developed for experimental aircraft. Tested in Russia, such a power plant is the first to be installed on a rocket. What type of detonation engine was tested is not specified.
While all progressive humanity from the NATO countries is preparing to start testing a detonation engine (tests can happen in 2019 (but rather much later)), backward Russia announced the completion of testing such an engine.
They announced it quite calmly and without frightening anyone. But in the West, as expected, they got scared and a hysterical howl began - we will be left behind for the rest of our lives. Work on a detonation engine (DD) is being carried out in the USA, Germany, France and China. In general, there is reason to believe that Iraq and North Korea are interested in solving the problem - this is a very promising development, which actually means a new stage in rocket science. And in general in engine building.
The idea of a detonation engine was first voiced in 1940 by the Soviet physicist Ya.B. Zel'dovich. And the creation of such an engine promised huge benefits. For a rocket engine, for example:
- The power is increased by 10,000 times compared to a conventional rocket engine. In this case, we are talking about the power received per unit volume of the engine;
- 10 times less fuel per unit of power;
- DD is simply significantly (many times) cheaper than a standard rocket engine.
A liquid propellant rocket engine is such a big and very expensive burner. And expensive because to maintain sustainable combustion requires a large number of mechanical, hydraulic, electronic and other mechanisms. A very complex production. So complicated that the United States has been unable to create its own liquid-propellant rocket engine for many years and are forced to purchase RD-180 in Russia.
Russia will very soon receive a serial reliable inexpensive light rocket engine. With all the ensuing consequences:
a rocket can carry at times large quantity payload- the engine itself weighs significantly less, fuel is needed 10 times less for the declared flight range. And you can simply increase this range by 10 times;
the cost of the rocket is reduced by a multiple. This is a good answer for those who like to organize an arms race with Russia.
And there is also deep space… Simply fantastic prospects for its development are opening up.
However, the Americans are right and now there is no time for space - packages of sanctions are already being prepared so that a detonation engine does not happen in Russia. They will interfere with all their might - our scientists have made a painfully serious claim for leadership.
07 Feb 2018 Tags: 1934Discussion: 3 comments
* 10,000 times more power compared to a conventional rocket engine. In this case, we are talking about the power received per unit volume of the engine;
10 times less fuel per unit of power;
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somehow does not fit with other posts:
“Depending on the design, it can exceed the original LRE in terms of efficiency from 23-27% for a typical design with an expanding nozzle, up to 36-37% increase in KVRD (wedge-air rocket engines)
They are able to change the pressure of the outflowing gas jet depending on atmospheric pressure, and save up to 8-12% of fuel throughout the entire structure launch site (The main savings occur at low altitudes, where it reaches 25-30%).»Answer
United Engine Corporation (UEC) intends to soon start creating new aircraft and rocket engines that will use detonation technologies.
Detonation subsonic and supersonic engine technology demonstrators have already been created. In tests, they showed 30-50% better specific thrust and fuel consumption compared to conventional power plants, RIA Novosti reported with reference to the corporation's data.
The Experimental Design Bureau im. Cradles. The Bureau proposed the development of a family of such propulsion systems that could be used on unmanned aerial vehicles, cruise missiles, aerospace aircraft and rockets.
Detonation engines are different:
- combustion of the fuel mixture, accompanied by the passage of a shock wave through it, which is formed due to supersonic propagation of the combustion front along the fuel mixture;
- a wide range of speeds - from subsonic to hypersonic, which can help in the creation of hypersonic missiles, the design of which has been actively carried out in Russia in recent years.
In 2013, the Experimental Design Bureau. Lyulki tested a prototype reduced sample of a pulsating resonator detonation engine with a two-stage combustion of a kerosene-air mixture. During the tests, the average measured thrust power plant amounted to about one hundred kilograms, and the duration continuous work- more than ten minutes. During the experiments, the new engine was switched on and off repeatedly, as well as traction control.
According to the design bureau, detonation engines will increase the aircraft's thrust-to-weight ratio by 1.5–2 times. Work on the creation of pulsating detonation engines has been carried out in Russia since 2011.
In addition to Russia, several companies in the world are developing detonation engines at once: the French company SNECMA and the American General Electric and Pratt & Whitney.
BASICS OF THE DETONATING ENGINE
If specific consumption fuel did not grow with increasing flight speed, then applying modern solutions to improve external aerodynamics, by increasing the flight altitude, at supersonic speeds, it would be possible to achieve the same range characteristics as that of a subsonic mainline aircraft. But the internal aerodynamics of supersonic aircraft has an unrecoverable drawback - at supersonic speeds, the specific fuel consumption of a traditional power plant increases monotonously with increasing speed at any flight altitudes. The way out is seen in the use of engines based on other principles than the traditional Brayton thermodynamic cycle of fuel combustion at constant pressure. The latter include pulse jet and detonation engines. The article discusses the advantages of using detonation combustion in turbojet and rocket engines.
One of the best in terms of thermodynamics is a detonation engine. Due to the fact that it burns fuel in shock waves about 100 times faster than with conventional slow combustion (deflagration), this type of engine is theoretically distinguished by a record power taken per unit volume compared to all other types of heat engines.
The question of using detonation combustion in power engineering and jet engines was first raised by Ya.B. Zeldovich back in 1940. According to his estimates, ramjet engines using detonation combustion of fuel should have the highest possible thermodynamic efficiency.
DIRECTIONS OF WORK ON PULSED DETONATION ENGINES
Direction #1 - Classic Pulse Detonation Engine
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, having 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 the pressure in the environment as far as possible. Very roughly, one can estimate the thrust of an 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.
Traditional impulse detonation engines are long tubes through which shock waves travel at low frequency. The system of compression and rarefaction waves automatically regulates the supply of fuel and oxidizer. Due to the low repetition rate of shock waves (units of Hz), the time during which fuel combustion occurs is short compared to the characteristic cycle time. As a result, despite high efficiency actually detonation combustion (20-25% more than engines with the Brayton cycle), the overall efficiency of such designs is low.
The main task in this area at the present stage is the development of engines with high frequency following shock waves in the combustion chamber or creating an engine with continuous detonation(CDE).
The classic appearance of the IDD is a cylindrical combustion chamber, which has a flat or specially profiled wall, called the "draft wall". The simplicity of the IDD device is its undeniable advantage. 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.
Direction No. 2 - Multipipe IDD
The main trend in the development of IDD is the transition to a multi-pipe scheme. 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, as well as the problem of bottom pressure, in particular, possible low-frequency oscillations in the bottom area between the pipes, are solved.
Direction No. 3 - PDD with a high-frequency resonator
The traction module of the IDD of the proposed scheme consists of a reactor and a resonator. The reactor serves to prepare the fuel-air mixture for detonation combustion, decomposing the molecules of the combustible mixture into chemically active components.
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. As an example, attempts at 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 turbulence models are based on averaging the Navier-Stokes equations (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 of a higher level, or direct numerical simulation based on the full Navier-Stokes equations without using turbulence models (a task that is too heavy at the present stage).
From the schemes presented above, it can be seen that the PDE schemes being studied today are single-mode engines with a very limited control range, so their direct use as the only power plant on an aircraft is impractical. Another thing is the rocket engine.
