A design method for the internal pressure diffuser flow path profile of the afterburner confluence ring expansion

Abstract

The present application belongs to the technical field of improved design of afterburner combustion chamber of aircraft engine, and specifically relates to a method for designing the internal pressure diffusion flow path profile of the merging ring expansion of the afterburner combustion chamber, including: step one, determining the radial position of the merging ring trailing edge; step two, determining the axial length of the merging ring; step three, roughly determining the merging ring profile according to the straight wall fold surface based on the installation position of the front end of the merging ring, the radial position of the trailing edge and the axial length; step four, designing the inner cone profile according to the design principle of equal pressure gradient of the internal flow path, and smoothing the uneven position; step five, optimizing the design of the merging ring profile into a curved wall expansion form according to the design principle of equal pressure gradient of the internal flow path or the design principle of equal pressure gradient change rate; step six, constructing the internal flow path with the merging ring profile and the inner cone profile, carrying out three-dimensional simulation analysis, and optimizing the design if flow separation exists.

Description

Technical Field

[0001] The present application belongs to the technical field of improved design of afterburner combustion chambers of aircraft engines, and specifically relates to a method for designing the internal diffuser flow path profile of the afterburner combustion chamber confluence ring expansion. Background Art

[0002] With the development of aviation engine technology, the performance requirements for afterburner are getting higher and higher, which makes the contradiction between afterburner performance and cooling increasingly prominent.

[0003] At present, the afterburner chamber includes an outer wall 1, a merging ring 2 arranged in the outer wall 1, and an inner cone 3 arranged in the merging ring 2. Figure 1 As shown, an outer flow path is formed between the merging ring 2 and the outer wall 1, and an inner flow path is formed between the merging ring 2 and the inner cone 3, and the inner flow path is a pressure diffusion flow path.

[0004] The confluence ring 2 in the afterburner is mostly a straight wedge-shaped structure with simple structural design and high reliability. The trailing edge of the confluence ring 2 is the mixing point of the outer and inner airflows. Its radial position directly affects the matching result of the outer and inner aerodynamic area of ​​the afterburner, and further affects the outer and inner pressure ratio and cooling effect of the mixing section of the afterburner.

[0005] When the state of the aircraft engine main engine is determined, reducing the aerodynamic area of ​​the afterburner outer circumference can effectively increase the outer-to-inner pressure ratio and improve the cooling effect. This requires moving the radial position of the trailing edge of the merge ring 2 outward and designing the merge ring 2 as an expansion structure. Without changing the front end position of the merge ring 2, the existing merge ring 2 with a straight wedge-shaped structure can no longer meet the usage requirements. In view of this, the present application is proposed. Summary of the invention

[0006] The purpose of the present application is to provide a method for designing the profile of the internal diffuser flow path of the expansion of the afterburner merging ring, to expand the merging ring, and to design the internal diffuser flow path to meet the needs of reducing the aerodynamic area of ​​the afterburner outer duct and improving the cooling effect.

[0007] The technical solution of this application is:

[0008] A method for designing a pressure diffuser flow path profile of an afterburner confluence ring expansion, comprising:

[0009] Step 1, determining the radial position of the trailing edge of the confluence ring;

[0010] Step 2, determine the axial length of the confluence ring;

[0011] Step 3: According to the installation position of the front end of the merging ring, the radial position of the trailing edge and the axial length, the profile of the merging ring is roughly determined according to the straight wall folding surface;

[0012] Step 4: Design the inner cone surface according to the design principle of pressure gradient of the inner flow path, and smooth the uneven position;

[0013] Step 5: According to the design principle of equal pressure gradient of the inner flow path or the design principle of equal pressure gradient change rate, the confluence ring surface is optimized to be a curved wall expansion form;

[0014] Step 6: Construct the internal flow path with the converging annular surface and the inner cone surface, and conduct three-dimensional simulation analysis. If flow separation exists, perform optimization design.

[0015] Optionally, in the above-mentioned method for designing the internal diffuser flow path profile of the afterburner merging ring expansion, step one is specifically as follows:

[0016] According to the matching results of the main engine and the afterburner combustion organization plan, the outer internal aerodynamic area of ​​the afterburner chamber is matched and designed to meet the needs of the whole machine, and then the radial position of the trailing edge of the confluence ring is determined.

[0017] Optionally, in the above-mentioned method for designing the internal diffuser flow path profile of the afterburner merging ring expansion, step 2 is specifically as follows:

[0018] ;

[0019] in,

[0020] is the equivalent expansion angle of the expansion flow path, which is less than 20°;

[0021] is the outlet flow area of ​​the expansion flow path;

[0022] is the flow area of ​​the diffuser flow path inlet;

[0023] is the axial length of the confluence ring.

[0024] Optionally, in the above-mentioned method for designing the internal diffuser flow path profile of the afterburner merging ring expansion, step three is specifically as follows:

[0025] According to the front end installation position of the merging ring, the radial position of the trailing edge and the axial length, the merging ring is divided into multiple sections along the axial direction, and the expansion angles of the profiles of each section are gradually increased from front to back to roughly determine the profile of the merging ring.

[0026] Optionally, in the above-mentioned method for designing the internal diffusion flow path profile of the afterburner merging ring expansion, in step six, the internal flow path is constructed with the merging ring profile and the inner cone profile, and a three-dimensional simulation analysis is carried out. When flow separation exists, the profile at the starting position of the flow separation is optimized to reduce the pressure change gradient at the profile at the starting position of the flow separation.

[0027] According to at least one embodiment of the present application,

[0028] This application has at least the following beneficial technical effects:

[0029] A method for designing the profile of an inner diffuser flow path of an afterburner merging ring expansion is provided. The merging ring is expanded and designed, and the inner diffuser flow path is designed to meet the needs of reducing the aerodynamic area of ​​the afterburner outer circumference and improving the cooling effect. At the same time, it can have higher aerodynamic stability, control flow separation, and reduce flow losses. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the structure of the afterburner;

[0031] Figure 2 It is a schematic diagram of a method for designing a profile of an internal pressure-diffusing flow path of an afterburner merging ring expansion provided in an embodiment of the present application;

[0032] Figure 3 It is a schematic diagram of roughly determining the confluence ring profile according to the straight wall fold surface provided in the embodiment of the present application;

[0033] Figure 4 It is a schematic diagram of optimizing the design of the confluence ring profile into a curved wall expansion form provided by an embodiment of the present application;

[0034] in:

[0035] 1-outer wall; 2-confluence ring; 3-inner cone.

[0036] In order to better illustrate the present embodiment, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product. In addition, the drawings are only used for illustrative purposes and should not be construed as limitations on the present application. DETAILED DESCRIPTION

[0037] In order to make the technical solution and advantages of the present application clearer, the technical solution of the present application will be further described in detail in detail with reference to the accompanying drawings. It can be understood that the specific embodiments described here are only partial embodiments of the present application, which are only used to explain the present application, not to limit the present application. It should be noted that, for the convenience of description, only the parts related to the present application are shown in the accompanying drawings, and other related parts can refer to the general design.

[0038] In addition, unless otherwise defined, the technical terms or scientific terms used in the description of this application shall have the usual meanings understood by those of ordinary skill in the art to which this application belongs. The words used in the description of this application to indicate orientation are only used to indicate relative directions or positional relationships. When the absolute position of the described object changes, its relative positional relationship may also change accordingly. The word "include" used in the description of this application indicates that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, but does not exclude other elements or objects.

[0039] In addition, it should be noted that, unless otherwise clearly specified and limited, the words "installation", "connection" and similar terms used in the description of this application should be understood in a broad sense. For example, the connection can be a fixed connection or a detachable connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. Technical personnel in the field can understand its specific meaning in this application according to the specific circumstances.

[0040] A design method for the internal diffuser flow path profile of the afterburner confluence ring expansion, such as Figure 2 shown.

[0041] The design input parameters include the inlet aerodynamic parameters of the afterburner, the installation position of the confluence ring, the installation position of the inner cone, and the design indicators related to the diffuser flow path.

[0042] Step 1: Determine the radial position of the trailing edge of the confluence ring.

[0043] According to the matching results of the main engine and the design ideas of the afterburner combustion organization scheme, the outer internal aerodynamic area of ​​the afterburner chamber that can meet the needs of the whole machine is matched and designed, and then the radial position of the trailing edge of the confluence ring is determined.

[0044] Step 2: Determine the axial length of the confluence ring.

[0045] For the afterburner, the larger the equivalent expansion angle of the diffuser flow path, the shorter the axial length of the confluence ring. However, an equivalent expansion angle that is too large can easily cause flow separation. The smaller the equivalent expansion angle, the longer the axial length of the confluence ring is required, but it will also increase the weight of the aircraft engine. According to the design experience of the afterburner, the equivalent expansion angle of the diffuser flow path should generally not exceed 20°.

[0046] ;

[0047] in,

[0048] is the equivalent expansion angle of the expansion flow path;

[0049] is the outlet flow area of ​​the expansion flow path;

[0050] is the flow area of ​​the diffuser flow path inlet;

[0051] is the axial length of the confluence ring.

[0052] Step 3: According to the installation position of the front end of the merging ring, the radial position of the trailing edge and the axial length, roughly determine the merging ring profile according to the straight wall folding surface.

[0053] According to the front installation position of the merging ring, the radial position of the trailing edge and the axial length, the merging ring is reasonably divided into multiple sections along the axial direction, which can be two ends or three sections. The expansion angle of each section profile is gradually increased from front to back. The merging ring profile is roughly determined, such as Figure 3 As shown, it is a preliminary scheme for the design of the confluence ring surface.

[0054] Step 4: Design the inner cone surface according to the design principle of pressure gradient such as internal flow path, and smooth the uneven positions.

[0055] The design principle of constant pressure gradient means that the growth rate of pressure in the axial direction is designed to be constant.

[0056] The smooth designed inner cone profile is used as the condition for further design of the confluence ring profile.

[0057] Step 5: According to the design principle of equal pressure gradient of the internal flow path or the design principle of equal pressure gradient change rate, the confluence ring surface is optimized to be a curved wall expansion form.

[0058] Based on the inner cone profile, the confluence ring profile is optimized and designed into a curved wall expansion form according to the design principle of equal pressure gradient or equal pressure gradient change rate of the inner flow path, such as Figure 4 shown.

[0059] The design principle of constant pressure gradient change rate means that the change rate of the pressure gradient in the axial direction is designed to be constant.

[0060] The converging annular surface is optimized to be a curved wall expansion form, and the design principle of equal pressure gradient change rate is recommended. The characteristic of the internal flow path designed in this way is that the pressure expansion is relatively gentle when the speed in the front section is relatively large, and then the pressure expansion gradually accelerates. Under the conditions of the same pressure expansion demand and the same pressure expansion length, aerodynamic separation can be effectively avoided from the front end, while reducing flow resistance loss.

[0061] The reason why the confluence ring profile is optimized to be designed as a curved wall expansion form is that for the afterburner of a turbofan engine with a relatively large internal flow rate, if the confluence ring is designed as a simple straight wall folded surface form, flow separation is likely to occur at the turning point. Compared with the straight wall folded surface form, the curved wall expansion form can effectively reduce flow losses.

[0062] Step 6: Construct the internal flow path with the converging annular surface and the inner cone surface, and conduct three-dimensional simulation analysis. If flow separation exists, perform optimization design.

[0063] The three-dimensional simulation analysis of the internal flow path focuses on optimizing the profile at the starting position of flow separation when flow separation exists, reducing the pressure change gradient at the profile at the starting position of flow separation, and completing the profile design of the internal pressure diffusion flow path of the afterburner confluence ring expansion. The output design includes the confluence ring profile, inner cone profile, key dimensions, etc.

[0064] In the method for designing the internal diffuser flow path profile of the afterburner merging ring expansion disclosed in the above-mentioned embodiment, the merging ring is expanded and the internal diffuser flow path is designed to meet the requirements of reducing the aerodynamic area of ​​the afterburner outer duct and improving the cooling effect, while having higher aerodynamic stability, controlling flow separation and reducing flow losses.

[0065] So far, the technical solution of the present application has been described in conjunction with the preferred embodiments shown in the accompanying drawings. Those skilled in the art should understand that the scope of protection of the present application is obviously not limited to these specific embodiments. Without departing from the principles of the present application, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the scope of protection of the present application.

Claims

1. A method for designing the profile of the internal pressure diffuser flow path of the afterburner confluence ring expansion, characterized in that: include: Step 1, determining the radial position of the trailing edge of the confluence ring; Step 2, determine the axial length of the confluence ring; Step 3: According to the installation position of the front end of the merging ring, the radial position of the trailing edge and the axial length, the profile of the merging ring is roughly determined according to the straight wall folding surface; Step 4: Design the inner cone surface according to the design principle of pressure gradient of the inner flow path, and smooth the uneven position; Step 5: According to the design principle of equal pressure gradient of the inner flow path or the design principle of equal pressure gradient change rate, the confluence ring surface is optimized to be a curved wall expansion form; Step 6: Construct the inner flow path with the converging annular surface and the inner cone surface, conduct three-dimensional simulation analysis, and optimize the design if flow separation exists; Step 1 is as follows: According to the matching result of the main engine and the combustion plan of the afterburner, the aerodynamic area outside the afterburner chamber that can meet the needs of the whole machine is matched and designed, and then the radial position of the trailing edge of the confluence ring is determined; Step 2 is as follows: ； in, is the equivalent expansion angle of the expansion flow path, which is less than 20°; is the outlet flow area of ​​the expansion flow path; is the inlet flow area of ​​the expansion flow path; is the axial length of the confluence ring.

2. The method for designing the internal diffuser flow path profile of the afterburner merge ring expansion according to claim 1, characterized in that: Step three is as follows: According to the front end installation position of the merging ring, the radial position of the trailing edge and the axial length, the merging ring is divided into multiple sections along the axial direction, and the expansion angles of the profiles of each section are gradually increased from front to back to roughly determine the profile of the merging ring.

3. The method for designing the internal diffuser flow path profile of the afterburner merge ring expansion according to claim 1, characterized in that: In step six, the internal flow path is constructed with the converging ring surface and the inner cone surface, and a three-dimensional simulation analysis is carried out. When flow separation exists, the surface at the starting position of flow separation is optimized to reduce the pressure change gradient at the surface at the starting position of flow separation.

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