A simulated blade test specimen and its design method for a bird strike rotating blade simulation test.

Abstract

This invention discloses a simulated blade test specimen and its design method for simulating bird strikes on rotating blades. The design method constructs a leading-edge feature segment by cutting a section at a certain blade height from a real engine blade to ensure the rationality of the blade shape of the simulated blade test specimen. Furthermore, a variable cross-section design is used to improve the rotational stability of the blade test specimen and ensure test safety by addressing the centrifugal force generated during the rotational state. The design of the simulated blade test specimen combines the results of centrifugal force action under rotational state analysis and the stress and strain distribution during the bird strike process, ensuring that the simulated blade test specimen can withstand the specified test speed and the concentrated damage, deformation, and failure of the target area after the bird strike. Simultaneously, it reduces test costs and difficulty, improves test repeatability, and facilitates data processing of test results.

Description

Technical Field

[0001] This disclosure relates to the field of aero-engines, and in particular to a method for designing a simulated blade with leading-edge features of a real engine blade based on bird strike testing, and the resulting test specimen. Background Technology

[0002] Current research on bird strikes on engine blades primarily employs finite element method simulation combined with data acquisition from real experiments. Data obtained from real experiments is crucial for the research; however, conducting real-world tests on the leading edge of engine blades under bird strike conditions requires significant funding, manpower, has a long testing period, and stringent safety requirements.

[0003] Therefore, a technical solution is needed to reasonably simplify the actual engine blades, thereby reducing the cost of the test and improving the safety of the test. Summary of the Invention

[0004] Purpose of the invention: This invention provides a design method for a simulated blade test piece for a bird strike rotating blade simulation test. The purpose of this design method is to design a simulated blade test piece that can reasonably summarize the damage pattern of the blade.

[0005] Technical Solution: To solve the above problems, the present invention provides a design method for a simulated blade test piece for bird strike rotating blade simulation testing, which adopts the following technical solution:

[0006] The simulated blade test piece includes a blade section with blade shape features and a tenon section connecting the blade section. The method includes:

[0007] Provide a turntable tenon groove for rotational testing, and design the tenon of the simulated blade test piece based on the turntable tenon groove so that the size of the simulated blade test piece tenon groove matches the turntable tenon groove;

[0008] The blade profile at the height of the blade was studied by cutting a real blade. Based on the size of the upper section of the tenon, the above-mentioned blade profile was scaled down and the leading edge was cut off to obtain the blade profile parameters of the lower section of the simulated blade test piece.

[0009] Based on the cross-sectional shape of the simulated blade test piece, a blade feature segment is constructed. According to the centrifugal force requirements of the simulated blade test piece in the rotation test, the blade feature segment adopts a variable cross-section design, with an overall design that is narrow at the top and wide at the bottom. The upper section of the blade feature segment is thin, while the section at the blade root is thick and suitable for the tenon size.

[0010] Based on the tenon and blade body of the simulated blade test piece, the geometric model of the simulated blade test piece is obtained by designing the chamfer parameters at the connection point to avoid stress concentration at the blade root and subsequent tearing.

[0011] Based on the geometric model of the simulated blade test specimen, a prestressed finite element analysis of the simulated blade test specimen under test rotation state was performed, and the first analysis result was obtained.

[0012] Based on the first analysis results, the geometric model of the simulated blade test piece is adjusted. If the result satisfies the requirement that the test can be carried out safely under the test speed conditions, a finite element analysis of the bird strike situation under the test conditions is performed, and a second analysis result is obtained.

[0013] Based on the second analysis results, the geometric model of the simulated blade test specimen was adjusted. The results showed that, under the condition that the test was conducted safely and the test results met the preset design conditions, the design of the simulated blade test specimen was completed based on the geometric model of the simulated blade test specimen.

[0014] Furthermore, the cross section of the simulated blade test piece is taken from the blade height cross section required by the actual blade test. In view of the test requirements of bird strike on the leading edge of the blade, the design of the trailing edge of the simulated blade test piece is ignored, and the trailing edge is cut off considering the tenon size.

[0015] Furthermore, the simulated blade test specimen adopts a variable cross-section design. The simulated blade test specimen as a whole includes a tenon section, a transition rounded section, a variable cross-section section of the blade, and a constant cross-section section of the blade; the connection between the variable cross-section section and the tenon section is a transition rounded section; the variable cross-section section is located between the constant cross-section section and the tenon section; the geometric model of the simulated blade test specimen is obtained as follows:

[0016] The leaf height and leaf shape were studied by cutting real leaves. Based on this, the leading edge part was cut and scaled to a suitable size on the upper surface of the tenon as the first section.

[0017] Based on the first section mentioned above, while keeping the leaf shape unchanged, the distance between the leaf base and the back of the leaf is widened to form the second section;

[0018] The first section is stretched to obtain a constant section segment of the blade, and then smoothly swept along the stretching direction to the second section to obtain a variable section segment of the blade.

[0019] The connection between the variable cross section of the blade and the tenon is rounded. The rounding parameters are set according to the distance between the blade back and the tenon section of the first cross section, resulting in a transition rounded section.

[0020] Furthermore, the modification of the geometric model of the simulated blade test specimen based on the first analysis results includes: constructing a finite element model using the finite element method, analyzing the stress and strain distribution of the simulated blade test specimen under centrifugal force in a rotating state under pre-set test conditions, identifying stress and strain concentration areas in the simulated blade test specimen as the damage hazard areas of the geometric model, and assessing the safety of the simulated blade test specimen's geometric model for the test based on the yield strength of the material used in the blade under pre-set test conditions, and changing the geometric model parameters to meet the test requirements, including:

[0021] The scaling parameters of the first and second cross sections, the proportion of the blade height direction of the constant cross section and the variable cross section of the blade, the rounding parameters of the transition rounding section, and the sweep curve parameters of the variable cross section of the blade.

[0022] Furthermore, the modification of the geometric model of the simulated blade test specimen based on the second analysis results includes: using the prestress distribution in the second analysis results, performing finite element analysis on the finite element model of the simulated blade test specimen under the pre-set test requirements for bird strike, obtaining the stress and strain concentration areas generated by the bird strike on the simulated blade test specimen under the pre-set test conditions and the damage form and location of the simulated blade test specimen, and changing the geometric model parameters according to the expected test requirements, including:

[0023] The scaling parameters of the first and second cross sections, the proportion of the blade height direction of the constant cross section and the variable cross section of the blade, the rounding parameters of the transition rounding section, and the sweep curve parameters of the variable cross section of the blade.

[0024] Furthermore, the bird strike test uses a gelatin-based simulated bird strike blade specimen, and then performs finite element analysis on the finite element model of the simulated bird strike blade specimen.

[0025] The present invention also provides a technical solution for a simulated blade test piece designed according to the above-mentioned simulated blade test piece design method for bird strike rotating blade simulation test application.

[0026] Furthermore, the blade of the simulated blade test piece includes the leading edge features of a real blade, but the trailing edge features of the real blade are removed to reduce manufacturing costs.

[0027] Furthermore, the simulated blade test piece includes a tenon section, a transition rounded section, a variable cross-section section of the blade, and a constant cross-section section of the blade.

[0028] Furthermore, the tenon head is divided into a rectangular cube structure.

[0029] Beneficial Effects: Compared with existing technologies, the significant advantage of this invention is that it reasonably simplifies the actual engine blade, thereby reducing testing costs and improving testing safety. A simulated blade test piece is fabricated using a variable cross-section design, retaining the leading-edge characteristics of the actual engine blade, and equipped with a suitable rotation device, to study the relevant laws of bird strike damage to rotating blades. The design of the geometric model of the simulated blade test piece is based on finite element simulation results, predicting the performance of the geometric model in the experiment, increasing the safety in real tests, ensuring that the local and overall rigidity of the blade at the impact location meets the test conditions, and that the damage location is a pre-set damage location in the experiment. This design method for the simulated blade test piece can reduce testing costs and provide a reasonable summary of blade damage laws. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the simulated blade test specimen structure for the bird strike rotating blade simulation test designed in this invention.

[0031] Figure 2 The flowchart illustrates the steps of a simulated blade test specimen design method for bird strike rotating blade simulation tests provided in this embodiment of the invention.

[0032] Figure 3 This is a schematic diagram of the first and second cross sections of the blade provided in an embodiment of the present invention.

[0033] Figure 4 This is a schematic diagram of the first analysis result provided in an embodiment of the present invention.

[0034] Figure 5 This is a schematic diagram of the second analysis result provided in an embodiment of the present invention. Detailed Implementation

[0035] like Figure 1 As shown, exemplary embodiments will now be described more fully with reference to the accompanying drawings.

[0036] This application proposes a design method for a simulated blade test specimen for a bird strike rotating blade simulation test, in order to obtain the blade damage pattern of a bird strike rotating blade at low cost. Figure 1 A schematic diagram of the structure of the simulated blade test piece obtained by the design method is shown, including the tenon part 110, the transition rounded section 120, the variable cross section of the blade 130, and the constant cross section of the blade 140.

[0037] against Figure 1 The simulated leaf test specimen shown has a generally narrower upper and wider lower shape to ensure that the leaf root will not tear, and the damage location is mainly at the pre-set leaf height in the test.

[0038] Figure 2A flowchart illustrating the steps of a simulated blade test specimen design method provided in an embodiment of this disclosure is shown. This method may include steps 210 to 260, as follows:

[0039] Step 210: Determine the tenon shape and dimensions based on the mortise and tenon groove dimensions of the turntable used in the rotation test. The tenon shape adopts a dovetail tenon, and the specific design parameters refer to the "Aerospace Industry Standard of the People's Republic of China: Dimensioning and Technical Requirements for Dovetail Tenons and Mortise Grooves".

[0040] Step 220: Based on the designed tenon dimensions and referring to the test requirements, determine the first and second cross-sections. Study the blade height and airfoil profile by cutting real blades for testing. Based on this, cut the leading edge portion and scale it to the size of the upper surface of the tenon as the first cross-section. To ensure the simulated blade test piece can be contained within the tenon component and to reduce processing costs, the trailing edge of the first cross-section is replaced by a straight line parallel to the wide side of the rectangle at the upper end of the tenon. If the long end of the tenon is still insufficient to contain the above cross-section, the replacement portion can extend into the middle of the blade. The leading edge radius of the first cross-section should meet the processing requirements and should not be too small. Different processing techniques affect the minimum design value of the leading edge radius.

[0041] Based on the first cross-section described above, while maintaining the same leaf shape, the distance between the leaf base and the leaf back is widened to create the second cross-section. The specific dimensions of the second cross-section should take into account subsequent chamfering design parameters. For example... Figure 3 The diagram shows the first section 410 and the second section 420 obtained by simulating the blade test specimen design method.

[0042] Step 230: Using the dimensional parameters of the first and second cross-sections, design the constant cross-section section and the variable cross-section section of the blade according to the test requirements. Stretch the first cross-section to obtain the constant cross-section section, and smoothly sweep it along the stretching direction to the aforementioned second cross-section to obtain the variable cross-section section. Bird strike tests require the blade to suffer some damage after impact, with the damage concentrated at the impact site. This means the designed blade simulation test piece needs to have low local stiffness at the impact site and high overall stiffness to prevent tearing at the blade root that could affect test safety. Therefore, the first and second cross-sections are designed. The second cross-section ensures that the blade root will not tear after impact, while the first cross-section reduces the local stiffness at the impact site, making it easier to observe the damage after the impact.

[0043] Step 240: Based on the dimensional parameters of the blade section and tenon, design the chamfer parameters to obtain the transition chamfer section, thereby obtaining the preliminary geometric model.

[0044] Step 250: Analyze the prestress distribution and magnitude of the geometric model under rotational test conditions using the finite element method, obtain the first analysis result, and adjust the geometric model based on this result. Due to the presence of centrifugal force, prestress will inevitably be generated during blade rotation, and this prestress will affect the damage condition and pattern of the blade, which cannot be ignored. For example... Figure 4 As shown, the distribution of prestress on the blade under rotation conditions and the magnitude of prestress under the test preconditions are shown.

[0045] The stress distribution of the simulated blade decreases at the blade tip as the blade height increases. The main stresses of the simulated blade are concentrated at the tail section and tenon. It should be ensured that the maximum prestress on the blade does not exceed the yield strength of the material, that is, the blade does not undergo plastic strain under rotational prestress conditions as shown in the finite element analysis results.

[0046] If the maximum stress at the tenon exceeds the yield limit of the material, consider changing the style of the tenon or rounding the right-angled edges of the tenon.

[0047] If the stress at the blade exceeds the yield stress of the material used, the scaling parameters of the first and second cross-sections, the proportion of the blade height in the constant and variable cross-section sections, the rounding parameters of the transition rounding section, and the sweep curve parameters of the variable cross-section section should be appropriately modified. Generally, a design with a thicker blade root, a thinner blade tip, and a thinner tail tangent can ensure the safety of the simulated blade during the experiment and meet the experimental requirement that the prestress should not be too high.

[0048] Step 260: Analyze the damage to the geometric model caused by the bird strike using the finite element method, obtain the second analysis result, and adjust the geometric model based on this result. For the gelatin bird used in the experiment, the SPH particle method was used for simulation. Under the pre-set experimental conditions, the deformation of the blade after the impact is as follows: Figure 5 As shown. Considering the experimental objective of summarizing patterns, the designed simulated blade geometry model should ensure appropriate local stiffness at the impact point, resulting in blade damage that facilitates the processing of experimental results, including bulges and notches. On the other hand, for experimental safety requirements, the test specimen should not experience blade body or root tearing after impact, leading to blade detachment.

[0049] In finite element analysis, if the blade is torn at the root after being struck by a bird, the spline curve parameters of the cross-section change at the variable cross-section section of the blade can be controlled, or the parameters of the fillet can be optimized.

[0050] The above description is merely a specific implementation method of this application.

Claims

1. A method for designing a simulated blade test piece for simulating a bird strike rotating blade test, the simulated blade test piece comprising a blade body feature segment with blade profile characteristics and a tenon feature segment connecting the blade body feature segment, characterized in that, The method includes: Provide a turntable tenon groove for rotational testing, and design the tenon of the simulated blade test piece based on the turntable tenon groove so that the size of the simulated blade test piece tenon groove matches the turntable tenon groove; The blade profile at the height of the blade was studied by cutting a real blade. Based on the size of the upper section of the tenon, the above-mentioned blade profile was scaled down and the leading edge was cut off to obtain the blade profile parameters of the lower section of the simulated blade test piece. Based on the cross-sectional shape of the simulated blade test piece, a blade feature segment is constructed. According to the centrifugal force requirements of the simulated blade test piece in the rotation test, the blade feature segment adopts a variable cross-section design, with an overall design that is narrow at the top and wide at the bottom. The upper section of the blade feature segment is thin, while the section at the blade root is thick and suitable for the tenon size. Based on the tenon and blade body of the simulated blade test piece, the geometric model of the simulated blade test piece is obtained by designing the rounding parameters at the connection point to avoid stress concentration at the blade root and subsequent tearing. Based on the geometric model of the simulated blade test specimen, a prestressed finite element analysis of the simulated blade test specimen under test rotation state was performed, and the first analysis result was obtained. Based on the first analysis results, the geometric model of the simulated blade test piece is adjusted. If the result satisfies the requirement that the test can be carried out safely under the test speed conditions, a finite element analysis of the bird strike situation under the test conditions is performed, and a second analysis result is obtained. Based on the second analysis results, the geometric model of the simulated blade test specimen was adjusted. The results showed that, under the condition that the test was conducted safely and the test results met the preset design conditions, the design of the simulated blade test specimen was completed based on the geometric model of the simulated blade test specimen.

2. The design method according to claim 1, characterized in that, The cross section of the simulated blade test piece is taken from the blade height section required by the actual blade test. In view of the test requirements of bird strike on the leading edge of the blade, the design of the trailing edge of the simulated blade test piece is ignored, and the trailing edge is cut off considering the tenon size.

3. The design method according to claim 1, characterized in that, The simulated blade prototype adopts a variable cross-section design. The entire simulated blade prototype includes a tenon section, a transition rounded section, a variable cross-section section, and a constant cross-section section. The connection between the variable cross-section section and the tenon section is a transition rounded section. The variable cross-section section is located between the constant cross-section section and the tenon section. The geometric model of the simulated blade prototype is obtained as follows: The leaf height and leaf shape were studied by cutting real leaves. Based on this, the leading edge part was cut and scaled to a suitable size on the upper surface of the tenon as the first section. Based on the first section mentioned above, while keeping the leaf shape unchanged, the distance between the leaf base and the back of the leaf is widened to form the second section; The first section is stretched to obtain a constant section segment of the blade, and then smoothly swept along the stretching direction to the second section to obtain a variable section segment of the blade. The connection between the variable cross section of the blade and the tenon is rounded. The rounding parameters are set according to the distance between the blade back and the tenon section of the first cross section, resulting in a transition rounded section.

4. The design method according to claim 3, characterized in that, Modifying the geometric model of the simulated blade test specimen based on the first analysis results includes: constructing a finite element model using the finite element method, analyzing the stress and strain distribution of the simulated blade test specimen under centrifugal force in a rotating state under pre-set test conditions, identifying stress and strain concentration areas in the simulated blade test specimen as the damage hazard areas of the geometric model, and assessing the safety of the simulated blade test specimen's geometric model for the test based on the yield strength of the material used in the blade under pre-set test conditions, and changing the geometric model parameters to meet the test requirements, including: The scaling parameters of the first and second cross sections, the proportion of the blade height direction of the constant cross section and the variable cross section of the blade, the rounding parameters of the transition rounding section, and the sweep curve parameters of the variable cross section of the blade.

5. The design method according to claim 4, characterized in that, Modifying the geometric model of the simulated blade test specimen based on the second analysis results includes: using the prestress distribution in the second analysis results, performing finite element analysis on the finite element model of the simulated blade test specimen under bird strike pre-test requirements, obtaining the stress and strain concentration areas, damage forms, and damage locations of the simulated blade test specimen under dangerous conditions of bird strike during the pre-test conditions, and changing the geometric model parameters according to the expected test requirements, including: The scaling parameters of the first and second cross sections, the proportion of the blade height direction of the constant cross section and the variable cross section of the blade, the rounding parameters of the transition rounding section, and the sweep curve parameters of the variable cross section of the blade.

6. The design method according to claim 5, characterized in that, The bird strike test uses gelatin to simulate a bird strike blade test piece, and then performs finite element analysis on the finite element model of the simulated bird strike blade test piece.

7. A simulated blade test specimen for bird strike rotating blade simulation tests, characterized in that, The simulated blade test specimen was obtained by the design method described in any one of claims 1 to 6.

8. The simulated blade test specimen according to claim 7, characterized in that, The simulated blade prototype includes the leading edge features of a real blade, but the trailing edge features of the real blade are removed to reduce manufacturing costs.

9. The simulated blade test specimen according to claim 7, characterized in that, The simulated blade test piece includes the tenon section, the transition rounded section, the variable cross section of the blade, and the constant cross section of the blade.

10. The simulated blade test specimen according to claim 9, characterized in that, The tenon head is divided into a rectangular cube structure.

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