Method for converting fatigue damage of water pump water turbine runner under varying load and start-stop machine

Abstract

The application is a kind of water pump water turbine runner variable load and start-stop machine fatigue damage conversion method. The application relates to the technical field of water pump water turbine operation safety and life assessment, and aims at the engineering difficulty that the existing technology cannot quantitatively equivalent conversion of fatigue damage caused by variable load operation and start-stop machine working condition fatigue damage. The application constructs a typical working condition sample set by discretizing the unit load interval, establishes a runner multi-physical field coupling finite element model; the linear interpolation method is used to analyze the stress response of the actual random variable load interval and the equivalent symmetric cyclic stress; based on the Miner linear cumulative damage theory and the power law relationship of material S-N curve, the damage conversion coefficient of variable load cycle is derived; and then the total equivalent start-stop machine number is obtained. The application realizes the unified quantification of variable load and start-stop machine fatigue damage, and the total equivalent start-stop machine number can be directly used as the unified evaluation index of runner life assessment, which provides a scientific basis for water pump water turbine unit operation and maintenance decision and overhaul plan.

Description

Technical Field

[0001] This invention relates to the field of pump-turbine operation safety and life assessment technology, and is a method for converting pump-turbine runner load variation and start-up / shutdown fatigue damage. Background Technology

[0002] With the advancement of new power system construction, the power output volatility of new energy sources has significantly increased. Pump turbines need to frequently participate in grid peak shaving and frequency regulation ancillary services, and the unit operation mode has changed from traditional low-frequency start-stop operation to high-frequency, large-scale dynamic load regulation operation. The actual operation of the unit includes two core operating conditions: standard start-stop cycle and random load fluctuation cycle. Both types of operating conditions will cause fatigue damage to the turbine runner, but the industry has not yet established quantitative benchmarking rules between the two types of fatigue damage.

[0003] This technological gap makes it impossible to uniformly quantify and statistically analyze fatigue damage under various operating conditions of the unit. The operation and maintenance evaluation results deviate from the actual operating status of the unit, and cannot provide accurate data support for refined operation and maintenance, maintenance cycle optimization, and operation mode control of the unit.

[0004] It is evident that the unit operation and maintenance evaluation results deviate significantly from the actual operating status of the units, failing to provide accurate data support for refined operation and maintenance, maintenance cycle optimization, and operation mode control. On the one hand, due to the inability to accurately quantify the fatigue damage contribution under different operating conditions, operation and maintenance personnel struggle to formulate scientific and reasonable maintenance plans, potentially leading to over-maintenance resulting in resource waste or under-maintenance causing equipment failure. On the other hand, the lack of a unified fatigue damage evaluation standard makes it difficult for power plants to accurately assess the impact of different operating modes on the turbine's fatigue life when formulating unit operation strategies, hindering the search for the optimal balance between grid regulation needs and safe equipment operation.

[0005] Therefore, there is an urgent need to develop a method that can achieve equivalent conversion between variable load on the pump turbine runner and fatigue damage during start-up and shutdown, establish a unified fatigue damage evaluation system, fill the gaps in existing technologies, and provide technical support for the safe, reliable, and economical operation of pump turbines.

[0006] This invention proposes a method for converting the fatigue damage of pump turbine runner under varying loads and during start-up and shutdown, thereby achieving unified quantitative statistics of fatigue damage under different operating conditions and filling the gaps in existing technologies. Summary of the Invention

[0007] This invention addresses the problem that existing technologies cannot quantitatively and equivalently convert the fatigue damage generated during variable load operation of a pump-turbine with the fatigue damage generated during start-up and shutdown, and cannot normalize and compare the fatigue contributions of the two operating conditions. The invention discloses a method for converting the fatigue damage of a pump-turbine runner under variable load and during start-up and shutdown.

[0008] This invention provides the following technical solutions: A method for converting pump-turbine runner load variation with start-up and shutdown fatigue damage, the method comprising the following steps: Step 1: Discretize the load range of the pump turbine, extract typical load nodes to construct a working condition sample set, and define the variable load cycle range and the benchmark start-stop cycle; Step 2: Construct a three-dimensional finite element solid model of the pump turbine runner, set the mesh and boundary constraints, and apply multiphysics coupled loads; Step 3: Perform static analysis on all typical load nodes of the working condition sample set, extract the stress amplitude and average stress of the benchmark start-stop cycle, and obtain the benchmark equivalent symmetrical cyclic stress by correcting it with the Goodman criterion. Step 4: For any actual variable load cycle, use linear interpolation to extract the stress response values ​​corresponding to the two ends of the variable load cycle interval, and then analyze its stress amplitude and average stress. The equivalent symmetrical cyclic stress of the variable load cycle is obtained by correcting it with the Goodman criterion. Step 5: Based on the power-law relationship between Miner's linear cumulative damage and the material's SN curve, derive the damage conversion factor for any variable load cycle relative to the reference start-stop cycle, and perform fatigue damage conversion.

[0009] Preferably, extraction A typical load node constructs a sample set of operating conditions:

[0010] No. The power corresponding to each load node satisfies:

[0011] in, ; Rated power of the water pump and turbine; any two nodes and The resulting power cycle is denoted as a variable load cycle; shutdown node With full load node The cycle formed is recorded as the baseline start-stop cycle.

[0012] Preferably, the finite element solid model includes load-bearing components such as the upper crown, lower ring, and blades of the impeller; The boundary constraints are set as follows: apply full-degree-of-freedom constraints to the end faces of the coupling bolts of the wheel and the main shaft; The load application strategy is as follows: apply the fluid pressure field corresponding to the working condition to the flow surface of the impeller, and at the same time apply the impeller's own gravity field and the centrifugal force field at the rated speed.

[0013] Preferably, the expression for the reference equivalent symmetrical cyclic stress is given by the following formula:

[0014] in, Based on the equivalent symmetrical cyclic stress, The stress amplitude extracted from the shutdown cycle is used as the reference. The average stress extracted from the shutdown cycle is used as the reference. This represents the ultimate tensile strength of the wheel material.

[0015] Preferably, for any actual variable load cycle The stress interpolation at the critical locations corresponding to its two endpoints is expressed by the following formula:

[0016]

[0017] in, , Power point Adjacent typical load nodes, , This represents the stress value at the corresponding critical location. , Power point Adjacent typical load nodes, , This represents the stress value at the corresponding critical location. Solve for the stress amplitude and mean stress of the actual variable load cycle, and then use the Goodman formula to correct for the equivalent symmetrical cyclic stress. .

[0018] Preferably, the damage conversion factor This can be expressed by the following formula:

[0019] in, Based on the equivalent symmetrical cyclic stress, The slope index of the SN curve for the impeller material.

[0020] Preferably, the method further includes: Step 6: Calculate the damage conversion coefficients for all variable load cycles within the monitoring period, sum them to obtain the total equivalent start-stop count for variable load, and combine them with the actual start-stop count to solve for the total equivalent start-stop count.

[0021] Preferably, the method further includes: The total equivalent number of start-stop cycles is expressed by the following formula:

[0022] in, This represents the total equivalent number of start-ups and shutdowns. This represents the actual number of start-ups and shutdowns. This represents the total number of variable load cycles. This is the damage conversion factor for a single variable load cycle.

[0023] A computer-readable storage medium having a computer program stored thereon, which is executed by a processor to implement a method for converting the load of a water pump turbine runner with fatigue damage during start-up and shutdown.

[0024] A computer device includes a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement a method for converting the load of a water pump turbine runner with fatigue damage during start-up and shutdown.

[0025] The present invention has the following beneficial effects: This invention constructs a quantitative conversion mechanism based on a benchmark start-stop cycle. Through damage conversion coefficients, it achieves equivalent conversion between various variable load fatigue damage and start-stop fatigue damage, solving the industry pain point that the two types of working conditions cannot be uniformly quantified.

[0026] This invention converts discrete and random variable load operation events into equivalent start-up and shutdown times, forming a single and intuitive quantitative evaluation index, which simplifies the damage statistics and evaluation process for complex operating conditions of the unit.

[0027] This invention uses a combination of discretization of typical working conditions and linear interpolation, which eliminates the need to simulate a large number of random variable load conditions one by one, greatly reducing the amount of computation and meeting the needs of rapid quantitative statistics in engineering sites. It is highly practical. Attached Figure Description

[0028] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0029] Figure 1 The diagram shows a method for converting the load of a water pump turbine runner with fatigue damage during start-up and shutdown. Detailed Implementation

[0030] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] The present invention will be described in detail below with reference to specific embodiments. Specific Implementation Example 1: according to Figure 1 As shown, the specific optimized technical solution adopted by the present invention to solve the above-mentioned technical problems is: The present invention relates to a method for converting the variable load of a water pump turbine runner with fatigue damage during start-up and shutdown.

[0033] This invention provides a method for converting the load changes of a water pump turbine runner with fatigue damage during start-up and shutdown. The method includes the following steps: A method for converting pump-turbine runner load variations with start-up and shutdown fatigue damage includes the following steps: S1: Discretize the unit load range, extract typical load nodes to construct a set of operating condition samples, and define the variable load cycle range and the benchmark start-stop cycle; In step S1, extract A typical load node constructs a sample set of operating conditions. , No. The power corresponding to each load node satisfies: ,in ; Rated power of the water pump and turbine; any two nodes and The resulting power cycle is denoted as a variable load cycle; shutdown node With full load node The cycle formed is recorded as the baseline start-stop cycle.

[0034] S2: Construct a three-dimensional finite element solid model of the pump turbine runner, set the mesh and boundary constraints, and apply multiphysics coupled loads; In step S2, the finite element solid model fully includes the upper crown, lower ring, and blades of the impeller, and other force-bearing components. The boundary constraints are set as follows: full degree of freedom constraints are applied to the end face of the impeller and the main shaft coupling bolt. The load application strategy is as follows: the fluid pressure field corresponding to the working condition is applied to the impeller flow surface, and the impeller's own gravity field and centrifugal force field at the rated speed are applied at the same time.

[0035] S3: Perform static analysis on all typical load nodes of the working condition sample set, extract the stress amplitude and average stress of the benchmark start-stop cycle, and obtain the benchmark equivalent symmetrical cyclic stress by correcting it with the Goodman criterion. In step S3, the stress characteristics of the reference start-stop cycle are extracted using the quasi-static equivalent method. The expression for the reference equivalent symmetrical cyclic stress is as follows: In the formula: Based on the equivalent symmetrical cyclic stress, The stress amplitude extracted from the shutdown cycle is used as the reference. The average stress extracted from the shutdown cycle is used as the reference. This represents the ultimate tensile strength of the wheel material.

[0036] S4: For any actual variable load cycle, the stress response values ​​corresponding to the two ends of the variable load cycle interval are extracted by linear interpolation, and then the stress amplitude and average stress are analyzed. The equivalent symmetrical cyclic stress of the variable load cycle is obtained by correcting it with the Goodman criterion. In step S4, for any actual variable load cycle Considering that the load and structural static stress of the unit exhibit an approximately linear monotonic response within the stable region of normal peak-shaving operation, the stress interpolation formula for the critical locations corresponding to its two endpoints is as follows: In the formula: , Power point Adjacent typical load nodes, , This represents the stress value at the corresponding critical location; , Power point Adjacent typical load nodes, , The stress values ​​are for the corresponding critical locations. The stress amplitude and mean stress of this actual variable load cycle are calculated, and the equivalent symmetrical cyclic stress is obtained by correcting using the Goodman formula. .

[0037] S5: Based on Miner's linear cumulative damage theory and the power law relationship of the material's SN curve, the formula for calculating the damage conversion factor of any variable load cycle relative to the reference start-stop cycle is derived. In step S5, the damage conversion coefficient The derivation formula is as follows: In the formula: This represents the equivalent symmetrical cyclic stress of an actual variable load cycle. Based on the equivalent symmetrical cyclic stress, The slope index of the SN curve for the impeller material.

[0038] S6: Calculate the damage conversion coefficients for all variable load cycles within the statistical monitoring period, sum them to obtain the total equivalent number of start-stop cycles for variable load, and combine them with the actual number of start-stop cycles to solve for the total equivalent number of start-stop cycles.

[0039] In step S6, the formula for calculating the total equivalent number of start-stop cycles is: In the formula: This represents the total equivalent number of start-ups and shutdowns. This represents the actual number of start-ups and shutdowns. This represents the total number of variable load cycles. This is the damage conversion factor for a single variable load cycle.

[0040] The present invention also provides a computer-readable storage medium having a computer program stored thereon, which is executed by a processor to implement a method for converting the load of a water pump turbine runner with fatigue damage during start-up and shutdown.

[0041] The present invention also provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement a method for converting the load of a water pump turbine runner with fatigue damage during start-up and shutdown. Specific Implementation Example 2: The only difference between Embodiment 2 and Embodiment 1 of this application is that: This embodiment provides a method for converting pump-turbine runner load variations with start-up and shutdown fatigue damage, specifically for a certain type of pump-turbine runner with a rated power of [missing information]. The fatigue conversion of the water pump turbine is performed, and the specific implementation steps are as follows: S1: The full load range is equally isolated according to a 5% power span, and 21 are extracted (i.e. Typical load nodes, constructing a set of operating condition samples. . No. The power values ​​of a typical load node satisfy Any two operating points and The resulting load fluctuation range is denoted as a variable load cycle. A shutdown node is selected. (0% power) and full load node The cycle consisting of (100% rated power) serves as the reference start-stop cycle.

[0043] S2: A three-dimensional finite element solid model of the pump-turbine runner was established using finite element analysis software. The model fully includes core load-bearing components such as the upper crown, blades, and lower ring of the runner. Boundary conditions were selected: full-degree-of-freedom constraints were applied to the end faces of the bolts connecting the runner and the main shaft to simulate the rigid connection between the runner and the main shaft. The load application strategy was as follows: a fluid pressure field under the corresponding operating condition was applied to the runner's flow surface; simultaneously, the runner's own gravity field and centrifugal force field at its rated speed were applied.

[0044] S3: Static strength analysis was performed on 21 typical load nodes in the operating condition sample set. Based on the calculated stress distribution cloud map of the entire runner region, the local area where the equivalent stress peak was located was selected as the critical part of the runner. The quasi-static equivalent method was used to extract the critical part under the reference shutdown cycle ( to Stress amplitude under action With average stress By applying the Goodman criterion to correct the mean stress, the baseline equivalent symmetrical cyclic stress is obtained: .

[0045] S4: For any actual variable load cycle Based on the critical locations identified in S3, the endpoint stress is extracted using linear interpolation. Considering that the load and structural static stress exhibit an approximately linear monotonic response within the stable region of normal peak-shaving operation, linear interpolation offers reliable engineering accuracy.

[0046] This embodiment captures one load variation cycle in actual operation. to % ,Right now , .for Find its neighboring typical nodes (45%) )and (50%) Read the stress corresponding to the dangerous parts. and Linear interpolation solution Corresponding stress: Similarly, regarding Utilizing adjacent nodes (50%) )and (55%) The corresponding stress and Interpolation yields the following: Based on the interpolated endpoint stresses, the stress amplitude and mean stress of this variable load cycle are analyzed: , Then, the equivalent symmetrical cyclic stress of the variable load cycle is obtained by correcting it using the Goodman criterion. : .

[0047] S5: Based on Miner's linear cumulative damage theory and the power-law relationship of the material's SN curve, the formula for calculating the damage conversion factor of the variable load cycle relative to the baseline start-stop cycle is derived. The material's SN curve satisfies: The structural fatigue damage caused by a single load cycle is as follows: The standard damage value for the baseline start-stop cycle is: Define the damage conversion factor for variable load cycles. The ratio of this variable load damage to the baseline start-stop damage can be derived as follows: By substituting the equivalent symmetrical cyclic stress of all variable load cycles into this formula, the equivalent number of start-stop cycles for each fluctuation can be quantified.

[0048] S6: The design life is selected as 50 years, and the cumulative occurrence within the design life... For each variable load cycle event, calculate its damage conversion factor. The summation yields the total equivalent number of start-stop cycles under varying loads. This is then combined with the actual number of start-stop cycles within the design life. The total equivalent number of start-stop cycles used for macroscopic evaluation is synthesized and solved: .

[0049] After obtaining the total equivalent number of start-stop cycles, subsequent runner life assessments can be conducted based on existing industry standards and design specifications, combined with the characteristics of the runner material.

[0050] The above description is merely a preferred embodiment of a method for converting the load variation of a pump-turbine runner with fatigue damage during start-up and shutdown. The scope of protection for this method is not limited to the above embodiments; all technical solutions falling within this conceptual framework are within the scope of protection of this invention. It should be noted that for those skilled in the art, any improvements and variations made without departing from the principles of this invention should also be considered within the scope of protection of this invention.

Claims

1. A method for converting variable load and start-up / shutdown fatigue damage of a water pump turbine runner, characterized by: The method includes the following steps: Step 1: Discretize the load range of the pump-turbine unit, extract typical load nodes to construct a working condition sample set, and define the variable load cycle range and the benchmark start-stop cycle; Step 2: Construct a three-dimensional finite element solid model of the pump turbine runner, set the mesh and boundary constraints, and apply multiphysics coupled loads; Step 3: Perform static analysis on all typical load nodes of the working condition sample set, extract the stress amplitude and average stress of the benchmark start-stop cycle, and obtain the benchmark equivalent symmetrical cyclic stress by correcting it with the Goodman criterion. Step 4: For any actual variable load cycle, use linear interpolation to extract the stress response values ​​corresponding to the two ends of the variable load cycle interval, and then analyze its stress amplitude and average stress. The equivalent symmetrical cyclic stress of the variable load cycle is obtained by correcting it with the Goodman criterion. Step 5: Based on the power-law relationship between Miner's linear cumulative damage and the material's SN curve, derive the damage conversion factor for any variable load cycle relative to the reference start-stop cycle, and perform fatigue damage conversion.

2. The method according to claim 1, characterized in that: extract A typical load node constructs a sample set of operating conditions: No. The power corresponding to each load node satisfies: in, ; Rated power of the water pump and turbine; any two nodes and The resulting power cycle is denoted as a variable load cycle; shutdown node With full load node The cycle formed is recorded as the baseline start-stop cycle.

3. The method according to claim 2, characterized in that: The finite element solid model includes the upper crown, lower ring, and blade load-bearing components of the runner; The boundary constraints are set as follows: apply full-degree-of-freedom constraints to the end faces of the coupling bolts of the wheel and the main shaft; The load application strategy is as follows: apply the fluid pressure field corresponding to the working condition to the flow surface of the impeller, and at the same time apply the impeller's own gravity field and the centrifugal force field at the rated speed.

4. The method according to claim 3, characterized in that: The expression for the reference equivalent symmetrical cyclic stress is given by the following equation: in, Based on the equivalent symmetrical cyclic stress, The stress amplitude extracted from the shutdown cycle is used as the reference. The average stress extracted from the shutdown cycle is used as the reference. This represents the ultimate tensile strength of the wheel material.

5. The method according to claim 4, characterized in that: For any actual variable load cycle The stress interpolation at the critical locations corresponding to its two endpoints is expressed by the following formula: in, , Power point Adjacent typical load nodes, , This represents the stress value at the corresponding critical location. , Power point Adjacent typical load nodes, , This represents the stress value at the corresponding critical location. Solve for the stress amplitude and mean stress of the actual variable load cycle, and then use the Goodman formula to correct for the equivalent symmetrical cyclic stress. .

6. The method according to claim 5, characterized in that: Damage conversion factor This can be expressed by the following formula: in, Based on the equivalent symmetrical cyclic stress, The slope index of the SN curve for the impeller material.

7. The method according to claim 6, characterized in that: The method further includes: Step 6: Calculate the damage conversion coefficients for all variable load cycles within the monitoring period, sum them to obtain the total equivalent start-stop count for variable load, and combine them with the actual start-stop count to solve for the total equivalent start-stop count.

8. The method according to claim 7, characterized in that: The method further includes: The total equivalent number of start-stop cycles is expressed by the following formula: in, This represents the total equivalent number of start-ups and shutdowns. This represents the actual number of start-ups and shutdowns. This represents the total number of variable load cycles. This is the damage conversion factor for a single variable load cycle.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, The program is executed by the processor to implement the method as claimed in any one of claims 1-8.

10. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that: When the processor executes the computer program, it implements the method of any one of claims 1-8.

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