A boiler heating surface wall temperature prediction method, device and storage medium
By dividing the screen-type superheater into multiple tube bundle calculation units and performing iterative solutions, the problem of large wall temperature prediction deviation in the existing technology is solved, and accurate prediction of boiler heating surface and improved safety are achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- XI AN JIAOTONG UNIV
- Filing Date
- 2026-05-27
- Publication Date
- 2026-07-24
AI Technical Summary
In the existing technology, the method for calculating the wall temperature of the screen-type superheater assumes that the working fluid mass flow rate is constant or adopts uniform heat flow boundary conditions, which leads to a large deviation in the prediction of the boiler heating surface wall temperature under low load and rapid changing operating conditions, affecting the boiler peak-shaving safety and design optimization.
By dividing the screen-type superheater into multiple tube bundle calculation units along the width direction and discretizing them into several axial calculation segments, numerical solutions are obtained by combining turbulence model, combustion model and radiation heat transfer model. The total pressure drop, temperature field and wall temperature field are determined segment by segment, and coupled iterative correction of mass flow rate is performed until convergence, and the final wall temperature distribution is output.
It enables accurate prediction of boiler heating surface wall temperature, improves boiler peak-shaving safety and design optimization level, and is applicable to the retrofitting of coal-fired boilers and the optimization of rapid peak-shaving strategies.
Smart Images
Figure CN122452867A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of thermal numerical simulation technology, specifically relating to a method, equipment, and storage medium for predicting the wall temperature of a boiler heating surface. Background Technology
[0002] With a high proportion of renewable energy integrated into the power system, coal-fired power units need to frequently participate in deep peak-shaving operations. Under low load and rapid changes in operating conditions, the high-temperature heating surfaces of boilers are prone to local overheating. As a key high-temperature component of the boiler, the wall temperature distribution of the screen-type superheater directly affects the safety and reliability of the equipment.
[0003] In existing technologies, most methods for calculating the wall temperature of screen-type superheaters assume that the working fluid mass flow rate in each parallel tube bundle calculation unit is constant, or use uniform heat flow boundary conditions for simplification. This does not match the actual operating conditions, resulting in large deviations in the predicted wall temperature of the boiler heating surface under wide load operation. Consequently, these methods are of little guiding significance for boiler peak-shaving safety and optimization design. Summary of the Invention
[0004] In view of this, the present invention provides a method, device and storage medium for predicting the wall temperature of a boiler heating surface, thereby solving the problems in the prior art.
[0005] The technical solution of this invention is: A method for predicting the wall temperature of a boiler heating surface includes the following steps: Obtain boiler heating surface structural parameters and operating condition parameters; Based on the structural parameters, a three-dimensional geometric model of the boiler furnace and flue is established. The screen-type superheater in the three-dimensional geometric model is divided into multiple tube bundle calculation units along the width direction, and each tube bundle calculation unit is discretized into several axial calculation segments. A. Map the flue gas side parameters in the operating condition parameters to the corresponding tube bundle calculation unit - axial calculation segment according to the spatial location, so as to obtain the convective heat transfer drive and radiative heat transfer drive corresponding to each segment, and define the turbulence model, combustion model and radiative heat transfer model as constraints, perform numerical solution until convergence, and then obtain the spatial non-uniform heat load distribution on the outer surface of the screen superheater. B. Based on the spatial non-uniform heat load distribution on the outer surface of the screen-type superheater, the total pressure drop, temperature field and wall temperature field of each tube bundle calculation unit are determined segment by segment to obtain the pressure drop-flow rate relationship of each tube bundle calculation unit; Based on the pressure drop-flow rate relationship of each tube bundle calculation unit, the mass flow rate distribution is coupled and iteratively corrected. After each round of correction, the iterative calculation is repeated and returned to B to continue execution until the pressure drop of each tube bundle calculation unit tends to be consistent, thereby obtaining the corresponding wall temperature spatial distribution. An equivalent heat source term or equivalent boundary condition is introduced between the flue gas side and the steam side, and the heat absorbed by the steam side is fed back to the flue gas side. The heat load distribution on the flue gas side is updated and coupled with the flow correction to form an iteration. The process returns to A to continue execution until the wall temperature distribution change and the flue gas side parameter change in the two adjacent iterations are both less than the preset threshold. At this point, the coupling is determined to be converged and the final boiler heating surface wall temperature distribution is output.
[0006] Furthermore, the length of the axial calculation segment is between 0.05m and 0.2m.
[0007] Furthermore, the turbulence model employs Realizable k-ε and enables swirl correction to reflect the characteristics of swirl combustion and recirculation zones.
[0008] Furthermore, the combustion model adopts a non-premixed PDF model, which is used to determine key field quantities based on fuel composition.
[0009] Furthermore, the radiation model uses the P1 model to calculate the contribution of furnace radiation heat transfer, and the solver and discretization scheme use the Coupled algorithm to enhance the stability of pressure-velocity coupling.
[0010] Furthermore, based on the spatially non-uniform heat load distribution on the outer surface of the screen-type superheater, the temperature field and wall temperature field of each tube bundle calculation unit are determined segment by segment, including the following steps: Given the mass flow rate of the tube bundle calculation unit, the outlet working medium state of the previous axial calculation segment is used as the inlet working medium state of the next axial calculation segment. Steam physical property parameters are calculated based on the inlet temperature and pressure of each axial calculation section, and the steam-side convective heat transfer coefficient is obtained. Based on the spatial non-uniform heat load distribution on the outer surface of the screen-type superheater, the convective heat transfer coefficient on the flue gas side, the radiative heat transfer coefficient on the flue gas side, and the convective heat transfer coefficient on the steam side are calculated respectively, and the total heat transfer coefficient is obtained by combining the thermal resistance of the tube wall and the external resistance of the oxide layer. Based on the total heat transfer coefficient and the flue gas-steam temperature difference, the heat absorption of each axial calculation segment is calculated and the steam outlet temperature and corresponding wall temperature are updated to obtain the temperature field and wall temperature field of the tube bundle calculation unit.
[0011] Furthermore, the mass flow rate allocation is coupled and iteratively corrected, including: Under the current mass flow rate, determine the total pressure drop, wall temperature, average pressure drop, and relative pressure drop deviation of each tube bundle calculation unit until the preset pressure drop consistency convergence criterion is met; If the relative deviation of the pressure drop is less than the preset threshold, the parallel flow distribution is considered to have converged, the mass flow rate is output and the process proceeds to the next step. If the relative deviation of the pressure drop is greater than the preset threshold, the mass flow rate is updated according to the pressure drop-flow rate matching relationship: the flow rate is reduced for tube bundle calculation units with large pressure drop and increased for tube bundle calculation units with small pressure drop. After the update, the total mass flow rate is conserved and normalized to keep the total mass flow rate unchanged.
[0012] Furthermore, the updated flue gas heat load distribution is coupled with flow correction in an iterative process, employing a two-layer iterative structure of "outer flue gas update - inner flow matching": In the m-th iteration of the outer layer, the flue gas side is first solved under the current source term / boundary to obtain new flue gas temperature, flue gas velocity and other parameters and update the equivalent heat flux. Then, the mass flow rate allocation is coupled and iteratively corrected under the equivalent heat flux.
[0013] An electronic device includes: a memory, a processor, and a computer program stored in the memory and executable on the processor, the processor executing the computer program to implement the boiler heating surface wall temperature prediction method as described above.
[0014] A computer-readable storage medium having a computer program stored thereon, which is executed by a processor to implement the boiler heating surface wall temperature prediction method as described above.
[0015] Compared with existing technologies, this invention provides a method, device, and storage medium for predicting boiler heating surface wall temperature. The method considers the coupling effect of non-uniform heat load on the flue gas side and flow redistribution between tube bundle calculation units. It divides the screen-type superheater in a three-dimensional geometric model into multiple tube bundle calculation units along its width, discretizes each tube bundle calculation unit into several axial calculation segments, and maps the flue gas side parameters in the operating condition parameters to the corresponding tube bundle calculation unit-axial calculation segment according to their spatial location. This obtains the convective heat transfer drive and radiative heat transfer drive corresponding to each segment. Turbulence models, combustion models, and radiative heat transfer models are defined as constraints, and numerical solutions are performed until convergence. This yields the spatial non-uniform heat load distribution on the outer surface of the screen-type superheater, based on spatial... For non-uniform heat load distribution, the total pressure drop, temperature field, and wall temperature field of each tube bundle calculation unit are determined segment by segment to obtain the pressure drop-flow rate relationship of each tube bundle calculation unit. Based on the pressure drop-flow rate relationship of each tube bundle calculation unit, the mass flow rate distribution is coupled and iteratively corrected. After each round of correction, the iterative calculation is repeated until the pressure drop of each tube bundle calculation unit tends to be consistent, thereby obtaining the corresponding wall temperature spatial distribution. An equivalent heat source term or equivalent boundary condition is introduced between the flue gas side and the steam side, and the heat absorbed by the steam side is fed back to the flue gas side to update the heat load distribution of the flue gas side and form a coupled iteration with the flow rate correction. When the wall temperature distribution change and the flue gas side parameter change in two adjacent iterations are both less than the preset threshold, the coupling is determined to be converged and the final boiler heating surface wall temperature distribution is output. The above method takes into account the wall temperature prediction deviation caused by the non-uniform distribution of the working fluid flow. By introducing a pressure drop-flow matching model, it can achieve accurate prediction of the boiler heating surface wall temperature. It can provide a reference for the selection of the throttling coefficient of the throttling orifice ring at the outlet of the screen-type superheater, improve the boiler peak-shaving safety, design optimization level and boiler operation safety. It is applicable to the design and transformation of coal-fired boilers and the optimization of rapid peak-shaving strategies. It is highly practical and worth promoting. Attached Figure Description
[0016] Figure 1 This is a schematic diagram of the process of the present invention.
[0017] Figure 2 This is a schematic diagram of the k-th correction of the mass flow rate of the heated surface pipe for pressure drop-flow matching in a multi-tube bundle calculation unit.
[0018] Figure 3 This is a comparison chart of the measured steam outlet temperature of the screen-type superheater of the present invention with the numerical values of different simulation methods.
[0019] Figure 4 This is a comparison diagram of the flow resistance and flow rate correction of the tube screen in this invention before and after. Detailed Implementation
[0020] This invention provides a method, device, and storage medium for predicting the wall temperature of a boiler heating surface to solve the above-mentioned problems. In order to enable those skilled in the art to better understand the technical solution of this invention and to implement it, the technical solution of this invention will be clearly and thoroughly described below with reference to the accompanying drawings.
[0021] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.
[0022] Furthermore, it should be further explained that in the description of the embodiments of the present invention, unless otherwise stated, " / " means "or". For example, A / B can mean A or B. The "and / or" in the text is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone. In addition, in the description of the embodiments of the present invention, "multiple" means two or more.
[0023] The terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as implying or suggesting relative importance or implicitly indicating the number of indicated technical features. Thus, a feature defined as "first," "second," "third," or "fourth" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.
[0024] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.
[0025] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature and the second feature are in direct contact, or that the first feature and the second feature are in indirect contact through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "below" of the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.
[0026] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this invention are for illustrative purposes only and do not represent the only possible implementation.
[0027] Example 1 This embodiment uses a screen-type superheater as an example, and provides the following... Figure 1 The implementation flow shown is used to couple the flow redistribution and heat transfer surface wall temperature distribution of the parallel tube bundle calculation unit under non-uniform heat load conditions on the flue gas side. The flow first calculates the non-uniform heat load on the flue gas side, completes the segmented thermodynamic calculation and pressure drop-flow matching on the steam side, and finally achieves the coupling convergence of the flue gas side and the steam side.
[0028] Step 1: Input Parameter Acquisition and Calculation Object Definition Obtain the structural parameters and operating condition parameters of the boiler heating surface. The structural parameters should include at least: the number of superheater tube panels, the number of parallel branch pipes per panel, the pipe outer / inner diameter / wall thickness, the thermal conductivity of the pipe material, the equivalent external resistance of the oxide layer, and the geometric position of each tube bundle calculation unit (for mapping with the flue gas side mesh). The operating condition parameters should include at least: the steam inlet temperature. Inlet pressure Total mass flow rate of screen-type superheater Flue gas side parameters and flue gas side boundary conditions (load, air distribution, inlet temperature / flow rate, outlet pressure, etc.), among which the flue gas side parameters include the temperature of each grid cell. T y ,speed u y ,density ρ y Specific heat c p，y thermal conductivity k y viscosity coefficient μ y And radiation-related quantities (such as the absorptivity of the participating medium, the viewing angle coefficient, or the radiation intensity).
[0029] Step 2: Three-dimensional combustion / flow calculation and non-uniform heat load acquisition on the flue gas side A three-dimensional geometric model of the boiler furnace and flue was established based on the structural parameters of the boiler heating surface.
[0030] For ease of calculation, the screen-type superheater in the three-dimensional geometric model is divided into J tube bundle calculation units along the width direction. The J tube bundle calculation units are numbered j, j=1…J respectively, and each tube bundle calculation unit contains several parallel branches.
[0031] Each tube bundle calculation unit is discretized into I axial calculation segments along the direction of working fluid flow. The I axial calculation segments are numbered i, i=1…I. Since calculations are inaccurate and errors occur when the segment length is too long, there are basically no errors when the segment length is less than 0.2m. However, if it is too short, the calculation workload will increase and the calculation speed will slow down. Therefore, the segment length of the axial calculation segment can be taken as 0.05m-0.2m.
[0032] Define the inlet state of the i-th segment of the j-th tube bundle calculation unit as (steam inlet temperature) Steam inlet pressure The outlet condition is (steam outlet temperature). Steam outlet pressure The corresponding external flue gas parameters are (flue gas temperature). flue gas velocity , wait).
[0033] The flue gas side parameters in the operating condition parameters are mapped spatially to the tube bundle calculation unit - axial calculation segment (j, i) to obtain the corresponding convective heat transfer drive and radiative heat transfer drive for each segment. The calculation mesh is divided, and turbulence model, combustion model, and radiative heat transfer model are defined as constraints. Numerical solutions are performed until convergence, thereby forming the spatial non-uniform heat load distribution on the outer surface of the screen superheater. .
[0034] It should be noted that the above turbulence model adopts Realizable k-ε and enables swirl correction to reflect the characteristics of swirl combustion and recirculation zone.
[0035] The combustion model adopts the non-premixed PDF model. The fuel composition is input into the non-premixed PDF model to solve and obtain key field quantities, such as the flame center temperature and the distribution of flue gas components in the entire boiler.
[0036] The radiation model uses the P1 model to calculate the contribution of furnace radiation heat transfer, and the Coupled algorithm is used in the solver and discretization scheme to enhance the stability of pressure-velocity coupling. First-order accuracy is used in the initial stage to ensure convergence, and a second-order upwind scheme is switched after near convergence to improve the accuracy of field quantities and gradient capture capability.
[0037] Step 3: Equivalent heat-flow model of the heated surface and step-by-step calculation Given the mass flow rate of the j-th tube bundle calculation unit, the axial calculation segment is calculated segment by segment: the outlet state of the previous segment is used as the inlet state of the next segment, and the steam properties (density) are calculated based on the inlet temperature and pressure of the current segment. viscosity coefficient thermal conductivity Specific heat And obtain the steam-side convective heat transfer coefficient. .
[0038] Simultaneously, the flue gas side parameter temperature obtained from step 2 is used. ,speed ,density Specific heat thermal conductivity viscosity coefficient And radiation-related quantities (such as the absorptivity of the participating medium, the viewing angle coefficient, or the radiation intensity) are used to calculate the convective heat transfer coefficient on the flue gas side. and radiative heat transfer equivalent coefficient .
[0039] The flue gas side convective heat transfer coefficient Radiative heat transfer equivalent coefficient The overall heat transfer coefficient of this section is obtained by combining the steam-side convective heat transfer coefficient, the pipe wall thermal resistance, and the oxide layer external resistance. .
[0040] The heat absorption of this section is calculated based on the flue gas-steam temperature difference and the heat exchange area. The steam outlet temperature is updated by energy conservation. Then, calculate the outer wall temperature of the pipe based on the equivalent thermal resistance distribution relationship. The above calculations are performed sequentially along i=1…I to obtain the temperature field and wall temperature field of the tube bundle calculation unit.
[0041] Specifically, the convective heat transfer coefficient on the flue gas side is calculated using Equation 1. subscript Representative smoke: in, The Reynolds number of the flue gas. The Prandtl number of the flue gas. The thermal conductivity of the flue gas. This refers to the outer diameter of the heated surface pipe.
[0042] The radiative heat transfer coefficient on the flue gas side is calculated using Equation 2. h a 'a' represents radiative heat transfer. in, For absorption ratio, Let be the blackbody radiation constant. The flue gas temperature. The subscript represents the wall temperature of the heated pipe surface. and These represent flue gas and the wall surface, respectively.
[0043] Based on the steam inlet temperature, the steam density, specific heat, thermal conductivity, and viscosity are calculated, and the steam Reynolds number and Prandtl number are obtained.
[0044] The convective heat transfer coefficient on the steam side is calculated using Equation 3. : in, The Reynolds number of steam. The Prandtl number of steam. The thermal conductivity of steam. This refers to the inner diameter of the pipe on the heated surface.
[0045] The overall heat transfer coefficient is calculated using Equation 4 by combining the convective and radiative heat transfer coefficients of the flue gas side surface. : in, It is the overall heat transfer coefficient. For the external resistance of the pipeline oxide layer, The outer diameter of the heating surface pipe. The inner diameter of the heated surface pipe. The convective heat transfer coefficient on the flue gas side is... The radiative heat transfer coefficient on the flue gas side is... The thermal conductivity of the wall is . It is the convective heat transfer coefficient on the steam side.
[0046] Specifically, the total heat transfer of the pipe section is calculated by the temperature difference between the flue gas and the steam, and then the steam outlet temperature and the outer wall temperature of the pipe are obtained.
[0047] The steam outlet temperature of the heated surface pipe is calculated using Equation 5. : in, The steam inlet temperature of the heated surface pipe. The steam outlet temperature of the heated surface pipe. This refers to the heat exchange area on the flue gas side. For flue gas temperature, This refers to the steam mass flow rate. For the specific heat capacity of steam at constant pressure, subscript and They represent the entrance and the exit, respectively. It is the overall heat transfer coefficient.
[0048] The temperature of the pipe wall surface of the heated surface is calculated using Equation 6. : in, The pipe wall temperature is the temperature of the heated surface. The flue gas temperature. The overall heat transfer coefficient is... The steam inlet temperature of the heated surface pipe. It is the convective heat transfer coefficient on the steam side. The thermal conductivity of the wall is . This refers to the wall thickness of the heated surface tube.
[0049] Step 4: Calculate the total pressure drop During the segmented advancement process, the flow impedance of each tube bundle calculation unit is calculated simultaneously, thereby obtaining the "flow impedance" characteristic of each tube bundle calculation unit. The flow impedance is used to characterize the total pressure drop. .
[0050] Specifically, the flow resistance inside the pipe is calculated using Equation 7. : in, It is flow resistance. The coefficient of friction, For the working fluid density, This represents the steam flow rate.
[0051] The aforementioned friction coefficient can be determined based on the Reynolds number and relative roughness according to Equation 8: in, For pipe wall roughness, This refers to the inner diameter of the pipe on the heated surface.
[0052] Step 5: Pressure drop-flow matching iteration (parallel tube bundle calculation unit flow adaptive correction) Initial allocation: in total mass flow rate Under constraints, given initial flow allocation For example, by uniform distribution or by empirical impedance distribution such as throttling orifice / pipe length, so that .
[0053] like Figure 2 The iterative correction shown: For the k-th iteration, perform the following sub-steps: 1) At the current mass flow rate Next, perform steps 3 and 5 on all j to obtain the total pressure drop of each tube bundle calculation unit. and wall temperature .
[0054] 2) Calculate the average pressure drop And calculate the relative deviation of the pressure drop. The process continues until the preset pressure drop consistency convergence criterion is met, and the relative deviation between the total pressure drop and the average pressure drop of each tube bundle calculation unit is less than 0.1%.
[0055] 3) If the relative deviation of the pressure drop If the parallel flow distribution is considered to have converged, the output mass flow rate will be considered to be... Then proceed to step 6.
[0056] 4) If the relative deviation of the pressure drop Then update the mass flow rate according to the pressure drop-flow matching relationship. For tube bundle calculation units with excessive pressure drop, the flow rate is reduced; for tube bundle calculation units with excessive pressure drop, the flow rate is increased. After updating, the total mass flow rate is normalized to maintain a constant total mass flow rate. ,make k=k+1 And return to step 1).
[0057] Through the above iterations, the pressure drop of each tube bundle calculation unit tends to be consistent under non-uniform heat load, thereby obtaining a flow redistribution result that is closer to the actual operating state and obtaining the corresponding spatial distribution of wall temperature.
[0058] Calculate the corrected mass flow rate using Equation 9: in, Let be the initial mass flow rate of the i-th tube. Let be the mass flow rate of the i-th tube after the first correction. The average pressure drop across the pipeline. Let be the pressure drop of the i-th tube.
[0059] Equation 10 ensures that the total mass flow rate within the boiler's heating surface pipes remains constant: in, This represents the total mass flow rate of the working fluid after the Nth calculation of the heated surface pipe. To calculate the total mass flow rate of the working fluid under initial conditions, This represents the total mass flow rate after the (N+1)th calculation for the i-th heated surface pipe.
[0060] Step 6: Flue gas-steam coupling iteration and convergence criteria To reflect the feedback effect of heat absorption on the steam side on the temperature field of the flue gas side, an equivalent heat source term / equivalent heat flux boundary is applied to the solid domain or boundary of the screen-type superheater in the numerical model of the flue gas side.
[0061] The specific steps are as follows: The heat absorption of each segment obtained in step 3 or equivalent heat flux density The spatial location is mapped to the flue gas side mesh and used as the boundary / source term for the next round of flue gas side solution.
[0062] The coupled iteration adopts a two-layer iterative structure of "outer layer flue gas renewal - inner layer flow matching": In the m-th iteration of the outer layer, the flue gas side is first solved under the current source term / boundary to obtain the new flue gas temperature. flue gas velocity Parameters are equalized and the equivalent heat flux is updated. Subsequently, in the equivalent heat flow Next, execute steps 4 and 5 to obtain the converged steam-side mass flow rate. and wall temperature .
[0063] When the changes in wall temperature distribution and key parameters on the flue gas side in two adjacent outer layer iterations are both less than a preset threshold, coupling convergence is determined and the final wall temperature distribution is output. It should be noted that in this embodiment, the preset threshold is 0.1%.
[0064] The above method can also be implemented using electronic devices. The structure of such electronic devices specifically includes a memory, a processor, and a computer program stored in the memory and capable of running on the processor. The processor executes the computer program to implement a method for predicting the wall temperature of a boiler heating surface as described above.
[0065] A communication interface is established between the memory and the processor to establish signal connections and enable data transfer. This communication interface can be either a serial interface or a parallel interface.
[0066] The processor can be a central processing unit (CPU), a specific integrated circuit (ASIC), or one or more integrated circuits configured to implement embodiments of the present invention.
[0067] The above method can also be implemented using a computer-readable storage medium storing a computer program that is executed by a processor to implement a method for predicting the wall temperature of a boiler heating surface as described above.
[0068] Taking a 660MW DG2150 / 25.4-II6 type coal-fired boiler with opposing front and rear walls as an example, the screen-type superheater is arranged above the flame deflector zone and consists of 30 tube screens, each containing 5 parallel branch pipes. The boiler furnace has geometric dimensions of 22.16m (width) × 15.46m (depth) × 62.00m (height). Burners, burnout air nozzles, and side burnout air inlets are evenly and symmetrically arranged on the front and rear walls of the furnace. Each wall has 3 layers of burners, with 6 swirl burners per layer, for a total of 36 burners. There are 12 burnout air nozzles and 4 side burnout air inlets. The screen-type superheater is arranged above the flame deflector zone and consists of 30 tube screens, each containing 5 parallel branch pipes. The outer diameter of the tubes is 0.35 m, and the wall thickness is 0.5 mm. The entire screen-type superheater is divided into 4 independent calculation units.
[0069] To verify the accuracy of the model, an unstructured grid was used for mesh generation: 0.6 m for the furnace flue gas zone, 0.3 m for the burner zone, and 0.1 m for the screen-type superheater hexahedron, with a total of approximately 5 million meshes.
[0070] The calculations were performed using Fluent software. The swirl angle was 45°. The fuel composition input into the non-premixed PDF model is shown in Table 1. The simulation was carried out under full load conditions.
[0071] Table 1 Fuel Composition Table A three-dimensional combustion model is established based on Fluent, the flue gas side parameters on the outer surface of the screen superheater are extracted and a spatial non-uniform heat load distribution is formed, and then the flow redistribution and wall temperature prediction of the parallel tube bundle calculation unit are completed according to the above steps 3-6.
[0072] In this case, the steam outlet temperature distribution of the heated surface obtained by the method of the present invention matches well with the measured value. Figure 3 This chart compares the measured steam outlet temperature of the superheater in this invention with numerical values from different simulation methods. Compared to the traditional model assuming a constant flow rate, this invention significantly reduces the pressure drop deviation between parallel pipes through pressure drop consistency constraints, thereby improving the accuracy of wall temperature prediction. The steam outlet temperature distribution of the boiler heating surface pipes obtained from numerical simulation shows good agreement with the measured results. The maximum temperature difference between the predicted and measured results is 19.92 K, with a relative error of 2.46%. The deviation between the predicted average temperature and the average value of the measured data is 2.08 K, with a relative error of only 0.26%. The comparative results indicate that the coupled calculation model proposed in this invention has better accuracy in predicting the wall temperature characteristics of the boiler heating surface.
[0073] also, Figure 4 This is a comparison chart of the pressure drop and flow rate correction before and after the present invention. When the flow rate is constant, the pressure drop deviation between parallel pipes is ignored, and the average deviation of the relative pressure drop between pipes reaches 2.18%, while the maximum deviation is 5.64%. However, after using the boiler heating surface wall temperature prediction method proposed in this invention, the calculated average pressure drop deviation is less than 0.07%, and the maximum pressure drop deviation is also reduced to 0.189%. It can be used for wall temperature overheating risk assessment and structural / throttling coefficient optimization under wide load peak shaving conditions. It is suitable for the design and renovation of coal-fired boilers and the optimization of rapid peak shaving strategies. It is highly practical and worth promoting.
[0074] The above-disclosed embodiments are merely preferred embodiments of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.
Claims
1. A method for predicting the wall temperature of a boiler heating surface, characterized in that, Includes the following steps: Obtain boiler heating surface structural parameters and operating condition parameters; Based on the structural parameters, a three-dimensional geometric model of the boiler furnace and flue is established. The screen-type superheater in the three-dimensional geometric model is divided into multiple tube bundle calculation units along the width direction, and each tube bundle calculation unit is discretized into several axial calculation segments. A. Map the flue gas side parameters in the operating condition parameters to the corresponding tube bundle calculation unit - axial calculation segment according to the spatial location, so as to obtain the convective heat transfer drive and radiative heat transfer drive corresponding to each segment, and define the turbulence model, combustion model and radiative heat transfer model as constraints, perform numerical solution until convergence, and then obtain the spatial non-uniform heat load distribution on the outer surface of the screen superheater. B. Based on the spatial non-uniform heat load distribution on the outer surface of the screen-type superheater, the total pressure drop, temperature field and wall temperature field of each tube bundle calculation unit are determined segment by segment to obtain the pressure drop-flow rate relationship of each tube bundle calculation unit; Based on the pressure drop-flow rate relationship of each tube bundle calculation unit, the mass flow rate distribution is coupled and iteratively corrected. After each round of correction, the iterative calculation is repeated and returned to B to continue execution until the pressure drop of each tube bundle calculation unit tends to be consistent, thereby obtaining the corresponding wall temperature spatial distribution. An equivalent heat source term or equivalent boundary condition is introduced between the flue gas side and the steam side, and the heat absorbed by the steam side is fed back to the flue gas side. The heat load distribution on the flue gas side is updated and coupled with the flow correction to form an iteration. The process returns to A to continue execution until the wall temperature distribution change and the flue gas side parameter change in the two adjacent iterations are both less than the preset threshold. At this point, the coupling is determined to be converged and the final boiler heating surface wall temperature distribution is output.
2. The method for predicting boiler heating surface wall temperature according to claim 1, characterized in that, The length of the axial calculation segment is between 0.05m and 0.2m.
3. The method for predicting boiler heating surface wall temperature according to claim 1, characterized in that, The turbulence model employs Realizable k-ε and enables swirl correction to reflect the characteristics of swirl combustion and recirculation zones.
4. The method for predicting boiler heating surface wall temperature according to claim 1, characterized in that, The combustion model uses a non-premixed PDF model, which is used to determine key field quantities based on fuel composition.
5. The method for predicting boiler heating surface wall temperature according to claim 1, characterized in that, The radiation model uses the P1 model to calculate the contribution of furnace radiation heat transfer, and the solver and discretization scheme use the Coupled algorithm to enhance the stability of pressure-velocity coupling.
6. The method for predicting boiler heating surface wall temperature according to claim 1, characterized in that, Based on the spatially non-uniform heat load distribution on the outer surface of the screen-type superheater, the temperature field and wall temperature field of each tube bundle calculation unit are determined segment by segment, including the following steps: Given the mass flow rate of the tube bundle calculation unit, the outlet working medium state of the previous axial calculation segment is used as the inlet working medium state of the next axial calculation segment. Steam physical property parameters are calculated based on the inlet temperature and pressure of each axial calculation section, and the steam-side convective heat transfer coefficient is obtained. Based on the spatial non-uniform heat load distribution on the outer surface of the screen-type superheater, the convective heat transfer coefficient on the flue gas side, the radiative heat transfer coefficient on the flue gas side, and the convective heat transfer coefficient on the steam side are calculated respectively, and the total heat transfer coefficient is obtained by combining the thermal resistance of the tube wall and the external resistance of the oxide layer. Based on the total heat transfer coefficient and the flue gas-steam temperature difference, the heat absorption of each axial calculation segment is calculated and the steam outlet temperature and corresponding wall temperature are updated to obtain the temperature field and wall temperature field of the tube bundle calculation unit.
7. The method for predicting boiler heating surface wall temperature according to claim 1, characterized in that, Coupled iterative correction of mass flow rate allocation, including: Under the current mass flow rate, determine the total pressure drop, wall temperature, average pressure drop, and relative pressure drop deviation of each tube bundle calculation unit until the preset pressure drop consistency convergence criterion is met; If the relative deviation of the pressure drop is less than the preset threshold, the parallel flow distribution is considered to have converged, the mass flow rate is output and the process proceeds to the next step. If the relative deviation of the pressure drop is greater than the preset threshold, the mass flow rate is updated according to the pressure drop-flow rate matching relationship: the flow rate is reduced for tube bundle calculation units with large pressure drop and increased for tube bundle calculation units with small pressure drop. After the update, the total mass flow rate is conserved and normalized to keep the total mass flow rate unchanged.
8. The method for predicting boiler heating surface wall temperature according to claim 1, characterized in that, The updated flue gas heat load distribution is coupled with flow correction in an iterative process, employing a two-layer iterative structure of "outer flue gas update - inner flow matching": In the m-th iteration of the outer layer, the flue gas side is first solved under the current source term / boundary to obtain the new flue gas temperature and flue gas velocity and update the equivalent heat flux. Then, the mass flow rate allocation is coupled and iteratively corrected under the equivalent heat flux.
9. An electronic device, characterized in that, include: The system includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the boiler heating surface wall temperature prediction method as described in claim 1.
10. A computer-readable storage medium having a computer program stored thereon, characterized in that, The computer program is executed by a processor to implement the boiler heating surface wall temperature prediction method as described in claim 1.