On-line evaluation method and system for fatigue pull crack of boiler water-cooled wall

Abstract

The invention discloses an on-line evaluation method and system for fatigue pull cracks of a boiler water-cooled wall, and relates to the technical field of thermal power generation. The method is used for evaluating the fatigue pull crack of the boiler water-cooled wall. According to the method, the whole high water cooling wall is broken up into parts, and segmented analysis is carried out. The position points are used for replacing each water wall tube and each fin, a stress calculation formula of each position point is given, and then the fatigue life of the fins is predicted by combining the calculation formulas with a multi-axis strain criterion. According to the method, the long water cooling wall tubes and fins are analyzed in a segmented mode, the water cooling wall tubes and the fins with certain lengths are simplified into position points, continuous stress distribution is changed into single-point stress, the calculated amount is greatly reduced, the distance not longer than 2 m is selected during length division, and therefore the stress calculation error can be reduced as much as possible. The method is used for evaluating the fatigue pull crack of the boiler water-cooled wall, and huge social pressure and economic loss caused by pull crack and leakage of the boiler water-cooled wall of a thermal power plant to a power plant are prevented.

Description

Technical Field

[0001] The invention relates to the technical field of thermal power generation, and in particular to an online evaluation method for fatigue cracking of a boiler water-cooled wall. Background Art

[0002] The water-cooled wall is the steam heating surface of the boiler in a thermal power plant. It is arranged around the furnace of the boiler, absorbs the radiant heat of the high-temperature flame in the furnace, heats the water and gradually turns it into a mixture of saturated steam and water. There are three types of water-cooled walls: bare tube water-cooled wall, pin water-cooled wall and membrane water-cooled wall. Modern large boilers all use membrane water-cooled walls made of welded tubes and fins. For membrane water-cooled walls, when the combustion is uneven or the quality is poor during the start-up and shutdown or peak-shaving process of the unit, and the matching with the feed water is not good, it will cause uneven temperatures of the tubes and fins at various positions of the water-cooled wall, thereby generating thermal stress. When the thermal stress and the mechanical stress of the equipment itself are superimposed and concentrated in the weak area of ​​the water-cooled wall, it will cause the water-cooled wall to crack and leak. Generally, the cracking and leakage of water-cooled wall tubes are mainly concentrated in the middle of the front and rear walls of the water-cooled wall, the main burner, the AA duct screen and the secondary wind box connected to the water-cooled wall. The location and degree of the cracking are different for furnaces of different grades and structures. The cracking and leakage of the water-cooled wall of the boiler in a thermal power plant will bring huge social pressure and economic losses to the power plant, but there is currently no mature solution and early warning measure for this problem.

[0003] The existing applicant Beijing Bosu Zhiyuan Artificial Intelligence Technology Co., Ltd. published a patent document on June 28, 2022: CN114674008A, which discloses a water-cooled wall crack identification method and system based on time correlation and spatial correlation, and measures the risk of water-cooled wall cracking from the perspective of temperature change. This method has certain feasibility, but the correlation between temperature and cracking is not intuitive.

[0004] The patent document CN103605329A published on February 26, 2014 by the existing applicant Shanghai Power Equipment Complete Design Institute discloses a method for monitoring the cumulative low-cycle fatigue life loss of thermal power generator set components. This method is mainly applicable to the main thick-walled components of thermal power plants, such as headers, boiler drums, steam-water separators, turbine rotors, etc., and is not applicable to the assessment of water-cooled wall cracking.

[0005] Therefore, there is an urgent need for an online evaluation method for boiler water wall fatigue cracking to realize the evaluation of boiler water wall fatigue cracking. Summary of the invention

[0006] The purpose of the present invention is to provide an online evaluation method for fatigue cracking of water-cooled wall, which is used to realize the evaluation of fatigue cracking of boiler water-cooled wall and prevent the cracking and leakage of boiler water-cooled wall in thermal power plant from bringing huge social pressure and economic losses to the power plant.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention provides an online evaluation method for fatigue cracking of a water-cooled wall, the evaluation method comprising the following steps:

[0009] S1: Divide the water-cooled wall into regions and set the position points of water-cooled wall tubes and fins in different regions;

[0010] S2: Based on the temperature and pressure measurement point data of the water-cooled wall intermediate header in the DCS system at a certain moment, the medium temperature and pressure of each water-cooled wall tube in the designated area are calculated according to the elevation difference between the designated area and the water-cooled wall intermediate header, and the outlet temperature and pressure of the water-cooled wall lower header;

[0011] S3: Calculate the thermal expansion of a single water-cooled wall tube at that moment under unconstrained conditions according to the medium temperature and pressure of the water-cooled wall tube in the designated area;

[0012] S4: Calculate the thermal expansion of a single fin under unconstrained conditions;

[0013] S5: according to the thermal expansion difference of all water-cooled wall tubes and fin positions, the superimposed stress values ​​of different fin positions at that moment are obtained;

[0014] S6: taking the data of the next moment in the DCS system at a time interval of dt, and then repeating the above process to obtain the stress value of each fin position point at the next moment;

[0015] S7: Repeat the above process to obtain the stress change curve of the water-cooled wall fin position point during the unit startup, shutdown and peak regulation process;

[0016] S8: Based on the multi-axial equivalent strain criterion, according to the stress change curve in step S7, the fatigue tensile crack life loss of the water-cooled wall in a single start-stop or peak regulation cycle is calculated;

[0017] S9: Multiple single water-cooled wall fatigue cracking life losses are used to linearly accumulate and calculate the total life loss. When the total life loss exceeds 70%, an alarm is triggered. When it is less than 70%, the above calculation process is repeated.

[0018] Furthermore, there is another preferred embodiment, the above step S1 is specifically as follows:

[0019] S11: In the height direction of the boiler, the water wall intermediate header is used as the marking line, and each 2m is demarcated as an area;

[0020] S12: Each zone includes the water-cooled walls on all four sides of the boiler at that elevation;

[0021] S13: A single water-cooled wall tube and a single fin in the water-cooled wall of the four walls of the boiler are regarded as a position point respectively.

[0022] Furthermore, in another preferred embodiment, the medium temperature of the water-cooled wall tubes in the above-defined area is:

[0023]

[0024] The medium pressure of the above water-cooled wall tube is:

[0025]

[0026] Among them, H 区 , H 中 and H 下 They are the elevations of the designated area, the middle header and the lower header, T 中 and T 下 are the temperatures of the intermediate header and lower header pipes, P 中 and P 下 They are the pressures of the intermediate header and the lower header distribution pipes respectively.

[0027] Furthermore, there is another preferred embodiment, the above step S4 is specifically as follows:

[0028] A machine learning model based on heat flux, temperature difference between adjacent tubes, and fin geometry is used to calculate the temperature of the fin locations between the water-cooled wall tubes, and then the thermal expansion of a single fin under unconstrained conditions is calculated.

[0029] Furthermore, in another preferred embodiment, the superimposed stress values ​​at different fin positions are:

[0030] σ=σ T +σ P

[0031]

[0032] A t =π(R 2 -r 2 )

[0033] A f =ab

[0034]

[0035] Among them, α and E are the linear expansion coefficient and elastic modulus of the fin, respectively, ΔT is the temperature difference between the water-cooled wall tube and the fin, R and r are the outer radius and inner radius of the water-cooled wall tube, respectively, a and b are the length and width of the fin, respectively, and v is the Poisson's ratio.

[0036] Furthermore, in a preferred embodiment, the above dt time interval is ≥ 1 min.

[0037] Furthermore, there is another preferred embodiment, the above multi-axis equivalent strain criterion is specifically:

[0038]

[0039] ε2=ε3=-vε1

[0040]

[0041] Among them, Δε eff is the strain range, σ f ′ is the fatigue strength coefficient, N f is the number of fatigue cycles, b is the fatigue strength index, c is the fatigue ductility index, ε2 is the axial strain, ε3 is the hoop strain, ε1 is the normal strain, and v is the Poisson's ratio.

[0042] The online evaluation method for fatigue cracking of a water-cooled wall described in the present invention can be fully implemented by computer software. Therefore, correspondingly, the present invention also provides an online evaluation system for fatigue cracking of a water-cooled wall, the system comprising:

[0043] A storage device for dividing the water-cooled wall into regions and setting the position points of the water-cooled wall tubes and fins in different regions;

[0044] A storage device used to calculate the medium temperature and pressure of each water-cooled wall tube in the designated area based on the temperature and pressure measurement point data of the water-cooled wall intermediate header in the DCS system at a certain moment, according to the elevation difference between the designated area and the water-cooled wall intermediate header, and the outlet temperature and pressure of the water-cooled wall lower header;

[0045] A storage device for calculating the thermal expansion amount of a single water-cooled wall tube position point under unconstrained conditions at that moment based on the medium temperature and pressure of the water-cooled wall tube in the defined area;

[0046] A storage device for calculating the thermal expansion of a single fin under unconstrained conditions;

[0047] A storage device for obtaining the superimposed stress values ​​of different fin positions at that moment according to the thermal expansion differences of all water-cooled wall tubes and fin positions;

[0048] A storage device for obtaining data at the next moment in the DCS system at a time interval of dt, and then repeating the above process to obtain the stress value of each fin position point at the next moment;

[0049] A storage device for repeating the above process to obtain a stress variation curve of the water-cooled wall fin position point during the unit startup, shutdown and peak regulation process;

[0050] A storage device for calculating the fatigue tensile cracking life loss of the water-cooled wall in a single start-stop or peak regulation cycle based on a multi-axis equivalent strain criterion and the stress change curve in the above steps;

[0051] A storage device for linearly accumulating the total life loss using multiple single water-cooled wall fatigue cracking life losses, alarming when the total life loss exceeds 70%, and repeating the above calculation process when it is less than 70%.

[0052] The present invention also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is run by a processor, any one of the above-mentioned online evaluation methods for fatigue cracking of a water-cooled wall is executed.

[0053] The present invention also provides a computer device, which includes a memory and a processor, wherein the memory stores a computer program, and when the processor runs the computer program stored in the memory, the processor executes any one of the above-mentioned online evaluation methods for fatigue cracking of a water-cooled wall.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] 1. The online evaluation method for fatigue cracking of water-cooled wall proposed in the present invention breaks down the water-cooled wall with a high height (50-70 meters) into small pieces and analyzes them in sections. Each water-cooled wall tube and fin is replaced by a position point, and the stress calculation formula of each position point is given, and then the fatigue life of the fin is predicted by combining the calculation formula with the multi-axial strain criterion.

[0056] 2. In the existing calculation method, since the stress distribution of the longer water-cooled wall tubes is a continuous distribution, there are many stress data. If all of them are input into the computer for life calculation, the calculation amount is huge and real-time calculation cannot be achieved. The present invention analyzes the longer water-cooled wall tubes and fins in sections, and simplifies the water-cooled wall tubes and fins of a certain length into position points, so that the continuous stress distribution becomes a single-point stress, and the calculation amount is greatly reduced. Therefore, when dividing the length, a distance of no more than 2m is selected, so that the stress calculation error can be minimized. In addition, the present invention also provides a calculation method for the superimposed stress value of the fin position point. All parameters in the formula are from the DCS system of the power plant, which is easy to retrieve. The use of this formula for calculation can greatly reduce the amount of calculation and improve the stability of the online system operation.

[0057] The present invention provides an online evaluation method for fatigue cracking of a water-cooled wall, which is used to evaluate fatigue cracking of a boiler water-cooled wall and prevent cracking and leakage of the boiler water-cooled wall of a thermal power plant from causing huge social pressure and economic losses to the power plant. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] 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.

[0059] Figure 1 It is a simplified schematic diagram of the water-cooled wall tube and fin position points of the present invention;

[0060] Figure 2 It is a flow chart of the online evaluation method for water-cooled wall fin cracking according to the present invention;

[0061] Figure 3 It is a temperature variation diagram of three adjacent water-cooled wall intermediate header pipes at different times according to the present invention;

[0062] Figure 4 It is a diagram of pressure changes of three adjacent water-cooled wall intermediate header pipes at different times according to the present invention;

[0063] Figure 5 It is a temperature variation diagram of the fin position point in the middle header area of ​​the water-cooled wall according to the present invention;

[0064] Figure 6 It is a diagram of superimposed stress changes at the fin position points described in the present invention. DETAILED DESCRIPTION

[0065] The specific embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

[0066] Implementation method 1, see Figure 2 This embodiment describes an online evaluation method for fatigue cracking of water-cooled wall, which is used to evaluate fatigue cracking of boiler water-cooled wall, and prevent the cracking and leakage of boiler water-cooled wall in thermal power plant from causing huge social pressure and economic losses to the power plant. The evaluation method includes the following steps: Figure 2 As shown:

[0067] Step 1: Divide the water-cooled wall into regions and set the position points of water-cooled wall tubes and fins in different regions;

[0068] Step 2: Based on the temperature and pressure measurement point data of the water-cooled wall intermediate header in the DCS system at a certain moment, calculate the medium temperature and pressure of each water-cooled wall tube in the designated area according to the elevation difference between the designated area and the water-cooled wall intermediate header, and the outlet temperature and pressure of the water-cooled wall lower header;

[0069] Step 3: According to the medium temperature and pressure of the water-cooled wall tubes in the designated area, calculate the thermal expansion of a single water-cooled wall tube at that moment under unconstrained conditions;

[0070] Step 4: Calculate the thermal expansion of a single fin under unconstrained conditions;

[0071] Step 5: According to the thermal expansion difference of all water-cooled wall tubes and fin positions, the superimposed stress values ​​of different fin positions at that moment are obtained;

[0072] Step 6: Get the data of the next moment in the DCS system at a time interval of dt, and then repeat the above process to obtain the stress value of each fin position point at the next moment;

[0073] Step 7: Repeat the above process to obtain the stress change curve of the water-cooled wall fin position during the unit startup, shutdown and peak regulation process;

[0074] Step 8: Based on the multi-axial equivalent strain criterion and the stress change curve in step S7, the fatigue tensile crack life loss of the water-cooled wall in a single start-stop or peak regulation cycle is calculated;

[0075] Step 9: Use multiple single water-cooled wall fatigue cracking life losses to linearly accumulate and calculate the total life loss. When the total life loss exceeds 70%, an alarm will be triggered. If it is less than 70%, the above calculation process will be repeated.

[0076] Implementation Method 2: See Figure 1 This embodiment is described. This embodiment is a specific description of the online evaluation method for fatigue cracking of the water-cooled wall described in the first embodiment:

[0077] Step 1: Divide the water-cooled wall into regions and set the position points of water-cooled wall tubes and fins in different regions;

[0078] The specific steps are:

[0079] like Figure 1 As shown in the figure, the middle header of the water wall is used as the mark in the height direction of the boiler, and each 2m is demarcated as an area (applicable to both the upper and lower parts), and each area includes the water walls of the four walls of the boiler at that elevation. Since the temperature change between the inlet and outlet of a single water wall tube within the 2m elevation is not large, a single water wall tube can be regarded as a position point. The fins are also treated in the same way and regarded as another position point. With this setting, the water wall tubes and fins in this area can be regarded as a collection of position points.

[0080] This embodiment analyzes the water-cooled wall tubes and fins of a long length in sections, and simplifies the water-cooled wall tubes and fins of a certain length into position points, so that the continuous stress distribution becomes a single-point stress, and the calculation amount is greatly reduced. When dividing the length, a distance of no more than 2m is selected, so that the stress calculation error can be minimized.

[0081] Step 2: Based on the temperature and pressure measurement point data of the water-cooled wall intermediate header in the DCS system at a certain moment, calculate the medium temperature and pressure of each water-cooled wall tube in the designated area according to the elevation difference between the designated area and the water-cooled wall intermediate header, and the outlet temperature and pressure of the water-cooled wall lower header;

[0082] The specific steps are:

[0083] Based on the temperature and pressure measurement point data of the water-cooled wall intermediate header in the DCS system at a certain moment, the medium temperature and pressure of each water-cooled wall tube in the designated area are calculated according to the elevation difference between the designated area and the water-cooled wall intermediate header, and the outlet temperature and pressure of the water-cooled wall lower header. The calculation formula is as follows:

[0084]

[0085] Among them, T 区 and P 区 are the medium temperature and pressure of the water-cooled wall tubes in the designated area, H 区 , H 中 and H 下 They are the elevations of the designated area, the middle header and the lower header, T 中 and T 下 are the temperatures of the intermediate header and lower header pipes, P 中 and P 下 They are the pressures of the intermediate header and the lower header distribution pipes respectively.

[0086] In step 2 of this embodiment, the pressure and temperature of the water wall position point are calculated based on the collected data of the DCS, providing a data basis for the subsequent calculation of stress. Since the division distance of the water wall in step 1 is small, the calculation method of this step is simple and the calculation reliability is high.

[0087] Step 3: According to the medium temperature and pressure of the water-cooled wall tubes in the designated area, calculate the thermal expansion of a single water-cooled wall tube at that moment under unconstrained conditions;

[0088] The specific steps include:

[0089] According to the medium temperature and pressure of the water-cooled wall tubes in the designated area, the thermal expansion of a single water-cooled wall tube position at that moment under unconstrained conditions is calculated.

[0090] Step 4: Calculate the thermal expansion of a single fin under unconstrained conditions;

[0091] The specific steps include:

[0092] The temperature of the fin positions between the water-cooled wall tubes is calculated using a machine learning model based on heat flux density, temperature difference between adjacent tubes, and fin geometry, and the thermal expansion of a single fin under unconstrained conditions is then calculated.

[0093] Step 5: According to the thermal expansion difference of all water-cooled wall tubes and fin positions, the superimposed stress values ​​of different fin positions at that moment are obtained;

[0094] The specific steps include:

[0095] According to the temperature and pressure of all water-cooled wall tube positions and the temperature of the fin positions, the superimposed stress value σ of different fin positions at that moment is obtained. The calculation formula is as follows:

[0096] σ=σ T +σ P

[0097]

[0098] A t =π(R 2 -r 2 )

[0099] A f =ab

[0100]

[0101] Among them, α and E are the linear expansion coefficient and elastic modulus of the fin, ΔT is the temperature difference between the water-cooled wall tube and the fin, R and r are the outer radius and inner radius of the water-cooled wall tube, a and b are the length and width of the fin, and v is the velocity of the medium. Since each fin is connected to two water-cooled wall tubes, there are two sets of stress data at each fin position.

[0102] Step 6: Get the data of the next moment in the DCS system at a time interval of dt, and then repeat the above process to obtain the stress value of each fin position point at the next moment;

[0103] The specific steps include:

[0104] The data of the next moment is obtained in the DCS system at a time interval of dt, and then the above process is repeated to obtain the stress value of each fin position point at the next moment. Among them, the time interval of dt is ≥1min and can be determined according to specific needs.

[0105] Step 7: Repeat the above process to obtain the stress change curve of the water-cooled wall fin position during the unit startup, shutdown and peak regulation process;

[0106] Step 8: Based on the multi-axial equivalent strain criterion and the stress change curve in step S7, the fatigue tensile crack life loss of the water-cooled wall in a single start-stop or peak regulation cycle is calculated;

[0107] The specific steps include:

[0108] According to the stress distribution and changes of the water-cooled wall fin position points, the strain change is obtained, and based on the multi-axis equivalent strain criterion, the fatigue tensile cracking life loss of the water-cooled wall in a single start-stop or peak-shaving cycle is calculated.

[0109] The multiaxial equivalent strain criterion has the following expression:

[0110]

[0111] For water-cooled wall components, it can be approximately simplified to a uniaxial stress state, so

[0112] ε2=ε3=-vε1

[0113]

[0114] The rain flow counting method is used to count the stress cycle history.

[0115] Among them, Δε eff is the strain range, σ f ′ is the fatigue strength coefficient, N f is the number of fatigue cycles, b is the fatigue strength index, c is the fatigue ductility index, ε2 is the axial strain, ε3 is the hoop strain, ε1 is the normal strain, and v is the Poisson's ratio.

[0116] This step performs fatigue life calculation based on the multiaxial equivalent strain criterion. For water-cooled wall components, the multiaxial stress is converted to uniaxial stress, thereby reducing the amount of calculation and increasing the calculation speed. Although converted to uniaxial state, the multiaxial equivalent strain criterion can still be used to perform calculations in this process to ensure calculation accuracy.

[0117] Step 9: Use multiple single water-cooled wall fatigue cracking life losses to linearly accumulate and calculate the total life loss. When the total life loss exceeds 70%, an alarm will be triggered. If it is less than 70%, the above calculation process will be repeated.

[0118] Implementation method three, see Figure 1 , Figures 3 to 6 This embodiment is described. This embodiment is to verify the online evaluation method of fatigue cracking of water-cooled wall described in the above embodiment.

[0119] In order to make the present embodiment more clear and understandable, the water-cooled wall changes of a 660MW ultra-supercritical boiler during the process of the load increasing from 25% THA to 35% THA and then decreasing back to 25% THA are taken as an example.

[0120] The first step is to divide the water-cooled wall into areas based on the water-cooled wall intermediate header, such as Figure 1 Taking the area 2m below the water-cooled wall intermediate header as an example, the water-cooled wall tubes and fins are set as position points respectively.

[0121] The second step is to retrieve the temperature and pressure data of the bulk pipes of the water-cooled wall intermediate header and the water-cooled wall lower header in the DCS system. In this embodiment, the intermediate header area is taken as an example, so the temperature and pressure of the bulk pipes of the intermediate header can be directly used, and the above formula is used for calculation in other designated areas. Figure 3 and Figure 4 The temperature and pressure changes of three adjacent tubes at different times are shown respectively. Figure 3 and Figure 4 The data in the fins are calculated based on the machine learning model to obtain the temperature of the fins, such as Figure 5 As shown. Figures 3 to 5 The temperature and pressure data of the water wall tubes and fin positions in the middle header area of ​​the middle water wall are used to calculate the superimposed stress value of the fin position using the above formula, such as Figure 6 As shown in Figure 2. Since one fin is connected to two water-cooled wall tubes, there are two sets of stress data at one fin position point.

[0122] according to Figure 6 The stress change data of the fin position point is used to obtain its strain change data, and the corresponding fatigue life can be obtained by comparing it with the multi-axial equivalent strain criterion, and then the single life loss can be obtained. Taking the fatigue curve of P22 material in GB30580-2014 standard as an example, the strain amplitude in this embodiment is 1.5e -4 , the corresponding fatigue life is 10 7 times, the single life loss is 10 -7 .

[0123] Since the current life loss has not reached 0.7, the calculation process for the next cycle will begin until the cumulative fatigue life loss reaches 0.7, then an alarm will be issued.

[0124] Embodiment 4: Since the online evaluation method for fatigue cracking of a water-cooled wall described in the above embodiment can be fully implemented by computer software, accordingly, this embodiment provides an online evaluation system for fatigue cracking of a water-cooled wall, and the evaluation system includes:

[0125] A storage device for dividing the water-cooled wall into regions and setting the position points of the water-cooled wall tubes and fins in different regions;

[0126] A storage device used to calculate the medium temperature and pressure of each water-cooled wall tube in the designated area based on the temperature and pressure measurement point data of the water-cooled wall intermediate header in the DCS system at a certain moment, according to the elevation difference between the designated area and the water-cooled wall intermediate header, and the outlet temperature and pressure of the water-cooled wall lower header;

[0127] A storage device for calculating the thermal expansion amount of a single water-cooled wall tube position point under unconstrained conditions at that moment based on the medium temperature and pressure of the water-cooled wall tube in the defined area;

[0128] A storage device for calculating the thermal expansion of a single fin under unconstrained conditions;

[0129] A storage device for obtaining the superimposed stress values ​​of different fin positions at that moment according to the thermal expansion differences of all water-cooled wall tubes and fin positions;

[0130] A storage device for obtaining data at the next moment in the DCS system at a time interval of dt, and then repeating the above process to obtain the stress value of each fin position point at the next moment;

[0131] A storage device for repeating the above process to obtain a stress variation curve of the water-cooled wall fin position point during the unit startup, shutdown and peak regulation process;

[0132] A storage device for calculating the fatigue tensile cracking life loss of the water-cooled wall in a single start-stop or peak regulation cycle based on a multi-axis equivalent strain criterion and the stress change curve in the above steps;

[0133] A storage device for linearly accumulating the total life loss using multiple single water-cooled wall fatigue cracking life losses, alarming when the total life loss exceeds 70%, and repeating the above calculation process when it is less than 70%.

[0134] Embodiment 5: This embodiment provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, an online evaluation method for fatigue cracking of a water-cooled wall as described in any one of the above embodiments is executed.

[0135] For example:

[0136] Step 1: Divide the water-cooled wall into regions and set the position points of water-cooled wall tubes and fins in different regions;

[0137] Step 2: Based on the temperature and pressure measurement point data of the water-cooled wall intermediate header in the DCS system at a certain moment, calculate the medium temperature and pressure of each water-cooled wall tube in the designated area according to the elevation difference between the designated area and the water-cooled wall intermediate header, and the outlet temperature and pressure of the water-cooled wall lower header;

[0138] Step 3: According to the medium temperature and pressure of the water-cooled wall tubes in the designated area, calculate the thermal expansion of a single water-cooled wall tube at that moment under unconstrained conditions;

[0139] Step 4: Calculate the thermal expansion of a single fin under unconstrained conditions;

[0140] Step 5: According to the thermal expansion difference of all water-cooled wall tubes and fin positions, the superimposed stress values ​​of different fin positions at that moment are obtained;

[0141] Step 6: Get the data of the next moment in the DCS system at a time interval of dt, and then repeat the above process to obtain the stress value of each fin position point at the next moment;

[0142] Step 7: Repeat the above process to obtain the stress change curve of the water-cooled wall fin position during the unit startup, shutdown and peak regulation process;

[0143] Step 8: Based on the multi-axial equivalent strain criterion and the stress change curve in step 7, calculate the fatigue cracking life loss of the water-cooled wall in a single start-stop or peak regulation cycle;

[0144] Step 9: Use multiple single water-cooled wall fatigue cracking life losses to linearly accumulate and calculate the total life loss. When the total life loss exceeds 70%, an alarm will be triggered. If it is less than 70%, the above calculation process will be repeated.

[0145] Embodiment 6. This embodiment provides a computer device, which includes a memory and a processor, wherein the memory stores a computer program. When the processor runs the computer program stored in the memory, the processor executes an online evaluation method for fatigue cracking of a water-cooled wall as described in any one of the above embodiments.

[0146] A computer device provided in this embodiment, the hardware device of this part is a general model and is not shown in the form of a diagram. The system includes a processor and a memory, wherein the processor and the memory can be connected via a bus or other means. The memory, as a non-transient computer-readable storage medium, can be used to store non-transient software programs, non-transient computer executable programs and modules, and corresponding program instructions / modules. The processor executes various functional applications and data processing of the processor by running the non-transient software programs, instructions and modules stored in the memory, so as to realize the online evaluation method and steps of water-cooled wall fatigue cracking in the above method embodiment.

[0147] It should be understood that when used in this specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0148] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0149] The above description is only the implementation mode of the present invention and is not limited to the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of the claims of the present invention.

Claims

1. An online evaluation method for fatigue cracking of water-cooled wall, characterized in that: The method is: S1: Divide the water-cooled wall into regions and set the position points of water-cooled wall tubes and fins in different regions; S2: Based on the temperature and pressure measurement point data of the water-cooled wall intermediate header in the DCS system at a certain moment, the medium temperature and pressure of each water-cooled wall tube in the designated area are calculated according to the elevation difference between the designated area and the water-cooled wall intermediate header, and the outlet temperature and pressure of the water-cooled wall lower header; S3: Calculate the thermal expansion of a single water-cooled wall tube at that moment under unconstrained conditions according to the medium temperature and pressure of the water-cooled wall tube in the designated area; S4: Calculate the thermal expansion of a single fin under unconstrained conditions; S5: according to the thermal expansion difference of all water-cooled wall tubes and fin positions, the superimposed stress values ​​of different fin positions at that moment are obtained; S6: taking the data of the next moment in the DCS system at a time interval of dt, and then repeating the above process to obtain the stress value of each fin position point at the next moment; S7: Repeat the above process to obtain the stress change curve of the water-cooled wall fin position point during the unit startup, shutdown and peak regulation process; S8: Based on the multi-axial equivalent strain criterion, according to the stress change curve in step S7, the fatigue tensile crack life loss of the water-cooled wall in a single start-stop or peak regulation cycle is calculated; S9: Multiple single water-cooled wall fatigue cracking life losses are used to linearly accumulate and calculate the total life loss. When the total life loss exceeds 70%, an alarm is triggered. When it is less than 70%, the above calculation process is repeated.

2. The online evaluation method for fatigue cracking of a water-cooled wall according to claim 1 is characterized in that: S1 is specifically: S11: In the height direction of the boiler, the water wall intermediate header is used as the marking line, and each 2m is demarcated as an area; S12: Each zone includes the water-cooled walls on all four sides of the boiler at that elevation; S13: A single water-cooled wall tube and a single fin in the water-cooled wall of the four walls of the boiler are regarded as a position point respectively.

3. The online evaluation method for fatigue cracking of a water-cooled wall according to claim 1, characterized in that: The medium temperature of the water-cooled wall tubes in the designated area is: The medium pressure of the water-cooled wall tube is: Among them, H 区 , H 中 and H 下 They are the elevations of the designated area, the middle header and the lower header, T 中 and T 下 are the temperatures of the intermediate header and lower header pipes, P 中 and P 下 They are the pressures of the intermediate header and the lower header distribution pipes respectively.

4. The online evaluation method for fatigue cracking of a water-cooled wall according to claim 1, characterized in that: S4 is specifically: using a machine learning model based on heat flux density, temperature difference between adjacent tubes, and fin geometry to calculate the temperature of the fin position points between the water-cooled wall tubes, and then calculate the thermal expansion of a single fin under unconstrained conditions.

5. The online evaluation method for fatigue cracking of water-cooled wall according to claim 1, characterized in that: The superimposed stress values ​​at different fin positions are: s = s T +s P A t =π(R 2 -r 2 ) A f =ab Among them, α and E are the linear expansion coefficient and elastic modulus of the fin, respectively, ΔT is the temperature difference between the water-cooled wall tube and the fin, R and r are the outer radius and inner radius of the water-cooled wall tube, respectively, a and b are the length and width of the fin, respectively, and v is the Poisson's ratio.

6. The online evaluation method for fatigue cracking of a water-cooled wall according to claim 1, characterized in that: dt time interval ≥ 1min.

7. The online evaluation method for fatigue cracking of water-cooled wall according to claim 1, characterized in that: The multiaxial equivalent strain criterion is as follows: ε2=ε3=-vε1 Among them, Δε eff is the strain range, σ f ′ is the fatigue strength coefficient, N f is the number of fatigue cycles, b is the fatigue strength index, c is the fatigue ductility index, ε2 is the axial strain, ε3 is the hoop strain, ε1 is the normal strain, and v is the Poisson's ratio.

8. An online evaluation system for fatigue cracking of water-cooled wall, characterized in that: The system includes: A storage device for dividing the water-cooled wall into regions and setting the position points of the water-cooled wall tubes and fins in different regions; A storage device used to calculate the medium temperature and pressure of each water-cooled wall tube in the designated area based on the temperature and pressure measurement point data of the water-cooled wall intermediate header in the DCS system at a certain moment, according to the elevation difference between the designated area and the water-cooled wall intermediate header, and the outlet temperature and pressure of the water-cooled wall lower header; A storage device for calculating the thermal expansion amount of a single water-cooled wall tube position point under unconstrained conditions at that moment based on the medium temperature and pressure of the water-cooled wall tube in the defined area; A storage device for calculating the thermal expansion of a single fin under unconstrained conditions; A storage device for obtaining the superimposed stress values ​​of different fin positions at that moment according to the thermal expansion differences of all water-cooled wall tubes and fin positions; A storage device for obtaining data at the next moment in the DCS system at a time interval of dt, and then repeating the above process to obtain the stress value of each fin position point at the next moment; A storage device for repeating the above process to obtain a stress variation curve of the water-cooled wall fin position point during the unit startup, shutdown and peak regulation process; A storage device for calculating the fatigue cracking life loss of the water-cooled wall in a single start-stop or peak regulation cycle based on a multi-axis equivalent strain criterion and the stress change curve in the above steps; A storage device for linearly accumulating the total life loss using multiple single water-cooled wall fatigue cracking life losses, alarming when the total life loss exceeds 70%, and repeating the above calculation process when it is less than 70%.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the online evaluation method for fatigue cracking of a water-cooled wall according to any one of claims 1 to 7 is executed.

10. A computer device, characterized in that: The device comprises a memory and a processor, wherein a computer program is stored in the memory, and when the processor runs the computer program stored in the memory, the processor executes an online evaluation method for fatigue cracking of a water-cooled wall as claimed in any one of claims 1 to 7.

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