Approximately equal strength design method for aero-engine combustion chamber outer casing

Abstract

The application discloses an aero-engine combustion chamber outer casing approximate equal strength design method, comprising the following steps: step one, combustion chamber outer casing static strength calculation; step two, combustion chamber outer casing axial stress gradient calculation; step three, output combustion chamber outer casing deformation model; step four, combustion chamber outer casing before and after deformation axial stress gradient change calculation; step five, combustion chamber outer casing approximate equal strength solution is obtained. In the case of constant combustion chamber outer casing wall thickness, the stress level of the examination part can be effectively reduced, and the strength reliability is improved; in the case of the same strength reserve coefficient, the wall thickness of the combustion chamber outer casing can be reduced, and the weight of the combustion chamber outer casing is reduced, and the design effect is more obvious for the combustion chamber outer casing with large axial stress gradient. The technical problem that the weight of the combustion chamber outer casing is increased due to the increase of the wall thickness of the combustion chamber outer casing to meet the strength reserve is solved.

Description

Technical Field

[0001] This invention relates to a method for designing an approximately equal-strength outer casing for an aero-engine combustor, belonging to the field of engine technology. Background Technology

[0002] The outer combustor casing is one of the main force-transmitting components of an aero-engine, and is part of the core high-pressure casing of the aero-engine, containing the high-temperature, high-pressure combustion gases flowing at high speed within the engine. During engine operation, the pressure differential load causes the outer casing to bear significant circumferential tensile stress; this pressure differential is the primary load used to assess the design strength of the outer casing. Due to the inconsistent radii of the front and rear mounting edges of the outer combustor casing, it is typically composed of a conical section, a straight section, and a rounded transition section, such as... Figure 1 and Figure 2 As shown, the discontinuity in the stiffness of the outer combustion chamber casing leads to a large axial stress gradient within it. Given the generally low average stress level of the outer combustion chamber casing, the stress reserve in localized areas is insufficient, resulting in the material's mechanical properties not being fully utilized. Therefore, it is necessary to design the outer combustion chamber casing to have approximately equal strength.

[0003] To improve the strength and reliability of the engine combustion chamber outer casing, a common method is to adjust the design wall thickness of the outer casing to ensure sufficient strength reserve. The specific steps are as follows:

[0004] 1. Simulate and calculate the static strength of each part of the outer casing of the combustion chamber to obtain the stress distribution of each part of the outer casing of the combustion chamber, and then determine the strength test parts of the outer casing of the combustion chamber.

[0005] 2. Calculate the strength reserve coefficient of the test part of the outer combustion chamber casing, and ensure that the outer combustion chamber casing has sufficient strength reserve by adjusting the wall thickness of the outer combustion chamber casing.

[0006] While the current design method can ensure sufficient strength and reliability of the combustion chamber outer casing, it requires increasing the wall thickness of the combustion chamber outer casing, thereby increasing its weight. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a method for designing an aero-engine combustor outer casing with approximately equal strength.

[0008] The present invention is achieved through the following technical solutions.

[0009] This invention provides a method for designing an approximately equal-strength outer casing for an aero-engine combustor, comprising the following steps:

[0010] Step 1: Static strength calculation of the outdoor combustion chamber casing;

[0011] Step 2: Calculation of axial stress gradient in the outer casing of the combustion chamber;

[0012] Step 3: Output the model of the deformed outer casing of the combustion chamber;

[0013] Step 4: Calculate the change in axial stress gradient before and after deformation of the combustion chamber casing;

[0014] Step 5 yields an approximate isointense solution for the combustion chamber outside the casing.

[0015] Step one, the static strength calculation of the combustion chamber outdoor unit casing, is as follows: under appropriate differential pressure load, the static strength of the combustion chamber outdoor unit casing is calculated using the finite element method to obtain the stress distribution of the combustion chamber outdoor unit casing;

[0016] In step two, the axial stress gradient of the outer casing of the combustion chamber is calculated as follows: based on the static strength calculation results of the combustion chamber casing, the maximum axial stress gradient Tn-1 is calculated.

[0017] Step three, outputting the deformed model of the combustion chamber outer casing, is as follows: output the coordinates and deformation values ​​of each grid node of the combustion chamber outer casing. The coordinate values ​​of each node after deformation can be obtained by superimposing the initial coordinate values ​​of each node with the deformation values.

[0018] In step four, the change in axial stress gradient before and after deformation of the outer combustion chamber casing is calculated as follows: using the deformed model as the initial calculation model, the static strength of the outer combustion chamber casing is calculated; its maximum axial stress gradient Tn is calculated, and then the change in stress gradient ΔT = Tn - Tn-1 is calculated.

[0019] In step five, the approximate equal strength solution for the combustion chamber is obtained as follows: Repeat step four, and when the change in stress gradient ΔT = Tn - Tn-1 is less than a certain value, the final solution of the approximate equal strength design method is obtained. At this time, the axial stress gradient of the combustion chamber is the minimum.

[0020] The beneficial effects of this invention are as follows: While maintaining a constant wall thickness of the outer combustion chamber casing, it effectively reduces the stress level at its testing points, thereby improving its strength reliability; with the same strength reserve coefficient, it can reduce the wall thickness of the outer combustion chamber casing, thus reducing its weight. The design effect is even more pronounced for outer combustion chamber casings with large axial stress gradients. It solves the technical problem that increasing the wall thickness of the outer combustion chamber casing for strength reserve leads to an increase in its weight. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the outer casing of an aircraft engine combustion chamber;

[0022] Figure 2 yes Figure 1This is a schematic diagram of a 1 / 36 cyclic symmetric model structure;

[0023] Figure 3 This is the stress distribution of the outer casing of the combustor of a certain type of aero-engine before equal strength design;

[0024] Figure 4 This is the stress distribution of the outer casing of the combustor of a certain type of aero-engine after approximately equal strength design;

[0025] Figure 5 It is a comparison of the combustion chamber casing models before and after the approximate equal strength design. Detailed Implementation

[0026] The technical solution of the present invention is further described below, but the scope of protection is not limited to what is described.

[0027] like Figures 3 to 5 As shown.

[0028] The present invention provides a method for approximately equal strength design of an aircraft engine combustor outer casing, comprising the following steps:

[0029] Step 1, Static Strength Calculation of the Combustion Outer Unit Casing: Under appropriate differential pressure load, the static strength of the combustion outer unit casing is calculated using the finite element method to obtain the stress distribution of the combustion outer unit casing. (See attached diagram) Figure 3 ;

[0030] Step 2, Calculation of axial stress gradient of the outer casing of the combustion chamber: Based on the static strength calculation results of the combustion chamber casing, calculate its maximum axial stress gradient Tn-1.

[0031] Step 3, output the deformed model of the outer combustion chamber: output the coordinates and deformation values ​​of each grid node of the outer combustion chamber. The coordinate values ​​of each node after deformation can be obtained by superimposing the initial coordinate values ​​of each node with the deformation values.

[0032] Step 4: Calculation of the change in axial stress gradient before and after deformation of the outer combustion chamber casing: Using the deformed model as the initial calculation model, calculate the static strength of the outer combustion chamber casing. (See...) Figure 4 ; Calculate its maximum axial stress gradient Tn, and then calculate the change in stress gradient ΔT=Tn-Tn-1.

[0033] Step 5: Obtain the approximate equal strength solution for the outer casing of the combustion chamber. Repeat step 4. When the change in stress gradient ΔT = Tn - Tn-1 is less than a certain value, the final solution of the approximate equal strength design method is obtained. At this time, the axial stress gradient of the outer casing of the combustion chamber is the minimum.

[0034] It should be noted that this method pertains to minor structural deformation adjustments; see [link / reference]. Figure 5When the final model does not meet the aerodynamic design requirements, the constraint value of ΔT = Tn - Tn-1 can be appropriately increased to reduce the structural adjustment amount and meet the aerodynamic design requirements. With the outer casing wall thickness remaining constant, the stress level at its test points can be effectively reduced, improving its strength reliability. Under the same strength reserve coefficient, the wall thickness of the outer casing can be reduced, thereby reducing its weight. The design effect is more pronounced for outer casings with large axial stress gradients. This solves the technical problem of increasing the outer casing wall thickness to meet strength reserves, which leads to an increase in the weight of the outer casing.

Claims

1. A method for designing an approximately equal-strength outer casing for an aero-engine combustor, characterized in that, Includes the following steps: Step 1: Static strength calculation of the outdoor combustion chamber casing; Step 2: Calculation of axial stress gradient in the outer casing of the combustion chamber; Step 3: Output the model of the deformed outer casing of the combustion chamber; Step 4: Calculate the change in axial stress gradient before and after deformation of the combustion chamber casing; In step four, the change in axial stress gradient before and after deformation of the combustion chamber outer casing is calculated as follows: using the deformed model as the initial calculation model, the static strength of the combustion chamber outer casing is calculated; its maximum axial stress gradient Tn is calculated, and then the change in stress gradient ΔT = Tn - Tn-1 is calculated. Step 5: Obtain the approximate isointense solution for the combustion chamber outside the casing; In step five, the approximate equal strength solution of the combustion chamber is obtained as follows: Repeat step four, and when the change in axial stress gradient ΔT = Tn - Tn-1 is less than a certain value, the final solution of the approximate equal strength design method is obtained. At this time, the axial stress gradient of the combustion chamber is minimized.

2. The approximate equal strength design method for the outer casing of an aero-engine combustor as described in claim 1, characterized in that: Step one, the static strength calculation of the combustion chamber outer casing, is as follows: under appropriate differential pressure load, the static strength of the combustion chamber outer casing is calculated using the finite element method to obtain the stress distribution of the combustion chamber outer casing.

3. The approximate equal strength design method for the outer casing of an aero-engine combustor as described in claim 1, characterized in that: In step two, the axial stress gradient of the outer casing of the combustion chamber is calculated as follows: based on the static strength calculation results of the combustion chamber casing, the maximum axial stress gradient Tn-1 is calculated.

4. The approximate equal strength design method for the outer casing of an aero-engine combustor as described in claim 1, characterized in that: Step three, outputting the deformed model of the combustion chamber outer casing, is as follows: output the coordinates and deformation values ​​of each grid node of the combustion chamber outer casing. The coordinate values ​​of each node after deformation can be obtained by superimposing the initial coordinate values ​​of each node with the deformation values.

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