Supersonic combustion chamber and scramjet engine for suppressing non-uniform flow separation

Abstract

The application belongs to the technical field of supersonic combustion chambers and ramjet engines, and relates to a supersonic combustion chamber and a scramjet engine for inhibiting non-uniform flow separation. The supersonic combustion chamber comprises a concave cavity flame holder and a throat section connected in sequence, the inlet of the concave cavity flame holder is connected with the isolator section of the ramjet engine, the outlet of the throat section is connected with the tail nozzle of the ramjet engine, one side of the throat section is equal in distance to the center axis of the combustion chamber of the ramjet engine, and the other side is unequal in distance to the center axis of the combustion chamber of the ramjet engine, the throat section comprises a matching section, the two ends of the matching section are connected with the concave cavity flame holder and the tail nozzle respectively, the matching section has multiple cross sections with different areas, and each cross section is composed of a semicircular structure and a semi-elliptical structure. The application can inhibit non-uniform flow separation under the condition of non-uniform incoming flow.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of supersonic combustion chambers and ramjet engines, in particular to a supersonic combustion chamber for suppressing non-uniform flow separation and a scramjet engine. BACKGROUND

[0002] For a hypersonic vehicle using air-breathing propulsion, the high-speed incoming air is compressed in the forebody inlet, accompanied by a decrease in Mach number and a significant increase in static pressure and temperature, and then reaches the engine combustion chamber through the isolation section. Due to the complex shock wave system, turbulent pulsation and near-wall flow separation inside the inlet, combined with the structural constraints of the inlet wall surface and the certain flight angle under real flight conditions, it is impossible to achieve uniform axisymmetric distribution (for circular cross-section engines), so the air entering the isolation section is not uniformly distributed on the inlet cross-section.

[0003] For an inlet with a high compression ratio, under the condition of a low flight Mach number, the non-uniform incoming flow condition will have a non-negligible impact on the mixing and combustion efficiency in the combustion chamber. Specifically, the circumferentially uniform injection scheme will be affected by the differences in flow field parameters around the injection holes at different positions under the condition of circumferentially non-uniform incoming flow, so the mixing of fuel and air and their combustion in the downstream flame stabilizer will be affected by the incoming flow. The non-axisymmetric distribution of back pressure caused by the above non-uniform combustion will cause the circumferential non-uniform distribution of shock wave trains or flow separation zones in the isolation section, thereby affecting the overall performance of the engine.

[0004] In addition, except for the near-wall boundary layer region, the radial non-uniform distribution of the incoming flow will also interfere with the optimal design of the combustion chamber configuration and the injection scheme.

[0005] In the prior art, some studies have designed rectangular cross-section supersonic combustion chambers by introducing asymmetric single-sided expansion or double-sided expansion configurations to cope with the effects of non-uniform incoming flow. For example: Wang et al. Experimental study on the effect of combustor configuration on the performance of dual-mode combustor, Aerospace Science and Technology, 42: 169-175, 2015.

[0006] However, this design still belongs to a fully axisymmetric circular cross-section engine, which is prone to cause asymmetric flow separation under non-uniform incoming flow conditions, thereby reducing the engine's resistance to back pressure and making it difficult to optimize the fuel combustion efficiency in the combustion chamber. SUMMARY

[0007] Based on this, it is necessary to provide an ultrasonic combustion chamber and a scramjet engine capable of inhibiting non-uniform flow separation under non-uniform inflow conditions to solve the above technical problems.

[0008] An ultrasonic combustion chamber capable of inhibiting non-uniform flow separation comprises:

[0009] A concave cavity flame holder and a throat section are sequentially connected, the inlet of the concave cavity flame holder is connected to the isolator section of the scramjet engine, and the outlet of the throat section is connected to the tail nozzle of the scramjet engine.

[0010] One side of the throat section is equal in distance to the center axis of the scramjet engine combustion chamber, and the other side is not equal in distance to the center axis of the scramjet engine combustion chamber.

[0011] The throat section comprises a matching section, two ends of the matching section are respectively connected to the concave cavity flame holder and the tail nozzle, and the matching section has a plurality of cross sections with different areas, each cross section is composed of a semicircular structure and a semi-elliptical structure.

[0012] In one embodiment, the diameter of the semicircular structure is taken as the major axis of the semi-elliptical structure, so that the wall surface on the other side of the throat section is recessed towards the center axis of the scramjet engine combustion chamber.

[0013] In one embodiment, the matching section comprises a first part and a second part, one end of the first part is connected to one end of the second part, the other end of the first part is connected to the concave cavity flame holder, and the other end of the second part is connected to the tail nozzle.

[0014] The length of the minor axis of the semi-elliptical structure in the cross section of the first part gradually decreases along the direction towards the tail nozzle.

[0015] The length of the minor axis of the semi-elliptical structure in the cross section of the second part gradually increases along the direction towards the tail nozzle.

[0016] In one embodiment, the matching section further comprises a third part, two ends of the third part are respectively connected to one end of the first part and one end of the second part.

[0017] The length of the minor axis of the semi-elliptical structure in the cross section of the third part is equal along the axial direction.

[0018] In one embodiment, the throat section further comprises a connecting section, two ends of the connecting section are respectively connected to the concave cavity flame holder and the matching section.

[0019] The connecting part is a circular structure with equal area, and the diameter of the circular structure is equal to the diameter of the semi-circular structure.

[0020] In one embodiment, the ratio of the lengths of the connecting part, the first part, the third part and the second part of the throat section is 12:23:33:32.

[0021] In one embodiment, the diameter of the semi-circular structure is greater than or equal to 1.04 times the diameter of the isolation section and less than or equal to 0.92 times the diameter of the cavity stabilizer.

[0022] In one embodiment, the minor axis of the semi-elliptical structure in the third part satisfies:

[0023] 1.42(πd1 2 / 4)≤πr2 2 / 2+πr2b / 2≤1.96(πd1 2 / 4)

[0024] where d1 is the diameter of the isolation section, r2 is the radius of the semi-circular structure in the third part, and b is half the length of the minor axis of the semi-elliptical structure in the third part.

[0025] In one embodiment, when the upper side near-wall region in the isolation section is more prone to separation, the upper side of the matching part in the throat section is a semi-circular structure, and the lower side is a semi-elliptical structure.

[0026] When the lower side near-wall region in the isolation section is more prone to separation, the upper side of the matching part in the throat section is a semi-elliptical structure, and the lower side is a semi-circular structure.

[0027] A scramjet engine, comprising: the supersonic combustion chamber for suppressing non-uniform flow separation.

[0028] The supersonic combustion chamber and scramjet engine for inhibiting non-uniform flow separation have the advantages that the supersonic combustion chamber and scramjet engine for inhibiting non-uniform flow separation are aimed at the problem that the performance of an existing axisymmetric circular cross-section combustion chamber in a scramjet engine is poor under the working condition that the inflow is non-uniform and the heat release is non-uniform, the influence of the non-uniform inflow into the isolation section is considered, the non-uniform flow separation upstream is inhibited from the perspective of combustion chamber configuration design, the design idea of conforming to the inflow condition and the heat release distribution is adopted, the connection section between the combustion chamber cavity flame holder and the tail nozzle inlet is no longer maintained in an axisymmetric configuration, but is adjusted according to the inflow condition into the combustion chamber internal flow passage, the combustion chamber internal profile, especially the throat section of the cavity flame holder, is designed in a non-axisymmetric configuration, so that the feedback of the heat release in the combustion chamber to the upstream does not cause significant non-uniform flow separation, under the non-uniform inflow condition at the isolation section inlet, the risk of thermal choke caused by strong heat release is prevented on the basis of ensuring the flame holding performance, the non-uniform flow separation in the internal flow passage of the engine is effectively inhibited, the combustion efficiency is further improved, the anti-back pressure capability of the engine is improved, the comprehensive performance is optimized, the working robustness of the engine is improved, the structure space of the lower part of the combustion chamber of the engine is saved, and especially for the inflow of the air inlet passage with strong non-axisymmetric characteristics, the combustion chamber can effectively work under a higher equivalence ratio condition. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The figure is a configuration profile schematic diagram of the supersonic combustion chamber and scramjet engine for inhibiting non-uniform flow separation in an embodiment.

[0030] Figure 2 The figure is a configuration profile size diagram of the supersonic combustion chamber and scramjet engine for inhibiting non-uniform flow separation in an embodiment. BRIEF DESCRIPTION OF DRAWINGS:

[0032] 1 - isolation section, 2 - cavity flame holder, 3 - throat section, 4 - tail nozzle

[0033] 3-1 - connection part, 3-2 - first part, 3-3 - third part, 3-4 - second part

[0034] l1 - cavity flame holder bottom wall length, l2 - connection part length, l3 - first part length, l4 - third part length, l5 - second part length

[0035] d1 - isolation section diameter, d2 - cavity flame holder diameter

[0036] r1 - connection part radius, r2 - radius of semicircular structure in third part, r3 - second part outlet circular cross-section radius

[0037] a - concave cavity rear edge wall surface inclination, b - half of the length of the minor axis of the semi-elliptical structure in the third portion. DETAILED DESCRIPTION

[0038] In order to make the purposes, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0039] It should be noted that all directional indications, such as upper, lower, left, right, front, back, etc., described in the embodiments of the present application are only used to explain the relative positional relationship, movement condition, etc. between components in a certain posture (as shown in the drawings), and if the certain posture changes, the directional indications also change accordingly.

[0040] In addition, the descriptions such as "first", "second" and the like in the present application are only for descriptive purposes, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "multiple groups" is at least two groups, such as two groups, three groups, etc., unless otherwise specifically limited.

[0041] In the present application, unless otherwise specifically defined and limited, the terms "connection", "fixation" and the like should be understood broadly, for example, "fixation" can be fixed connection, or detachable connection, or integral; can be mechanical connection, or electrical connection, or physical connection or wireless communication connection; can be directly connected, or indirectly connected through an intermediate medium, or the internal communication of two elements or the interaction relationship between two elements, unless otherwise specifically limited. For those of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0042] In addition, the technical solutions of each embodiment of the present application can be combined with each other, but it must be based on the fact that a person of ordinary skill in the art can realize it, and when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, nor is it within the scope of protection claimed by the present application.

[0043] The application provides a supersonic combustion chamber for inhibiting non-uniform flow separation, which comprises, in one embodiment, a cavity flame holder and a throat section connected in sequence, wherein the inlet of the cavity flame holder is connected with the isolator section of a ramjet engine, and the outlet of the throat section is connected with the tail nozzle of the ramjet engine. In other words, the isolator section, the cavity flame holder, the throat section and the tail nozzle are connected in sequence from upstream to downstream.

[0044] It should be noted that the isolator section, the cavity flame holder and the tail nozzle are all axisymmetric circular cross-section configurations. The connection between the isolator section and the cavity flame holder is a vertical step, and the outlet edge of the throat section is tangent to the inlet edge of the tail nozzle.

[0045] The cavity flame holder is mainly used for ignition and flame stabilization.

[0046] The throat section is arranged downstream of the cavity flame holder, and one side of the throat section is equal in distance to the central axis of the ramjet engine combustion chamber, and the other side of the throat section is unequal in distance to the central axis of the ramjet engine combustion chamber, so as to form an asymmetric configuration of the ramjet engine combustion chamber.

[0047] The throat section comprises a matching section, and the two ends of the matching section are connected with the cavity flame holder and the tail nozzle respectively. The matching section has a plurality of cross sections with different areas, and each cross section is composed of a semicircular structure and a semi-elliptical structure.

[0048] Preferably, the semicircular structures of all the cross sections of the matching section are the same, and the diameter of the semicircular structure is taken as the major axis of the semi-elliptical structure, so that the wall surface on the other side of the throat section is recessed towards the central axis of the ramjet engine combustion chamber. In other words, the profile of the ramjet engine combustion chamber along the central axis of the combustion chamber is a non-axisymmetric structure, and the profile of the throat section on one side is a straight line, and the profile on the other side is a curve (including a smooth curve and a broken line), and the distance between the curve and the central axis first decreases and then increases in the direction towards the tail nozzle.

[0049] Further preferably, the matching section comprises a first part and a second part, one end of the first part is connected with one end of the second part, the other end of the first part is connected with the cavity flame holder, and the other end of the second part is connected with the tail nozzle, the length of the minor axis of the semi-elliptical structure in the cross section of the first part gradually decreases in the direction towards the tail nozzle, and the length of the minor axis of the semi-elliptical structure in the cross section of the second part gradually increases in the direction towards the tail nozzle.

[0050] More preferably, the matching section further comprises a third part, and the two ends of the third part are connected with one end of the first part and one end of the second part respectively, the length of the minor axis of the semi-elliptical structure in the cross section of the third part is equal in the axial direction, that is, the third part is straight, and the semi-elliptical structure of each cross section in the third part is the same, and the length of the minor axis is fixed.

[0051] More preferably, the throat section further includes: a connecting part; the two ends of the connecting part are respectively connected to the concave flame stabilizer and the matching part; the cross-section of the connecting part is a circular structure with equal area, and the diameter of the circular structure is equal to that of the semi-circular structure.

[0052] In this embodiment, when the upper near-wall region within the isolation segment is easier to separate, the upper side of the mating portion in the throat segment has a semi-circular structure, and the lower side has a semi-elliptical structure; when the lower near-wall region within the isolation segment is easier to separate, the upper side of the mating portion in the throat segment has a semi-elliptical structure, and the lower side has a semi-circular structure.

[0053] like Figure 1 and Figure 2 As shown, in a specific embodiment, the throat segment includes: a connecting portion, a first portion, a third portion, and a second portion, wherein:

[0054] The connecting section, as the straight section of the throat segment with a circular cross-section, has an axisymmetric circular cross-section configuration.

[0055] The first part serves as the throat segment contraction transition zone, and except for the inlet, it has a semi-circular and semi-elliptical cross-section configuration, with the upper part being round and the lower part being elliptical.

[0056] The third part, as the throat section, is a straight area with a semi-circular and semi-elliptical cross section. It has a semi-circular and semi-elliptical cross section configuration, with an upper circle and a lower ellipse, and is the narrowest part of the inner channel downstream of the isolation section.

[0057] The second part serves as the throat segment expansion transition area, and except for the outlet, it has a semi-circular and semi-elliptical cross-section configuration, with the upper part being round and the lower part being elliptical.

[0058] The range of the throat segment length is: 1.5l1≤l0≤4l1, preferably, l0=2.5l1, where l0 is the throat segment length, l1 is the bottom wall length of the concave cavity flame stabilizer, l0=l2+l3+l4+l5, l2 is the length of the connecting part, l3 is the length of the first part, l4 is the length of the third part, and l5 is the length of the second part.

[0059] The length ratio of the connecting part, the first part, the third part, and the second part of the throat segment is 12:23:33:32, that is: l2:l3:l4:l5=0.12:0.23:0.33:0.32.

[0060] The radii of the semicircular structures of the connecting part, the third part, and the second part are equal. That is, the cross-sections of the straight section of the throat segment, the upper half of the semicircular cross-section of the throat segment, and the exit circular cross-section of the throat segment expansion transition area have the same radius, i.e., r1 = r2 = r3.

[0061] The diameter of the semicircular structure is greater than or equal to 1.04 times the diameter of the isolation section and less than or equal to 0.92 times the diameter of the cavity flame holder, i.e. 0.52d1≤r1≤0.46d2, wherein d1 is the diameter of the isolation section, r1 is the radius of the semicircular structure, and d2 is the diameter of the cavity flame holder.

[0062] In the throat section, the half of the minor axis length b of the semi-elliptical structure in the third part (i.e. the length of the minor axis of the semi-ellipse under the equal-length section of the semi-circular semi-elliptical section) needs to meet the constraint of the engine on the throat area, i.e. the minor axis of the semi-elliptical structure in the third part needs to meet:

[0063] 1.42(πd1 2 / 4)≤πr2 2 / 2+πr2b / 2≤1.96(πd1 2 / 4)

[0064] In the formula, d1 is the diameter of the isolation section, r2 is the radius of the semicircular structure in the third part, and b is the half of the minor axis length of the semi-elliptical structure in the third part.

[0065] Preferably, for the engine cruising Mach number of 6, πr2 2 / 2+πr2b / 2=1.5, and for the engine cruising Mach number of 4, πr2 2 / 2+πr2b / 2=1.86.

[0066] Meanwhile, the geometric constraint b

[0067] In addition, the upper half of the cross section of the throat section contraction transition area is kept as a semicircle with a radius of r1, the major axis of the lower half semi-ellipse is kept as r1, and the minor axis length is linearly reduced from r1 to b along the distance along the inlet to the outlet. The upper half of the cross section of the throat section expansion transition area is kept as a semicircle with a radius of r2, the major axis of the lower half semi-ellipse is kept as r2, and the minor axis length is linearly increased from b to r3 along the distance along the inlet to the outlet.

[0068] It also needs to be explained that the ratio of the cavity flame holder diameter d2 to the isolation section diameter d1 is in the range of 1.4≤d2 / d1≤1.8; for the engine cruising Mach number of 6, the ratio is preferably 1.45, and for the engine cruising Mach number of 4, the ratio is preferably 1.73.

[0069] The range of the length l1 of the bottom wall of the cavity flame holder satisfies 2.7(d2-d1)≤l1≤3.8(d2-d1), and preferably l1=3.25.

[0070] The inclination angle a of the rear edge wall surface of the cavity is taken as 45°.

[0071] The supersonic combustion chamber for inhibiting non-uniform flow separation is designed in view of the poor performance of the existing axisymmetric circular cross-section combustion chamber in a ramjet engine under the working condition of strong non-uniform inflow and non-uniform heat release effect, considers the influence of the non-uniform inflow into the isolation section, and inhibits the non-uniform flow separation upstream from the perspective of combustion chamber configuration design. The design idea of conforming to the inflow condition and heat release distribution is adopted, so that the connecting section between the combustion chamber cavity flame holder and the tail nozzle inlet is no longer maintained in an axisymmetric configuration, but is adjusted according to the inflow condition into the combustion chamber internal flow passage for the non-uniform inflow in the combustion chamber internal flow passage, and a non-axisymmetric configuration design is adopted for the combustion chamber internal profile, especially the throat section of the cavity flame holder. Specifically, the through-plane profile configuration of the upper and lower sides of the throat section is appropriately changed to realize smooth flow in the flow passage on the side with strong back pressure in the combustion zone and to make the flow passage on the side with weak back pressure experience contraction and then expansion, so that the spatial distribution of heat release in the combustion chamber can be adjusted according to the upper and lower non-uniform inflow, thereby relieving the non-uniform flow separation in the isolation section. The design can prevent the risk of thermal choke caused by strong heat release on the basis of ensuring the flame holding performance, effectively inhibits the non-uniform flow separation in the internal flow passage of the engine, thereby further improving the combustion efficiency, improving the anti-back pressure capability of the engine, optimizing the comprehensive performance, improving the working robustness of the engine, saving the structural space of the lower part of the combustion chamber of the engine, and effectively working at a higher equivalence ratio for the inflow of the air inlet with strong non-axisymmetric characteristics.

[0072] The application also provides a scramjet engine (which belongs to a ramjet engine), which in one embodiment comprises: a supersonic combustion chamber for inhibiting non-uniform flow separation.

[0073] The technical features of the above embodiments can be combined in any manner. To make the description concise, not all possible combinations of the technical features in the above embodiments are described, but as long as the combinations of the technical features do not contradict, they should be considered as within the scope of the present application.

[0074] The above embodiments only express several implementation manners of the application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the patent scope of the application. It should be pointed out that, for ordinary skilled persons in the art, some modifications and improvements can be made without departing from the concept of the application, and these are within the protection scope of the application. Therefore, the patent protection scope of the application should be subject to the appended claims.

Claims

1. A supersonic combustion chamber that suppresses non-uniform flow separation, characterized by, The supersonic combustion chamber comprises: a cavity flameholder and a throat section connected in sequence, the cavity flameholder being connected with the isolator section of the ramjet engine, and the throat section being connected with the nozzle of the ramjet engine; one side of the throat section is equidistant from the central axis of the combustion chamber of the ramjet engine, and the other side is not equidistant from the central axis of the combustion chamber of the ramjet engine; the throat section comprises a matching section, two ends of the matching section being connected with the cavity flameholder and the nozzle respectively, the matching section having a plurality of cross sections with different areas, each cross section being composed of a semicircular structure and a semi-elliptical structure; the diameter of the semicircular structure is taken as the major axis of the semi-elliptical structure, so that the wall surface on the other side of the throat section is recessed towards the central axis of the combustion chamber of the ramjet engine; when the upper near-wall region in the isolator section is more prone to separation, the upper side of the matching section in the throat section is a semicircular structure, and the lower side is a semi-elliptical structure; when the lower near-wall region in the isolator section is more prone to separation, the upper side of the matching section in the throat section is a semi-elliptical structure, and the lower side is a semicircular structure.

2. The supersonic combustor to inhibit separation of non-uniform flow of claim 1, wherein, the matching section comprises a first part and a second part, one end of the first part being connected with one end of the second part, the other end of the first part being connected with the cavity flameholder, and the other end of the second part being connected with the nozzle; the length of the minor axis of the semi-elliptical structure in the cross section of the first part gradually decreases along the direction towards the nozzle; the length of the minor axis of the semi-elliptical structure in the cross section of the second part gradually increases along the direction towards the nozzle.

3. The supersonic combustor of claim 2 wherein, the matching section further comprises a third part, two ends of the third part being connected with one end of the first part and one end of the second part respectively; the length of the minor axis of the semi-elliptical structure in the cross section of the third part is equal along the axial direction.

4. The supersonic combustor of claim 3 wherein, the throat section further comprises a connecting section, two ends of the connecting section being connected with the cavity flameholder and the matching section respectively; the cross section of the connecting section is a circular structure with equal areas, and the diameter of the circular structure is equal to that of the semicircular structure.

5. The supersonic combustor of claim 4 wherein, the length ratio of the connecting section, the first part, the third part and the second part of the throat section is 12:23:33:

32.

6. The supersonic combustor to inhibit separation of non-uniform flow of any of claims 3 to 5, wherein, the diameter of the semicircular structure is greater than or equal to 1.04 times the diameter of the isolator section and less than or equal to 0.92 times the diameter of the cavity flameholder.

7. The supersonic combustor to suppress non-uniform flow separation according to claim 6, characterized by, the minor axis of the semi-elliptical structure in the third part satisfies: 1.42( πd1 2 / 4) ≤ πr2 2 / 2+ πr2b / 2 ≤ 1.96( πd1 2 / 4) wherein d1 is the diameter of the isolation segment, r2 is the radius of the semicircular structure in the third portion, b is half the length of the minor axis of the semi-elliptical structure in the third portion.

8. A scramjet engine characterized by, The supersonic combustion chamber for inhibiting separation of non-uniform flow according to any one of claims 1 to 7. The supersonic combustion chamber for inhibiting separation of non-uniform flow according to any one of claims 1 to 7.

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