A low-drag shock wave generator for supersonic combustion flame stabilization enhancement

Abstract

The present application belongs to the technical field of scramjet combustion chambers and relates to a low-drag shock wave generator for enhancing supersonic combustion flame stabilization, comprising: a shock wave generator disposed on a fuel injection section of a scramjet combustion chamber, the fuel injection section connected to an isolation section and a concave section of the scramjet, and the fuel injection section expanding along the isolation section toward the concave section; the shock wave generator comprising: a first portion, a second portion, and a third portion connected in sequence; one end of the first portion connected to the isolation section and having an inclination toward the central axis of the scramjet combustion chamber; the second portion being an arc-shaped structure concave toward the central axis of the scramjet combustion chamber; and the third portion having the same shape and size as the second portion, with one end of the third portion being tangent to the second portion. The present application can improve the combustion stability and combustion efficiency of a scramjet engine.

Description

Technical Field

[0001] The present application relates to the technical field of scramjet engine combustion chambers, and in particular to a low-drag shock wave generator for enhancing flame stabilization of supersonic combustion. Background Art

[0002] At present, conventional scramjet engines have a high risk of flame flashback and flameout when operating at low equivalence ratios.

[0003] Existing technology uses a simple geometric form to generate strong oblique shock waves in the engine's flow path, compressing the incoming air and increasing its static temperature and pressure. With proper design, shock wave generators are expected to further improve combustion efficiency while maintaining controllable resistance and losses, thereby enhancing engine combustion.

[0004] For example, in his 2015 doctoral dissertation, "Study on the Organizational Structure of the Flow Field of Shock Wave / Turbulent Boundary Layer Interaction," Wang Bo designed a shock wave generator mounted on the inner wall of the combustion chamber. This design primarily generates shock waves to induce boundary layer transition, a method for controlling the boundary layer flow within the engine. In his 2021 doctoral dissertation, "Research on the Mechanism and Enhancement Method of Ramjet Mode Flame Stabilization in Rocket-Based Combined Cycle Engines," An Bin proposed a scheme for installing wedge-shaped shock wave generators on both sides of the central fuel-air mixing reaction layer in the engine to enhance combustion downstream of the mixing layer. This scheme can expand the engine's effective combustion zone and improve its thrust performance.

[0005] However, the core flow combustion mode of the existing shock wave generator is not suitable for conventional scramjet engines, and the resistance and pressure loss of this scheme are relatively large. Summary of the Invention

[0006] Based on this, it is necessary to address the above technical problems and provide a low-resistance shock wave generator for supersonic combustion flame stabilization enhancement, which can improve the combustion stability and combustion efficiency of the scramjet engine.

[0007] A low-drag shock wave generator for flame stabilization and enhancement of supersonic combustion, wherein the shock wave generator is arranged on the fuel injection section of the scramjet combustion chamber, the fuel injection section is connected to the isolation section and the concave section of the scramjet engine, and the fuel injection section has an expansion trend along the isolation section toward the concave section;

[0008] The shock wave generator comprises: a first part, a second part and a third part which are connected in sequence;

[0009] One end of the first portion is connected to the isolation segment and has an inclination angle toward the central axis of the scramjet engine combustion chamber;

[0010] The second portion is an arc-shaped structure that is recessed toward the central axis of the scramjet engine combustion chamber;

[0011] The shape and size of the third portion are the same as those of the second portion, and one end of the third portion is tangent to the second portion.

[0012] In one embodiment, a series of nozzle holes are provided on the fuel injection section at positions corresponding to between the third portion and the concave cavity section, so that the fuel is distributed on a spanwise plane perpendicular to the center trace direction after being sprayed from the nozzle holes.

[0013] In one embodiment, the shock wave reflected by the shock wave generator intersects the center trajectory of the nozzle jet at the leading edge flow channel of the cavity.

[0014] In one embodiment, the inclination angle of the first portion ranges from 15° to 25°.

[0015] In one embodiment, the central angle of the arc-shaped structure ranges from 30° to 40°.

[0016] In one embodiment, the radius of the arc-shaped structure satisfies:

[0017] R(1-cosθ2)=h / 2

[0018] Where R is the radius of the arc-shaped structure, θ2 is the central angle of the arc-shaped structure, and h is the distance between the highest point of the shock wave generator and the wall of the fuel injection section.

[0019] In one embodiment, the distance between the highest point of the shock wave generator and the wall of the fuel injection section is 0.1 to 0.2 times the height of the outlet flow channel of the isolation section.

[0020] In one embodiment, the expansion angle range of the fuel injection section wall is 1° to 2°.

[0021] In one embodiment, the ratio of the height of the flow channel at the trailing edge of the cavity to the height of the flow channel at the inlet of the isolation section is in the range of: [1.25, 1.5].

[0022] In one embodiment, the cavity aspect ratio ranges from [6, 8].

[0023] The above-mentioned low-resistance shock generator for supersonic combustion flame stabilization enhancement uses the shock wave upstream of the fuel injection position to compress the incoming air, increase the static temperature and pressure of the air, and interact with the fuel mixing zone to enhance turbulent pulsation and mixing efficiency, reduce the risk of flame flashback and flameout in conventional wall-injection combustion chambers, and solve the problem of possible combustion oscillation caused by the inability of the concentrated heat release zone to be stable in space; with the help of the shock generator to generate pre-combustion oblique shock waves, considering the engine operating range and the Mach number of the incoming flow, the size and shape of the shock generator are matched and designed, while generating shock waves of sufficient intensity, bringing as little resistance and total pressure loss as possible, and utilizing the high temperature and high pressure area at the intersection of the shock wave and the wave system to promote the mixing and chemical reaction of the fuel jet in space, enhance the combustion robustness while increasing the combustion efficiency, and improve the overall performance of the engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic cross-sectional view of a scramjet engine combustion chamber equipped with a low-drag shock wave generator for enhancing supersonic combustion flame stabilization in one embodiment;

[0025] Figure 2 A diagram showing the nozzle positions and cross-sectional dimensions of a scramjet combustion chamber equipped with a low-drag shock wave generator for enhanced supersonic combustion flame stabilization in one embodiment;

[0026] Figure 3 Schematic diagram of a low-drag shock wave generator for supersonic combustion flame stabilization enhancement in one embodiment. Description of the drawings:

[0028] 1 - isolation section, 2 - fuel injection section, 3 - cavity section, 4 - expansion section;

[0029] l1 - length of the isolation section, l2 - length of the fuel injection section, l3 - length of the cavity section, l4 - length of the expansion section;

[0030] d1——the height of the flow channel at the inlet of the isolation section, d2——the height of the flow channel at the outlet of the isolation section, d 31 ——Height of the flow channel at the leading edge of the cavity, d 32 ——Height of the flow channel in the middle of the cavity, d 33 ——the height of the flow channel at the trailing edge of the cavity, d4——the height of the flow channel at the outlet of the expansion section;

[0031] α——inclination angle of the back wall of the cavity;

[0032] l jet —The distance between the center of the fuel injection hole and the leading edge of the cavity (the arrow represents the location of the fuel injection hole and the injection direction);

[0033] θ1 is the inclination angle of the front part of the shock wave generator, θ2 is the arc angle of the rear part of the shock wave generator, and θ3 is the expansion angle of the fuel injection section.

[0034] h is the height of the front part of the shock wave generator, R is the radius of the arc at the rear part of the shock wave generator. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely for explaining this application and are not intended to limit this application. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments in this application without creative work are within the scope of protection of this application.

[0036] It should be noted that all directional indications in the embodiments of the present application (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0037] In addition, the terms "first," "second," and so on, used in this application are for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, features specified as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of this application, "multiple groups" means at least two groups, such as two groups, three groups, and so on, unless otherwise specifically defined.

[0038] In this application, unless otherwise specified or limited, the terms "connect," "fix," etc. should be understood in a broad sense. For example, "fix" can mean a fixed connection, a detachable connection, or an integral connection; it can mean a mechanical connection, an electrical connection, a physical connection, or a wireless communication connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean internal communication between two elements or an interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0039] In addition, the technical solutions between the various embodiments of the present application can be combined with each other, but it must be based on the fact that ordinary technicians in this field can implement it. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0040] The present application provides a low-resistance shock wave generator for supersonic combustion flame stabilization enhancement, such as Figures 1 to 3As shown, in one embodiment, the scramjet engine includes: an isolation section, a fuel injection section, a cavity section, and an expansion section, which are connected in sequence from upstream to downstream.

[0041] The isolation section has an iso-straight configuration, and there is a pre-combustion shock wave train in the isolation section to reduce the incoming flow velocity and achieve pressure balance between low-pressure intake and high-pressure combustion.

[0042] A series of nozzle holes (i.e., fuel nozzle holes, used to inject fuel) are provided on the fuel injection section at the position between the third portion and the concave cavity section, so that the fuel is distributed on a spanwise plane perpendicular to the centerline after being ejected from the nozzle holes. The nozzle hole position is determined by the size of the thermal throat required for the actual cruise state. The length of the transverse flow channel at the upstream nozzle hole of the fuel injection section is l jet It is mainly determined by the thermal throat of the cruise state Ma=6 and affects the effect of the thermal throat to a great extent. (l jet The value range of +l3) / l3 is (1, 1.25], preferably 1.12. The nozzle holes are preferably round holes and hot oil nozzles. The distance from the nozzle hole to the front edge of the cavity is l jet As long as the flame stability of the combustion process is met, no key constraints are imposed. For a two-dimensional rectangular cross-section combustion chamber, the number of fuel injection holes is preferably 10; for a circular cross-section combustion chamber, the number of fuel injection holes is preferably 10; all nozzle arrangements are preferably uniformly distributed along the radial direction. The diameter of a single nozzle is preferably d jet ≤5mm. The nozzle configuration of all nozzle holes is preferably a sonic nozzle, which is set perpendicular to the axial direction at 90°.

[0043] The cavity section is equipped with a cavity flame stabilizer, which is mainly used for ramjet combustion organization within a certain range of flight Mach numbers (Ma4-6).

[0044] The expansion section connects the combustion chamber and the tail nozzle, and the airflow gradually increases in speed and decreases in pressure.

[0045] It should be noted that the engine configuration can be a rectangular cross-section or an axisymmetric circular cross-section; in the rectangular cross-section engine combustion chamber, the concave cavity is a structure symmetrically arranged on the upper and lower walls; in the axisymmetric circular cross-section engine combustion chamber, the concave cavity is an annular structure.

[0046] The shock wave generator is arranged on the fuel injection section of the scramjet engine combustion chamber, and the fuel injection section has an expansion trend along the isolation section toward the concave cavity section.

[0047] The shock wave generator comprises a first part, a second part and a third part which are connected in sequence.

[0048] One end of the first part is connected to the isolation segment and has an inclination angle toward the central axis of the scramjet engine combustion chamber.

[0049] The second part is an arc-shaped structure that is concave toward the central axis of the scramjet engine combustion chamber.

[0050] The shape and size of the third part are the same as those of the second part, and one end of the third part is tangent to the second part.

[0051] The flame-stabilizing low-resistance shock generator takes the entire wall of the fuel injection section as the reference line. The inclination angle of the first part, that is, the inward inclination angle of the front part, θ1, ranges from 15° to 25°, preferably 20°; the height of the highest point of the shock generator from the reference line is h, which ranges from 0.1d2≤h≤0.2d2, preferably 0.15d2; the rear part of the shock generator is formed by two arcs of the same angle and radius spliced together in a tangential manner to form an "S" shape. The range of the central angle of the arc-shaped structure is 30°≤θ2≤40°, preferably 35°; according to the geometric relationship, the radius R of the arc-shaped structure satisfies the equation: R(1-cosθ2)=h / 2, where R is the radius of the arc-shaped structure, θ2 is the central angle of the arc-shaped structure, and h is the distance between the highest point of the shock wave generator and the wall of the fuel injection section; the range of the overall wall expansion angle θ3 of the fuel injection section is between 1.0° and 2.0°, preferably 1.5°.

[0052] When the incoming air passes through the isolation section and is about to pass through the fuel injection section and enter the concave cavity section, the front of the flame-stabilizing low-resistance shock wave generator causes the flow channel profile to shrink, thereby generating a compressed oblique shock wave. The shock wave collides in the center of the flow channel and then reflects, such as Figure 3 The solid line shown in B.

[0053] The fuel is ejected from the nozzle at a speed u jet After ejection, it is distributed on the spanwise plane perpendicular to the center trace direction, where the center trace (such as Figure 3 The formula for (shown by X in the figure) is:

[0054] y / d jet =c1(x / d jet ) c2 J c3

[0055] The formula is based on a coordinate system with the nozzle center as the origin, the mainstream direction as the positive direction of the x-axis, and the injection direction as the positive direction of the y-axis; J is the fuel / air momentum ratio: J = (ρ jet u 2 jet ) / (ρ air u 2 air ), where ρ jet is the fuel density, ρ air and u airare the density and velocity of the incoming air; where the empirical constants are c1=1.6, c2=1 / 3, c3=1 / 3.

[0056] Let the distance between the center of the fuel nozzle and the front edge of the cavity be l jet The shock wave reflected by the shock generator converges with the centerline of the jet from the nozzle at the entrance to the cavity. This means the reflected shock wave and the jet's centerline intersect precisely at the axial location of the flow path at the cavity's leading edge. At this point, the compressed shock wave generates extremely high pressure, which mixes thoroughly with the injected fuel jet before entering the cavity for combustion. This significantly reduces the risk of flame flashback and blowout, enhancing stability and improving combustion efficiency.

[0057] At Mach 4-6 cruise state, the ratio of the cavity trailing edge flow channel height to the inlet duct entrance height satisfies: 1.25≤d 33 / d1≤1.50, preferably, d 33 / d1=1.4. The cavity length-to-depth ratio range satisfies: 6<(d 32 -d 31 ) / (2l3)<8, preferably, (d 32 -d 31 ) / (2l3)=7. The inclination angle of the rear wall of the cavity is 45°. The expansion angle of the inclined wall of the expansion section ranges from 1.5° to 3.5°, preferably 2°.

[0058] The above-mentioned low-resistance shock generator for supersonic combustion flame stabilization enhancement uses the shock wave upstream of the fuel injection position to compress the incoming air, increase the static temperature and pressure of the air, and interact with the fuel mixing zone to enhance turbulent pulsation and mixing efficiency, reduce the risk of flame flashback and flameout in conventional wall-injection combustion chambers, and solve the problem of possible combustion oscillation caused by the inability of the concentrated heat release zone to be stable in space; with the help of the shock generator to generate pre-combustion oblique shock waves, considering the engine operating range and the Mach number of the incoming flow, the size and shape of the shock generator are matched and designed, while generating shock waves of sufficient intensity, bringing as little resistance and total pressure loss as possible, and utilizing the high temperature and high pressure area at the intersection of the shock wave and the wave system to promote the mixing and chemical reaction of the fuel jet in space, enhance the combustion robustness while increasing the combustion efficiency, and improve the overall performance of the engine.

[0059] The flame-stabilizing low-drag shock wave generator of the present application (a shock wave generator capable of enhancing the flame-stabilizing effect of supersonic combustion and improving efficiency and reducing drag) can operate in the scramjet engine combustion chamber of both subsonic and scramjet combustion modes. The slope design of the front portion is used to generate shock waves to enhance flame stabilization in the concave cavity, and the arc design of the rear portion can take into account the low-drag and low-loss characteristics and the ability to resist backpressure, which helps to enhance the full mixing of fuel and air and the stability of combustion. It can effectively improve the flame-stabilizing performance and combustion stability of the scramjet engine combustion chamber, improve combustion efficiency, and at the same time take into account the least possible flow resistance and total pressure loss.

[0060] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0061] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A low-resistance shock wave generator for supersonic combustion flame stabilization enhancement, characterized in that: The shock wave generator is provided on the fuel injection section of the scramjet combustion chamber, the fuel injection section is connected to the isolation section and the concave section of the scramjet engine, and the fuel injection section has an expansion trend along the isolation section toward the concave section; The shock wave generator comprises: a first part, a second part and a third part which are connected in sequence; One end of the first portion is connected to the isolation segment and has an inclination angle toward the central axis of the scramjet combustion chamber; The second portion is an arc-shaped structure that is recessed toward the central axis of the scramjet engine combustion chamber; The shape and size of the third portion are the same as those of the second portion, and one end of the third portion is tangent to the second portion; The second part and the third part are formed by two arcs of the same angle and radius connected tangentially to each other to form an "S" shape; A series of spray holes are provided on the fuel injection section at positions corresponding to the positions between the third portion and the concave cavity section, so that the fuel is distributed on a spanwise plane perpendicular to the centerline after being sprayed from the spray holes; The shock wave reflected by the shock generator intersects the center line of the nozzle jet at the leading edge flow channel of the cavity.

2. The low-resistance shock wave generator for supersonic combustion flame stabilization enhancement according to claim 1, characterized in that: The inclination angle of the first part ranges from 15° to 25°.

3. The low-resistance shock wave generator for supersonic combustion flame stabilization enhancement according to claim 2, characterized in that: The range of the central angle of the arc-shaped structure is: 30°~40°.

4. The low-resistance shock wave generator for supersonic combustion flame stabilization enhancement according to claim 3, characterized in that: The radius of the arc-shaped structure satisfies: R (1-cos θ 2) = h / 2 Where, R is the radius of the arc-shaped structure, θ 2 is the central angle of the arc structure, h is the distance between the highest point of the shock wave generator and the wall of the fuel injection section.

5. The low-resistance shock wave generator for supersonic combustion flame stabilization enhancement according to claim 4, characterized in that: The distance between the highest point of the shock wave generator and the wall of the fuel injection section is 0.1~0.2 times the height of the isolation section outlet flow channel.

6. The low-resistance shock wave generator for supersonic combustion flame stabilization enhancement according to any one of claims 1 to 5, characterized in that: The expansion angle range of the fuel injection section wall is: 1°~2°.

7. The low-resistance shock wave generator for supersonic combustion flame stabilization enhancement according to any one of claims 1 to 5, characterized in that: The range of the ratio of the height of the flow channel at the rear edge of the cavity to the height of the flow channel at the inlet of the isolation section is: [1.25, 1.5].

8. The low-resistance shock wave generator for supersonic combustion flame stabilization enhancement according to any one of claims 1 to 5, characterized in that: The range of cavity aspect ratio is: [6,8].

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