RU2567528C2 - Acoustic oscillation generator for supersonic air breather engine combustion chamber - Google Patents

Abstract

FIELD: aircraft engineering.

SUBSTANCE: claimed generator comprises ignition plug, fuel atomisers, shaped geometry of flow section, mixing chamber, vortex chamber, outlet diffuser, blade-type swirler and supersonic diffuser.

EFFECT: decreased emission of nitrogen oxides, higher fuel efficiency, no power consumption for pressure development.

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Description

The invention relates to the field of aircraft engine manufacturing and can be used in the combustion chamber of a hypersonic jet engine.

A known combustion chamber of a hypersonic ramjet engine (SCJP) with a combustion stabilizer, which is a ledge located on the wall of the chamber (US patent No. 5097663, CL F02K 7/10, 1992).

The disadvantage of this device is the large hydraulic losses, resulting in a decrease in specific traction characteristics. Oblique shock waves complicate the organization of combustion over the entire cross section of the chamber, and also reduce the stability of the boundary layer to perturbations in the flow.

The closest in technical essence to the proposed device is a device for stabilizing combustion in a supersonic flow (patent RU 2119118 C1, 09/20/1998), designed to increase the effective stabilization of diffusion combustion, containing a main nozzle, a shell, a pipe with an additional nozzle for supplying liquid or gaseous fuel.

The main and main drawback of this design is diffusion combustion, which, as you know, causes the formation of a large amount of nitric oxide NO _x . In addition, the flame propagates in the limited axial region of the combustion chamber, which is probably not able to ignite a significant amount of fuel in the undisturbed stream. There is a possibility of low combustion in the stabilizing torch itself. Significant energy consumption is required when creating an air flow with a pressure sufficient to attach the boundary of the jet to the shell.

The technical result of the invention is to reduce the emissions of nitrogen oxides, increase the completeness of fuel combustion both in the volume of the undisturbed flow and in the flow part of the acoustic oscillator itself, minimizing the energy consumption to create the necessary pressure.

The technical result of the proposed technical solution is achieved by the fact that the acoustic oscillation generator containing the spark plug further comprises fuel nozzles, a profiled geometry of the flow part, a mixing chamber, a swirl chamber and an output diffuser, a blade swirl device, a supersonic diffuser.

Reducing the concentration of nitrogen oxides is achieved using fuel nozzles; increasing the completeness of fuel combustion both in the volume of the undisturbed flow and in the flow part of the acoustic oscillator generator itself is achieved due to the content of the mixing chamber, the swirl chamber and the outlet diffuser, and the blade swirl device in the geometry of the flow part; the pressure in the mixing chamber rises due to the organization of the compression process in a supersonic diffuser.

The invention is illustrated in the drawing, where the drawing shows a longitudinal section of an acoustic oscillator for a combustion chamber scramjet.

The acoustic oscillation generator 1 is attached to the housing of the combustion chamber 2 using six pylons 3, in the housing of which there is a channel 4 for connecting the fuel manifold 5, fuel nozzles 6 and the mixing chamber 7. For braking the supersonic flow in the acoustic oscillation generator 1 there is a supersonic diffuser 11, consisting of a central body 12 of the shell 13. The flow part of the acoustic oscillation generator 1 consists of a blade swirl device 14, a mixing chamber 7, a swirl chamber 8, an output diffuser 9 and a spark plug 1 0.

The generator of acoustic vibrations for the combustion chamber scramjet is as follows.

The supersonic air flow (M ~ 2 ... 5) from the scramjet air intake 15 enters the flow path 16 of the combustion chamber 2. Next, a small part of the flow (~ 10 ... 11%) enters the acoustic oscillator 1 through a supersonic diffuser 11. Due to the formation between the edge of the shell 13 and the central body of a series of 12 conical shock waves, in accordance with Bernoulli’s law, the flow rate decreases and the total pressure rises, while no additional systems are involved, which minimizes the energy consumption for creating the necessary pressure and I. Passing through the blade swirl device 14, the flow acquires a swirling character and enters the mixing chamber 7.

The fuel from the fuel manifold 5 through the channel 4, which passes through the pylon 3, is divided into two parts: one enters the fuel nozzles 6. It is due to their presence that a local reverse current zone (vortex) is generated when the air flows around the pylons 3, which increases the mass transfer rate of the fuel , and air. As a result, a pre-mixed air-fuel mixture is obtained, during combustion of which (in contrast to diffusion combustion), local high-temperature regions are not formed, as a result of which the formation of nitrogen oxides is reduced.

The second part of the fuel flow enters (also through channel 4) into the mixing chamber 7, where it is mixed with the swirling air stream passing through the blade swirling device 14. By organizing the swirling flow, the residence time of the fuel in the mixing chamber increases, which improves the quality of mixing and, as consequence, increases the completeness of fuel combustion in the flow part of the generator of acoustic vibrations 1.

Further, the air-fuel mixture, passing in a swirling flow through the vortex chamber 8, enters the outlet diffuser 9. Due to the fact that the flow of the air-fuel mixture in the acoustic oscillation generator 1 is constant, and the passage area of the vortex chamber 8 is less than the area of the mixing chamber 7, the flow velocity (especially radial and tangential components) in it (vortex chamber 8) increases. As a result, after the vortex chamber 8, the flow tends to the periphery of the output diffuser 9, and a toroidal secondary vortex is formed, which has an unsteady character. In the center of the vortex, a region of pressure pulsations is formed, causing acoustic vibrations that propagate further downstream. Ignition in the generator of acoustic vibrations 1 is carried out by the spark plug 10. The mixing chamber 7 is profiled with a vortex chamber 8 using a Bernoulli lemniscate; the vortex chamber 8 and the output diffuser 9 are profiled with each other using a mating radius - these factors improve the aerodynamic characteristics of the flow part of the acoustic oscillation generator 1 - this leads to a decrease in energy loss and, as a result, to an increase in the intensity of acoustic vibrations. The propagating oscillations cause the formation of local rarefaction regions; as a result, small-scale reverse current zones are generated, which increase the residence time of the air-fuel mixture in the combustion zone, the quality of mixing, and, as a result, increase the completeness of fuel combustion in the stream. Thus, it is the presence of profiled mixing chambers, a vortex chamber, and an output diffuser that provides an increase in the completeness of combustion in the entire volume of the combustion chamber.

Claims (1)

An acoustic oscillation generator for a scramjet combustion chamber containing a spark plug, characterized in that it further comprises fuel nozzles, a profiled geometry of the flow part, a mixing chamber, a vortex chamber and an output diffuser, a blade swirl device, a supersonic diffuser.
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