Compressor simulation blade stress gradient test piece and optimization method

Abstract

The application discloses a compressor simulation blade stress gradient test piece and an optimization method, and has the advantages that a three-dimensional model of a real blade is subjected to finite element simulation, a maximum stress position of a leading edge is taken as a characteristic position, a cross section size of the characteristic position is extracted, stress gradient distribution and geometric size characteristics of a characteristic leading edge cross section are extracted from a result of the finite element simulation, a simulation blade model is established according to the cross section size of the characteristic position, the stress gradient distribution and the geometric size characteristics of the leading edge cross section, numerical simulation is carried out on stress distribution of the simulation blade model, and correction is carried out until the stress distribution of the simulation blade model matches the stress distribution of the real blade to obtain final parameters of the simulation blade, the leading edge slope is corrected through the numerical simulation stress distribution, the stress characteristics of the leading edge of the characteristic position of the real blade can be reflected, the shape size parameters of the real blade in the prior art are abandoned as a simulation basis, and the stress characteristics of the leading edge of the characteristic position of the real blade are taken as a simulation basis, finally, the shape size of the simulation blade can be different from the shape size of the real blade, the stress state of the leading edge of the real blade in working can be accurately reflected, and the accuracy of test results is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aircraft engine blade simulation test, and particularly relates to a compressor simulation blade stress gradient test piece and an optimization method. BACKGROUND

[0002] A typical fan blade in an aero-engine is a complex geometric structure with a continuously changing out-of-plane angle and twisted surface, and some compressor blades further include a shock-absorbing boss for enhancing the stability of the blade in operation and making the stress distribution of the blade more complex. The stress generated at the leading edge of the blade is the result of the combined action of the inertial force (F z ), the pressure load (F x ), and the complex load (F y ) and moment varying along the length of the blade caused by the change in geometric shape, and the distribution of these loads and moments is shown in FIG. Figure 1

[0003] During the operation of the engine, the blade is subjected to the combined action of low-cycle and high-cycle loads, and research shows that the stress ratio of the blade changes when moving from the root region to the front end region. In the root and middle regions, the leading edge of the blade is subjected to relatively large stress, and the generated stress gradually decreases in the direction of the exhaust edge. This will cause the stress ratio of the blade to change from R=0.8 to R=-1. In addition, the leading edge region also has a stress gradient caused by the out-of-plane angle of the blade. The change in stress ratio and the leading edge stress gradient have a very important influence on the design of the blade specimen.

[0004] In the design and manufacture of an aero-engine, the research on compressor blades is very extensive, involving multiple fields such as impact, vibration, fatigue, etc. The real blade is expensive and has a long production cycle, and the design of a simulation blade for test research is particularly important. In the prior art, the design of a simulation blade has experienced early flat plate simulation blades, dog bone simulation blades, and front edge simulation blades and curved front edge simulation blades developed in recent years. The design concept has evolved from the initial material performance research to the current structural part characteristic research, and great progress has been made.

[0005] ​Most of the leading edge simulation blades directly consider the geometric size characteristics of the leading edge section of the blade, but in the actual engine blade work, the stress characteristics are more important, and the connection with the working performance of the blade is more close. Therefore, in order to more accurately carry out research on the engine blade, it is necessary to invent a simulation blade that can accurately simulate the stress characteristics of the leading edge position, which requires that the simulation blade can carry out impact and fatigue test, and the simulation blade can accurately reflect the stress state of the engine leading edge in work. Since the design of the simulation blade in the prior art is mostly directly copied from the shape parameters of the real blade, but due to the difference in materials and processes, the consistent shape parameters cannot make the simulation blade accurately reflect the stress state of the engine leading edge of the real blade in work, resulting in inaccurate test results, and the real blade leading edge stress distribution cannot be accurately simulated, so that effective experimental data cannot be obtained. SUMMARY

[0006] The purpose of the present application is to provide a compressor simulation blade stress gradient test piece and optimization method to overcome the shortcomings of the prior art.

[0007] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0008] A parameter optimization method of a compressor simulation blade stress gradient test piece, comprising the following steps:

[0009] S1, finite element simulation is performed on the three-dimensional model of the real blade, the maximum stress position of the leading edge is taken as the characteristic position, and the cross-sectional size of the characteristic position is extracted;

[0010] S2, the stress gradient distribution and geometric size characteristics of the characteristic leading edge cross section are extracted from the results of the finite element simulation;

[0011] S3, according to the cross-sectional size of the characteristic position, the stress gradient distribution and geometric size characteristics of the leading edge cross section, a simulation blade model is established, the stress distribution of the simulation blade model is simulated, and is corrected until the stress distribution of the simulation blade model matches the stress distribution of the real blade to obtain the final parameters of the simulation blade.

[0012] Further, the cross-sectional size of the characteristic position includes the leading edge curvature radius and the slope slope.

[0013] Further, the stress distribution of the real blade at the actual working speed is calculated, the cross-sectional stress distribution of the characteristic position is extracted, the gradient distribution law from the leading edge to the blade is analyzed, the ratio of the maximum tensile stress to the maximum compressive stress is obtained as the objective function value of the iteration convergence judgment; the tensile stress of the simulation blade model is calculated, and when the ratio of the maximum tensile stress to the maximum compressive stress of the simulation blade model from the leading edge to the blade is less than the objective function value, the size of the simulation blade model is established as the final size.

[0014] Further, the leading edge radius is kept unchanged in the iteration process, and the remaining two parameters are taken as initial values of the simulated blade size, the bevel angle is defined as θ, and the 1 / 2 blade thickness is defined as d, and a simulated blade model is established.

[0015] Further, the tensile stress of the simulated blade is calculated, and the stress gradient distribution characteristics on the maximum stress section of the leading edge are extracted, so that the ratio of the maximum tensile stress to the maximum compressive stress is obtained, and the ratio of the maximum tensile stress to the maximum compressive stress on the characteristic section of the real blade obtained by numerical simulation is compared.

[0016] Further, when the ratio of the maximum tensile stress to the maximum compressive stress of the simulated blade model from the leading edge to the blade is less than 5% of the difference value of the target function, the size corresponding to the simulated blade model is the final size, otherwise the optimization algorithm is used to adjust the data of θ and d for the next round of iteration until the optimization end condition is met.

[0017] Further, the final parameters of the simulated compressor blade considering the stress gradient include:

[0018] The leading edge radius of the blade is the characteristic section leading edge radius, and θ and d meeting the optimization end condition after multiple iteration calculations are the bevel angle and the flat plate segment thickness of the blade.

[0019] Further, the clamping end thickness is greater than 3 times the flat plate segment thickness.

[0020] A simulated blade structure includes a clamping end and a blade, the thickness of the blade is less than the thickness of the clamping end, the blade includes a flat plate segment and a leading edge located on both sides of the flat plate segment, both ends of the flat plate segment are connected to the clamping end through a circular arc transition connection, both ends of the leading edge are connected to the clamping end through a circular arc transition connection, and the two leading edges are symmetrically arranged on both sides of the flat plate segment.

[0021] Further, the leading edge radius of the blade is the characteristic section leading edge radius.

[0022] θ and d meeting the optimization end condition after multiple iteration calculations are the bevel angle and the flat plate segment thickness of the blade, the flat plate segment width of the blade is 2 times the leading edge width, the length of the blade is set to 1.5 times the width of the blade, the transition section of the blade and the clamping end is rounded, the rounding radius is the thickness of the clamping end, and the clamping end thickness is greater than 3 times the flat plate segment thickness.

[0023] Compared with the prior art, the present application has the following beneficial technical effects:

[0024] This invention discloses a method for optimizing the parameters of a compressor blade stress gradient test specimen. It involves performing finite element simulation on a three-dimensional model of a real blade, selecting the location of maximum stress at the leading edge as a feature position, extracting the cross-sectional dimensions of this feature position, and extracting the stress gradient distribution and geometric features of the leading edge cross-section from the finite element simulation results. A simulated blade model is then established based on the cross-sectional dimensions of the feature position and the stress gradient distribution and geometric features of the leading edge cross-section. Numerical simulation of the stress distribution in the simulated blade model is performed and corrected until it matches the stress distribution of the real blade, yielding the final parameters of the simulated blade. The leading edge slope is corrected through numerical simulation of the stress distribution to reflect the stress characteristics of the leading edge at the feature position of the real blade. This method abandons the existing technique of using the external dimensions of the real blade as the basis for simulation, instead using the stress characteristics of the leading edge at the feature position of the real blade as the basis for simulation. The final simulated blade dimensions can differ from the actual blade dimensions, accurately reflecting the stress state of the engine's leading edge during operation, thus improving the accuracy of the test results. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating the optimization of simulated blade size parameters in an embodiment of the present invention.

[0026] Figure 2 This is a schematic diagram of the stress distribution state of the actual blade cross section in an embodiment of the present invention.

[0027] Figure 3 This is a schematic diagram of the stress distribution state of the blade cross section in an embodiment of the present invention.

[0028] Figure 4 This is the cross-sectional stress variation curve in an embodiment of the present invention.

[0029] Figure 5 This is the front view of the test specimen used in the embodiments of the present invention.

[0030] Figure 6 This is a schematic diagram of the forces acting on the blade during operation.

[0031] In the figure, 1—cutting blade; 2—clamping end; 101—flat plate section; 102—leading edge. Detailed Implementation

[0032] The present invention will now be described in further detail with reference to the accompanying drawings:

[0033] like Figure 5As shown in the figure, a compressor simulation blade stress gradient test piece includes a clamping end 2 and a blade edge 1, the thickness of the blade edge 1 is less than the thickness of the clamping end 2, the blade edge 1 includes a flat section 101 and a leading edge 102 on both sides of the flat section 101, the leading edge 102 is blade-shaped, the flat section 101 is located between the two leading edges 102, and the two ends of the flat section 101 are connected to the clamping end 2 through a circular arc transition connection, and the two ends of the leading edge 102 are connected to the clamping end through a circular arc transition connection; the two leading edges are symmetrically arranged on both sides of the flat section. Figure 5 As shown in the figure, the distance between the two leading edges 102 is the width of the flat section of the blade edge; the size of the leading edge 102 along the width of the flat section of the blade edge is the width of the blade edge; the included angle of the bevel of the blade edge at the end of the blade edge is the thickness of the flat section of the blade edge in the width direction of the blade edge.

[0034] As shown in the figure, Figure 1 A size optimization method of a compressor simulation blade stress gradient test piece, comprising the following steps:

[0035] S1, finite element simulation is performed on the three-dimensional model of the real blade, the maximum stress position of the leading edge is taken as the characteristic position, and the cross-sectional size of the characteristic position is extracted;

[0036] Specifically, a three-dimensional model of the real blade is established according to the size and material of the real blade to be analyzed, then finite element simulation is performed on the three-dimensional model of the real blade, the maximum stress position of the leading edge is selected as the characteristic position, and the cross-sectional size of the characteristic position is extracted;

[0037] The vibration stress distribution of the characteristic position cross section of the leading edge of the engine blade is as shown in the figure: Figure 2 Tensile stress is generated at the leading edge of the blade, and compressive stress is generated in the middle region of the blade, as shown in the figure. Figure 6 Taking the position where the maximum stress occurs as the starting point, the blade surface stress is extracted and analyzed along the cross section, as shown in the figure. Figure 4 (a) is the extraction result, from the curve it can be seen that the cross-sectional stress value first decreases and then increases; the maximum tensile stress exists at the leading edge of the blade, about 19MPa, and the maximum compressive stress is located in the middle of the sample, about -20MPa. From this, the ratio of the maximum stress to the minimum stress on the cross section is about 0.95.

[0038] The cross-sectional size of the characteristic position includes the curvature radius of the leading edge and the slope of the bevel;

[0039] S2, the stress gradient distribution and geometric size characteristics of the characteristic leading edge cross section are extracted from the results of the finite element simulation;

[0040] S3, according to the cross-sectional size of the characteristic position, the stress gradient distribution and geometric size characteristics of the leading edge cross section, a simulated blade model is established, the stress distribution of the simulated blade model is numerically simulated, and correction is performed until the stress distribution of the simulated blade model matches the stress distribution of the real blade to obtain the final parameters of the simulated blade.

[0041] The correction method is specifically: using the finite element numerical simulation software ABAQUS to repeatedly replace parameters to calculate the stress distribution of the simulated blade, using Python to write code to realize the process of automatically extracting data, judging and repeatedly calculating, and finally obtaining the geometric parameters of the simulated blade.

[0042] Firstly, ABAQUS is used to calculate the stress distribution of the real engine blade at the actual working speed, the maximum stress position of the leading edge is selected as the characteristic position, the stress distribution of the characteristic position cross section is extracted, the gradient distribution law of the leading edge to the blade is analyzed, and the ratio of the maximum tensile stress to the maximum compressive stress is obtained as the objective function value for iteration convergence judgment.

[0043] Subsequently, the leading edge radius, the included angle of the bevel and 1 / 2 blade thickness are extracted from the initial size parameters of the characteristic position cross section of the real blade, wherein the leading edge radius remains unchanged during the iteration process, and the remaining two parameters are used as the initial values of the simulated blade size, the included angle of the bevel is defined as θ, and 1 / 2 blade thickness is defined as d. ABAQUS software is called to calculate the tensile stress of the simulated blade, and after the calculation is completed, the stress gradient distribution characteristics on the maximum stress cross section of the leading edge are extracted by writing a program with Python, and the ratio of the maximum tensile stress to the maximum compressive stress is obtained. The ratio of the maximum tensile stress to the maximum compressive stress on the characteristic cross section of the real blade obtained by numerical simulation is compared; the tensile stress of the simulated blade model is calculated, as shown in the formula (1), when the ratio of the maximum tensile stress to the maximum compressive stress of the simulated blade model in the leading edge to the blade is less than the objective function value, the size of the simulated blade model corresponding to the establishment is the final size. Figure 3

[0044] Finally, it is compared whether the difference satisfies the optimization end condition (the difference of the ratio of the maximum tensile stress to the maximum compressive stress is within 5%), if not, the optimization algorithm is used to adjust the data of θ and d for the next round of iteration, until the optimization end condition is satisfied, and the target that the ratio of the tensile stress to the compressive stress of the simulated blade and the result on the characteristic cross section of the real blade are within the tolerance range is reached; at this time, the corresponding size parameter is the final parameter of the simulated blade considering the stress gradient.

[0045] In step S3, the final parameters of the simulated compressor blade considering the stress gradient include:

[0046] The blade edge blade leading edge radius is the characteristic cross section leading edge radius;

[0047] After multiple iteration calculations, θ and d that satisfy the optimization end condition are the included angle of the bevel of the blade edge blade and the thickness of the flat plate segment.​

[0048] The width of the blade flat section is 2 times the width of the leading edge;

[0049] The length of the blade is set to 1.5 times the width of the blade;

[0050] The blade and the clamping end transition section are rounded, and the radius of the rounded corner is the thickness of the clamping end;

[0051] The size of the clamping end is determined by the contour size of the blade, and the thickness of the clamping end is greater than 3 times the thickness of the flat section.

[0052] The test piece for simulating the stress gradient of the compressor blade can simulate the stress characteristics of the real blade leading edge. The clamping end can effectively clamp during the foreign object damage simulation test and the tensile fatigue test, avoiding the influence of the test result due to the loosening of the test piece. The blade takes the curvature radius of the leading edge, the slope of the bevel, and half of the thickness of the blade as the initial leading edge radius, the leading edge slope, and the thickness of the flat section of the simulated blade. The leading edge slope is corrected through numerical simulation of stress distribution, so that it can reflect the stress characteristics of the real blade at the characteristic position of the leading edge. The greatest innovation of the technical scheme is that the shape size parameters of the real blade are abandoned as the basis for simulation, and the stress characteristics of the real blade at the characteristic position of the leading edge are taken as the basis for simulation. The shape size of the simulated blade can be different from that of the real blade, but it can accurately reflect the stress state of the real blade engine leading edge in operation, and improve the accuracy of the test result.

Claims

1. A method for parameter optimization of a compressor simulated blade stress gradient test piece, characterized in that, The method comprises the following steps: S1, finite element simulation is performed on a three-dimensional model of a real blade, a maximum stress position of a leading edge is taken as a characteristic position, and a cross-sectional size of the characteristic position is extracted; S2, a stress gradient distribution and a geometric size feature of a characteristic leading edge cross section are extracted from a result of the finite element simulation; S3, a simulation blade model is established according to the cross-sectional size of the characteristic position, the stress gradient distribution and the geometric size feature of the leading edge cross section, numerical simulation is performed on a stress distribution of the simulation blade model, and correction is performed until the stress distribution of the simulation blade model matches a stress distribution of the real blade to obtain final parameters of the simulation blade; A stress distribution of the real blade under an actual working rotating speed is calculated, a characteristic position cross-sectional stress distribution is extracted, a gradient distribution rule from the leading edge to the blade is analyzed, a ratio of a maximum tensile stress to a maximum compressive stress is obtained, and the ratio is taken as a target function value for iteration convergence judgment; a tensile stress of the simulation blade model is calculated, and when a ratio of a maximum tensile stress to a maximum compressive stress of the simulation blade model from the leading edge to the blade is less than the target function value, sizes of the simulation blade model corresponding to the ratio are taken as final sizes; A leading edge radius, an included angle of a bevel edge and 1 / 2 blade thickness are extracted from initial size parameters of a characteristic position cross section of the real blade, the leading edge radius remains unchanged in an iteration process, the remaining two parameters are taken as initial values of simulation blade sizes, the included angle of the bevel edge is defined as θ, and the 1 / 2 blade thickness is defined as d, and a simulation blade model is established; Final parameters of the simulation compressor blade considering the stress gradient comprise: The blade edge blade leading edge radius is the characteristic cross section leading edge radius; θ and d satisfying an optimization end condition after multiple iteration calculations are an included angle value and a flat plate segment thickness value of the blade edge blade; The blade edge blade leading edge radius is the characteristic cross section leading edge radius; θ and d satisfying an optimization end condition after multiple iteration calculations are an included angle value and a flat plate segment thickness value of the blade edge blade; a flat plate segment width of the blade edge blade is 2 times a leading edge width; a length of the blade edge blade is set to 1.5 times a width of the blade edge blade; a transition section fillet is arranged between the blade edge blade and the clamping end, and a fillet radius of the transition section fillet is a clamping end thickness; the clamping end thickness is greater than 3 times the flat plate segment thickness value.

2. The method of claim 1, wherein, The cross-sectional size of the characteristic position comprises a leading edge curvature radius and a bevel edge slope.

3. The method of claim 1, wherein, The tensile stress of the simulation blade is calculated, a stress gradient distribution feature on a maximum stress cross section of the leading edge is extracted, a ratio of a maximum tensile stress to a maximum compressive stress is obtained, and the ratio is compared with a ratio of a maximum tensile stress to a maximum compressive stress of the real blade obtained through numerical simulation.

4. The method of claim 1, wherein, When a difference between the ratio of the maximum tensile stress to the maximum compressive stress of the simulation blade model from the leading edge to the blade and the target function value is less than 5%, sizes of the simulation blade model corresponding to the ratio are taken as the final sizes, otherwise, data of θ and d are adjusted by using an optimization algorithm for next round iteration until the optimization end condition is satisfied.

5. The method of claim 1, wherein, The clamping end thickness is greater than 3 times the flat plate segment thickness value.

6. A simulated blade structure based on the method of claim 1, characterized by It includes clamping end (2) and blade edge blade (1), the thickness of blade edge blade (1) is less than the thickness of clamping end (2), the blade edge blade (1) includes flat plate section (101) and front edge (102) located at the front and back of flat plate section (101), both ends of flat plate section (101) are connected with clamping end (200) through arc transition, both ends of front edge (102) are connected with clamping end through arc transition, two front edges are symmetrically arranged on both sides of flat plate section.

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