Method for determining rotating speed of gas turbine in high-speed pre-rotating test

Abstract

The invention provides a method for determining the rotating speed of a high-speed pre-rotating test of a gas turbine. The method comprises the following steps: S1, obtaining a material test bar; s2, carrying out a tensile test on the test bar to obtain an engineering stress-engineering strain curve; s3, obtaining a median engineering stress-engineering strain curve; s4, acquiring a real stress-real strain curve; s5, judging whether plastic strain needs to be input or not by simulation calculation software, if so, performing S6, and if not, performing S7; s6, obtaining a real stress-real plastic strain curve; s7, inputting the material data into simulation calculation software; s8, setting load steps of pre-rotation speed loading and unloading for calculation; s9, extracting the residual strain of the disc center after unloading; and S10, judging the residual strain value, if the residual strain value meets the requirement, stopping, and if the residual strain value does not meet the requirement, repeating the step S8, and resetting the pre-rotation speed. According to the method for determining the rotating speed of the high-speed pre-rotating test of the gas turbine, the disc center of the wheel disc can be subjected to effective plastic deformation.

Description

Technical Field

[0001] This invention belongs to the field of rotating machinery, and specifically relates to a method for determining the high-speed pre-rotation test speed of a gas turbine. Background Technology

[0002] As a key component of gas turbines, the turbine disk is extremely expensive to manufacture. Improving its lifespan can effectively reduce overall costs and enhance market competitiveness. High-speed pre-rotation testing of the disk can effectively extend its service life. The specific principle is that before service, the disk is rotated at a higher speed than during operation, causing the stress in key areas (such as the disk core) to exceed the material's yield stress. This induces plastic deformation in the material. When the high-speed centrifugal force and temperature are unloaded, the plastically deformed portion hinders the recovery of elastic deformation in other areas, generating residual compressive stress (negative value) at that location. After the disk enters service, the stress in its key areas is the sum of the working stress before pre-rotation (positive value) and the residual compressive stress (negative value), thus reducing the post-service stress level of the disk and increasing its strength reserve and lifespan. However, excessively high pre-rotation speeds may damage the disk before use, reducing its service life; excessively low pre-rotation speeds may not induce plastic deformation in the disk core. Summary of the Invention

[0003] The purpose of this invention is to provide a method for determining the high-speed pre-rotation test speed of a gas turbine.

[0004] A method for determining the high-speed pre-rotation test speed of a gas turbine includes the following steps: S1, Obtain the material test bar; S2, conduct a tensile test on the test bar to obtain the engineering stress-engineering strain curve; S3, obtain the median engineering stress-engineering strain curve; S4, obtain the true stress-strain curve; S5, the simulation software will determine whether plastic strain needs to be input. If so, proceed to S6; otherwise, proceed to S7. S6, obtain the true stress-true plastic strain curve; S7, input the material data into the simulation calculation software; S8, set the load step for pre-rotation speed loading and unloading for calculation; S9, extract the residual strain of the disk core after unloading; S10: Determine the residual strain value. If the requirement is met, stop; otherwise, repeat S8 to reset the pre-rotation speed.

[0005] Furthermore, in S1, the test bars must be obtained from the test ring attached to the disc blank, and the test ring must be obtained from the center of the disc, and the number of test bars for each temperature must be at least 3.

[0006] Furthermore, the test temperature of the tensile test in S2 includes the ambient temperature of the pre-rotation test of the control wheel.

[0007] Furthermore, the true stress-true strain curve in S4 is obtained using the following formula: in, This represents the actual stress, expressed in MPa. This refers to engineering stress, expressed in MPa. For engineering strain, the unit is mm / mm; For actual strain, the unit is mm / mm.

[0008] Furthermore, the true stress-true plastic strain curve in S6 is obtained using the following formula: in, The values ​​represent the actual plastic strain, in mm / mm; E represents the elastic modulus, in MPa.

[0009] Furthermore, the residual strain value requirement in S10 is: after pre-rotation simulation calculation, the residual strain value of the disk center is between 500 and 2000 με, which meets the test requirements.

[0010] The beneficial effects of the present invention are as follows: The method for determining the high-speed pre-rotation test speed of a gas turbine proposed in this invention can cause effective plastic deformation of the turbine disk center. Attached Figure Description

[0011] Figure 1 This is a flowchart of the present invention.

[0012] Figure 2 These are drawings of the test ring and test bar for the gas turbine disk material of this invention; Figure 3 The median tensile stress-strain curve of the gas turbine disk material test bar of this invention; Figure 4 This is the actual stress-strain curve of the gas turbine disk material test bar of this invention; Figure 5 This is the true stress-true plastic strain curve of the gas turbine disk material test bar of the present invention; Figure 6This is a structural diagram of the gas turbine disk test piece of the present invention; Figure 7 This is the rotational speed spectrum of the gas turbine disk test specimen for the present invention during pre-rotation testing. Detailed Implementation

[0013] The present invention will now be further described with reference to the accompanying drawings.

[0014] The present invention provides a method for determining the high-speed pre-rotation test speed of a gas turbine, combined with... Figure 1 The specific implementation method is as follows: S1, Obtain the material test bar, such as Figure 2 As shown; Test bars must be obtained from the test ring attached to the disc blank, and the test ring must be located at the center of the disc. At least three test bars must be used for each temperature.

[0015] S2, conduct a tensile test on the test bar to obtain the engineering stress-engineering strain curve; The test temperature for the tensile test must include the ambient temperature of the pre-rotation test of the drive disc.

[0016] S3, obtain the median engineering stress-strain curve from the engineering stress-strain curves of multiple test bars, such as... Figure 3 As shown. S4 obtains the true stress-strain curve, such as Figure 4 As shown; The true stress-strain curve is obtained using the following formula: (1) (2) In the formula, This represents the actual stress, expressed in MPa. This refers to engineering stress, expressed in MPa. For engineering strain, the unit is mm / mm; For actual strain, the unit is mm / mm.

[0017] S5 determines whether the simulation software needs to input plastic strain. If so, proceed to S6; otherwise, proceed to S7. This example requires plastic strain.

[0018] S6, obtain the true stress-true plastic strain curve, such as Figure 5 As shown; The true stress-true plastic strain curve is obtained using the following formula: (3) In the formula, The values ​​represent the actual plastic strain, in mm / mm; E represents the elastic modulus, in MPa.

[0019] S7, input the material data into the simulation calculation software.

[0020] S8, Set the pre-rotation speed loading and unloading load steps for a certain disk (e.g., Figure 6 Simulation calculations were performed (as shown). The load step is as follows: Load step 1: 10300 rpm Load step 2:0 Load step 3: 10815 rpm Load step 4:0 Load step 5: 11330 rpm Load step 6:0 Load step 7: 11845 rpm Load step 8:0 Load step 9: 12360 rpm Load step 10:0 Load step 11: 12875 rpm Load step 12:0 Load step 13: 13390 rpm Load step 14:0 Load step 15: 13905 rpm Load step 16:0 Load step 17: 14420 rpm Load step 18:0 S9, extract the residual strain of the disk core after unloading.

[0021] S10: Determine the residual strain value. If the requirement is met, stop; otherwise, repeat S8 to reset the pre-rotation speed.

[0022] The residual strain value requirement is: after pre-rotation simulation calculation, the residual strain value of the disk center should be between 500 and 2000 με, or meet the test requirements.

[0023] Based on the pre-rotation calculation, when the pre-rotation test speed is 11845 rpm, the average residual strain of the disk center is 598 με, which meets the requirements. Therefore, the pre-rotation test speed is set to 11845 rpm.

[0024] A high-speed pre-rotation test was conducted on a certain wheel disc test piece using the high-speed pre-rotation test speed determined by the method described above. The test speed spectrum is as follows: Figure 7 As shown.

[0025] After the test, the average residual strain at the center of the disk was 977 με, which meets the test requirement that the residual strain value at the center of the disk be between 500 and 2000 με.

[0026] The life prediction model commonly used in engineering (SWT model) was used to predict the life before and after high-speed pre-rotation. The prediction results showed that after high-speed pre-rotation, the life prediction value of the disk center part was 4.5 times higher than that of the disk center part without pre-rotation. (4) In the formula, σmax is the peak operating stress in MPa; Δεt is the strain range in mm / mm; Nf is the lifespan in cycles; b is the fatigue strength index; and c is the fatigue ductility index. — Fatigue strength coefficient, in MPa; —Fatigue ductility coefficient.

[0027] This method can quickly and accurately determine the high-speed pre-rotation test speed, reduce the trial and error costs of exploring the test speed through experiments, and greatly shorten the test cycle and test costs.

[0028] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for determining the high-speed pre-rotation test speed of a gas turbine, characterized in that, Includes the following steps: S1, Obtain the material test bar; S2, conduct a tensile test on the test bar to obtain the engineering stress-engineering strain curve; S3, obtain the median engineering stress-engineering strain curve; S4, obtain the true stress-strain curve; S5, the simulation software will determine whether plastic strain needs to be input. If so, proceed to S6; otherwise, proceed to S7. S6, obtain the true stress-true plastic strain curve; S7, input the material data into the simulation calculation software; S8, set the load step for pre-rotation speed loading and unloading for calculation; S9, extract the residual strain of the disk core after unloading; S10: Determine the residual strain value. If the requirement is met, stop; otherwise, repeat S8 to reset the pre-rotation speed.

2. The method for determining the high-speed pre-rotation test speed of a gas turbine according to claim 1, characterized in that, In S1, the test bars must be obtained from the test ring attached to the disc blank. The test ring must be obtained from the center of the disc, and the number of test bars for each temperature must be at least 3.

3. The method for determining the high-speed pre-rotation test speed of a gas turbine according to claim 1, characterized in that, The test temperature for the tensile test in S2 includes the ambient temperature of the pre-rotation test of the control wheel.

4. The method for determining the high-speed pre-rotation test speed of a gas turbine according to claim 1, characterized in that, The true stress-true strain curve in S4 is obtained using the following formula: in, This represents the actual stress, expressed in MPa. This refers to engineering stress, expressed in MPa. For engineering strain, the unit is mm / mm; For actual strain, the unit is mm / mm.

5. The method for determining the high-speed pre-rotation test speed of a gas turbine according to claim 1, characterized in that, The true stress-true plastic strain curve in S6 is obtained using the following formula: in, The values ​​represent the actual plastic strain, in mm / mm; E represents the elastic modulus, in MPa.

6. The method for determining the high-speed pre-rotation test speed of a gas turbine according to claim 1, characterized in that, The residual strain value requirement in S10 is: after pre-rotation simulation calculation, the residual strain value of the disk center is between 500 and 2000 με, which meets the test requirements.

Images