阅读说明：本技术 一种超燃冲压发动机双喉道燃烧室及超燃冲压发动机 (Scramjet engine and double-throat combustion chamber thereof ) 是由 孙明波 赵国焱 王前程 蔡尊 杨揖心 于 2020-12-04 设计创作，主要内容包括：本发明公开一种超燃冲压发动机双喉道燃烧室及超燃冲压发动机,包括沿燃烧室来流方向依次相连的燃烧室上游等值段、一级凹腔、一级喉道、二级凹腔、二级喉道、燃烧室下游等值段；所述一级喉道与所述一级凹腔、所述二级凹腔之间均平滑相连,所述二级喉道与所述二级凹腔、所述燃烧室下游等值段之间均平滑相连。采用双喉道设计,形成二级燃烧室提供额外的燃烧组织空间,有效降低激波损失,拓展了燃烧室飞行马赫数下限。(The invention discloses a scramjet engine double-throat combustion chamber and a scramjet engine, which comprise a combustion chamber upstream equivalent section, a first-stage concave cavity, a first-stage throat, a second-stage concave cavity, a second-stage throat and a combustion chamber downstream equivalent section which are sequentially connected along the inflow direction of the combustion chamber; the primary throat is smoothly connected with the primary concave cavity and the secondary concave cavity, and the secondary throat is smoothly connected with the secondary concave cavity and the downstream equivalent section of the combustion chamber. By adopting the design of double throats, a secondary combustion chamber is formed to provide extra combustion organization space, shock wave loss is effectively reduced, and the lower limit of the flight Mach number of the combustion chamber is expanded.)

1. A scramjet engine double-throat combustion chamber is characterized by comprising a combustion chamber upstream equivalent section, a first-stage concave cavity, a first-stage throat, a second-stage concave cavity, a second-stage throat and a combustion chamber downstream equivalent section which are sequentially connected in the incoming flow direction of the combustion chamber; the primary throat is smoothly connected with the primary concave cavity and the secondary concave cavity, and the secondary throat is smoothly connected with the secondary concave cavity and the downstream equivalent section of the combustion chamber.

2. The scramjet dual throat combustor of claim 1, wherein the secondary throat has a radius greater than the radius of the primary throat.

3. The scramjet dual throat combustor of claim 1, wherein the radius of the primary throat is greater than the radius of the upstream equivalent section of the combustor.

4. The scramjet engine dual throat combustor of claim 1, wherein the radius of the secondary cavity is less than or equal to the radius of the primary cavity.

5. The scramjet engine double-throat combustion chamber as claimed in any one of claims 1 to 4, wherein the primary throat comprises a primary throat contraction section and a primary throat expansion section which are smoothly connected, the molded lines of the primary throat contraction section and the primary throat expansion section are spline curves, the primary throat contraction section is smoothly connected with the primary cavity, and the primary throat expansion section is smoothly connected with the secondary cavity.

6. The scramjet engine double-throat combustor according to any one of claims 1 to 4, wherein the secondary throat comprises a secondary throat contraction section and a secondary throat expansion section which are smoothly connected, the molded lines of the secondary throat contraction section and the secondary throat expansion section are spline curves, the secondary throat contraction section is smoothly connected with the secondary cavity, and the secondary throat expansion section is smoothly connected with a downstream equivalent section of the combustor.

7. A design method of a double-throat combustion chamber of the scramjet engine as claimed in any one of claims 1 to 6, characterized by comprising the following steps:

step 1, determining the initial radius of a primary throat, the initial front edge depth of a primary cavity and the initial bottom wall length of the primary cavity according to the requirements including stamping starting characteristics, flame stabilizing performance, combustion efficiency and structural constraints on the premise of knowing the inflow air parameters of a combustion chamber, a fuel injection scheme and the inlet size of the combustion chamber;

step 2, obtaining a molded line of a first-stage throat contraction section based on a spline curve design method, and performing wave absorption design on the molded line of the first-stage throat expansion section by adopting a characteristic line iteration method of a supersonic velocity nozzle to obtain a molded line configuration of the first-stage throat, wherein the initial radius of the first-stage throat is larger than the inlet radius of a combustion chamber so as to stabilize supersonic velocity combustion flame;

step 3, designing the length of the initial bottom wall of the secondary concave cavity and the initial radius of the secondary concave cavity to ensure that the secondary concave cavity can completely contain flame when the combustion chamber is in a subsonic combustion state, and the initial radius of the secondary concave cavity is smaller than or equal to the initial radius of the primary concave cavity;

step 4, obtaining a molded line of a contraction section of the secondary throat based on a spline curve design method, and performing wave elimination design on the molded line of an expansion section of the secondary throat by adopting a characteristic line iteration method of an ultrasonic nozzle to obtain a molded line configuration of the secondary throat, wherein the initial radius of the secondary throat is larger than that of the primary throat so as to meet the condition that the combustion flame cannot be reversely pushed to an isolation section in a high fuel equivalence ratio combustion state under the condition of low incoming flow Mach number;

and 5, performing numerical simulation based on the initial values obtained in the steps 1 to 4 to optimize the ratio of the radius and the length between the primary concave cavity and the secondary concave cavity and between the primary throat and the secondary throat, further slowing down or even eliminating severe changes such as sudden drop along the way of the pressure after passing through the throat, prolonging the characteristic combustion scale, increasing the effective combustion volume and obtaining the optimal configuration scheme of the combustion chamber in the given working range of the engine.

8. A scramjet engine, characterized by having a combustion chamber according to any one of claims 1 to 6.

Technical Field

The invention relates to the technical field of engines, in particular to a scramjet engine and a dual-throat combustion chamber thereof.

Background

The prior art scramjet engine combustion chamber configuration mostly adopts a corner type combustion chamber throat, as shown in fig. 1. Usually, a subsonic-supersonic transition (sonic velocity line) occurs after the throat corner, and a strong shock wave exists behind the sonic velocity line and a sudden pressure drop exists, so that great shock wave loss is caused.

The combustion zone of the existing scramjet engine combustion chamber configuration under high Mach number is moved to the downstream equal straight section of the concave cavity, and the flame is in an unoptimized organization combustion state. Under the condition of low Mach number and when fuel with large equivalence ratio is injected, the combustion is too strong, and thermal blockage is easy to occur, so that the combustion of the engine is easy to be unstable.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides the scramjet dual-throat combustion chamber and the scramjet, and the scramjet adopts the dual-throat design to form a secondary combustion chamber to provide extra combustion organization space, thereby effectively reducing shock wave loss and expanding the lower limit of the flight Mach number of the combustion chamber.

In order to achieve the purpose, the invention provides a scramjet engine double-throat combustion chamber, which comprises a combustion chamber upstream equivalent section, a first-stage concave cavity, a first-stage throat, a second-stage concave cavity, a second-stage throat and a combustion chamber downstream equivalent section which are sequentially connected along the inflow direction of the combustion chamber; the primary throat is smoothly connected with the primary concave cavity and the secondary concave cavity, and the secondary throat is smoothly connected with the secondary concave cavity and the downstream equivalent section of the combustion chamber.

Further preferably, the radius of the secondary throat is greater than the radius of the primary throat.

Further preferably, the radius of the primary throat is greater than the radius of the upstream contour of the combustor.

Further preferably, the radius of the secondary cavity is smaller than or equal to the radius of the primary cavity.

Further preferably, the primary throat comprises a primary throat contraction section and a primary throat expansion section which are smoothly connected, molded lines of the primary throat contraction section and the primary throat expansion section are spline curves, the primary throat contraction section is smoothly connected with the primary cavity, and the primary throat expansion section is smoothly connected with the secondary cavity.

Further preferably, the secondary throat comprises a secondary throat contraction section and a secondary throat expansion section which are smoothly connected, molded lines of the secondary throat contraction section and the secondary throat expansion section are spline curves, the secondary throat contraction section is smoothly connected with the secondary cavity, and the secondary throat expansion section is smoothly connected with a downstream equivalent section of the combustion chamber.

In order to achieve the aim, the invention provides a design method of a dual-throat combustion chamber of a scramjet engine, which comprises the following steps:

step 1, determining the initial radius of a primary throat, the initial front edge depth of a primary cavity and the initial bottom wall length of the primary cavity according to the requirements including stamping starting characteristics, flame stabilizing performance, combustion efficiency and structural constraints on the premise of knowing the inflow air parameters of a combustion chamber, a fuel injection scheme and the inlet size of the combustion chamber;

step 2, obtaining a molded line of a first-stage throat contraction section based on a spline curve design method, and performing wave absorption design on the molded line of the first-stage throat expansion section by adopting a characteristic line iteration method of a supersonic velocity nozzle to obtain a molded line configuration of the first-stage throat, wherein the initial radius of the first-stage throat is larger than the inlet radius of a combustion chamber so as to stabilize supersonic velocity combustion flame;

step 3, designing the length of the initial bottom wall of the secondary concave cavity and the initial radius of the secondary concave cavity to ensure that the secondary concave cavity can completely contain flame when the combustion chamber is in a subsonic combustion state, and the initial radius of the secondary concave cavity is smaller than or equal to the initial radius of the primary concave cavity;

step 4, obtaining a molded line of a contraction section of the secondary throat based on a spline curve design method, and performing wave elimination design on the molded line of an expansion section of the secondary throat by adopting a characteristic line iteration method of an ultrasonic nozzle to obtain a molded line configuration of the secondary throat, wherein the initial radius of the secondary throat is larger than that of the primary throat so as to meet the condition that the combustion flame cannot be reversely pushed to an isolation section in a high fuel equivalence ratio combustion state under the condition of low incoming flow Mach number;

and 5, performing numerical simulation based on the initial values obtained in the steps 1 to 4 to optimize the ratio of the radius and the length between the primary concave cavity and the secondary concave cavity and between the primary throat and the secondary throat, further slowing down or even eliminating severe changes such as sudden drop along the way of the pressure after passing through the throat, prolonging the characteristic combustion scale, increasing the effective combustion volume and obtaining the optimal configuration scheme of the combustion chamber in the given working range of the engine.

In order to achieve the above object, the present invention provides a scramjet engine having the above combustion chamber.

Compared with the existing structure of the combustion chamber of the scramjet, the scramjet combustion chamber and the scramjet provided by the invention have the following beneficial effects:

1. the double-throat design is adopted, so that the shock wave loss is effectively reduced;

2. through the design of double throats, a secondary combustion chamber is formed to provide additional combustion tissue space;

3. the lower limit of the flying Mach number of the combustion chamber is expanded.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.

FIG. 1 is a schematic view of a prior art scramjet combustion chamber configuration;

FIG. 2 is a schematic configuration diagram of a dual-throat combustion chamber of a scramjet engine in an embodiment of the invention;

FIG. 3 is a flow chart of the design of a dual throat combustor of the scramjet engine according to the embodiment of the invention;

FIG. 4 is a sound velocity line schematic diagram of a primary throat of a dual-throat combustion chamber of the scramjet engine in the embodiment of the invention;

FIG. 5 is a sound velocity diagram of a secondary throat of a dual-throat combustion chamber of the scramjet engine in an embodiment of the invention.

The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that all the directional indicators (such as up, down, left, right, front, and rear … …) in the embodiment of the present invention are only used to explain the relative position relationship between the components, the movement situation, etc. in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indicator is changed accordingly.

In addition, the descriptions related to "first", "second", etc. in the present invention are only for descriptive purposes and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the present invention, unless otherwise expressly stated or limited, the terms "connected," "secured," and the like are to be construed broadly, and for example, "secured" may be a fixed connection, a removable connection, or an integral part; the connection can be mechanical connection, electrical connection, physical connection or wireless communication connection; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In addition, the technical solutions in the embodiments of the present invention may be combined with each other, but it must be based on the realization of those skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination of technical solutions should not be considered to exist, and is not within the protection scope of the present invention.

As shown in fig. 2, the dual-throat combustion chamber of the scramjet engine disclosed in the present embodiment comprises an upstream equivalent section 1, a first-stage cavity 2, a first-stage throat 3, a second-stage cavity 4, a second-stage throat 5, and a downstream equivalent section 6, which are connected in sequence along the inflow direction of the combustion chamber; the primary throat 3 is smoothly connected with the primary cavity 2 and the secondary cavity 4, and the secondary throat 5 is smoothly connected with the secondary cavity 4 and the downstream equivalent section 6 of the combustion chamber.

The radius of the secondary throat 5 is larger than that of the primary throat 3, so that the combustion flame cannot be reversely pushed to the isolation section under the condition of low incoming flow Mach number in a high fuel equivalence ratio combustion state. The radius of the primary throat 3 is greater than the radius of the upstream equivalent section 1 of the combustion chamber for the purpose of stabilizing the supersonic combustion flame. The radius of the secondary cavity 4 is smaller than or equal to the radius of the primary cavity 2.

Further specifically, the first-stage throat 3 comprises a first-stage throat contraction section and a first-stage throat expansion section which are connected smoothly, molded lines of the first-stage throat contraction section and the first-stage throat expansion section are spline curves, the first-stage throat contraction section is connected smoothly with the first-stage cavity 2, and the first-stage throat expansion section is connected smoothly with the second-stage cavity 4.

Further specifically, the secondary throat 5 comprises a secondary throat contraction section and a secondary throat expansion section which are smoothly connected, molded lines of the secondary throat contraction section and the secondary throat expansion section are spline curves, the secondary throat contraction section is smoothly connected with the secondary cavity 4, and the secondary throat expansion section is smoothly connected with the equivalent section 6 at the downstream of the combustion chamber.

Based on the dual-throat combustion chamber of the scramjet engine, the embodiment also discloses a design method of the dual-throat combustion chamber of the scramjet engine, and the design method comprises the following steps with reference to fig. 2-3:

step 1, determining an initial radius r3 of a primary throat, an initial front edge depth h2 of a primary cavity and an initial bottom wall length l2 of the primary cavity according to requirements including stamping start characteristics, flame holding performance, combustion efficiency and structural constraints on the premise of knowing an inflow air parameter of a combustion chamber, a fuel injection scheme and a combustion chamber inlet size r 1. The specific process comprises the following steps:

firstly, obtaining an initial radius r3 of a primary throat based on an air parameter of an engine inflow direction:

wherein r3 is the initial radius of the primary throat;is the engine flow, T is the combustion chamber temperature, p is the combustion chamber pressure, M is the Mach number, R is the gas constant, and gamma is the specific heat ratio;

the initial leading edge depth h2 of the primary cavity and the initial bottom wall length L2 of the primary cavity can be obtained according to the following technical means including the punch start characteristic, flame holding performance, combustion efficiency and structural constraint, and therefore the detailed description is omitted in this embodiment, and reference may be made to the patent "engine, flame stabilizer and cavity design method, ZL 201410230831.8" and the document "Davis D L, Bowersox R D w. rigid reactor of cavity parameter recesses for scam keys [ R ]. AIAA Paper 97-3274,1997".

And 2, obtaining a molded line of the first-stage throat contraction section based on a spline curve design method, and performing wave absorption design on the molded line of the first-stage throat expansion section by adopting a characteristic line iteration method of a supersonic velocity nozzle to obtain the molded line configuration of the first-stage throat, wherein the initial radius r2 of the first-stage throat is larger than the inlet radius r1 of the combustion chamber to stabilize supersonic velocity combustion flame, and the radius of the first-stage throat refers to the radius of the connecting position of the first-stage throat contraction section and the first-stage throat expansion section. Preferably, the initial radius r2 of the primary throat in this embodiment is slightly larger than the inlet radius r1 of the combustor. The specific process comprises the following steps:

for the primary throat contraction section, on the basis of obtaining the initial bottom wall length l2 of the primary cavity in the step 1, the initial radius r2 of the primary cavity can be obtained by combining the size of the inlet of the combustion chamber; because the initial radius r2 of the first-level concave cavity and the initial radius r3 of the first-level throat are known, namely the heights of two ends of the contraction section of the first-level throat are known, two ends of the contraction section of the first-level throat are connected by a line segment with continuous first derivative to be used as the initial line shape of the contraction section of the first-level throat; then, a numerical simulation method is adopted for verification; if the flow field in the numerical simulation generates shock waves, the length of the first-stage throat contraction section in the axial direction of the combustion chamber needs to be properly increased, the second derivative of the section of curve is further reduced, then the numerical simulation is carried out again, and the process is repeated until no shock waves are generated in the flow field in the numerical simulation.

For the first-stage throat expansion section, the characteristic line iteration method of the supersonic nozzle adopted in this embodiment is a known technical means by those skilled in the art, and therefore, details are not described in this embodiment.

And 3, designing the initial bottom wall length l4 of the secondary cavity and the initial radius r4 of the secondary cavity to ensure that the secondary cavity can completely contain flame when the combustion chamber is in a subsonic combustion state, and meeting the requirement that the initial radius r4 of the secondary cavity is smaller than or equal to the initial radius r2 of the primary cavity to ensure that the combustion chamber has the same external contour line.

And 4, obtaining a molded line of the contraction section of the secondary throat based on a spline curve design method, and performing wave elimination design on the molded line of the expansion section of the secondary throat by adopting a characteristic line iteration method of the supersonic velocity nozzle to obtain the molded line configuration of the secondary throat, wherein the initial radius r5 of the secondary throat is larger than the initial radius r3 of the primary throat, so that the combustion flame cannot be pushed back to the isolation section when the combustion state is in a large fuel equivalence ratio under the condition of low incoming flow Mach number. The specific process of designing the second-stage throat contraction section and the second-stage throat expansion section is the same as the design process of the first-stage throat contraction section and the first-stage throat expansion section in step 2, and therefore details are not repeated in this embodiment.

And 5, performing numerical simulation based on the initial values obtained in the steps 1 to 4 to optimize the ratio of the radius and the length between the primary concave cavity and the secondary concave cavity and between the primary throat and the secondary throat, further slowing down or even eliminating severe changes such as sudden drop along the way of the pressure after passing through the throat, prolonging the characteristic combustion scale, increasing the effective combustion volume and obtaining the optimal configuration scheme of the combustion chamber in the given working range of the engine.

In the embodiment, whether the shock wave exists in the flow field in the numerical simulation is taken as an optimization target, the aim is to reduce the secondary derivative of the contraction section curve to weaken or even eliminate the shock wave intensity at the position, but the rigid requirement of the total length of the engine is also considered; the adjustable parameter of the expansion section is the distance in the axial direction of the combustion chamber, if the flow field is over-expanded, the length of the expansion section in the axial direction of the combustion chamber needs to be reduced, and if the flow field is under-expanded, the length of the expansion section in the axial direction of the combustion chamber needs to be increased.

The double-throat combustor in the embodiment has the following benefits:

no exhaust shock wave loss of high pressure combustion chamber

When the incoming flow air of the combustion chamber is in a low Mach number state, the pressure of the combustion chamber is high, the combustion is positioned in a primary concave cavity in front of a primary throat, and the subsonic velocity-supersonic velocity transformation (sonic velocity line) of the heat flow occurs at the primary throat, as shown in figure 4. Because the first-stage throat adopts a wave-absorbing design similar to a spray pipe behind, shock wave loss caused by the fact that a straight pipeline in the figure 1 brings a steep Mach number cannot be generated, a full-through-flow supersonic speed state is maintained behind the first-stage throat, and no shock wave exists at the second-stage throat, so that shock wave loss is avoided.

Second, moving back the combustion zone at high Mach numbers and optimizing exhaust

The pressure of the combustion chamber is reduced, the air flow speed is increased, the primary cavity can not stabilize flame, the secondary cavity in front of the secondary throat is responsible for burning tissues, and the inner diameter of the secondary throat of the secondary cavity is reduced compared with the inner diameter of the throat of the downstream equal straight section of the cavity in the figure 1, as shown in figure 5; but adds a recirculation zone (increased characteristic volume of combustion) that accommodates combustion of the flame tissue, generally facilitating the combustion of the tissue. In addition, a direct combustion chamber such as that of FIG. 1 can have a flame stabilized in the straight section downstream of the cavity at higher chamber pressures, meaning that the combustion chamber is not designed optimally. The secondary throat added to the combustion chamber in the configuration of the embodiment is beneficial to the secondary combustion chamber to establish chamber pressure and has certain optimization effect on exhaust.

Combustion at low Mach number

The flame under the conditions of low incoming flow Mach number and high equivalence ratio fuel injection cannot burn in the primary cavity structure, is responsible for easily leading a combustion chamber to generate thermal blockage, and can burn in front of a secondary throat with larger throat diameter.

And fourthly, relieving unstable combustion.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and all modifications and equivalents of the present invention, which are made by the contents of the present specification and the accompanying drawings, or directly/indirectly applied to other related technical fields, are included in the scope of the present invention.