Forward Design Method for Aeroengine Casing Structure

Abstract

The present invention discloses a forward design method for an aero-engine casing structure, comprising the following steps: discretizing a casing model with a known two-dimensional structure diagram into independent "surface elements"; recombining the respective "surface elements" according to their positions to form a complete single-sided body; calculating the thicknesses of the "surface elements" in the single-sided body by using finite element method after applying the constraint conditions of strength and stiffness; constructing a preliminary three-dimensional model of the casing according to the thickness calculation results; checking and fine-tuning the preliminary three-dimensional model of the casing to obtain the final three-dimensional model of the casing. The design method of the present invention can quickly complete the three-dimensional design of the thin-walled casing of an aero-engine, greatly improve the completion degree and design efficiency of the aero-engine casing in the preliminary design, and can complete the strength and stiffness analysis during the design process, avoiding the subversive repetition that occurs when checking after design according to experience in the traditional design, effectively saving the time cost and labor cost, and greatly improving the design efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of aero-engine structure design, and in particular, to a forward design method for an aero-engine casing structure. Background Art

[0002] At present, the aero-engine structure design is changing from measurement and imitation design to independent forward research and development. The traditional aero-engine casing structure design usually adopts the design process as shown in Figure 1 . In this process, the preliminary structure design usually depends on measurement and imitation experience, and the design quality varies due to the differences in designers' experience and preferences. Generally, if the preliminary structure design meets the requirements of strength, vibration, and life, the stage structure design is completed. There is usually room for optimization in the stage structure design; if the requirements are not met, it usually enters multiple rounds of iteration. Along with the collaborative design changes, it generally takes a long time, and sometimes even subversive repetitions occur; an engine has many parts, and the design completion degree and iteration cycle of each part will also vary greatly due to different designers, sometimes seriously affecting the engine development progress. This design method obviously can no longer meet the requirements of independent forward design. Summary of the Invention

[0003] The present invention provides a forward design method for an aero-engine casing structure to solve the technical problems of the traditional measurement and imitation design, such as taking a long time, sometimes even having subversive repetitions, and seriously affecting the engine development progress.

[0004] The technical solution adopted by the present invention is as follows:

[0005] A forward design method for an aero-engine casing structure includes the following steps: discretizing the casing model of the known two-dimensional structure diagram into separate "surface elements"; recombining the "surface elements" according to their positions to form a complete partial surface body; applying the constraint conditions of strength and stiffness and then using finite element to calculate the thickness of each "surface element" in the partial surface body; constructing a preliminary three-dimensional model of the casing according to the thickness calculation result; checking and fine-tuning the preliminary three-dimensional model of the casing to obtain the final three-dimensional model of the casing.

[0006] Further, the step of "discretizing the casing model of the known two-dimensional structure diagram into separate'surface elements'" specifically includes the following steps: dividing the casing model of the known two-dimensional structure diagram into several blocks according to the design elements; simplifying each block to form a separate "surface element".

[0007] Further, in the step of "dividing the casing model of the known two-dimensional structure diagram into several blocks according to the design elements", the design elements include one or more of function, position, and shape.

[0008] Further, in the step of "simplifying each block to form separate 'face elements'", the 'face element' is the surface of the separated block or the middle surface within any thickness range of the block.

[0009] Further, in the step of "re - combining each 'face element' according to the position to form a complete single - plane body", the single - plane body is compared and analyzed with the structure of the mature casing part to preliminarily judge the rationality of the single - plane body structure design and adjust it in a timely manner.

[0010] Further, when performing the step of "using finite element method to calculate the thickness of each 'face element' in the single - plane body after applying the strength and stiffness constraint conditions", the thickness of the 'face element' is used as the design variable, the optimal mass is taken as the design goal, and after inputting the boundary conditions and constraint conditions, the thickness of each 'face element' is solved.

[0011] Further, the step of "using finite element method to calculate the thickness of each 'face element' in the single - plane body after applying the strength and stiffness constraint conditions" specifically includes the following steps: defining each 'face element'; setting the initial value and variation range of each 'face element'; applying loads; setting constraint conditions and optimization goals; calculating and solving.

[0012] Further, in the step of "applying loads", the loads include the aerodynamic load on the flow - passage surface, the axial force load and torque load on the front mounting edge and the rear mounting edge, and the acting force load on the auxiliary mounting section on the front mounting edge.

[0013] Further, in the step of "setting constraint conditions and optimization goals", the optimization goal is to minimize the mass or other design elements.

[0014] Further, the step of "checking and fine - tuning the preliminary three - dimensional model of the casing to obtain the final three - dimensional model of the casing" specifically includes the following steps: calculating and checking the strength, vibration and life of the preliminary three - dimensional model of the casing; if the strength, vibration and life all meet the design requirements, the checking ends; if one of the strength, vibration and life does not meet the design requirements, the dimensions of the preliminary three - dimensional model of the casing are fine - tuned, and then the above two steps are repeated in turn until the strength, vibration and life all meet the design requirements, and then the checking ends.

[0015] The present invention has the following beneficial effects:

[0016] In the traditional design method, when it is necessary to adjust the design variables, various elements of points, lines, and surfaces can be changed, so the selection of design variables has great randomness, and the design results also have great uncertainty. In the forward design method of the present invention, in step "S10: Discretize the casing model of the known two-dimensional structure diagram into independent 'plane elements'", that is, in the design method of the present invention, the plane elements in the two-dimensional diagram are set as design variables, and the selection of design variables is more specific, so the design results are more certain, reducing the workload of subsequent adjustment operations, and thus improving the design efficiency; in step "S30: After applying the constraint conditions of strength and stiffness, use finite element to calculate the thickness of each 'plane element' in the single-sided body", the optimal thickness of the mass under the constraint conditions can be obtained, and this thickness combination is a design benchmark in the three-dimensional design of the casing part. With this design "benchmark", there is the biggest difference from the traditional design method. Because in the traditional design method, the selection of design variables has randomness and lacks necessary benchmark constraints, the design results have great uncertainty. Sometimes the local strength and stiffness do not meet the requirements and need to be redone. Sometimes the design margin is too large and elements such as weight exceed the standard, and later optimization and weight reduction design are also required. All these require multiple rounds of iteration, which will cost a lot of manpower and material resources, and have certain requirements for the experience of designers. Sometimes it may also affect the development progress. However, in the method of the present invention, after having this design "benchmark", when carrying out the three-dimensional design of the casing part, there is a reference, and this "benchmark" value is close to the optimal value of the casing part under the condition of meeting the verification conditions. As long as the design value is not lower than the "benchmark value" and is near this "benchmark value", a basic three-dimensional model that initially meets the design requirements and has a high design quality can be obtained. Therefore, compared with the traditional design method, the completion degree of a single part in the preliminary design can reach a relatively high level.

[0017] Therefore, through the design method of the present invention, the three-dimensional design of the thin-walled casing of the aero-engine can be quickly completed, greatly improving the completion degree of the aero-engine casing in the preliminary design. Compared with the traditional iterative design method, the design efficiency is greatly improved; and the strength and stiffness analysis can be completed during the design process, avoiding the subversive repetition that occurs when checking after designing according to experience in the traditional design, effectively saving time costs and labor costs, greatly improving the design efficiency, shortening the design cycle by 80%. It provides an effective design tool for the transformation of the aero-engine structure design from measurement and imitation to independent forward design. The newly designed aero-engine casing has passed the strength verification test and has been officially installed and used.

[0018] In addition to the purposes, features, and advantages described above, the present invention has other purposes, features, and advantages. The following will refer to the drawings to make a further detailed description of the present invention. Brief Description of the Drawings

[0019] The accompanying drawings, which form a part of this application, are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0020] Figure 1 is a flow chart of the structural design of a traditional aero-engine casing;

[0021] Figure 2 is the preliminary design of a traditional casing Figure 1 ;

[0022] Figure 3 is the preliminary design of a traditional casing Figure 2 ;

[0023] Figure 4 is a schematic diagram of dividing the casing model of a known two-dimensional structure diagram into blocks according to design elements;

[0024] Figure 5 is a schematic diagram of simplifying each block to form a separate "surface element";

[0025] Figure 6 is a schematic diagram of recombining each "surface element" according to its position to form a complete planar solid;

[0026] Figure 7 is a schematic diagram of defining each "surface element";

[0027] Figure 8 is a schematic diagram of calculating the thickness of each surface element by finite element analysis;

[0028] Figure 9 is a schematic diagram of optimizing the preliminary three-dimensional model of the casing;

[0029] Figure 10 is a schematic diagram of checking the preliminary three-dimensional model of the casing Figure 1 ;

[0030] Figure 11 is a schematic diagram of checking the preliminary three-dimensional model of the casing Figure 2 。 Detailed implementation manners

[0031] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways defined and covered by the following.

[0032] Referring to Figure 1 , the preferred embodiment of the present invention provides a forward design method for the structure of an aero-engine casing, including the following steps:

[0033] S10: Discretize the casing model of the known two-dimensional structure diagram into separate "surface elements";

[0034] S20: Recombining each "surface element" according to position to form a complete flake face;

[0035] S30: After applying the constraints of strength and stiffness, the thickness of each "surface element" in the faceted body is calculated using finite element method;

[0036] S40: constructing a preliminary three-dimensional model of the casing according to the thickness calculation result;

[0037] S50: Check and fine-tune the preliminary three-dimensional model of the receiver to obtain the final three-dimensional model of the receiver.

[0038] like Figure 1-3 As shown, according to the traditional design method, the preliminary structural design usually relies on the designer's experience. If the preliminary structural design meets the strength, vibration and life requirements, the stage structural design is completed, and there is usually room for optimization after the stage structural design; according to the development time limit, after the strength, vibration and life of the verification model meet the requirements, if time is tight, the design will be directly completed and transferred to the next stage; if time is sufficient, it will enter a long cycle of adjusting the structure-verification-adjusting the structure-re-verification, and in this process, it may also be accompanied by the situation that other parts are changed due to the adjustment of the part structure, so that the cycle of improving the model will be longer. Therefore, in view of the problems existing in the traditional design method, the present invention proposes a forward design method of the casing structure of an aircraft engine based on simulation calculation. In the forward design method, the casing model of the known two-dimensional structure diagram is first discretized into independent "surface elements", and then each "surface element" is recombined according to the position to form a complete flake body, and then the thickness of each "surface element" in the flake body is calculated by finite element after applying the constraints of strength and stiffness, and finally the preliminary three-dimensional model of the casing can be quickly constructed according to the thickness calculation result.

[0039] In the traditional design method, when it is necessary to adjust the design variables, various elements such as points, lines, and planes can be changed, so the selection of design variables has great randomness, and the design results also have relatively large uncertainties. In the forward design method of the present invention, in step "S10: Discretize the casing model of the known two-dimensional structure diagram into independent 'plane elements'", that is, in the design method of the present invention, the plane elements in the two-dimensional diagram are set as design variables, and the selection of design variables is more specific, so the design results are more certain, reducing the workload of subsequent adjustment operations, and thus improving the design efficiency; in step "S30: After applying the constraint conditions of strength and stiffness, use finite element to calculate the thickness of each 'plane element' in the plane body", the optimal thickness of the mass under the constraint conditions can be obtained, and this thickness combination is a design benchmark in the three-dimensional design of the casing part. With this design "benchmark", there is the biggest difference from the traditional design method. Because the selection of design variables in the traditional design method has randomness and lacks necessary benchmark constraints, the design results have relatively large uncertainties. Sometimes the local strength and stiffness do not meet the requirements and need to be redone. Sometimes the design margin is too large and elements such as weight exceed the standard, and later optimization and weight reduction design are also required. All these require multiple rounds of iteration, which will cost a lot of manpower and material resources, and have certain requirements for the experience of designers. Sometimes it may also affect the development progress. However, in the method of the present invention, after having this design "benchmark", when carrying out the three-dimensional design of the casing part, there is a reference, and this "benchmark" value is close to the optimal value of the casing part under the condition of meeting the verification conditions. As long as the design value is not lower than the "benchmark value" and is near this "benchmark value", a basic three-dimensional model that initially meets the design requirements and has relatively high design quality can be obtained. Therefore, compared with the traditional design method, the completion degree of a single part in the preliminary design can reach a relatively high level.

[0040] Therefore, through the design method of the present invention, the three-dimensional design of the thin-walled casing of the aero-engine can be quickly completed, greatly improving the completion degree of the aero-engine casing in the preliminary design. Compared with the traditional iterative design method, the design efficiency is greatly improved; and the strength and stiffness analysis can be completed during the design process, avoiding the subversive repetition that occurs when checking after designing according to experience in the traditional design, effectively saving time costs and labor costs, greatly improving the design efficiency, shortening the design cycle by 80%, providing an effective design tool for the transformation of aero-engine structure design from measurement and imitation to independent forward design, and the newly designed aero-engine casing has passed the strength verification test and has been officially installed and used.

[0041] Optionally, as Figure 4-5 shown, step "S10: Discretize the casing model of the known two-dimensional structure diagram into independent 'plane elements'" specifically includes the following steps:

[0042] S101: Divide the casing model of the known two-dimensional structure diagram into several blocks according to the design elements;

[0043] S102: Simplify each block to form individual "surface elements".

[0044] In this alternative solution, different from the traditional optimization method, when decomposing and discretizing the two-dimensional casing structure, there is no need to be restricted to a specific method. It can be divided into different surface elements according to factors such as function, position, and shape, which not only does not affect the effectiveness of the calculation but also has greater flexibility and stronger applicability, and can also be applied to particularly complex engine casings. In traditional designs, when design variables need to be adjusted, various elements of points, lines, and surfaces can be changed, and the selection of design variables is highly arbitrary, and the design results also have great uncertainties. In the method of the present invention, the surface elements in the two-dimensional drawing are set as design variables, and the selection of design variables is more specific. At the same time, when dividing the surface elements, it can be flexible and has strong applicability and practicality.

[0045] In this alternative solution, as Figure 4 shown, in step "S101: Divide the casing model of the known two-dimensional structure diagram into several blocks" of the present invention, the design elements include one or more of function, position, and shape. In a specific embodiment of this alternative solution, the casing model is divided into several blocks according to the functional elements.

[0046] In this alternative solution, as Figure 5 shown, in step "S102: Simplify each block to form individual'surface elements'", the "surface element" is the surface of the divided block or the middle surface within any thickness range of the block. In a specific embodiment of this alternative solution, as Figure 5 shown, the surface element is the surface of the block, so that when designing the thickness of the subsequent surface element, the thickness only increases in one direction, making the subsequent operations simple; when the surface element is the middle surface within any thickness range of the divided block, when designing the thickness of the subsequent surface element, the thickness can increase from the middle surface to both sides respectively, so that the thickness design is flexible and suitable for mechanical parts with more complex structures.

[0047] Optionally, as Figure 6As shown, in step "S20: Re - combine each 'face element' according to its position to form a complete partial surface body", the partial surface body is compared and analyzed with the structure of the mature casing part to preliminarily judge the rationality of the partial surface body structure design and make timely adjustments. In actual operation, when the discrete 'face elements' are recombined according to their positions to form a preliminary complete partial surface body, the partial surface body is a continuous spatial sheet body composed of multiple faces, which has initially taken on the three - dimensional appearance of the casing part. At this time, although the three - dimensional design of the casing part has not been completely completed, based on the preliminary three - dimensional appearance of the casing part and combined with the structure of the mature casing part for comparative analysis, a preliminary judgment can be given on the rationality of the structure design and adjustments can be made in a timely manner, thus effectively avoiding the repetition in traditional design where, sometimes after all the design work is completed, it has to be redone due to unreasonable structural layout, thereby improving the design efficiency and reducing the intensity of the design work.

[0048] Optionally, when performing step "S30: After applying the constraint conditions of strength and stiffness, use finite element method to calculate the thickness of each 'face element' in the partial surface body", the thickness of the 'face element' is used as the design variable, the optimal mass is taken as the design goal, and after inputting the boundary conditions and constraint conditions, the thickness of each 'face element' is solved. In specific operation, the thickness of each 'face element' in the partial surface body formed in step S20 is used as the design variable, and an interval value is assigned to each 'face element' as the design interval. At the same time, boundary load conditions are applied to the partial surface body, and constraint conditions are applied according to criteria such as strength and stiffness. Taking the optimal mass as the design goal, finite element calculation is carried out to obtain the best thickness of each face with the optimal mass under the constraint conditions. This thickness combination is a design benchmark in the three - dimensional design of the casing part. With this design 'benchmark', there is the biggest difference from the traditional design method. In the traditional design method, the selection of design variables is arbitrary and lacks necessary benchmark constraints, so the design results have great uncertainty. Sometimes the local strength and stiffness do not meet the requirements and need to be redone. Sometimes the design margin is too large and elements such as weight exceed the standard, and later optimization for weight reduction is also required. All these need multiple iterations, which will consume a lot of manpower and material resources and have certain requirements for the designer's experience, and may sometimes affect the research and development progress. But after having this design 'benchmark', when carrying out the three - dimensional design of the casing part, there is a reference, and this 'benchmark' value is close to the optimal value of the casing part that meets the verification conditions. As long as the design value is not lower than the 'benchmark value' and is near this 'benchmark value', a basic three - dimensional model that initially meets the design requirements and has a relatively high design quality can be obtained. Therefore, compared with the traditional design method, the completion degree of a single part in the preliminary design can reach a relatively high level.

[0049] In this optional solution, such as Figure 7-8As shown, the step "S30: After applying the constraint conditions of strength and stiffness, calculate the thickness of each 'face element' in the single-sided body using finite element method" specifically includes the following steps:

[0050] S301: Define each "face element"; in this alternative solution, as Figure 7 shown, six design variables of six face elements are defined by using six faces of T-1, T-2, T-3, T-4, T-5, and jin.

[0051] S302: Set the initial values and variation ranges of each "face element". The specific initial values are designed as follows:

[0052] Design variable Initial value (mm) Variation range (mm) Jin 4 1-8 T-1 4 1-8 T-2 4 1-8 T-3 4 1-8 T-4 4 1-8 T-5 4 1-8

[0053] S303: Apply loads; in this alternative solution, the loads include the aerodynamic load on the runner surface, the axial force loads and torque loads on the front mounting edge and the rear mounting edge, and the acting force load on the auxiliary mounting section on the front mounting edge.

[0054] S304: Set the constraint conditions and optimization objectives; in this alternative solution, the constraint conditions are to constrain the maximum stress and the maximum displacement; the optimization objective is to minimize the mass, or it can also be other design elements.

[0055] S305: Calculate and solve. The final thickness optimization result is as Figure 8 shown, and the calculation results are specifically as follows:

[0056] Design variable Initial value (mm) Designed value (mm) Rate of change Jin 4 2 -50% T-1 4 3.9 -2.5% T-2 4 5 +25% T-3 4 2.7 -32.5% T-4 4 5 +25% T-5 4 2.8 -30%

[0057] Optionally, as Figure 9 shown, in step S40, based on the three-dimensional design size benchmark of the casing obtained in step S30, complete the preliminary three-dimensional design of the casing, and finely adjust the three-dimensional structure size of the casing according to the interface design requirements and other general design requirements. It should be noted that the adjusted size should not be lower than the design benchmark value as much as possible to avoid the situation that the local strength or life design does not meet the requirements, and conduct a check calculation on the casing part model. Decide whether to finely adjust the size according to the calculation results, and obtain the final three-dimensional design model of the casing part. In the scheme design stage, each part is designed synchronously. If the design method of the present invention is adopted for all, compared with the isolated design of each part in the traditional design method, not only the quality of the design process is controllable, the design quality of each individual part obtained finally is relatively high, the design coordination of the whole engine is better, the completion degree in the preliminary design is also higher, and the overall design quality can also reach a relatively high level.

[0058] Optionally, as Figure 10-11 shown, the step "S50: Check and finely adjust the preliminary three-dimensional model of the casing to obtain the final three-dimensional model of the casing" specifically includes the following steps:

[0059] S501: Calculate and verify the strength, vibration and life of the preliminary three-dimensional model of the casing;

[0060] S502: If all of the strength, vibration and life meet the design requirements, the verification ends;

[0061] S503: If any one of the strength, vibration and life does not meet the design requirements, slightly adjust the dimensions of the preliminary three-dimensional model of the casing, and then repeat the above two steps in sequence until all of the strength, vibration and life meet the design requirements, then the verification ends. In actual operation, due to the operations of the aforementioned S10-S40, the stress level of the model is within a reasonable range and the model completion degree is relatively high. Even if adjustment is required in step S50, only slight adjustment is needed. Moreover, compared with the traditional casing structure design method, the design cycle is shortened by 80%. The preliminary design completion degree of the parts is relatively high, avoiding subversive repetitions and greatly shortening the part design cycle.

[0062] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A forward design method for an aircraft engine casing structure, characterized in that: The following steps are involved: The casing model of the known two-dimensional structure diagram is discretized into independent "surface elements" respectively; specifically, the steps include: dividing the casing model of the known two-dimensional structure diagram into a plurality of blocks according to design elements; simplifying each block to form an independent "surface element"; Recombine each "face element" according to its position to form a complete flake-hedron; After applying the constraints of strength and stiffness, the thickness of each "surface element" in the flake body is calculated by using finite element method. During the operation, the thickness of the "surface element" is used as the design variable, the optimal quality is taken as the design goal, and the thickness of each "surface element" is solved after inputting the boundary conditions and constraints. During the specific operation, the thickness of each "surface element" in the flake body formed in the step "recombining each "surface element" according to the position to form a complete flake body" is used as the design variable, and an interval value is assigned to each "surface element" as the design interval. At the same time, boundary load conditions are applied to the flake body, and constraints are applied according to the strength and stiffness criteria. The optimal quality is taken as the design goal, and finite element calculation is carried out to obtain the optimal thickness of each surface with the optimal quality under the constraints. The specific operation steps are as follows: Define each "surface element"; Set the initial value and variation range of each "surface element"; Apply loads; the loads include aerodynamic loads on the flow channel surface, axial force loads and torque loads on the front and rear mounting edges, and force loads on the auxiliary mounting joint on the front mounting edge; Set constraints and optimization goals; the constraints are the maximum stress and maximum displacement; the optimization goal is to minimize the mass; Calculate and solve; A preliminary three-dimensional model of the receiver is constructed based on the thickness calculation results; The preliminary three-dimensional model of the receiver is checked and fine-tuned to obtain the final three-dimensional model of the receiver.

2. The forward design method for aircraft engine casing structure according to claim 1, characterized in that: In the step of "dividing the casing model of the known two-dimensional structure diagram into several blocks according to design elements", the design elements include one or more of function, position, and shape.

3. The forward design method for aircraft engine casing structure according to claim 1, characterized in that: In the step of “simplifying each block into a separate “surface element””, the “surface element” is the surface of the separated block, or the middle surface within any thickness range of the separated block.

4. The forward design method for aircraft engine casing structure according to claim 1, characterized in that: In the step "recombining each "surface element" according to the position to form a complete one-sided body", the one-sided body is compared and analyzed with the mature receiver part structure to preliminarily judge the rationality of the one-sided body structure design and make timely adjustments.

5. The forward design method for aircraft engine casing structure according to claim 1, characterized in that: The step of "checking and fine-tuning the preliminary three-dimensional model of the casing to obtain the final three-dimensional model of the casing" specifically includes the following steps: Calculate and verify the strength, vibration and life of the preliminary three-dimensional model of the casing; If strength, vibration and life all meet the design requirements, the verification is completed; If one of the strength, vibration and life does not meet the design requirements, the size of the preliminary three-dimensional model of the casing is fine-tuned, and then the above two steps are repeated in sequence until the strength, vibration and life all meet the design requirements, and the verification is completed.

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