Marine gas turbine start-stop frequency and operation time equivalent test method

Abstract

The invention provides an equivalent test method for start-stop times and operation time of a marine gas turbine. The method comprises the following steps: S1, carrying out static strength calculation; s2, carrying out temperature calibration; s3, performing a low-cycle fatigue test and a long-time endurance test respectively; s4, carrying out component state evaluation, if cracks with the length exceeding 0.76 mm appear, carrying out S5, and if cracks with the length exceeding 0.76 mm do not appear, repeating S3; s5, working condition judgment is carried out, S6 is carried out if all the working conditions are finished, and S2 is repeated if the working conditions are not finished; s6, carrying out life equivalence; and S7, carrying out working condition equivalence. According to the invention, a long-time endurance test and a low-cycle fatigue test can be carried out on a real wheel disc blade part in a rotating environment, real and reliable data accumulation is provided for a designer, and the real service life of the part is given. The method is mainly used for service life equivalence of wheel disc blade components.

Description

Technical Field

[0001] The invention belongs to the field of rotating machinery, and in particular relates to an equivalent test method for start-stop times and operating time of a marine gas turbine. Background Art

[0002] Gas turbines are compact rotating machines with high power density. The moving blades that drive the rotor to rotate at high speed are their core components. Working in a high temperature, high pressure, and high speed environment, the moving blades are subjected to the combined effects of centrifugal force, vibration stress, thermal stress, and other loads, making them prone to fracture failure. As a result, in the design and development process of the Xinyan gas turbine unit, the main development cost is spent on simulation calculations and experimental testing of the moving blades.

[0003] According to domestic and foreign data statistics, most of the fracture failures of gas turbine moving blades originate from fatigue fracture of the blades (including low-cycle fatigue fracture and high-cycle fatigue fracture). Among them, low-cycle fatigue fracture is caused by the stress level of the local part of the blade under the operating conditions exceeding the yield stress level that its material can withstand, resulting in plastic deformation and damage to the blade. The damage accumulates every time the engine is started and stopped, and eventually leads to fracture; high-cycle fatigue fracture is fatigue fracture caused by blade resonance. The main reason for the resonance is that when the natural frequency of the blade is equal to the excitation frequency in the working environment, the blade is prompted to produce a large amplitude vibration response. After superimposing the centrifugal force during the high-speed rotation of the blade, the fracture failure occurs. Considering the impact of the structural strength of the moving blade on the safety of the gas turbine, detailed calculation analysis and bench test verification must be carried out before the moving blade is installed and operated. Whether it is possible to simulate the service environment of the moving blade to the maximum extent to conduct targeted assessment is an important research direction of gas turbine professionals at home and abroad.

[0004] When designing a new gas turbine, we often need to give the overhaul life of the gas turbine and the number of starts and stops of the gas turbine during the overhaul period. It is known that the life of a gas turbine mainly depends on the life of key components (blades, impellers). Existing methods are mostly to estimate its life through simulation calculations. Its value is usually found in the material manual based on its stress conditions and temperature. However, this value is usually obtained by a smooth standard test rod on a tensile machine. The structure of gas turbine impeller blades is complex, and stress concentration is obvious at the corners. At the same time, the tensile machine cannot simulate the gradual effect of centrifugal force gradually increasing from the blade tip to the blade root. A more accurate method is needed to give the life. In addition, unlike aircraft engines, marine gas turbines do not require many combat flight subjects. Marine gas turbines only need a few commonly used stable conditions. Therefore, how to design a test method for the equivalent number of starts and stops and running time of marine gas turbines is particularly important. Summary of the invention

[0005] The purpose of the present invention is to provide an equivalent test method for the number of starts and stops and the operating time of a marine gas turbine, which solves the problem that a standard test rod with smooth material cannot simulate the stress concentration at the edges and corners of complex structures such as gas turbine disk blades, and that a stretching machine cannot simulate the influence of the gradual effect of the gradually increasing centrifugal force from the blade tip to the blade root on the life of the gas turbine.

[0006] A method for testing the equivalence between the number of starts and stops and the operating time of a marine gas turbine, comprising the following steps:

[0007] S1, perform static strength calculation;

[0008] S2, perform temperature calibration;

[0009] S3, low cycle fatigue test and long-term endurance test respectively;

[0010] S4, perform component status assessment. If cracks longer than 0.76 mm are found, proceed to S5. If cracks longer than 0.76 mm are not found, repeat S3.

[0011] S5, judge the working condition. If all working conditions are completed, proceed to S6. If not, repeat S2.

[0012] S6, perform life equivalence;

[0013] S7, perform working condition equivalence.

[0014] Furthermore, the static strength calculation in S1 specifically includes: analyzing the static strength reserve of each stage of the gas turbine rotor, determining the test piece to be selected, and for the multi-stage disk or multi-stage blade of the same model of engine, satisfying the following conditions:

[0015] 1) The materials are the same;

[0016] 2) The processing method and heat treatment process are the same;

[0017] 3) The structural shapes are similar, and the service stress and temperature conditions are close;

[0018] That is, among these discs or blades, the representative level with the lowest static strength reserve can be selected for testing through strength analysis and calculation, and the part with the lowest reserve can be determined as the assessment part.

[0019] Furthermore, in S2, the temperature T' of the test part under each working condition is used as the standard, a thermocouple is pasted at the test part, and the temperature control program is adjusted until the temperature T of each working condition reaches a given temperature T', and the calibration is completed within an error of ±10°C. The temperature control program at this time is recorded, and the formal test is carried out according to this program. The temperature remains unchanged during the test. When the blade is the test piece and the disc is the accompanying test piece, it is ensured that the temperature of each part of the disc is not higher than the design temperature.

[0020] Furthermore, two groups of tests are carried out under each working condition in S3, namely, low cycle fatigue test and long-term endurance test. When the temperature reaches the temperature calibrated in S2 and is kept warm for more than 60 minutes, a low cycle fatigue test is carried out, wherein the working speed is the speed of the gas turbine under this operating condition.

[0021] Furthermore, the normal operation of the marine gas turbine in S5 is divided into three operating conditions, namely 1.0, 0.8 and 0.6 conditions, each of which requires the S3 test. The number of low-cycle fatigue test conditions of 1.0, 0.8 and 0.6 are N1, N2 and N3 respectively, and the long-term endurance test conditions of 1.0, 0.8 and 0.6 are tt1, tt2 and tt3 respectively.

[0022] Furthermore, in the S6, one start and stop under the 1.0 condition is equivalent to tt1 / N1 hour of operation; one start and stop under the 0.8 condition is equivalent to tt2 / N2 hours of operation; and one start and stop under the 0.6 condition is equivalent to tt3 / N3 hours of operation.

[0023] Furthermore, in S7, one start and stop under the 1.0 condition is equivalent to N2 / N1 starts and stops under the 0.8 condition, and one start and stop under the 1.0 condition is equivalent to N3 / N1 starts and stops under the 0.6 condition.

[0024] The beneficial effects of the present invention are that the present invention can perform long-term endurance tests and low-cycle fatigue tests on real wheel blade components in a rotating environment, provide equivalent methods for the start-stop times and operating time of key components, and equivalent methods between operating conditions, thereby providing users with real and reliable data. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a flow chart of the present invention;

[0026] Figure 2 It is a schematic diagram of the low cycle fatigue test spectrum under the blade rotation environment of the present invention;

[0027] Figure 3 This is a schematic diagram of the long-term endurance life test spectrum under the blade rotation environment of the present invention. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with the accompanying drawings.

[0029] A test method for the equivalence of the number of starts and stops and the running time of a marine gas turbine, combined with Figure 1 The specific implementation is as follows:

[0030] S1, perform static strength calculation, analyze the static strength reserve of each stage of gas turbine rotor, determine the test piece, for the same model of engine multi-stage disk or multi-stage blade, only need to meet the following conditions:

[0031] 1) The materials are the same;

[0032] 2) The processing method and heat treatment process are the same;

[0033] 3) The structural shapes are similar, and the operating stress and temperature conditions are close.

[0034] That is, among these discs or blades, the representative level with the lowest static strength reserve can be selected for testing through strength analysis and calculation, and the part with the lowest reserve can be determined as the assessment part.

[0035] S2, perform temperature calibration, take the temperature T' of the test part under each working condition as the standard, paste the thermocouple on the test part, adjust the temperature control program until the temperature T of each working condition reaches the given temperature T', and the calibration is completed within ±10℃. Record the temperature control program at this time, and the formal test is carried out according to this program (such as Figure 2 , Figure 3 During the test, the temperature remains constant. When the blade is the test piece and the disc is the accompanying test piece, it should be ensured that the temperature of each part of the disc is not higher than the design temperature.

[0036] S3, respectively carry out low cycle fatigue test and long endurance test. When the temperature reaches the temperature calibrated by S2 and is kept warm for more than 60 minutes, carry out low cycle fatigue test (load spectrum as shown in Figure 2 As shown, the duration t1 and t3 are generally 2s, and the speed increase and decrease times t2 and t4 are determined according to the tester capacity. ), long-term endurance test (load spectrum as shown Figure 3 As shown), the operating speed is the speed of the gas turbine under this operating condition.

[0037] S4, perform component status inspection. After a certain number of cycles or time for each test, stop the machine to check whether there are cracks longer than 0.76 mm. If there are no cracks longer than 0.76 mm, continue the test until all cracks longer than 0.76 mm appear. Record the number of cycles of the low-cycle fatigue test and the time t of the long-term endurance test.

[0038] S5. The normal operation of marine gas turbines is divided into three working conditions, namely 1.0, 0.8 and 0.6 working conditions. Each working condition needs to be subjected to low-cycle fatigue test and long-term endurance test. The test times of 1.0, 0.8 and 0.6 working conditions of low-cycle fatigue test are recorded as N1, N2 and N3 respectively. The test times of 1.0, 0.8 and 0.6 working conditions of long-term endurance test are recorded as tt1, tt2 and tt3 respectively.

[0039] S6, perform life equivalence, assuming that the damage is cumulative, under the 1.0 condition, the cumulative damage of N1 times reaches 1, the test piece is damaged, the damage of 1 start and stop is 1 / N1, under the 1.0 condition, the cumulative damage of tt1 hour reaches 1, the test piece is damaged, and the damage of running for 1 hour is 1 / tt1, then 1 start and stop is equivalent to (1 / N1) / (1 / tt1)=tt1 / N1 hour running; similarly, under the 0.8 condition, 1 start and stop is equivalent to tt2 / N2 hour running; under the 0.6 condition, 1 start and stop is equivalent to tt3 / N3 hour running.

[0040] S7, perform working condition equivalence, 1 start and stop under working condition 1.0 is equivalent to (1 / N1) / (1 / N2)=N2 / N1 times under working condition 0.8, 1 start and stop under working condition 1.0 is equivalent to (1 / N1) / (1 / N3)=N3 / N1 times under working condition 0.6.

[0041] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A test method for the equivalence of the number of starts and stops and the operating time of a marine gas turbine, characterized in that: The following steps are involved: S1, perform static strength calculation; S2, perform temperature calibration; S3, low cycle fatigue test and long-term endurance test respectively; S4, perform component status assessment. If cracks longer than 0.76 mm are found, proceed to S5. If cracks longer than 0.76 mm are not found, repeat S3. S5, judge the working condition. If all working conditions are completed, proceed to S6. If not, repeat S2. S6, perform life equivalence; S7, perform working condition equivalence.

2. A method for testing the equivalence of the number of starts and stops and the operating time of a marine gas turbine according to claim 1, characterized in that: The static strength calculation in S1 specifically includes: analyzing the static strength reserve of each stage of the gas turbine rotor, determining the test piece to be selected, and for the multi-stage disk or multi-stage blade of the same model of engine, satisfying the following conditions: 1) The materials are the same; 2) The processing method and heat treatment process are the same; 3) The structural shapes are similar, and the service stress and temperature conditions are close; That is, among these discs or blades, the representative level with the lowest static strength reserve can be selected for testing through strength analysis and calculation, and the part with the lowest reserve can be determined as the assessment part.

3. A method for testing the equivalence of the number of starts and stops and the operating time of a marine gas turbine according to claim 1, characterized in that: In S2, the temperature T' of the test part under each working condition is used as the standard, a thermocouple is pasted at the test part, and the temperature control program is adjusted until the temperature T of each working condition reaches the given temperature T'. The calibration is completed within an error of ±10°C, and the temperature control program at this time is recorded. The formal test is carried out according to this program. The temperature remains unchanged during the test. When the blade is the test piece and the disc is the accompanying test piece, it is ensured that the temperature of each part of the disc is not higher than the design temperature.

4. A method for testing the equivalence of the number of starts and stops and the operating time of a marine gas turbine according to claim 1, characterized in that: Two groups of tests are carried out under each working condition in S3, namely low cycle fatigue test and long-term endurance test. When the temperature reaches the temperature calibrated in S2 and is kept warm for more than 60 minutes, a low cycle fatigue test is carried out, wherein the working speed is the speed of the gas turbine under this operating condition.

5. A method for testing the equivalence of the number of starts and stops and the operating time of a marine gas turbine according to claim 1, characterized in that: The normal operation of the marine gas turbine in S5 is divided into three working conditions, namely 1.0, 0.8 and 0.6 working conditions. Each working condition needs to be tested in S3. The number of tests of 1.0, 0.8 and 0.6 working conditions of the low-cycle fatigue test are N1, N2 and N3 times respectively. The test time of 1.0, 0.8 and 0.6 working conditions of the long-term endurance test are tt1, tt2 and tt3 respectively.

6. A method for testing the equivalence of the number of starts and stops and the operating time of a marine gas turbine according to claim 5, characterized in that: In the S6, one start and stop under the 1.0 condition is equivalent to tt1 / N1 hour of operation; one start and stop under the 0.8 condition is equivalent to tt2 / N2 hours of operation; and one start and stop under the 0.6 condition is equivalent to tt3 / N3 hours of operation.

7. A method for testing the equivalence of the number of starts and stops and the operating time of a marine gas turbine according to claim 6, characterized in that: In the S7, one start and stop under the 1.0 condition is equivalent to N2 / N1 starts and stops under the 0.8 condition, and one start and stop under the 1.0 condition is equivalent to N3 / N1 starts and stops under the 0.6 condition.

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