A method and device for calculating the cumulative fatigue damage of a runner blade of a pump turbine

Abstract

The invention relates to the technical field of operation and maintenance of hydropower equipment, and discloses a method and device for calculating the cumulative fatigue damage of a runner blade of a water pump turbine. The method comprises: performing fluid-solid coupling calculation based on a finite element model of a water pump turbine runner and a full flow channel model of the runner to obtain stress change information of the blade during a preset transition process, wherein the preset transition process includes a number of different operating paths during a working condition conversion process; obtaining a high-frequency stress fluctuation curve and a low-frequency stress fluctuation curve of the blade according to the stress change information; respectively calculating the cumulative fatigue damage corresponding to the high-frequency stress and the cumulative fatigue damage corresponding to the low-frequency stress according to the high-frequency stress fluctuation curve and the low-frequency stress fluctuation curve; and calculating the cumulative fatigue damage of the blade during the preset transition process based on the cumulative fatigue damage corresponding to the high-frequency stress and the cumulative fatigue damage corresponding to the low-frequency stress. The invention can improve the accuracy of the calculation of the cumulative fatigue damage of the water pump turbine runner blade.

Description

Technical Field

[0001] The present invention relates to the technical field of hydropower equipment operation and maintenance, and in particular to a method and device for calculating the cumulative fatigue damage of a runner blade of a water pump turbine. Background Art

[0002] The core equipment of a pumped-storage power station is a pump-turbine. Unlike a general turbine that is only used for power generation, a pump-turbine needs to have the bidirectional operation capability of a pump and a turbine. According to the changes in the grid load, it is necessary to perform more frequent operating mode conversions between power generation and pumping conditions. This complex operating condition and transition process results in unstable internal flow characteristics. Under turbine conditions and pump conditions, it will face extremely unstable flow areas in the S zone and the hump zone, respectively. Taking the S zone of the turbine condition as an example, when the pump-turbine is started and shut down under the turbine condition, the same speed can correspond to more than one (3 or four) operating points on the characteristic curve, which enables the unit to operate in any condition between these points, making it difficult to stabilize. A very unstable operating characteristic in the S zone is rotating stall. Once rotating stall occurs, the flow field near the runner and guide vanes will show obvious asymmetry in the entire circumference, with large flow rates in some flow channels and small flow rates in other flow channels. Such flow field distribution will induce strong low-frequency pressure pulsations, causing components such as the runner to be subjected to periodic alternating stress, and there is a risk of fatigue damage to important parts such as the blades, which has a great impact on the safe and stable operation of the unit.

[0003] For the analysis and research of rotating stall, the existing technology mainly uses unsteady numerical calculation methods or model test methods to analyze and study the designed flow path to determine in which operating range the rotating stall phenomenon exists. The existing methods can only analyze and study the impact of rotating stall on the operating conditions where rotating stall has occurred, including pressure pulsation, vibration and noise. However, it is difficult to identify and determine the characteristics of the starting point of rotating stall, and it is difficult to calculate the fatigue accumulation under rotating stall, resulting in inaccurate fatigue accumulation calculation results when the pump turbine is affected by rotating stall during operation. Summary of the invention

[0004] In view of this, the present invention provides a method and device for calculating the cumulative fatigue damage of a runner blade of a pump-turbine, so as to solve the technical problem that the cumulative fatigue damage calculation of the runner blade of the existing pump-turbine is not accurate enough.

[0005] In a first aspect, the present invention provides a method for calculating the cumulative fatigue damage of a runner blade of a pump-turbine, comprising: performing fluid-solid coupling calculations based on a finite element model of a pump-turbine runner and a full-flow channel model of the runner to obtain stress change information of the blades during a preset transition process, wherein the preset transition process includes several different operating paths during the operating condition conversion process; obtaining a high-frequency stress fluctuation curve and a low-frequency stress fluctuation curve of the blades according to the stress change information; respectively calculating the cumulative fatigue damage corresponding to the high-frequency stress and the cumulative fatigue damage corresponding to the low-frequency stress according to the high-frequency stress fluctuation curve and the low-frequency stress fluctuation curve; and calculating the cumulative fatigue damage of the blades during the preset transition process based on the cumulative fatigue damage corresponding to the high-frequency stress and the cumulative fatigue damage corresponding to the low-frequency stress.

[0006] The present invention provides a method for calculating the cumulative fatigue damage of a runner blade of a water pump turbine. The method performs fluid-solid coupling calculation by jointly performing a finite element model and a runner full flow channel model to obtain stress change information of the blade during a preset transition process. The high-frequency stress fluctuation curve and the low-frequency stress fluctuation curve of the blade are obtained according to the stress change information. The cumulative fatigue damage corresponding to the high-frequency stress and the cumulative fatigue damage corresponding to the low-frequency stress are calculated according to the high-frequency stress fluctuation curve and the low-frequency stress fluctuation curve, respectively, so as to obtain the cumulative fatigue damage of the blade during the preset transition process. When a rotational stall occurs in the water turbine, the blade will be subjected to stresses superimposed by high and low frequencies, wherein the low-frequency vibration comes from the rotational frequency of the rotational stall, causing the blade to also be subjected to a low-frequency alternating stress of a fixed frequency, which is different from other high-frequency influences in the water turbine blades. Therefore, by calculating the cumulative fatigue damage corresponding to the high-frequency stress and the cumulative fatigue damage corresponding to the low-frequency stress according to the high-frequency stress fluctuation curve and the low-frequency stress fluctuation curve, respectively, the influence of the rotational stall can be fully considered, and the accuracy of the calculation of the cumulative fatigue damage of the runner blade of the water pump turbine can be improved.

[0007] Optionally, the cumulative fatigue damage corresponding to the high-frequency stress and the cumulative fatigue damage corresponding to the low-frequency stress are calculated respectively according to the high-frequency stress fluctuation curve and the low-frequency stress fluctuation curve, including: counting the number of cycles of each constant-amplitude load under high-frequency fluctuation according to the high-frequency stress fluctuation curve; obtaining the damage coefficient of each load cycle under low-frequency stress fluctuation and the derivative of the amplitude of the low-frequency stress fluctuation in each load cycle with respect to time according to the low-frequency stress fluctuation curve; calculating the cumulative fatigue damage corresponding to the high-frequency stress according to the number of cycles of each constant-amplitude load under high-frequency fluctuation; calculating the cumulative fatigue damage corresponding to the low-frequency stress according to the damage coefficient of each load cycle and the derivative of the amplitude of the low-frequency stress fluctuation in each load cycle with respect to time.

[0008] This method can distinguish the effects of high-frequency and low-frequency stresses on blade fatigue damage, thereby more accurately calculating the fatigue damage of the blade.

[0009] Optionally, calculating the cumulative fatigue damage corresponding to the high-frequency stress according to the number of cycles of each constant amplitude load under high-frequency fluctuations includes: calculating the cumulative fatigue damage corresponding to the high-frequency stress according to the number of cycles of each constant amplitude load under high-frequency fluctuations based on a first preset formula, wherein the first preset formula is:

[0010]

[0011] In the formula, is the cumulative fatigue damage corresponding to high-frequency stress, Constant amplitude load The number of cycles under high-frequency fluctuations, Constant amplitude load under high frequency fluctuation The corresponding fatigue life.

[0012] This method can reduce the amount of calculation by calculating the fatigue damage accumulation corresponding to the high-frequency stress based on the number of cycles of the constant amplitude load and the fatigue life corresponding to each constant amplitude load.

[0013] Optionally, calculating the fatigue damage accumulation corresponding to the low-frequency stress according to the damage coefficient of each load cycle and the derivative of the amplitude of the low-frequency stress fluctuation in each load cycle with respect to time includes: calculating the fatigue damage accumulation corresponding to the low-frequency stress according to the damage coefficient of each load cycle and the derivative of the amplitude of the low-frequency stress fluctuation in each load cycle with respect to time based on a second preset formula, wherein the second preset formula is:

[0014]

[0015] In the formula, is the cumulative fatigue damage corresponding to the low-frequency stress, is the low frequency safety factor, It is The damage factor of a load cycle is is the derivative of the amplitude of the low-frequency stress fluctuation with respect to time, For the The number of load cycles under low-frequency fluctuations, For the Fatigue life corresponding to the load level for a load cycle.

[0016] This method can accurately calculate the fatigue damage accumulation corresponding to low-frequency stress.

[0017] Optionally, obtaining a high-frequency stress fluctuation curve and a low-frequency stress fluctuation curve of the blade according to the stress change information includes: generating a stress time series curve of the blade according to the stress change information; and decomposing the stress time series curve to obtain a high-frequency stress fluctuation curve and a low-frequency stress fluctuation curve of the blade.

[0018] This method can separate high-frequency and low-frequency components from complex stress changes, providing a clear data basis for the quantitative calculation of fatigue damage.

[0019] Optionally, after calculating the cumulative fatigue damage of the blades in the preset transition process based on the cumulative fatigue damage corresponding to the high-frequency stress and the cumulative fatigue damage corresponding to the low-frequency stress, it also includes: evaluating the corresponding operating paths according to the cumulative fatigue damage of the blades in different operating paths in the preset transition process and preset evaluation indicators to obtain evaluation results; and generating operating strategy optimization suggestions for the pump turbine based on the evaluation results.

[0020] This method evaluates the corresponding operation path according to the accumulated fatigue damage of the blades and the preset evaluation indicators, and can provide a better operation strategy for the operation of the pump turbine, which helps to improve the operating efficiency of the equipment and extend its service life.

[0021] In a second aspect, the present invention provides a device for calculating the cumulative fatigue damage of a runner blade of a pump-turbine, comprising: a stress change acquisition module, which is used to perform fluid-solid coupling calculation based on a finite element model of the pump-turbine runner and a full flow channel model of the runner, to obtain stress change information of the blade during a preset transition process, wherein the preset transition process includes several different operating paths during the operating condition conversion process; a high- and low-frequency curve generation module, which is used to obtain a high-frequency stress fluctuation curve and a low-frequency stress fluctuation curve of the blade according to the stress change information; a high- and low-frequency damage cumulative calculation module, which is used to calculate the cumulative fatigue damage corresponding to the high-frequency stress and the cumulative fatigue damage corresponding to the low-frequency stress according to the high-frequency stress fluctuation curve and the low-frequency stress fluctuation curve respectively; a total damage cumulative calculation module, which is used to calculate the cumulative fatigue damage of the blade during the preset transition process based on the cumulative fatigue damage corresponding to the high-frequency stress and the cumulative fatigue damage corresponding to the low-frequency stress.

[0022] In a third aspect, the present invention provides a computer device comprising: a memory and a processor, the memory and the processor being communicatively connected to each other, the memory storing computer instructions, and the processor executing the method for calculating the cumulative fatigue damage of a runner blade of a pump turbine according to the first aspect or any corresponding embodiment thereof by executing the computer instructions.

[0023] In a fourth aspect, the present invention provides a computer-readable storage medium having computer instructions stored thereon, the computer instructions being used to enable a computer to execute the method for calculating the cumulative fatigue damage of a runner blade of a pump turbine according to the first aspect or any corresponding embodiment thereof.

[0024] In a fifth aspect, the present invention provides a computer program product, comprising computer instructions for causing a computer to execute the method for calculating the cumulative fatigue damage of a runner blade of a pump turbine as in the first aspect or any corresponding embodiment thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 It is a flow chart of a method for calculating the cumulative fatigue damage of a runner blade of a pump turbine according to an embodiment of the present invention;

[0027] Figure 2 is a schematic diagram of a stress timing curve according to an embodiment of the present invention;

[0028] Figure 3 It is a structural block diagram of a pump turbine runner blade fatigue damage accumulation calculation device according to an embodiment of the present invention;

[0029] Figure 4 It is a schematic diagram of the hardware structure of a computer device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0031] In view of the influence of rotational stall of a pump-turbine on blade fatigue damage, an embodiment of the present invention provides an embodiment of a method for calculating the cumulative fatigue damage of a runner blade of a pump-turbine. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0032] In this embodiment, a method for calculating the cumulative fatigue damage of a runner blade of a pump turbine is provided, which can be used in mobile terminals, such as mobile phones, tablet computers, etc. Figure 1 As shown, the process includes the following steps:

[0033] Step S101, based on the finite element model of the pump-turbine runner and the full flow channel model of the runner, fluid-solid coupling calculation is jointly performed to obtain the stress change information of the blades during the preset transition process, wherein the preset transition process includes several different operation paths during the working condition conversion process.

[0034] Specifically, a refined finite element method (FEM) model of the pump-turbine runner is established, combined with the full flow channel model of the runner based on computational fluid dynamics (CFD), and fluid-solid coupling calculations are carried out jointly, focusing on the fluid-solid coupling boundaries such as the runner blades, upper crown and lower ring, and the mesh is encrypted to better calculate and obtain accurate results.

[0035] Considering the overall operating conditions of the pump-turbine unit, it is divided into the operating area and the transition process (including load rejection, start-up and shutdown processes). When the unit is operating in the operating area, the guide vane opening is fixed, the internal flow field is basically stable, and the stress and strain changes on the runner are stable. When the unit undergoes the transition process, the non-steady-state characteristics of the internal flow field of the pump-turbine are significant, and the pressure pulsation, vibration, cavitation and other effects of the unit are strong. The damage to key parts such as the runner is significantly higher than in the stable operating area. Therefore, it is necessary to focus on the runner fatigue damage process during the transition process.

[0036] The preset transition process is a transition process between two different operating conditions, which includes multiple operation paths, that is, the switching between the two operating conditions can be achieved through multiple operation paths. Select a specific key transition process as the preset transition process, determine the change process of key parameters such as guide vane opening and flow rate during the preset transition process of the unit, and parameterize the dynamic process of the preset transition process such as unit shutdown, startup and operating condition conversion. Clarify the several commonly used paths in the preset transition process from operating condition A to operating condition B, such as from unit no-load to grid connection, from all guide vanes closed to no-load state, etc., and record the change process of key parameters such as flow rate, guide vane opening, head, etc. in each path process.

[0037] Through CFD flow calculation, the whole process of each preset transition process is calculated. The pressure and other data on the fluid-solid coupling interface are extracted from the CFD calculation results as the boundary conditions for calculating the structural field in the FEM model, and the load conditions such as centrifugal force and gravity applied during conventional structural calculation are applied to the FEM model to calculate the stress change information of the runner under different working conditions.

[0038] Specifically, the stress change information includes the stress amplitude and stress fluctuation period at each time point. The stress amplitude of the runner blades during the entire preset transition process is recorded and analyzed. Taking into account the stress asymmetry between the blades of the runner caused by rotational stall, it is necessary to record the stress changes of all blades, and focus on dangerous parts such as the main stress concentration locations such as the root of the blade. At the same time, considering the influence of flow field asymmetry on the non-uniformity and asymmetry of the force applied to the runner in all directions, the non-steady-state characteristics of the overall force of the runner and the shaft are recorded during each transition process, such as the fluctuation period and stress amplitude of the radial force of the runner in different directions.

[0039] Step S102: acquiring a high-frequency stress fluctuation curve and a low-frequency stress fluctuation curve of the blade according to the stress variation information.

[0040] Specifically, according to the stress change information recorded in the above step S101, the high-frequency stress fluctuation curve and the low-frequency stress fluctuation curve are extracted. After the rotational stall occurs, the blade will be subjected to the stress of high and low frequency superposition, wherein the low-frequency vibration comes from the low-frequency rotation frequency of the rotational stall. This causes the blade to also be subjected to a low-frequency alternating stress of a fixed frequency, which is different from other high-frequency influences in the turbine blade. Based on this, the high-frequency stress fluctuation curve and the low-frequency stress fluctuation curve of the blade are extracted from the extracted stress change information.

[0041] Step S103, respectively calculating the fatigue damage accumulation corresponding to the high-frequency stress and the fatigue damage accumulation corresponding to the low-frequency stress according to the high-frequency stress fluctuation curve and the low-frequency stress fluctuation curve.

[0042] In one example, based on the mature rain flow counting method, the high-frequency stress fluctuation part and the low-frequency stress fluctuation part are counted according to the high-frequency stress fluctuation curve and the low-frequency stress fluctuation curve, and the number of constant amplitude load cycles under different amplitude stress levels is statistically obtained. Then, based on the Miner linear fatigue damage accumulation calculation method, the high-frequency stress fluctuation part and the low-frequency fluctuation part are calculated for damage, and the fatigue damage accumulation corresponding to the high-frequency stress is obtained. The fatigue damage accumulation corresponding to the low-frequency stress .

[0043] Step S104, calculating the accumulated fatigue damage of the blade during the preset transition process based on the accumulated fatigue damage corresponding to the high-frequency stress and the accumulated fatigue damage corresponding to the low-frequency stress.

[0044] Specifically, the fatigue damage corresponding to the high-frequency stress is accumulated The fatigue damage accumulation corresponding to the low-frequency stress Add together to get the accumulated blade fatigue damage during the preset transition process.

[0045] A method for calculating the cumulative fatigue damage of a runner blade of a pump-turbine according to an embodiment of the present invention performs fluid-solid coupling calculations jointly by a finite element model and a runner full-flow channel model to obtain stress change information of the blade during a preset transition process, obtains a high-frequency stress fluctuation curve and a low-frequency stress fluctuation curve of the blade according to the stress change information, and calculates the cumulative fatigue damage corresponding to the high-frequency stress and the cumulative fatigue damage corresponding to the low-frequency stress according to the high-frequency stress fluctuation curve and the low-frequency stress fluctuation curve, respectively, thereby obtaining the cumulative fatigue damage of the blade during the preset transition process. When a rotational stall occurs in the turbine, the blade will be subjected to a stress of superposition of high and low frequencies, wherein the low-frequency vibration comes from the rotational frequency of the rotational stall, causing the blade to also be subjected to a low-frequency alternating stress of a fixed frequency, which is different from other high-frequency influences in the turbine blades. Therefore, by calculating the cumulative fatigue damage corresponding to the high-frequency stress and the cumulative fatigue damage corresponding to the low-frequency stress according to the high-frequency stress fluctuation curve and the low-frequency stress fluctuation curve, respectively, the influence of the rotational stall can be fully considered, thereby improving the accuracy of the calculation of the cumulative fatigue damage of the pump-turbine runner blade.

[0046] In some embodiments, step S102, obtaining a high-frequency stress fluctuation curve and a low-frequency stress fluctuation curve of the blade according to the stress variation information, includes:

[0047] Step S1021, generating a stress time series curve of the blade according to the stress change information.

[0048] Specifically, according to the stress change information recorded in the above step S101, a stress time series curve of the blade is generated.

[0049] The stress time series curve reflects the change of stress amplitude over time.

[0050] Step S1022, decomposing the stress time series curve to obtain a high-frequency stress fluctuation curve and a low-frequency stress fluctuation curve of the blade.

[0051] Specifically, Figure 2 As shown in the figure, after the rotating stall occurs, the blades will be subjected to high and low frequency superposition stress, among which the low frequency vibration comes from the rotating frequency of the rotating stall. This results in the blades also being subjected to a low-frequency alternating stress of a fixed frequency, which is different from other high-frequency effects in the turbine blades. Based on this, the stress time series curve is decomposed into a low-frequency stress fluctuation curve ( Figure 2 The dashed line in the figure) and the high-frequency stress fluctuation curve.

[0052] The embodiment of the present invention provides a clear data basis for quantitative calculation of fatigue damage by separating high-frequency and low-frequency components from complex stress changes.

[0053] In some embodiments, step S103, respectively calculating the fatigue damage accumulation corresponding to the high-frequency stress and the fatigue damage accumulation corresponding to the low-frequency stress according to the high-frequency stress fluctuation curve and the low-frequency stress fluctuation curve, includes:

[0054] Step S1031 , counting the number of cycles of each constant amplitude load under high frequency fluctuation according to the high frequency stress fluctuation curve.

[0055] Specifically, for the high-frequency stress fluctuation curve, each constant amplitude load may have multiple cycles, so the Miner linear fatigue damage accumulation calculation method can be directly used to calculate the fatigue damage accumulation of the high-frequency stress fluctuation part.

[0056] The Miner linear fatigue damage accumulation calculation method requires counting the number of cycles of each constant amplitude load. In one example, the number of cycles of each constant amplitude load under high-frequency fluctuations is counted based on the high-frequency stress fluctuation curve using the rain flow counting method.

[0057] Step S1032, obtaining the damage coefficient of each load cycle under the low-frequency stress fluctuation and the derivative of the amplitude of the low-frequency stress fluctuation in each load cycle with respect to time according to the low-frequency stress fluctuation curve.

[0058] Specifically, for low-frequency stress fluctuations, the amplitudes in different cycles are usually different. Therefore, when calculating the cumulative fatigue damage corresponding to the low-frequency stress, it is not necessary to accumulate the calculations for each cycle with the same load level, but to calculate each cycle separately. Therefore, it is necessary to obtain the damage coefficient of each load cycle and the derivative of the amplitude of the low-frequency stress fluctuation in each load cycle with respect to time.

[0059] Step S1033, calculating the fatigue damage accumulation corresponding to the high-frequency stress according to the number of cycles of each constant amplitude load under high-frequency fluctuation.

[0060] Specifically, based on the first preset formula, the fatigue damage accumulation corresponding to the high-frequency stress is calculated according to the number of cycles of each constant amplitude load under high-frequency fluctuation. The first preset formula is:

[0061]

[0062] In the formula, is the cumulative fatigue damage corresponding to high-frequency stress, Constant amplitude load The number of cycles under high-frequency fluctuations, Constant amplitude load under high frequency fluctuation The corresponding fatigue life.

[0063] Constant amplitude load Number of cycles under high frequency fluctuations and constant amplitude load under high frequency fluctuations The corresponding fatigue life is measured using the SN curve test.

[0064] The fatigue damage accumulation corresponding to the high-frequency stress is calculated by the first preset formula based on the Miner linear fatigue damage accumulation calculation method. This method is based on the number of cycles of the constant amplitude load and the fatigue life corresponding to each constant amplitude load to calculate the fatigue damage accumulation corresponding to the high-frequency stress, which can reduce the amount of calculation.

[0065] Step S1034, calculating the fatigue damage accumulation corresponding to the low-frequency stress according to the damage coefficient of each load cycle and the derivative of the amplitude of the low-frequency stress fluctuation in each load cycle with respect to time.

[0066] Based on the second preset formula, the fatigue damage accumulation corresponding to the low-frequency stress is calculated according to the damage coefficient of each load cycle and the derivative of the amplitude of the low-frequency stress fluctuation in each load cycle with respect to time. The second preset formula is:

[0067]

[0068] In the formula, is the cumulative fatigue damage corresponding to the low-frequency stress, is the low frequency safety factor, It is The damage factor of a load cycle is is the derivative of the amplitude of the low-frequency stress fluctuation with respect to time, For the The number of load cycles under low-frequency fluctuations, For the The fatigue life corresponding to the load level of a load cycle. Since each cycle is calculated separately, The default value is 1.

[0069] Specifically, the second preset formula is improved based on the Miner linear fatigue damage accumulation calculation method. In the Miner linear fatigue damage accumulation calculation method, the calculation formula for fatigue damage accumulation corresponding to low-frequency stress is:

[0070]

[0071] Constant amplitude load The number of cycles under low frequency fluctuations, Constant amplitude load under low frequency fluctuation The corresponding fatigue life.

[0072] It should be understood that the above low-frequency stress changes are not independent of the stress on the blade surface. The cumulative effects of the two-frequency stresses on blade fatigue damage are not linearly superimposed. The fatigue damage caused by the low-frequency stress caused by rotating stall is also related to the derivative of the amplitude of the low-frequency stress fluctuation with respect to time. That is, when the rotating stall intensity increases, the amplitude of the low-frequency stress fluctuation curve increases, and when the rotating stall intensity decreases, the amplitude of the low-frequency stress fluctuation curve decreases. Therefore, the accumulation of fatigue damage caused by low-frequency stress can be further written as:

[0073]

[0074] In addition, since the rotating stall causes low-frequency alternating stress, it may resonate with the natural frequency of the runner, causing greater damage to the blades than high-frequency excitation. Therefore, a low-frequency safety factor is introduced. , low frequency safety factor is the absolute value of the difference between the rotating stall frequency and the rotor natural frequency The function of Finally, the second preset formula for calculating the cumulative fatigue damage corresponding to the low-frequency stress is obtained:

[0075]

[0076] The fatigue damage accumulation corresponding to the low-frequency stress can be accurately calculated by the second preset formula.

[0077] Furthermore, the fatigue damage corresponding to the high-frequency stress is accumulated The fatigue damage accumulation corresponding to the low-frequency stress Add together to get the cumulative fatigue damage of the blades during the preset transition process, that is, the cumulative fatigue damage of the blades during the preset transition process for:

[0078]

[0079] In the embodiment of the present invention, the fatigue damage accumulation corresponding to the high-frequency stress and the low-frequency stress is calculated respectively by the first preset formula and the second preset formula, so as to more accurately calculate the fatigue damage of the blade.

[0080] In some embodiments, after calculating the accumulated fatigue damage of the blade in the preset transition process based on the accumulated fatigue damage corresponding to the high-frequency stress and the accumulated fatigue damage corresponding to the low-frequency stress in step S103, the method further includes:

[0081] Step S104, evaluating the corresponding running paths according to the accumulated fatigue damage of the blades in different running paths during the preset transition process and the preset evaluation index, and obtaining an evaluation result;

[0082] Step S105: generating an optimization suggestion for the operation strategy of the pump-turbine according to the evaluation result.

[0083] Specifically, for the same operating condition conversion process, that is, from operating condition A to operating condition B, the above process is used to calculate and analyze the various operating paths between the two operating conditions, and the accumulated blade fatigue damage of the preset transition process under different operating paths is obtained, and the different operating path selections of the same preset transition process are evaluated. In addition to the accumulated blade fatigue damage, the evaluation index also includes preset evaluation indicators, which include multiple parameters such as process experience time and grid connection difficulty.

[0084] The evaluation results of each operation path are obtained by calculation, and based on the evaluation results, a database of various preset transition processes and multiple unit operation paths is established.

[0085] Furthermore, using the data from CFD flow field calculation and FEM model calculation, we established a proxy model to calculate the stress and strain of the runner blades under different operation paths of the preset transition process, continuously updated the data of the operation strategy library, and provided operation strategy optimization suggestions for typical transition processes such as start-stop and operating condition conversion. For the operation optimization strategies with greater improvements, we further conducted detailed calculation and analysis to verify their accuracy and feasibility.

[0086] The embodiment of the present invention evaluates the corresponding operation path according to the accumulated fatigue damage of the blades and the preset evaluation index, and can provide a better operation strategy for the operation of the pump turbine, which helps to improve the operation efficiency of the equipment and extend its service life.

[0087] The method for calculating the cumulative fatigue damage of the runner blades of a pump-turbine in an embodiment of the present invention separately considers the preset transition process with strong non-steady-state characteristics, considers the influence of rotational stall on blade fatigue damage, and calculates the cumulative fatigue damage corresponding to low-frequency fluctuations and high-frequency fluctuations respectively. This can more accurately calculate the cumulative damage, which will help to more accurately predict the fatigue life and damage of the unit.

[0088] In addition, for the same preset transition process, different operating paths are evaluated according to the accumulated blade fatigue damage of different operating paths, which provides a more complete and perfect reference for the operation of the unit and a more flexible and reliable operation mode for the unit.

[0089] The embodiment of the present invention also provides a pump turbine runner blade fatigue damage accumulation calculation device, such as Figure 3 As shown, including:

[0090] The stress change acquisition module 301 is used to perform fluid-solid coupling calculation based on the finite element model of the pump-turbine runner and the full flow channel model of the runner to obtain the stress change information of the blades during the preset transition process, wherein the preset transition process includes several different operation paths during the working condition conversion process;

[0091] A high- and low-frequency curve generation module 302 is used to obtain a high-frequency stress fluctuation curve and a low-frequency stress fluctuation curve of the blade according to the stress variation information;

[0092] A high- and low-frequency damage accumulation calculation module 303 is used to calculate the fatigue damage accumulation corresponding to the high-frequency stress and the fatigue damage accumulation corresponding to the low-frequency stress according to the high-frequency stress fluctuation curve and the low-frequency stress fluctuation curve respectively;

[0093] The total damage accumulation calculation module 304 is used to calculate the fatigue damage accumulation of the blade during the preset transition process based on the fatigue damage accumulation corresponding to the high-frequency stress and the fatigue damage accumulation corresponding to the low-frequency stress.

[0094] The device for calculating the cumulative fatigue damage of the runner blades of a water pump turbine according to an embodiment of the present invention performs fluid-solid coupling calculation by jointly performing a finite element model and a runner full flow channel model to obtain stress change information of the blades during a preset transition process, obtains a high-frequency stress fluctuation curve and a low-frequency stress fluctuation curve of the blades according to the stress change information, and calculates the cumulative fatigue damage corresponding to the high-frequency stress and the cumulative fatigue damage corresponding to the low-frequency stress according to the high-frequency stress fluctuation curve and the low-frequency stress fluctuation curve, respectively, thereby obtaining the cumulative fatigue damage of the blades during the preset transition process. When a rotational stall occurs in the water turbine, the blades will be subjected to stresses superimposed by high and low frequencies, wherein the low-frequency vibration comes from the rotational frequency of the rotational stall, causing the blades to also be subjected to a low-frequency alternating stress of a fixed frequency, which is different from other high-frequency influences in the water turbine blades. Therefore, by calculating the cumulative fatigue damage corresponding to the high-frequency stress and the cumulative fatigue damage corresponding to the low-frequency stress according to the high-frequency stress fluctuation curve and the low-frequency stress fluctuation curve, respectively, the influence of the rotational stall can be fully considered, thereby improving the accuracy of the calculation of the cumulative fatigue damage of the runner blades of the water pump turbine.

[0095] Furthermore, the high and low frequency damage accumulation calculation module 303 includes:

[0096] The frequency statistics module is used to count the number of cycles of each constant amplitude load under high-frequency fluctuation according to the high-frequency stress fluctuation curve;

[0097] A parameter acquisition module, used to obtain the damage coefficient of each load cycle under low-frequency stress fluctuation and the derivative of the amplitude of low-frequency stress fluctuation in each load cycle with respect to time according to the low-frequency stress fluctuation curve;

[0098] High-frequency damage calculation module, used to calculate the fatigue damage accumulation corresponding to high-frequency stress according to the number of cycles of each constant amplitude load under high-frequency fluctuation;

[0099] The low-frequency damage calculation module is used to calculate the fatigue damage accumulation corresponding to the low-frequency stress according to the damage coefficient of each load cycle and the derivative of the amplitude of the low-frequency stress fluctuation in each load cycle with respect to time.

[0100] Furthermore, the high frequency damage calculation module includes:

[0101] Based on the first preset formula, the fatigue damage accumulation corresponding to the high-frequency stress is calculated according to the number of cycles of each constant amplitude load under high-frequency fluctuation. The first preset formula is:

[0102]

[0103] In the formula, is the cumulative fatigue damage corresponding to high-frequency stress, Constant amplitude load The number of cycles under high-frequency fluctuations, Constant amplitude load under high frequency fluctuation The corresponding fatigue life.

[0104] Furthermore, the low-frequency damage calculation module includes:

[0105] Based on the second preset formula, the fatigue damage accumulation corresponding to the low-frequency stress is calculated according to the damage coefficient of each load cycle and the derivative of the amplitude of the low-frequency stress fluctuation in each load cycle with respect to time. The second preset formula is:

[0106]

[0107] In the formula, is the cumulative fatigue damage corresponding to the low-frequency stress, is the low frequency safety factor, It is The damage factor of a load cycle is is the derivative of the amplitude of the low-frequency stress fluctuation with respect to time, For the The number of load cycles under low-frequency fluctuations, For the Fatigue life corresponding to the load level for a load cycle.

[0108] Furthermore, the high and low frequency curve generation module 302 includes:

[0109] A timing curve generating module is used to generate a stress timing curve of the blade according to stress variation information;

[0110] The curve decomposition module is used to decompose the stress time series curve to obtain the high-frequency stress fluctuation curve and the low-frequency stress fluctuation curve of the blade.

[0111] Furthermore, the pump-turbine runner blade fatigue damage accumulation calculation device also includes:

[0112] An evaluation module, used to evaluate the corresponding operation paths according to the accumulated fatigue damage of the blades in different operation paths during the preset transition process and preset evaluation indicators, and obtain an evaluation result;

[0113] The optimization module is used to generate optimization suggestions for the operation strategy of the pump-turbine based on the evaluation results.

[0114] The embodiment of the present invention also provides a schematic diagram of the structure of a computer device, such as Figure 4 As shown, the computer device includes: one or more processors 10, a memory 20, and interfaces for connecting various components, including high-speed interfaces and low-speed interfaces. Various components are connected to each other using different buses for communication, and can be installed on a common mainboard or installed in other ways as needed. The processor can process the instructions executed in the computer device, including instructions stored in or on the memory to display the graphical information of the GUI on an external input / output device (such as, a display device coupled to the interface). In some optional embodiments, if necessary, multiple processors and / or multiple buses can be used together with multiple memories and multiple memories. Similarly, multiple computer devices can be connected, and each device provides some necessary operations (for example, as a server array, a group of blade servers, or a multi-processor system). Figure 4 A processor 10 is taken as an example.

[0115] The processor 10 may be a central processing unit, a network processor or a combination thereof. The processor 10 may further include a hardware chip. The hardware chip may be a dedicated integrated circuit, a programmable logic device or a combination thereof. The programmable logic device may be a complex programmable logic device, a field programmable gate array, a general purpose array logic or any combination thereof.

[0116] The memory 20 stores instructions executable by at least one processor 10, so that at least one processor 10 executes the method shown in the above embodiment.

[0117] The memory 20 may include a program storage area and a data storage area, wherein the program storage area may store an operating system, an application required for at least one function; the data storage area may store data created according to the use of the computer device, etc. In addition, the memory 20 may include a high-speed random access memory, and may also include a non-transient memory, such as at least one disk storage device, a flash memory device, or other non-transient solid-state storage device. In some optional embodiments, the memory 20 may optionally include a memory remotely arranged relative to the processor 10, and these remote memories may be connected to the computer device via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0118] The memory 20 may include a volatile memory, such as a random access memory; the memory may also include a non-volatile memory, such as a flash memory, a hard disk or a solid state drive; the memory 20 may also include a combination of the above types of memory.

[0119] The computer device also includes an input device 30 and an output device 40. The processor 10, the memory 20, the input device 30 and the output device 40 may be connected via a bus or other means. Figure 4 The example of connecting through bus is taken in the following.

[0120] The input device 30 can receive input digital or character information, and generate key signal input related to the user settings and function control of the computer device, such as a touch screen, a keypad, a mouse, a track pad, a touch pad, an indicator bar, one or more mouse buttons, a trackball, a joystick, etc. The output device 40 may include a display device, an auxiliary lighting device (e.g., an LED) and a tactile feedback device (e.g., a vibration motor), etc. The above-mentioned display device includes but is not limited to a liquid crystal display, a light emitting diode, a display and a plasma display. In some optional embodiments, the display device may be a touch screen.

[0121] The embodiment of the present invention also provides a computer-readable storage medium. The method according to the embodiment of the present invention can be implemented in hardware, firmware, or can be implemented as a computer code that can be recorded in a storage medium, or can be implemented as a computer code that is originally stored in a remote storage medium or a non-temporary machine-readable storage medium and will be stored in a local storage medium through a network download, so that the method described herein can be stored in such software processing on a storage medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware. Among them, the storage medium can be a magnetic disk, an optical disk, a read-only storage memory, a random access memory, a flash memory, a hard disk or a solid-state hard disk, etc.; further, the storage medium can also include a combination of the above types of memories. It can be understood that a computer, a processor, a microprocessor controller, or programmable hardware includes a storage component that can store or receive software or computer code. When the software or computer code is accessed and executed by a computer, a processor, or hardware, the method shown in the above embodiment is implemented.

[0122] A part of the present invention may be applied as a computer program product, such as a computer program instruction, which, when executed by a computer, can call or provide the method and / or technical solution according to the present invention through the operation of the computer. Those skilled in the art should understand that the existence of the computer program instruction in a computer-readable medium includes, but is not limited to, a source file, an executable file, an installation package file, etc., and accordingly, the way in which the computer program instruction is executed by the computer includes, but is not limited to: the computer directly executes the instruction, or the computer compiles the instruction and then executes the corresponding compiled program, or the computer reads and executes the instruction, or the computer reads and installs the instruction and then executes the corresponding installed program. Here, the computer-readable medium may be any available computer-readable storage medium or communication medium accessible to the computer.

[0123] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A method for calculating the cumulative fatigue damage of a runner blade of a pump turbine, characterized in that: include: Based on the finite element model of the pump-turbine runner and the full flow channel model of the runner, fluid-solid coupling calculation is performed to obtain the stress change information of the blades during the preset transition process, wherein the preset transition process includes several different operation paths during the working condition conversion process; Acquire a high-frequency stress fluctuation curve and a low-frequency stress fluctuation curve of the blade according to the stress variation information; Calculating respectively the fatigue damage accumulation corresponding to the high-frequency stress and the fatigue damage accumulation corresponding to the low-frequency stress according to the high-frequency stress fluctuation curve and the low-frequency stress fluctuation curve; Calculating the accumulated fatigue damage of the blade during the preset transition process based on the accumulated fatigue damage corresponding to the high-frequency stress and the accumulated fatigue damage corresponding to the low-frequency stress; The step of calculating the fatigue damage accumulation corresponding to the high-frequency stress and the fatigue damage accumulation corresponding to the low-frequency stress respectively according to the high-frequency stress fluctuation curve and the low-frequency stress fluctuation curve includes: Counting the number of cycles of each constant amplitude load under high frequency fluctuation according to the high frequency stress fluctuation curve; According to the low-frequency stress fluctuation curve, the damage coefficient of each load cycle under the low-frequency stress fluctuation and the derivative of the amplitude of the low-frequency stress fluctuation in each load cycle with respect to time are obtained; Calculate the accumulated fatigue damage corresponding to the high-frequency stress according to the number of cycles of each constant amplitude load under high-frequency fluctuation; The fatigue damage accumulation corresponding to the low-frequency stress is calculated based on the damage coefficient of each load cycle and the derivative of the amplitude of the low-frequency stress fluctuation in each load cycle with respect to time.

2. The method for calculating the cumulative fatigue damage of the runner blades of a pump turbine according to claim 1, characterized in that: The fatigue damage accumulation corresponding to the high-frequency stress is calculated according to the number of cycles of each constant amplitude load under high-frequency fluctuation, including: Based on the first preset formula, the fatigue damage accumulation corresponding to the high-frequency stress is calculated according to the number of cycles of each constant amplitude load under high-frequency fluctuation. The first preset formula is: In the formula, is the cumulative fatigue damage corresponding to high-frequency stress, Constant amplitude load The number of cycles under high frequency fluctuations, Constant amplitude load under high frequency fluctuation The corresponding fatigue life.

3. The method for calculating the cumulative fatigue damage of the runner blades of a pump turbine according to claim 2, characterized in that: The fatigue damage accumulation corresponding to the low-frequency stress is calculated based on the damage coefficient of each load cycle and the derivative of the amplitude of the low-frequency stress fluctuation in each load cycle relative to time, including: Based on the second preset formula, the fatigue damage accumulation corresponding to the low-frequency stress is calculated according to the damage coefficient of each load cycle and the derivative of the amplitude of the low-frequency stress fluctuation in each load cycle with respect to time. The second preset formula is: In the formula, is the cumulative fatigue damage corresponding to the low-frequency stress, is the low frequency safety factor, It is The damage factor of a load cycle is is the derivative of the amplitude of the low-frequency stress fluctuation with respect to time, For the The number of load cycles under low-frequency fluctuations, For the Fatigue life corresponding to the load level for a load cycle.

4. The method for calculating the cumulative fatigue damage of the runner blades of a pump turbine according to claim 1, characterized in that: Acquiring a high-frequency stress fluctuation curve and a low-frequency stress fluctuation curve of the blade according to the stress change information includes: Generate a stress time series curve of the blade according to the stress change information; The stress time series curve is decomposed to obtain a high-frequency stress fluctuation curve and a low-frequency stress fluctuation curve of the blade.

5. The method for calculating the cumulative fatigue damage of the runner blades of a pump turbine according to claim 1, characterized in that: After calculating the accumulated fatigue damage of the blade in the preset transition process based on the accumulated fatigue damage corresponding to the high-frequency stress and the accumulated fatigue damage corresponding to the low-frequency stress, the method further includes: According to the accumulated fatigue damage of the blades in different operation paths during the preset transition process and the preset evaluation index, the corresponding operation paths are evaluated to obtain the evaluation results; An optimization suggestion for the operation strategy of the pump-turbine is generated according to the evaluation result.

6. A pump-turbine runner blade fatigue damage accumulation calculation device, characterized in that: include: A stress change acquisition module is used to perform fluid-solid coupling calculation based on the finite element model of the pump-turbine runner and the full flow channel model of the runner to obtain the stress change information of the blades during the preset transition process, wherein the preset transition process includes several different operation paths during the working condition conversion process; A high- and low-frequency curve generation module, used for obtaining a high-frequency stress fluctuation curve and a low-frequency stress fluctuation curve of the blade according to the stress change information; A high- and low-frequency damage accumulation calculation module, used to calculate the fatigue damage accumulation corresponding to the high-frequency stress and the fatigue damage accumulation corresponding to the low-frequency stress according to the high-frequency stress fluctuation curve and the low-frequency stress fluctuation curve respectively; A total damage accumulation calculation module, used to calculate the fatigue damage accumulation of the blade during the preset transition process based on the fatigue damage accumulation corresponding to the high-frequency stress and the fatigue damage accumulation corresponding to the low-frequency stress; Among them, the high and low frequency damage accumulation calculation module includes: The frequency statistics module is used to count the number of cycles of each constant amplitude load under high-frequency fluctuation according to the high-frequency stress fluctuation curve; A parameter acquisition module, used to obtain the damage coefficient of each load cycle under low-frequency stress fluctuation and the derivative of the amplitude of low-frequency stress fluctuation in each load cycle with respect to time according to the low-frequency stress fluctuation curve; High-frequency damage calculation module, used to calculate the fatigue damage accumulation corresponding to high-frequency stress according to the number of cycles of each constant amplitude load under high-frequency fluctuation; The low-frequency damage calculation module is used to calculate the fatigue damage accumulation corresponding to the low-frequency stress according to the damage coefficient of each load cycle and the derivative of the amplitude of the low-frequency stress fluctuation in each load cycle with respect to time.

7. A computer device, characterized in that: include: A memory and a processor, wherein the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the method for calculating the cumulative fatigue damage of the runner blades of a pump turbine according to any one of claims 1 to 5 by executing the computer instructions.

8. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer instructions, and the computer instructions are used to enable a computer to execute the method for calculating the cumulative fatigue damage of a runner blade of a pump-turbine according to any one of claims 1 to 5.

9. A computer program product, characterized in that The method comprises computer instructions for causing a computer to execute the method for calculating the cumulative fatigue damage of a runner blade of a pump turbine according to any one of claims 1 to 5.

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