Method for determining structure of large-size blade over-rotation test fixing device

Abstract

A method for determining the structure of a large-size blade over-rotation test fixing device comprises the following steps that control points are arranged on a fan blade and a fixing device of the fan blade, and control point displacement under the actual working condition is provided; establishing a fan blade-fixing device two-dimensional model, calculating the displacement of a control point of the fixing device in a vacuum test state, calculating a difference value between the displacement and the displacement under an actual working condition, and performing structure optimization by taking the difference value minimization as a target; and establishing a fan blade-fixing device three-dimensional model, calculating the displacement of a fan blade control point in a vacuum test state, calculating a difference value between the displacement and the displacement under an actual working condition, and carrying out structure optimization by taking difference value minimization as a target to obtain a final structure of the fixing device. According to the method, the deformation distribution of the blade in a vacuum test state and an actual working condition is as close as possible, and the test accuracy is improved.

Description

Technical Field

[0001] The invention belongs to the field of aeroengines, and in particular relates to a method for determining the structure of a large-size blade super-rotation test fixture. Background Art

[0002] The composite fan blades of aircraft engines are large in size and have high operating speeds. They are one of the core parts related to engine safety. Once they fail, they will cause serious safety problems. Therefore, the airworthiness clauses put forward strict overspeed requirements for composite fan blades. In order to meet the airworthiness requirements, in addition to simulating and analyzing the blade strength, it is also necessary to design an overspeed test 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. Limited by the power of the tester, the overspeed test is usually carried out under a vacuum state. However, under actual working conditions, in addition to the centrifugal load caused by rotation, the fan blades are also subject to loads caused by aerodynamic effects. Under vacuum conditions, relying solely on speed regulation cannot accurately simulate the stress and strain state of the blades under actual working conditions, which restricts the accuracy of the overspeed test results. Therefore, providing a solution to make the stress and strain distribution of the blades under the vacuum test state consistent with the actual working conditions is of great practical significance for improving the design level of aircraft engine fan blades. Summary of the invention

[0003] The object of the present invention is to provide a method for determining the structure of a fixture for a large-size blade over-rotation test, and to optimize the accuracy of the blade over-rotation test by adjusting the structure of the blade fixture.

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

[0005] This method simulates and calculates the deformation state of the blades under the vacuum test state by setting control points, and makes the deformation state of the blades as consistent as possible with the deformation state under actual working conditions by changing the constraints of the fixing device on the fan blades. This achieves the simulation of the strain of the fan blades under the combined effects of the centrifugal load and the starting load under actual working conditions under the vacuum state, thereby improving the accuracy of the vacuum simulation test.

[0006] Furthermore, in some embodiments, the control points are multiple, the displacement measurement base of the control points is set at the root of the blade, and the displacement D and the displacement d are respectively the maximum values ​​of the displacements of the multiple control points. Multiple control points can more accurately reflect the deformation of the fan blade.

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

[0008] Furthermore, in some embodiments, the fan blade-fixing device two-dimensional model is simplified by mass point method, and the blade is simplified to mass points to reduce the amount of calculation.

[0009] Furthermore, in some embodiments, the optimized area is located between the blade tenon installation position and the connection position between the fixing device and the engine shaft.

[0010] Furthermore, in some embodiments, the strength limit of the material of the fixture adopts the yield strength limit.

[0011] Furthermore, in some embodiments, before establishing the three-dimensional model of the fan blade-fixing device, the two-dimensional model of the fan blade-fixing device is firstly subjected to smoothing curve processing. The smoothing curve processing eliminates the structures that do not meet the design requirements, such as the edges and corners generated in the structural optimization iteration.

[0012] Furthermore, in some embodiments, the structural optimization of the fan blade-fixing device two-dimensional model adopts topology optimization.

[0013] Furthermore, in some embodiments, the topology optimization adopts a variable density method, which is an effective method for topology optimization. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of a partial cross-sectional structure of a fan blade testing device in one embodiment;

[0015] Figure 2 It is a schematic diagram of the two-dimensional model structure of a fan blade-fixing device in one embodiment.

[0016] The purpose of the above drawings is to explain the present invention in detail so that those skilled in the art can understand the technical concept of the present invention, but it is not intended to limit the present invention. For the sake of simplicity, the above drawings only schematically illustrate the structures related to the technical features of the present invention, and do not strictly draw the complete device and all details according to the actual proportion. DETAILED DESCRIPTION

[0017] The present invention is further described in detail below through specific embodiments in conjunction with the accompanying drawings.

[0018] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The phrase appearing in various locations in the specification does not necessarily refer to the same embodiment, nor is it limited to mutually exclusive independent or alternative embodiments. Those skilled in the art should be able to understand that the embodiments herein may be combined with other embodiments without causing structural conflicts.

[0019] In the description of this article, unless otherwise clearly specified and limited, the technical terms "installed", "connected", "connected" and the like should be understood in a broad sense, which can be a movable connection, a fixed connection or an integral connection. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of this application can be understood according to specific circumstances.

[0020] In the description of this document, terms indicating orientation or positional relationships, such as "up", "down", "left", "right", "horizontal", "vertical", "height", "length", and "width", are intended to accurately describe the embodiments and simplify the description, but are not intended to limit the parts or structures involved to have a specific orientation, be installed or operate in a specific orientation, and should not be construed as a limitation on the embodiments in this document.

[0021] In the description of this article, the terms "first", "second" and the like are only used to distinguish different objects, and cannot be understood as indicating relative importance or limiting the quantity, specific order or primary and secondary relationship of the described technical features. In the description of this article, the meaning of "plurality" is at least two.

[0022] When performing a super rotation test, Figure 1 As shown, the fan blade 7 is mounted on a fixture 9, and the fixture 9 is fixedly mounted on the test engine shaft 6 through a gear sleeve. Since the fan blade 7 is the direct source of power for the turbofan engine, the high-speed rotation of the fan blade under actual working conditions will generate very high aerodynamic loads and high energy consumption. Therefore, in the actual development process, the fan blade 7 overspeed test is usually carried out under vacuum conditions. However, under a vacuum environment, the fan blade 7 only bears the centrifugal load mainly in the radial direction generated by its own mass, and there is no aerodynamic load generated by the interaction with the airflow. Its deformation distribution is somewhat different from the actual working conditions. It is difficult to accurately simulate the mechanical behavior of the fan blade 7 under actual working conditions by adjusting the rotation speed alone, 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 actual working conditions under vacuum test conditions, an embodiment of one aspect of the present invention provides a method for determining the structure of a fixture for overspeed test of large-size blades.

[0023] The method comprises the following steps:

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

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

[0026] Next, if Figure 2 As shown, the fan blade 7 is simplified into a mass point 12, and a two-dimensional model of the fan blade-fixture device is established. The deformation of the fixture 9 under the vacuum test state is simulated and calculated, and the displacement of the control point 3 is recorded as d3', and the displacement of the control point 4 is recorded as d4'. An optimized area 11 is selected on the fixture 9, and the displacement difference between the control point 3 and the control point 4 under the vacuum test state and the control point 3 and the control point 4 under the actual working condition is minimized. The optimized area 11 is optimized iteratively through structural optimization. In a preferred embodiment, the optimized area 11 can be set between the installation position of the tenon 8 of the fan blade 7 and the connection position 10 between the fixture 9 and the engine shaft 6, and the structural optimization adopts topological optimization. Take the fixture 9 as the maximum stress σ max Not exceeding the strength limit (in the preferred embodiment, the strength limit is the yield strength limit σ 0.2 ) is a constraint condition, and the optimization formula is:

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

[0028] s,t,

[0029] σ max ≤σ 0.2 .

[0030] After iterative calculation, min|d-d'| is obtained, where min|d-d'| is the minimum value of the displacement of the control point with the larger displacement among control points 3 and 4.

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

[0032] In a preferred embodiment, the two-dimensional model of the fan blade-fixture device that has undergone topology optimization iterations is processed, small areas are ignored, and the curves are smoothed to obtain a preliminary solution for the structure of the optimized area 11.

[0033] Next, according to the preliminary plan for optimizing the structure of area 11, a three-dimensional model of the fan blade-fixing device is established, and the displacements D1' and D2' of control points 1 and 2 under the vacuum test state are calculated. The goal is to minimize the displacement difference between control points 1 and 2, making the deformation of the fan blade tip 7 under the vacuum test state consistent with that under actual working conditions. max Not exceeding the strength limit (in the preferred embodiment, the strength limit is the yield strength limit σ 0.2 ), and the displacement difference of control point 3 and control point 4 does not exceed min|d-d'| (i.e. max(|d3'-d3|,|d4'-d4|)≤min|d-d'|) as the constraint condition, the structure of the optimization area 11 is optimized, and shape optimization is used for iterative calculation in the preferred embodiment, and the optimization formula 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 structural solution of the fixing device 9 is obtained by calculation.

[0039] Through the above method, the structure of the fixing device 9 can be reasonably designed, and the rotation posture and stress distribution of the fan blade 7 can be adjusted by changing the structure of the fixing device 9. When the displacement of each control point under the vacuum test condition is basically consistent with the displacement under the actual working condition, it can be considered that the overall deformation state of the fan blade 7 under the vacuum test condition is consistent with that under the actual working condition, so that the over-rotation test under the vacuum test condition can more accurately reflect the performance of the over-rotation of the fan blade 7 under the actual working condition, thereby improving the accuracy of the test results.

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

[0041] The purpose of the above embodiments is to further explain the present invention in detail in conjunction with the accompanying drawings so that those skilled in the art can understand the technical concept of the present invention. Within the scope of the claims of the present invention, the optimization or equivalent replacement of the method steps involved, and the combination of implementation methods in different embodiments without conflict of principles, all fall within the protection scope of the present invention.

Claims

1. A method for determining the structure of a large-size blade super-rotation test fixture, comprising the following steps: Control points are respectively set on the fan blade and the fixing device of the fan blade, and a displacement D of the control point on the fan blade and a displacement d of the control point on the fixing device under actual working conditions are provided; Establishing a two-dimensional model of a fan blade-fixing device, and calculating the displacement d' of the control point on the fixing device under a vacuum test state; An optimization region is selected on the fixture, and |d-d'| is taken as the minimum value, and structural optimization iteration is performed 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 condition does not exceed the strength limit of the material of the fixture; A three-dimensional model of a fan blade-fixing device is established based on the two-dimensional model of the fan blade-fixing device obtained through structural optimization iteration, and a displacement D' of the control point on the fan blade under a vacuum test state is calculated; Taking |D-D'| as the minimum value as the goal, shape optimization iterations are performed on the optimization area to obtain an optimized structural model, wherein the constraints are that the stress borne by the fixture under the vacuum test conditions does not exceed the strength limit of the fixture material and |d-d'|≤min|d-d'|.

2. The method for determining the structure of a large-size blade super-rotation test fixture according to claim 1, characterized in that: There are multiple control points, and the measurement reference of the displacement of the control points is set at the root of the blade. The displacement D and the displacement d are respectively the maximum values ​​of the displacements of the multiple control points.

3. The method for determining the structure of a large-size blade super-rotation test fixture according to claim 2, characterized in that: Among the control points on the fan blade, two of the control points are respectively arranged at the leading edge and the trailing edge of the blade tip of the fan blade; among the control points on the fixing device, two of the control points are respectively arranged at the front end and the rear end of the fixing device.

4. The method for determining the structure of a large-size blade over-rotation test fixture according to claim 1, 2 or 3, characterized in that The fan blade-fixing device two-dimensional model is simplified by using a mass point method.

5. The method for determining the structure of a large-size blade super-rotation test fixture according to claim 1, 2 or 3, characterized in that: The optimized area is located between the blade tenon installation position and the connection position between the fixing device and the engine shaft.

6. The method for determining the structure of a large-size blade super-rotation test fixture according to claim 1, 2 or 3, characterized in that: The strength limit of the material of the fixture adopts the yield strength limit.

7. The method for determining the structure of a fixture for a large-size blade over-rotation test according to claim 1, 2 or 3, characterized in that: Before establishing the three-dimensional model of the fan blade-fixing device, firstly, the two-dimensional model of the fan blade-fixing device is subjected to smoothing curve processing.

8. The method for determining the structure of a fixture for a large-size blade over-rotation test according to claim 1, 2 or 3, characterized in that: The structural optimization of the fan blade-fixing device two-dimensional model adopts topology optimization.

9. The method for determining the structure of a large-size blade super-rotation test fixture according to claim 8, characterized in that: The topology optimization adopts a variable density method.

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