Method for determining the structure of a fixing device for overspeed testing of large-size blades

Abstract

A method for determining the structure of a large-size blade overspeed test fixing device, comprising the following steps: setting control points on a fan blade and a fixing device thereof, providing displacement of the control points under an actual working condition; establishing a two-dimensional model of the fan blade and the fixing device, calculating displacement of the control points of the fixing device under a vacuum test state and calculating a difference value with the displacement under the actual working condition, and performing structural optimization with minimization of the difference value as a target; establishing a three-dimensional model of the fan blade and the fixing device, calculating displacement of the control points of the fan blade under the vacuum test state and calculating a difference value with the displacement under the actual working condition, and performing structural optimization with minimization of the difference value as a target, to obtain a final structure of the fixing device. The method can make the deformation distribution of the blade under the vacuum test state and the actual working condition as close as possible, and improve test accuracy.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of aero-engines, and particularly relates to a method for determining the structure of a large-size blade overspeed test fixing device. BACKGROUND

[0002] The composite material fan blade of an aero-engine is large in size and high in working speed, and is one of the core parts related to the safety of the engine. Once failure occurs, serious safety problems will be caused. Therefore, the airworthiness clauses put forward strict overspeed requirements for the composite material fan blade. In order to meet the airworthiness requirements, in addition to simulating and analyzing the strength of the blade, an overspeed test needs to be designed to analyze and verify the simulation results. However, due to the large size of the fan, the power required to drive the fan under real conditions is very high, and it is limited by the power of the tester. Usually, the overspeed test is carried out under vacuum conditions. However, under actual working conditions, in addition to the centrifugal load caused by rotation, the fan blade will also be subjected to the load generated by aerodynamic influence. Under vacuum conditions, only the rotation speed is adjusted, and the stress and strain state of the blade under actual working conditions cannot be accurately simulated, which restricts the accuracy of the overspeed test results. Therefore, it is of high practical significance to provide a solution to make the stress and strain distribution of the blade under vacuum test conditions consistent with the actual working conditions, so as to improve the design level of the fan blade of the aero-engine. SUMMARY

[0003] The purpose of the present application is to provide a method for determining the structure of a large-size blade overspeed test fixing device, which optimizes the accuracy of the blade overspeed test by adjusting the structure of the blade fixing device.

[0004] According to an embodiment of the aspect of the present application, a method for determining the structure of a large-size blade overspeed test fixture is provided, the method comprising the following steps: setting control points on a fan blade and a fixture of the fan blade respectively, providing displacement D of the control points on the fan blade in an actual state and displacement d of the control points on the fixture; establishing a fan blade-fixture two-dimensional model, calculating displacement d' of the control points on the fixture in a vacuum test state; selecting an optimization region on the fixture, taking |d-d'| as a minimum value as a target, performing structural optimization iteration on the optimization region to obtain min|d-d'|, wherein a constraint condition is that a stress borne by the fixture in the vacuum test condition does not exceed a strength limit of a material of the fixture; establishing a fan blade-fixture three-dimensional model according to the fan blade-fixture two-dimensional model obtained by the structural optimization iteration, calculating displacement D' of the control points on the fan blade in the vacuum test state; taking |D-D'| as a minimum value as a target, performing shape optimization iteration on the optimization region to obtain an optimized structure model, wherein a constraint condition is that the stress borne by the fixture in the vacuum test condition does not exceed the strength limit of the material of the fixture and |d-d'|≤min|d-d'|.

[0005] The method simulates and calculates the deformation state of the blade in the vacuum test state by setting the control points, changes the constraint of the fixture on the fan blade to make the deformation state of the blade consistent with the deformation state in the actual working condition as much as possible, thereby simulating the strain of the fan blade under the combined action of the centrifugal load and the starting load in the actual working condition in the vacuum state, and further improving the accuracy of the vacuum simulation test.

[0006] Further, in some embodiments, the control points are provided in plurality, the measurement reference of the displacement of the control points is provided at the blade root of the blade, and the displacement D and the displacement d take the maximum value of the displacements of the plurality of control points respectively. The plurality of control points can more accurately reflect the deformation of the fan blade.

[0007] Further, in some embodiments, of the control points on the fan blade, two control points are respectively provided at the leading edge of the blade tip and the trailing edge of the blade tip; and of the control points on the fixture, two control points are respectively provided at the front end and the rear end of the fixture. The control points respectively provided at the front end and the rear end can better reflect the deformation state of the blade.

[0008] Further, in some embodiments, the fan blade-fixture two-dimensional model is simplified in a mass point manner. The blade is simplified as a mass point to reduce the calculation amount.

[0009] Further, in some embodiments, the optimization region is located between the fan blade tenon installation position and the fixed device and engine rotating shaft connection position.

[0010] Further, in some embodiments, the strength limit of the fixed device material adopts the yield strength limit.

[0011] Further, in some embodiments, before the three-dimensional model of the fan blade-fixed device is established, the two-dimensional model of the fan blade-fixed device is first processed by fairing curve. The fairing curve processing eliminates the structure of the corner and other structures that do not meet the design requirements generated in the structure optimization iteration.

[0012] Further, in some embodiments, the structure optimization of the two-dimensional model of the fan blade-fixed device adopts topology optimization.

[0013] Further, in some embodiments, the topology optimization adopts the variable density method. The variable density method is an effective method of topology optimization. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 It is an embodiment of the fan blade test device partial cross-sectional structure schematic diagram;

[0015] Figure 2 It is an embodiment of the fan blade-fixed device two-dimensional model structure schematic diagram.

[0016] The purpose of the above drawings is to make a detailed description of the present application so that those skilled in the art can understand the technical concept of the present application, and is not intended to limit the present application. In order to express briefly, the above drawings only schematically draw the structures related to the technical features of the present application, and do not strictly draw the complete device and all the details according to the actual proportion. DETAILED DESCRIPTION

[0017] The present application will be further described in detail below by specific embodiments combined with the drawings.

[0018] Reference to "embodiments" herein means that the specific features, structures or characteristics described in connection with the embodiments can be included in at least one embodiment herein. The phrase appears at various places in the specification does not necessarily refer to the same embodiment, nor is it limited to mutually exclusive or alternative embodiments. Those skilled in the art should understand that the embodiments herein can be combined with other embodiments without structural conflict.

[0019] In the description herein, unless specifically defined and limited otherwise, the terms "mounting", "connected", "connection" and the like should be interpreted broadly to encompass a mechanical connection, an electrical connection, or an interconnection that is active, passive, or both active and passive. The specific meaning of the above terms in the context of the embodiments of the present application will be apparent to those of ordinary skill in the art based on the specific circumstances.

[0020] In the description herein, the terms indicating orientation or positional relationship such as "upper", "lower", "left", "right", "transverse", "longitudinal", "height", "length", "width", and the like are intended to describe the embodiments and simplify the description, and are not intended to limit the parts or structures involved to have a specific orientation, to be installed or operated in a specific orientation, and should not be construed as limiting the embodiments herein.

[0021] In the description herein, the terms "first", "second", and the like are used only to distinguish different objects, and should not be construed as indicating relative importance or limiting the number, specific order, or primary and secondary relationship of the technical features described. In the description herein, the meaning of "a plurality of" is at least two.

[0022] When the overspeed test is performed, as shown in Figure 1 The fan blade 7 is mounted on the fixing device 9, and the fixing device 9 is fixedly mounted on the test engine rotating shaft 6 through the gear sleeve. Since the fan blade 7 is the direct source of power of the turbofan engine, the high-speed rotation of the fan blade 7 in the actual working condition will generate a very high aerodynamic load, and the energy consumption is high. Therefore, in the actual development process, the fan blade 7 overspeed test is usually performed under vacuum conditions. However, in the vacuum environment, the fan blade 7 only bears the centrifugal load mainly in the radial direction generated by its own mass, and does not bear the aerodynamic load generated by the interaction with the airflow, and the deformation distribution is different from that in the actual working condition. It is difficult to accurately simulate the mechanical behavior of the fan blade 7 in the actual working condition by adjusting the rotational speed only, which affects the accuracy of the overspeed test. In order to more accurately simulate the mechanical behavior of the blade under the influence of aerodynamic action in the actual working condition under the vacuum test condition, an embodiment of one aspect of the present application provides a method for determining the structure of a large-size blade overspeed test fixing device.

[0023] The method comprises the following steps:

[0024] First, control point 1 is set at the leading edge of the fan blade 7, control point 2 at the trailing edge of the blade tip, control point 3 at the front end of the fixing device 9, and control point 4 at the rear end of the fixing device 9. Considering the deformation distribution characteristics of the fan blade 7 under actual working conditions, the distance between each control point and the reference line a is measured, using the connection between the blade root and the tenon (i.e., the position shown by reference line a) as the measurement reference. Subsequently, the distance between each control point and the reference line a is measured at overspeed under actual working conditions in air. This value can be obtained through model calculation or numerical simulation. The displacement of control point 1 on the fan blade 7 is denoted as D1, and the displacement of control point 2 is denoted as D2; the displacement of control point 3 on the fixing device 9 is denoted as d3, and the displacement of control point 4 is denoted as d4.

[0025] In other embodiments, the number of control points on the fan blades 7 and the fixing device 9 can also be set to one or more; the position of the control points can also be set at the axial midpoint or the golden section point, etc.

[0026] Next step, such as Figure 2 As shown, the fan blade 7 is simplified to a point mass 12, and a two-dimensional model of the fan blade-fixed device is established. The deformation of the fixed device 9 under vacuum test conditions is simulated and calculated. The displacement of control point 3 is denoted as d3', and the displacement of control point 4 is denoted as d4'. An optimization region 11 is selected on the fixed device 9, with the goal of minimizing the difference between the displacements of control points 3 and 4 under vacuum test conditions and the displacements of control points 3 and 4 under actual working conditions. The optimization region 11 is iteratively optimized through structural optimization. In a preferred embodiment, the optimization region 11 can be set between the tenon 8 mounting position of the fan blade 7 and the connection position 10 between the fixed device 9 and the engine shaft 6. Topology optimization is used for structural optimization. The maximum stress σ borne by the fixed device 9 is considered. max Not exceeding the ultimate tensile strength (in the preferred embodiment, the ultimate tensile strength is taken as the yield strength σ). 0.2 Given the constraint , the optimized expression is:

[0027] Min(max(|d3'-d3|,|d4'-d4|))=F(x),

[0028] s,t,

[0029] σ max ≤σ 0.2 .

[0030] The minimum value of the displacement of the control point with the largest displacement among control point 3 and control point 4 is obtained through iterative calculation.

[0031] In a preferred embodiment, topology optimization is specifically performed using the variable density method.

[0032] In the preferred embodiment, the fan blade-fixing device two-dimensional model after the topology optimization iteration is processed, small areas are ignored, curve fairing is performed, and a preliminary scheme of the optimization area 11 structure is obtained.

[0033] Next, according to the preliminary scheme of the optimization area 11 structure, a three-dimensional model of the fan blade-fixing device is established, and the displacements D1', D2' of the control points 1, 2 under the vacuum test condition are calculated. The fan blade 7 tip deformation under the vacuum test condition is consistent with that under the actual working condition as much as possible, that is, the displacement difference of the control points 1, 2 is minimized, and the maximum stress σ max of the fixing device 9 does not exceed the strength limit (in the preferred embodiment, the strength limit is the yield strength limit σ 0.2 ), and the displacement difference of the control points 3, 4 does not exceed min|d-d'| (that is, max(|d3'-d3|, |d4'-d4|)≤min|d-d'|) as a constraint condition. The structure of the optimization area 11 is optimized, and in the preferred embodiment, shape optimization is used for iterative calculation, and the optimization expression is:

[0034] Min(max(|D1'-D1|, |D2'-D2|))=F(x),

[0035] s,t,

[0036] σ max ≤σ 0.2,

[0037] max(|d3'-d3|, |d4'-d4|)≤min|d-d'|.

[0038] The final structure scheme of the fixing device 9 is calculated.

[0039] Through the above method, the structure of the fixing device 9 can be reasonably designed, and the rotating posture and stress distribution of the fan blade 7 can be adjusted by changing the structure of the fixing device 9. When the displacements of the control points under the vacuum test condition are basically consistent with those under the actual working condition, it can be considered that the deformation state of the fan blade 7 as a whole under the vacuum test condition is consistent with that under the actual working condition, so that the over-speed test under the vacuum test condition can more accurately reflect the performance of the fan blade 7 under the actual working condition, and the accuracy of the test result is improved.

[0040] The method provided in the above embodiment can be completed by a computing device, which can be a general-purpose computer, a cloud computing device, or a special-purpose device with computing function such as a specially designed single-chip microcomputer. The computing program can use general-purpose mechanism optimization software or a specially written special-purpose simulation calculation program.

[0041] The above embodiments are intended to further illustrate the technical concept of the present application in conjunction with the drawings, so that those skilled in the art can understand the technical concept of the present application. Within the scope of the claims of the present application, optimization or equivalent replacement of the method steps involved, and combination of the embodiments in different embodiments without principle conflict, all fall within the protection scope of the present application.

Claims

1. A method for determining the structure of a large-size blade overspeed test fixture, comprising the following steps: respectively arranging control points on a fan blade and a fixture of the fan blade, providing displacement D of the control points on the fan blade and displacement d of the control points on the fixture under actual working conditions; establishing a two-dimensional model of the fan blade-fixture, and calculating displacement d' of the control points on the fixture under vacuum test conditions; selecting an optimization region on the fixture, taking min |d-d' | as an objective, and performing topological optimization iteration on the optimization region to obtain min |d-d' |, wherein the constraint condition is that the stress borne by the fixture under the vacuum test conditions does not exceed the strength limit of the material of the fixture; establishing a three-dimensional model of the fan blade-fixture according to the two-dimensional model of the fan blade-fixture obtained through the topological optimization iteration, and calculating displacement D' of the control points on the fan blade under vacuum test conditions; taking min |D-D' | as an objective, and performing shape optimization iteration on the optimization region to obtain an optimized structure model, wherein the constraint condition is that the stress borne by the fixture under the vacuum test conditions does not exceed the strength limit of the material of the fixture and |d-d' |≤min |d-d' |.

2. The method of determining the structure of a large size blade overspeed test fixture according to claim 1, wherein, The control points are multiple, and the measurement reference of the displacement of the control points is arranged at the blade root of the blade; the displacement D and the displacement d respectively take the maximum value of the displacements of the multiple control points.

3. The method of determining the structure of a large size blade overspeed test fixture according to claim 2, wherein, Among the control points on the fan blade, two control points are respectively arranged at the leading edge of the blade tip and the trailing edge of the blade tip; among the control points on the fixture, two control points are respectively arranged at the front end and the rear end of the fixture.

4. The method of determining the structure of a test fixture for overspeed testing of large size vanes according to claim 1 or 2 or 3, characterized in that The two-dimensional model of the fan blade-fixture is simplified in a mass point manner.

5. The method of determining the structure of a test fixture for overspeed testing of large size vanes according to claim 1 or 2 or 3, characterized in that, The optimization region is located between the blade tenon mounting position and the connection position of the fixture and the engine rotating shaft.

6. The method of determining the configuration of a test fixture for overspeed testing of large size vanes according to claim 1 or 2 or 3, characterized in that, The strength limit of the material of the fixture adopts the yield strength limit.

7. The method of determining the configuration of a test fixture for overspeed testing of large size vanes according to claim 1 or 2 or 3, characterized in that, Before establishing the three-dimensional model of the fan blade-fixture, the two-dimensional model of the fan blade-fixture is first processed through fairing curves.

8. The method of determining the structure of a test fixture for overspeed testing of large size vanes according to claim 1 or 2 or 3, characterized in that, The topological optimization adopts the variable density method.

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