RU2435059C1 - Intermittent detonation engine - Google Patents

Abstract

FIELD: engines and pumps. ^ SUBSTANCE: intermittent detonation engine includes housing, fuel and oxidiser supply means to reactor, annular nozzle and gas dynamic resonator; at that, resonator in the form of tube of smaller diameter is arranged in reactor tube so that outlet of annular Hartmann nozzle is directed into internal cavity of resonator; concave bottom of resonator consists of two parts separated with buffer; inner part is made from material resisting high pulse mechanical loads, and outer part consists of block of piezoelectric elements connected electrically and in parallel and being piezogenerator together with resonant circuit. ^ EFFECT: invention allows increasing conversion efficiency of chemical fuel energy to mechanical and electric energy of engine, simplifying the design, improving mass and dimension and operating parameters, and increasing thrust characteristics of intermittent detonation engine. ^ 5 cl, 3 dwg

Description

The invention relates to the field of engine manufacturing and can be used to create traction on aircraft.

The creation of a detonation engine is a new direction in the development of aircraft engine manufacturing. Compared to existing aviation gas turbine engines, pulsating detonation engines will provide a significant improvement in traction, economic and mass-dimensional parameters, simplifying the design and reducing their cost (Herald of the Air Fleet, July-August 2003, pp. 72-76). It has been theoretically and experimentally proved that such engines can provide an increase in thermal efficiency by 1.3 ... 1.5 times.

The construction of pulsating detonation engines is carried out according to the following schemes (Pulse detonation engines / Edited by S.M. Frolov, M .: TORUS PRESS, 2006):

- classic "Armory";

- scheme for ramjet engine;

- a scheme for burning a mixture using a stationary rotating detonation wave.

In addition, the “inverted” scheme is actively developing (J. Engine, 2003, No. 1 (25), pp. 14-17; G. Polet, 2006, No. 11, pp. 7-15, 2007, No. 5, pp. 22-30, 2008, No. 12, pp. 18-26).

The pulsating detonation engine, built according to the "weapons" scheme (US patent No. 6484492), is a straight pipe of a certain length, which is open from the rear end and has a valve device at the front end. When the engine is running, the air-fuel mixture is fed into the pipe through a valve, which then closes.

The detonation of the air-fuel mixture is initiated using an ignitor located in the pipe, and the shock waves resulting from detonation propagate “down” along the pipe, increasing the temperature and pressure of the resulting combustion products. These products are forced out of the open rear end, creating a forward momentum of reactive force. After the shock wave exits, a rarefaction wave occurs, which provides a new portion of the fuel-air mixture to the pipe through the valve, and the cycle repeats.

A knock control method in such an engine is described in US Pat. No. 6,751,943. The shock wave arising upon ignition and the detonation combustion front will tend to propagate in both longitudinal directions. Ignition is initiated at the front end of the pipe, so that the waves will propagate downstream to the open outlet end. The valve is necessary in order to prevent the shock wave from leaving the front of the pipe and, more importantly, to prevent the front of detonation combustion from passing into the fuel-air intake system. A pulsating detonation cycle requires the valve to operate at extremely high temperatures and pressures, and in addition, it must operate at very high frequencies in order to obtain a smoothed traction force. These conditions significantly reduce the reliability of mechanical valve systems due to multi-cycle fatigue.

For a pulsating detonation engine built according to the “weapon” scheme, control options for the “electric” valve are proposed in RF patent No. 2287713.

Such an engine includes a pipe having an open front end and an open rear end; fuel-air inlet made in the pipe at the front end; an ignitor located in the pipe at a location between the front end and the rear end, as well as a magnetohydrodynamic flow control system located between the igniter and the air-fuel inlet. Three variants of magnetohydrodynamic flow control are proposed.

The first version of the magnetohydrodynamic flow control system includes an electric field field winding wound around the pipe in a place located between the igniter and the air-fuel inlet, and a pair of permanent magnets located on opposite sides of the pipe to create a magnetic field in it, perpendicular to the longitudinal axis of the pipe. Detonation of the air-fuel mixture in the pipe will lead to the flow of electrically conductive ionized combustion products through the magnetic field, resulting in an electric current in the field coil, creating an electric field.

The interaction of magnetic and electric fields leads to the emergence of the Lorentz force directed against the motion of the shock and detonation waves. For the duration of its operation, the direct combustion front will dissipate and will not pass through the open front end of the pipe. In addition, the field winding of the electric field is connected to a power mode control system that provides current pulses to the ignitor at appropriate times.

The second variant of the magnetohydrodynamic flow control system includes a magnetic field field winding wound around the pipe in a place located between the ignitor and the air-fuel inlet. An energy source is connected to the winding through the control device, ensuring the flow of electric current through it and thereby creating a magnetic field. In the area of the winding, the ionized fuel-air mixture located at the inlet of the pipe under the influence of a magnetic field is divided into a fuel-rich zone surrounded by a depleted air zone. In detonation, a direct pressure wave and a direct combustion front, propagating to the inlet of the pipe, collide with separate fuel and air zones. As a result, the combustion process of the front detonation zone is violated, causing the scattering of the direct combustion front. As soon as the front edge of the flame dissipates, the power supply to the winding is cut off.

The third version of the magnetohydrodynamic flow control system combines the first and second options for energy selection and separation of the fuel-air mixture. It contains a magnetic field excitation winding and an electric field excitation winding, wound outside the pipe in the area between the igniter and the air-fuel inlet, a pair of permanent magnets located on opposite sides of the pipe near the electric field excitation winding to create a magnetic field in it perpendicular to the longitudinal axis of the pipe.

The proposed magnetohydrodynamic flow control options replace the mechanical valve with an “electric” one, preventing the detonation combustion front from entering the fuel-air intake system. However, at the same time, the detonation engine is significantly more complicated, its weight and size characteristics increase.

A known method and device for producing traction (RF patent 2215890). An engine based on this method consists of a fuel and oxidizer supply unit, a housing placed in the housing to form an annular channel of the combustion chamber, resonant activation zones of the fuel and oxidizer, in which activation means are placed in the form of spark gaps connected to the outputs of the control unit. The output of the power supply is connected to the input of the control unit. At the outlet of the combustion chamber, a reflector and a centrally located profile screen optically connected with it are arranged, made with a concave surface for focusing the reflected detonation wave. The reflector and the screen are made of a material with high magnetic permeability, they can move relative to each other and are designed to remove electric energy from their surface during impact interaction of an ionized gas stream along them.

However, the ionized gas stream in a collision with the screen loses part of the charges due to their attraction and spreading over the surface of the conical reflector. As a result, the degree of ionization and the speed of the reflected gas flow are reduced.

Double reflection of the detonation wave in opposite directions from the screen and the reflector creates a thrust equal to the difference in the forces of mechanical influences, which will lead, depending on their ratio, to a very small thrust value, or to zero thrust, or even change the direction of thrust. Therefore, such a device cannot be used as an engine.

In the annular combustion chamber, the resulting detonation wave propagates in both longitudinal directions. However, the engine design does not have devices that prevent the front of detonation combustion from passing into the oxidizer and fuel activation zones, which can cause detonation in these zones.

In addition, in such a device, electrical pulses are generated on the screen and the reflector and are removed from their surfaces when impacted by an ionized gas stream. To ensure high ionization values of the flow, it is necessary to use additional measures, for example, the introduction of lightly ionized additives into the fuel. Such a device is less efficient than a converter built on the conversion of shock to electrical pulses using ferroelectrics.

A known chamber of a pulsating detonation combustion engine constructed according to an inverted circuit (patent No. 2084675), containing a supersonic nozzle located in the housing and a Hartmann resonator coaxial with it in the form of a tube closed at one end and open at the other end. They are located in such a way that a cavity is formed between the inner surface of the casing and the outer surface of the nozzle, which is a mixing chamber, the outlet of which is a critical section with a further transition to a supersonic nozzle with an external expansion with a truncated central body.

Such a chamber of a pulsating engine does not have preliminary preparation of fuel for detonation combustion, and therefore its efficiency is low.

A pulsating detonation engine built according to an inverted circuit (USSR patent No. 1672933 dated 04/22/1991, RF patent No. 2034996 dated 05/10/1995, Chemical Physics, 2001, Volume 20, No. 6, pp. 90-98), consists of a reactor and a resonator interconnected through an annular nozzle. Compressed air and fuel are fed into the reactor, and the fuel is preliminarily prepared for detonation combustion by decomposing the components of the air-fuel mixture into chemically active components, for which the fuel is pyrolyzed to obtain a working mixture.

The prepared mixture is fed through the annular nozzle in the form of radial supersonic jets into the resonator; as a result, shock waves arise on the basis of the well-known Hartmann-Sprenger effect, which compress and heat the combustible mixture when moving toward the bottom. Reflecting from the bottom surface of the resonator having a concave shape, the shock waves are focused in a narrow region where there is a further increase in temperature and pressure, based on the well-known Hartmann-Sprenger effect, which contribute to the detonation of the combustible mixture. The resulting detonation wave travels along the fuel-air mixture at a supersonic speed in both longitudinal directions, with almost instantaneous (explosive) fuel combustion occurring, accompanied by a significant increase in temperature and pressure of the combustion products. The detonation wave, meeting with the supersonic flow of the working mixture, forms a "gas shutter", which blocks the path of the supersonic flow of the working mixture into the resonator. After reflection from the bottom wall, the detonation wave turns into a reflected shock wave, which moves along the burnt mixture toward the outlet and carries the combustion products along, releasing them into the atmosphere at supersonic speed. The impact of the detonation wave on the inner bottom surface of the resonator creates traction. The reflected shock wave is followed by a rarefaction wave, which, passing by the annular nozzle and having a pressure lower than the atmospheric pressure behind the front, ensures the opening of the “gas lock” and the absorption of a new portion of the working mixture. The process is then repeated.

The disadvantages of such a pulsating detonation engine are:

- decrease in efficiency the engine due to the consumption of part of the fuel during the pyrolysis of fuel in the reactor for decomposition of the fuel-air mixture into chemically active components;

- the Hartmann gas-dynamic valve does not completely exclude the penetration of the detonation combustion front through the annular nozzle into the reactor;

- the kinetic energy of the reflected shock and detonation waves from the bottom surface of the resonator into electrical pulse energy is not converted.

According to the greatest number of similar features, this technical solution is selected as a prototype.

The aim of creating the proposed pulsating detonation engine is to simplify the design, improve weight and size and operational parameters, increase specific traction characteristics.

The proposed pulsating detonation engine includes two main components: a reactor and a resonator.

In the reactor, to increase the efficiency of combustion, a mixture of oxidizing agent and fuel is preliminarily prepared. In the resonator, as a result of intersections of the jets of the mixture leaving the annular nozzle at a supersonic speed, the combustion process automatically occurs and shock and detonation waves are formed.

Combustion as an elementary chemical reaction can occur only in the volume where there is a collision of fuel molecules and an oxidizing agent.

The preparation of such a volume consists in the formation of the contact surface of the flows of oxidizing agent and fuel. It is possible to increase the area of the contact surface by generating vortex flows in the flows of fuel and oxidizer. In a perturbed turbulent flow, the contact surface areas of two media grow exponentially. The increase in the area of the contact surface contributes to the intensification of the process of mixing fuel and oxidizer.

The main link in the preliminary preparation of the oxidizing agent and fuel mixture is the activation of the mixture molecules by modernizing their electronic nuclear structure. The total binding energy in the activated molecule is significantly less than in the same molecule in the free ground state. In the activated molecule, the internuclear distances are increased, so that when the chemical reaction of combustion is completed, they completely leave each other and become parts of new final molecules. Activation is a decrease in the energy barrier of mixture molecules caused by exposure to its molecules by electromagnetic radiation or other types of effects.

Thus, to ensure preliminary preparation of the mixture in the reactor in order to increase the combustion efficiency in the resonator, it is necessary:

- create a vortex mixture of oxidizer and fuel;

- to carry out the activation of the molecules of the mixture by exposing them to electromagnetic radiation or a stream of various elementary particles.

Vortex mixing can be carried out by tangential introduction of fuel into the reactor volume and longitudinal introduction of an oxidizing agent, at which their jets intersect. The activation of the molecules of the mixture can be ensured by exposure to electromagnetic radiation.

In the proposed application, the technical implementation of the preliminary preparation of the mixture of oxidizer and fuel is carried out by installing in the reactor inlet fuel pipes tangentially directed along the inner cavity of the reactor and a longitudinally directed pipe of the oxidizing agent. When oxidizing agent and fuel are fed into them, a swirling flow swirling occurs in the reactor, providing intensive circular mixing. To activate the mixture in the reactor, electromagnetic action is applied to the oxidizer and fuel molecules by applying current pulses to the electrodes. In the presence of a magnetic field in the region of the electrodes, secondary vortex flows of the mixture flow arise, generated by the interaction of the electric discharge current with the magnetic field (Klementyev IB et al. “Interaction of an electric discharge with a gas medium in an external magnetic field and the effect of this interaction on flow structure and mixing ”, Thermophysics of High Temperatures, 2010, No. 1).

Since the lifetime of the activated states of the molecules is short, activation is carried out immediately before the mixture is fed into the resonator; therefore, a permanent magnet and electrodes are placed on the critical section of the annular nozzle. Activation is carried out during the duration of the current pulses supplied to the electrodes. The required power of such pulses is small, since the oxidizing agent and fuel are already mixed, and a small volume of the mixture located in the space of the critical section of the nozzle is subjected to activation. In this case, the pulse power must also be low so that during activation the process of ignition of the mixture does not occur.

The means of pulse activation of the mixture of oxidizer and fuel are electrodes placed in the reactor at the outputs of the Hartmann ring nozzle, which are connected to the electrical output of the piezoelectric generator.

The resonator is made of non-magnetic material in the form of a pipe of smaller diameter and is placed in the reactor tube so that the output of the Hartmann annular nozzle is directed into the internal cavity of the resonator.

The concave bottom of the resonator is made of two parts separated by a buffer, the inner part is made of material that can withstand high pulsed mechanical loads, and the outer part is made of a block of piezoelectric elements connected electrically in parallel, which together with the resonant circuit of the piezoelectric generator.

Mechanical shock effects of detonation and shock waves due to shock depolarization of a ferroelectric are converted into pulsed electrical energy. A piezoelectric generator consists of a block of piezoelectric elements connected in parallel and a resonant circuit.

In the resonator during the interaction of supersonic jets of the activated mixture emerging from the annular nozzle, a chemical ignition reaction of the mixture and a shock wave are initiated, which, after reflection from the concave bottom of the resonator, focuses and, creating a high temperature and pressure at the focusing point, causes detonation combustion and propagation of the detonation wave in both longitudinal directions. After the release of combustion products at a supersonic speed into the atmosphere, a rarefaction wave occurs, which ensures the absorption of a new portion of the activated mixture, and the process repeats.

The first version of a pulsating detonation engine consists of:

- housing;

- means for supplying fuel and oxidizer to the reactor;

- a reactor in the form of a pipe into which the air-fuel mixture enters in front and its rear end is bent inward and forms a Hartmann ring nozzle;

- means of pulse activation of the air-fuel mixture placed in the reactor at the exits of the Hartmann ring nozzle;

- a resonator made of non-magnetic material in the form of a pipe of smaller diameter placed in the reactor pipe. The front end of the resonator pipe has a concave bottom, and the rear is connected to the output of the annular nozzle;

- on the inner surface of the resonator there is a roughness in the form of a cut, on the outer surface of the resonator there are two permanent magnets that create a magnetic field inside the resonator directed perpendicular to its longitudinal axis;

- the concave bottom of the resonator consists of two parts separated by a buffer, providing a decrease in the force of impact. The inner part is made of material that can withstand high pulsed mechanical loads, and the outer part is made of a block of piezoelectric elements connected in parallel, providing the conversion of the kinetic energy of the shock wave into electrical energy;

- the electrical output of the piezoelectric generator is connected to the inputs of the pulse activation of the fuel-air mixture.

The second version of the device differs from the first in that:

- the point of intersection of the jets of the ionized fuel-air mixture flowing from the Hartmann nozzle is aligned with the focus point of the reflected shock wave. This combination improves the conditions for the detonation wave;

- the resonator output is made in the form of an expanding jet nozzle, providing additional gas-dynamic acceleration of the working fluid (ionized gas stream);

- on the outer surface of the jet nozzle there are two permanent magnets that create a magnetic field inside the nozzle, directed perpendicular to its longitudinal axis;

- on the inner surface of the resonator there is no roughness in the form of a cut.

New significant features of both devices are:

- placing the resonator in the form of a pipe of a smaller diameter in the reactor tube so that the output of the annular nozzle is directed into the internal cavity of the resonator;

- installation on the outer surface of the resonator or jet nozzle of two permanent magnets that create a magnetic field inside the resonator or nozzle, directed perpendicular to their longitudinal axis;

- manufacture of a concave bottom of the resonator from two parts, separated by a buffer that reduces shock loads. The inner part of the bottom is made of material that can withstand high pulsed effects of detonation waves, and the outer part is made of a block of piezoelectric elements connected in parallel, forming a piezoelectric generator;

- the output of the pulse current source is connected in series with the inputs of the pulse activation means located in the reactor at the outputs of the Hartmann ring nozzle.

The technical result that can be obtained by implementing a set of features is as follows:

- preliminary preparation of the mixture due to its vortex mixing and activation, as well as the design features of the resonator and reactor, increase the combustion efficiency and power of detonation waves, which increase the traction force and specific traction characteristics of the engine;

- the kinetic energy of the shock waves at the bottom of the resonator was previously used only to create traction, in the proposed device it is still converted into electrical energy, which is used to activate the mixture of oxidizer and fuel. This technical solution leads to a decrease in the overall dimensions of the engine and simplifies its design.

The invention is illustrated by drawings, where Fig. 1 shows a first embodiment of a device, Fig. 3 a second embodiment of a device, and Fig. 2 a diagram of a pulsed current source and its connection with activation means.

The devices include a housing 1, a reactor 2, filled with an oxidizing agent and fuel with a block 11, into which easily ionized additives are introduced, a pulse means for activating the fuel-air mixture 3, an annular nozzle 4, permanent magnets 5, a jet nozzle 7, or a roughness in the form of a cut 7 on the inner surface of the resonator 6 for turbulization of the gas stream. The bottom of the cavity consists of three parts. The inner part of the bottom 8 is made of high-strength material, the intermediate part is a buffer 9 to reduce the impact force on the piezoelectric elements, the outer part is in the form of a piezoelectric generator 10 with a resonant circuit 13. To strengthen the structure, the reactor and the resonator are connected by an annular strut 12, through which openings pass wires sequentially connecting the output of the piezoelectric generator 10 with the electrodes of the activation means.

The operation of a pulsating detonation engine begins with filling the reactor 11 with a block 11 under pressure with an oxidizing agent and fuel through tangentially and longitudinally directed nozzles. The jets of fuel, rotating, intersect with the stream of oxidizing agent, forming a vortex mixing.

From an external source, a triggering series of pulses is supplied to the fuel activation means 3, which ensure the decomposition of the fuel-air mixture at the outlet of the Hartmann nozzle into chemically active components. The ionized fuel-air mixture flows at a supersonic speed from the nozzle in the form of radial jets directed into the internal cavity of the resonator 6.

When they collide and mix, a chemical reaction of ignition of the fuel is initiated and a shock wave occurs, moving towards the bottom of the resonator 6.

The roughness of the inner walls 7 of the resonator 6 provides a high intensity of turbulent mixing in the shear layers due to vortex movements in the area behind the obstacles and due to the generation of transverse shock waves.

“Hot spots” arise between the accelerated turbulent combustion zone and the head shock wave due to the inhomogeneity of the flow on the contact surfaces formed by roughness 7. In such local exothermic centers, detonation arises.

In addition, the head shock wave, after reflection from the concave bottom of the resonator, is focused and, creating high temperature and pressure in this place, ensures the occurrence of detonation combustion and propagation of the detonation wave in both longitudinal directions. In the second embodiment of the device, when combining the point of intersection of the jets with the focus point of the reflected shock wave, the need for roughness of the inner surface of the resonator disappears.

Strongly ionized gas flows following detonation waves, passing through a magnetic field, cause the occurrence of forces acting on them in the direction of motion. As a result, the speeds of flows moving both towards the bottom of the resonator and in the opposite direction to the exit from the resonator increase.

After reflection from the bottom, the detonation wave becomes a reflected shock wave and, together with the ionized gas stream, passing through a magnetic field, increases the speed of the gas stream in the direction of exit from the resonator. The output of the resonator 6 is made in the form of an expanding jet nozzle, providing a further increase in the velocity of the outgoing gases.

During the mechanical action of the detonation wave at the bottom of the resonator, the depolarization of the elements of ferroelectrics occurs, made in the form of a block of several identical plates connected electrically in parallel and located relative to each other, as shown in Fig.2. Such a piezoelectric generator creates current pulses, the amplitude of which increases when tuning circuit 13 to resonance. Pulses with a frequency of detonation processes are fed to the input of the fuel activation devices, providing decomposition of the fuel-air mixture into chemically active components.

After the release of combustion products at a supersonic speed into the atmosphere, a rarefaction wave occurs. The reduced pressure in the cavity of the resonator ensures the absorption of a new portion of the activated mixture and the process is repeated.

The implementation of the claimed technical solution is not in doubt, since its manufacture will use well-known technologies for organizing detonation processes and converting detonation wave energy into electrical energy (Electrical phenomena in shock waves / Edited by V.A.Borisenka et al. - Sarov: RFNC- VNIIEF, 2005).

It was shown that explosive piezoelectric generators have optimal characteristics as current pulse generators, the power of which reaches several megawatts, energy - tens of joules, so they will ensure the effective operation of pulse activation means.

Claims (5)

1. A pulsating detonation engine containing a housing, means for supplying fuel and oxidizer to the reactor, an annular nozzle and a gas-dynamic resonator, characterized in that the resonator in the form of a pipe of smaller diameter is placed in the reactor tube so that the exit of the Hartmann ring nozzle is directed into the internal cavity resonator, and the concave bottom of the resonator is made of two parts separated by a buffer, the inner part is made of material that can withstand high pulsed mechanical loads, and the outer part is made of zoelektricheskih elements connected electrically in parallel, which are together with the resonant circuit pezogeneratorom. 2. The pulsating detonation engine according to claim 1, characterized in that on the outer surface of the resonator or jet nozzle there are two permanent magnets that create a magnetic field inside the resonator directed perpendicular to their longitudinal axis. 3. The pulsating detonation engine according to claim 1, characterized in that the output of the piezoelectric generator is connected to the inputs of the pulse activation means. 4. The pulsating detonation engine according to claim 1, characterized in that the resonator is designed so that the intersection point of the jets of the fuel-air mixture flowing from the annular nozzle and the focus point of the reflected shock wave are combined. 5. The pulsating detonation engine according to claim 1, characterized in that the means of pulse activation are located at the outputs of the Hartmann ring nozzle.

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