RU2446305C2 - Supersonic ramjet engine with pulsating combustion and method of its operation - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: fuel for starting said engine is fed into combustion chamber uniform cross-section part first zone to initiate pulsating combustion with intermittent formation of wave structure of pseudo-discontinuity type from thermal gas-dynamic pulses, for example, plasma, shock wave, gas jet of inert or reacting medium intensifying combustion. Combustion conditions are varied from diffusion combustion to pseudo-discontinuity combustion and back when leading edge of pseudo-discontinuity approaches fuel feed point, or used is combined intermittent diffusive- pseudo-discontinuity, or quasi-stationary pseudo-discontinuity with varying thermal gas-dynamic pulses frequency in uniform cross-section part of the combustion chamber. Note here that initiator of pulsating combustion is arranged at the end of uniform cross-section part and comprises generator of power thermal gas-dynamic pulses with elements of intermittent feed of pulses connected via pulsating combustion control system with pressure wave registration pickups on said uniform cross-section part. Further engine operation is maintained by feeding fuel into the next areas of combustion chamber variable cross section areas.

EFFECT: higher efficiency of engine.

2 cl, 8 dwg

Description

The invention relates to the WFD classes, conventionally called "pulsating engines" (PuVRD) and "pulsating detonation engines" (SDA). A feature of the operation of such engines is the implementation of a pulsating combustion mode due to the organization of periodic input of fuel and an oxidizer into the combustion chamber, the implementation of resonant, vibrational combustion modes, or (in SDA) the combustion of a fuel-air mixture in detonation waves. In this case, mechanical (valve) systems are used to control the periodic cycle of the process (filling the chamber with fuel and oxidizing agent, initiating and flowing combustion, expiration of combustion products) or gas-dynamic, valveless. A detailed review of the work in this direction is given in: "Pulsed and Continuous Detonations." G. Roy, S. Frolov, J. Sinibaldi. Torus Press Publishers. Moscow 2006. Examples of a running engine are described in AIAA Paper 2004-3402, and flight tests in Pulse Power: Pulse Detonation Engine-powered Flight Demonstration Marks Milestone in Mojave, Norris, G., Aviation Week & Space Technology, Vol.168, No.7, 2008, pp.60. The main disadvantage of technical solutions for such methods of organizing the working process in combustion chambers is the restriction on the use of once-through circuits in engines for flying aircraft with hypersonic speed (Mach number more than 4.5-5.0). The limitation is due to large losses in total pressure due to the need to slow down the air flow to subsonic speeds and, as a result, to reduce the efficiency (specific impulse) of the engine.

A technical solution is known (patent RU No. 2347098 C1, F02K 7/02, 2007), in which the pulsating combustion mode is carried out by pulse-periodic supply of fuel to several expanding sections of the combustion chamber. In this case, the quantity and frequency of fuel supply in each section is set from the condition of preserving the supersonic velocity of the unsteady flow along the entire channel of the combustion chamber. The main disadvantages of this technical solution are the high initial values of flight speeds (Mach numbers M> 6-7) and the lack of tools that provide high completeness of fuel combustion.

The invention is known, selected for the prototype (patent RU 2157909 C1, 05.26.1999), which proposes a solution to the problem of increasing the specific impulse of a ramjet engine when flying at hypersonic speeds (for a hydrogen-air engine with flight Mach numbers M from 4.5 to 7.5 ) The effect is achieved by burning a mixture of hydrogen with air in a detonation wave propagating up and down the supersonic flow in a constant-section combustion chamber during periodic enrichment or depletion of a combustible mixture by changing the amount of hydrogen supplied to the chamber. The effect is based on the realization of Chapman-Jouguet detonation, when the speed of the combustion products behind the wave is equal to the speed of sound. In this case, the combustion mode is implemented with minimal loss of total pressure. However, experiments have shown (see Structure and Propagation of Detonations in Gaseous Mixtures in Supersonic Flow. JC Bellet and G. Deshayes. Astronautica Acta. Vol.15, pp. 465-469. Pergamon Press 1970; ISABE-2005-1050, VGAlexandrov, ANKraiko, KSPyankov, KSReent, et al .; Detonation waves in a reacting supersonic flow. A.A. Vasiliev, V. I. Zvegintsev, D. G. Nalivaychenko. FGV. T.42, No. 5, p. 85-100, 2006), under real conditions in a supersonic flow when moving upstream of the air-fuel mixture, an over-compressed detonation wave propagates, and downstream - under-compressed. This leads to a noticeable increase in total pressure losses (when moving upstream) and a decrease in combustion efficiency (when moving downstream). It should be noted that in the experiments it is not possible to obtain a pulsating flow regime, as proposed in the technical solution. The authors consider the application of this technical solution for a hydrogen-air engine with flight numbers M from 4.5 to 7.5. The use of other types of fuel (for example, hydrocarbon) with such an organization of the process is unlikely due to the low propagation velocity of detonation waves.

The objective of the proposed technical solution is to increase the efficiency of the engine.

The present invention will increase the specific impulse of the engine when flying at high supersonic speeds, reduce heat loss in the walls of the combustion chamber, as well as reduce the length of the insulator and ensure a smooth start of the engine (without disturbing the flow at the inlet to the air intake). In the engine, in addition to hydrogen, hydrocarbon fuels for flight with a Mach number M from 5-5.5 to 7.5-8.0 can be used.

The technical result is achieved in a supersonic ramjet engine with a pulsating combustion mode (SPVRD with PRG) containing a supersonic air intake, an insulator, a supersonic combustion chamber, consisting of sections of constant and variable section, a supersonic nozzle, several fuel supply belts located along the length of the chamber of combustion, a device for initiating a pulsating combustion mode and sensors for detecting the passage of pressure waves in a section of a combustion chamber of constant cross section, the first belt under fuel is located at the beginning of the constant section, and the subsequent sections of the variable section of the combustion chamber, and the pulsating combustion initiation device is installed at the end of the constant section and contains a generator of energy thermodynamic pulses with elements of periodic pulse input connected through the pulsating mode control system combustion, with sensors for detecting the passage of pressure waves in the area of the combustion chamber of constant cross section.

The technical result is also achieved in the method of operation of a supersonic ramjet engine with a pulsating combustion mode (SPVRD with PRG), which consists in the fact that the fuel for starting the engine is supplied to the first belt of the constant section section of the combustion chamber and a pulsed combustion mode with periodic wave formation is initiated structures such as a pseudo-jump from a generator of heat-gas-dynamic pulses, for example, plasma, shock waves, inert or reactive gas jets, intensification of combustion, realizing on a constant section of the combustion chamber a change in the combustion mode from diffusion to pseudo-jump and vice versa when the head of the pseudo-jump approaches the place of fuel supply, or a mixed periodic diffusion-pseudo-jump, or quasistationary pseudo-jump, when changing the frequency of thermodynamic pulses, with further work the engine is supplied with fuel to subsequent belts of sections of variable section of the combustion chamber.

The basis of the proposed technical solution is the creation of a pseudo-hopping combustion regime in a channel of constant cross section, which can only be supported if there is an external energy effect on the flow. The flow parameters at the entrance to the channel are such that the initiation and development of diffusion combustion of fuel occurs. The amount of fuel supplied is determined by thermal blocking of the flow. The length of the constant section of the channel is chosen approximately equal to the length of the pseudo-jump with the complete combustion of this fuel. With a pulse-periodic energy (of a certain intensity) effect on the flow, combustion can be transferred from the diffusion mode to the pseudo-jump mode. At the same time, at the end of the pseudo-jump, approximately sound flow velocity will be set. The pseudo-jump combustion mode will go into diffusion mode when the head of the pseudo-jump moves to the fuel injection site due to the deterioration of the mixing process. The pseudo jump will fluctuate in the channel with a period equal to the period of the energy impact. The pulse duration and the magnitude of the period are associated with the energy necessary for the formation of the pseudo-jump, and determine the speed of its movement towards the flow.

The invention is a new scheme of a ramjet engine with a flow in the combustion chamber close to the speed of sound (M≥1.0) and with combustion in a pulsating wave structure of the pseudo-jump type - "supersonic ramjet engine with a pulsating combustion mode - SPVRD with PWG. " In SPARS with PRG, a pulsating non-stationary process is initiated by pulse-periodic heat-gas-dynamic pulses, which cause the formation of a pseudo-hopping combustion regime pulsating in a constant section of the combustion chamber.

Figure 1 shows the General scheme of the engine SPVRD with PRG; figure 2 - when the fuel is supplied to the first belt, the diffusion mode of combustion is implemented; figure 3 - wave structure when applying an energy pulse, the formation of a pseudo jump; 4 is a pseudo-hopping combustion mode with fuel supply to the second belt; figure 5 - diffusion mode of combustion; 6 is a diffusion-pseudo-hopping combustion mode upon termination of the pulse input; Fig.7 - diffusion-pseudo-hopping combustion mode with the introduction of the pulse; Fig - quasistationary combustion mode.

A supersonic ramjet engine with a pulsating combustion mode (SPVRD with PRG) contains a supersonic air intake 1, insulator 2, a supersonic combustion chamber, consisting of sections of constant 3 and variable 4 sections, a supersonic nozzle 5, several fuel supply belts 6, 7 and a device initiation of a pulsating combustion mode, consisting of a generator of energy thermodynamic pulses 8 with elements of periodic input of pulses 9, connected through a control system of a pulsating mode g 10 rhenium sensors registering the passage of pressure waves 11 in the region of constant cross section of the combustion chamber.

SPRDD with PRG operates as follows:

1. The incoming air flow (with a Mach number M = 5.0-8.0) is inhibited in the air intake 1 (Fig. 1) and insulator 2 and enters the constant section of the combustion chamber 3, while maintaining a supersonic speed with parameters providing ignition of fuel in conjunction with the design features of the elements of its supply.

2. Fuel is supplied through the first belt 6. Its amount is determined by the flow parameters at the entrance to the combustion chamber and from the condition of "thermal" locking of the flow in the constant section 3 of the chamber with complete combustion of fuel. In this section 3, fuel ignition occurs and a combustion mode is established, depending on the parameters of the thermodynamic pulses that the generator 8 forms (Fig. 2). Depending on the phase of the combustion mode, a change in the pulse parameters occurs. Thus, the control of the combustion mode is carried out by controlling the pulse generator.

3. The phases of the combustion regime are as follows.

3.1. In the output section of the constant section section of the combustion chamber from the generator 8, an energetic thermodynamic pulse is supplied through the elements of the periodic input 9 (Fig. 3), for example, in the form of a plasma (from a pulse-periodic plasmatron), a shock wave (from a detonation tube), inert or reacting jet, a medium conducive to intensification of combustion.

3.2. The impact of the pulse leads to inhibition of the supersonic flow and the formation of a wave structure such as a pseudo-jump, which leads to intensive combustion of fuel (see Figs. 3, 4), since the presence of such a structure improves the process of mixing it with air. There is a transition from a diffusion combustion regime to a pseudo-hopping one. The pseudo jump moves to the entrance to the combustion chamber due to increased pressure in the chamber (in the intense combustion zone).

3.3. When the pseudo-jump reaches the specified section of the constant section of the combustion chamber, determined by the duration and energy of the pulse, its further movement towards the flow stops due to insufficient braking (pressure increase in the combustion zone) of the flow from the combustion, and the wave structure drifts downstream during the period determined pulse repetition rate, as an example, diffusion combustion mode is possible (Fig. 5).

3.4. At the moment when the wave structure reaches a predetermined section near the exit from the constant section section of the chamber (Fig. 6) or the exit from it (as shown in Fig. 5), the next thermodynamic pulse is applied and a new phase of the combustion regime begins. The pseudo jump will fluctuate in the channel with a period equal to the period of the energy impact. Several pulsating combustion modes are possible. The transition from diffusion combustion to pseudo-jump and vice versa (at low frequencies, the pseudo-jump fluctuates with an amplitude close to the length of the constant section section). Mixed (diffusion-pseudo-jump), when with increasing frequency the pseudo-jump does not return to the end of the constant section (the extreme positions of the pseudo-jump are shown in Figs. 6, 7). Quasistationary, when the pseudo-jump maintains its position in the channel at a high pulse frequency (Fig. 8). The main advantage of this method of organizing combustion is the achievement of high efficiency of the process, which is determined by the minimum loss of total pressure and the maximum temperature increase. The flow rate behind the jump is close to the speed of sound. This mode corresponds to the maximum value of the total pressure recovery coefficient.

4. The further operation of the engine is ensured by the supply of fuel to the subsequent belts of the sections of the variable section of the combustion chamber (if necessary, to ensure the specified coefficient of excess air). The start of the fuel supply is preferably in the phase of the pseudo-hopping combustion mode in the constant section of the combustion chamber (see FIG. 4). The degree of expansion of the variable cross section is selected from the condition of ensuring an average speed close to the speed of sound (M≥1.0).

The pulsating combustion mode in the constant section section of the combustion chamber will help to improve the fuel mixing process in the variable section section and, consequently, reduce the length of the combustion chamber (decrease its surface) and reduce heat losses in the wall, as well as hydraulic resistance.

The implementation of the pseudo-hop mode with sound speed at the end of the constant section of the combustion chamber makes it impossible for high pressure to enter the insulator and to disrupt the flow in the air intake. This allows you to ensure a smooth start of the engine and reduce the length of the insulator, which for the marked values of the flight Mach numbers is more than 12 channel calibres.

All these effects contribute to improved traction characteristics of the engine.

Information sources

1. Pulsed and Continuous Detonations. "G. Roy, S. Frolov, J. Sinibaldi. Torus Press Publishers. Moscow 2006.

2 Patent RU No. 2347098 C1, F02K 7/02, 2007

3. Patent RU 2157909 C1, 05/26/1999 - prototype.

4. Detonation waves in a reacting supersonic flow. A.A. Vasiliev, V.I. Zvegintsev, D.G. Nalivaychenko. FGV. Vol. 42, No. 5, pp. 85-100, 2006.

Claims (2)

1. A supersonic ramjet engine with a pulsating combustion mode (SPVRD with PRG), containing a supersonic air intake, an insulator, a supersonic combustion chamber, consisting of sections of constant and variable section, a supersonic nozzle, several fuel supply belts located along the length of the combustion chamber, device for initiating a pulsating combustion mode and sensors for detecting the passage of pressure waves in a section of a combustion chamber of constant cross section, characterized in that the first belt for supplying fuel located at the beginning of the constant section, and the subsequent sections of the variable section of the combustion chamber, while the pulsating combustion initiation device is installed at the end of the constant section and contains a generator of energetic thermodynamic pulses with elements of periodic pulse input connected through a pulsed combustion control system with sensors for recording the passage of pressure waves in a section of a combustion chamber of constant cross section. 2. The method of operation of a supersonic ramjet engine with a pulsating combustion mode (SPVRD with PRG), characterized in that the fuel for starting the engine is fed into the first belt of the constant section section of the combustion chamber and a pulsed combustion mode is initiated with periodic formation of a pseudo-jump wave structure from heat-gas-dynamic pulses, for example, plasma, shock waves, gas jets of an inert or reacting medium that promotes combustion intensification, realizing in a section of constant cross section I of the combustion chamber, a change in the combustion mode from diffusion to pseudo-jump and vice versa when the head of the pseudo-jump approaches the place of fuel supply, or a mixed periodic diffusion-pseudo-jump, or quasistationary pseudo-jump when the frequency of thermodynamic-gas pulses changes, while the further operation of the engine is ensured by the fuel supply to subsequent zones variable section of the combustion chamber.

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