A steam turbine flow and boiler reheater coordinated transformation system adapting to high-pressure heat supply upgrading

Abstract

This invention discloses a turbine flow path and boiler reheater collaborative retrofit system adapted to high-pressure heating upgrades, relating to the field of thermal power equipment retrofit and heating upgrade technology. The system includes a flow path parameter modeling module, a reheater thermodynamic impedance calculation module, a collaborative matching solution module, and a retrofit scheme output module. It can establish a bidirectional coupling mapping between flow path enthalpy drop and reheater thermodynamic impedance, and complete the matching of retrofit parameters on both sides through bidirectional iteration. This invention replaces the traditional separate retrofit mode with different specialties, realizes parameter adaptation under all operating conditions, reduces unnecessary equipment replacement, reduces retrofit investment, reduces the amplitude of reheat steam temperature fluctuation, and the supporting operation coordination mechanism can improve the unit's operating stability.

Description

Technical Field

[0001] This invention relates to the field of thermal power generation equipment retrofit and heating upgrade technology, specifically a turbine flow path and boiler reheater co-modification system adapted to high-pressure heating upgrade. Background Technology

[0002] In high-pressure heating upgrade projects for coal-fired power units, it is usually necessary to adjust the turbine flow path to extract heating steam at different pressure levels. Simultaneously, the boiler reheater needs to be adapted to ensure that the reheat steam temperature remains within the design range after extraction. Currently, industry upgrades are often implemented separately for the turbine and boiler, with each side undergoing individual modifications based on its rated heating operating parameters. The final connection between the two systems is achieved using fixed interface parameters.

[0003] This separate modification model has significant drawbacks. Because the two sides are only connected at a single point under rated operating conditions, it doesn't consider the dynamic fluctuations in the extraction steam volume during actual operation due to user demand. When the extraction steam volume deviates from the design value, the flow rate, temperature, and pressure of the high-pressure cylinder exhaust will also deviate from the design conditions, resulting in a large deviation between the reheater inlet parameters and the design values. This easily leads to problems such as localized tube panel overheating, decreased heat exchange efficiency, and large fluctuations in reheat steam temperature. To compensate for these problems, some schemes use an expansion of the reheater heating surface to reserve excessive margin, but this can cause the reheat steam temperature to exceed limits under pure condensing conditions, requiring long-term desuperheating water supply, which actually reduces the unit's operating economy. Other schemes only compensate for design flaws through parameter adjustments on the operating side, but the adjustment range is limited and cannot fundamentally solve the parameter mismatch problem. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a turbine flow path and boiler reheater collaborative retrofit system adapted to high-pressure heating upgrades. This invention establishes a bidirectional coupling mapping relationship between the enthalpy drop distribution of the flow path group and the thermal impedance of the reheater heating surface, and uses a bidirectional iterative approach to complete the collaborative matching of retrofit parameters on both sides, breaking the traditional single-direction parameter docking mode for turbines and boilers. The system is equipped with staged extraction steam flow distribution, thermal stress collaborative control, and multi-physics field coupling simulation functions, covering the entire process from retrofit design to operation and control. It can adapt to scenarios such as dynamic fluctuations in heating load and switching between pure condensing and heating modes, stabilizing reheat steam temperature while reducing the thermal stress impact caused by sudden changes in extraction steam. It is suitable for heating upgrade retrofits of various coal-fired units.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a turbine flow path and boiler reheater collaborative retrofit system adapted to high-pressure heating upgrade, the system including a flow path parameter modeling module, a reheater thermodynamic impedance calculation module, a collaborative matching solution module, and a retrofit scheme output module; The flow parameter modeling module is used to collect the original design parameters and historical operating data of each stage of the high-pressure cylinder of the unit to be modified. Combined with the parameter level and flow range of the newly added heating steam extraction, it constructs a flow stage group variable operating condition calculation model, outputs the high-pressure cylinder exhaust parameter range and the adjustable range of enthalpy drop of each stage under different heating steam extraction volumes, and provides flow side parameter adjustment boundaries for subsequent coordinated matching. The reheater thermal impedance calculation module is used to collect the tube group structural parameters and historical operating data of the boiler reheater, construct the reheater thermal characteristic calculation model, output the tube group flow resistance, heat transfer coefficient and outlet steam temperature variation law under different inlet steam parameters, and clarify the optimal heat transfer condition range of the reheater as the reheater side characteristic boundary for coordinated matching. The collaborative matching solution module is used to establish a two-way coupled mapping relationship between the enthalpy drop distribution of the flow stage group and the thermodynamic impedance of the reheater heating surface. With the optimization objectives of the optimal heat exchange efficiency of the reheater and the minimum outlet steam temperature deviation under all operating conditions, the module iteratively adjusts the enthalpy drop distribution scheme of the flow stage group and the thermodynamic impedance parameters of the reheater tube group in both directions until the parameter matching degree of the two meets the preset threshold, so as to realize the two-way constraint and synchronous optimization of the parameters on both sides, rather than the traditional one-way parameter docking. The modification scheme output module is used to generate a collaborative modification technical document containing modification parameters for the flow side and the reheater side. The parameters in the two documents correspond one-to-one and can be directly used to guide on-site construction.

[0006] Furthermore, the bidirectional iterative adjustment of the collaborative matching solution module is performed according to the following steps: The first step is to adjust the enthalpy drop distribution scheme of the last stage group of the high-pressure cylinder based on the rated heating condition as the initial benchmark, and output the corresponding high-pressure cylinder exhaust parameters. This condition is the condition with the highest proportion of unit operation throughout the year. Starting from this condition can reduce the overall number of iterations. The second step is to input the exhaust steam parameters into the reheater thermodynamic characteristic calculation model to calculate the reheater heat transfer coefficient, outlet steam temperature and flow resistance values ​​under the corresponding operating conditions. The third step is to compare the deviation between the calculation results and the optimization target. If the deviation exceeds the allowable range, the thermodynamic impedance parameters of the corresponding tube group of the reheater are adjusted in reverse. At the same time, the enthalpy drop distribution scheme on the flow side is corrected. The reheater adjustment methods include locally changing the transverse pitch of the tube bank and adding or removing a small number of heat exchange pipes. The flow adjustment methods include fine-tuning the stationary vane installation angle and slightly changing the local flow area. Fourth, repeat steps two and three until the parameter matching degree under all operating conditions reaches the preset threshold, and output the final flow adjustment parameters and reheater adjustment parameters.

[0007] Furthermore, the bidirectional iteration of the collaborative matching solution module takes the overall collaborative optimization objective function as the iteration direction, and the overall collaborative optimization objective function is: In the formula, The total objective function value; This represents the maximum deviation between the reheater outlet steam temperature and the rated value under all operating conditions. The percentage decrease in efficiency after the modification of the flow stage group; This represents the percentage increase in flow resistance after the reheater modification. , , These are the weighting coefficients corresponding to steam temperature deviation, flow efficiency, and flow resistance increment, respectively. They are preset according to the focus of the modification. When focusing on steam temperature stability, the weight of the steam temperature deviation item can be increased, and when focusing on flow efficiency, the weight of the efficiency item can be increased.

[0008] Furthermore, during the bidirectional iteration of the collaborative matching solution module, the adjustment range of the enthalpy drop of the flow path in a single iteration does not exceed the preset proportion corresponding to the enthalpy drop value of the previous round, and the adjustment range of the reheater thermal impedance in a single iteration does not exceed the preset proportion corresponding to the impedance value of the previous round. Setting a step size limit can avoid excessive adjustment range in a single iteration, which may cause the iteration results to oscillate and diverge, and ensure that the calculation process converges smoothly.

[0009] Furthermore, the parameter matching degree of the collaborative matching solution module is quantitatively determined by the flow-reheater parameter matching degree calculation formula, which is: In the formula, The parameter matching degree between the flow path and the reheater is 0 to 1; The total number of typical operating conditions participating in the verification; For the first A typical working condition; For the first Under each operating condition, the reheater tube mass flow rate corresponding to the current flow and exhaust parameters; For the first Under each operating condition, the design value of the in-tube mass flow rate corresponding to the optimal heat exchange efficiency of the reheater is determined. The closer the matching degree value is to 1, the higher the degree of adaptation between the parameters on both sides.

[0010] Furthermore, it also includes a staged steam extraction and coordinated distribution module; the staged steam extraction and coordinated distribution module is equipped with bypass pipe groups connected to the corresponding temperature section of the reheater for heating steam extraction ports of different pressure levels. The bypass connection position matches the pressure level of the corresponding steam extraction port to reduce energy loss caused by steam throttling; the module collects the flow rate data of heating steam extraction at each level in real time. When the steam extraction volume of a certain level changes, the steam flow compensation amount of the corresponding bypass pipe group is adjusted according to the steam extraction enthalpy value. The larger the steam extraction volume, the larger the flow compensation amount of the corresponding pipe group, controlling the steam flow velocity of each pipe section of the reheater to be within the preset design range.

[0011] Furthermore, it also includes a thermal stress collaborative management and control module; the thermal stress collaborative management and control module has a built-in coupled thermal stress calculation model of the flow path components and the reheater tube wall. When the heating steam extraction rate changes abruptly, a gradient extraction valve opening adjustment strategy is adopted to control the temperature change rate of the flow path to match the temperature rise or fall rate of the reheater tube wall, so as to avoid sudden changes in the equipment temperature caused by sudden changes in the steam extraction rate and reduce the risk of metal fatigue damage; at the same time, the desuperheating water flow rate at the reheater inlet is adjusted synchronously to compensate for the thermal expansion difference between the two.

[0012] Furthermore, the adjustment process of the thermal stress collaborative control module satisfies the thermal stress collaborative constraint inequality, which is: In the formula, The temperature change rate of the flow stage components; This represents the allowable rate of temperature change of the reheater tube wall; The safety matching coefficient ranges from 0.8 to 1.0, and is set according to the equipment material and service life. The upper limit can be used when the equipment of a new unit is in good condition, while the lower limit can be used for units with a long service life and signs of aging, so as to reserve a safety margin.

[0013] Furthermore, it also includes a coupled digital twin simulation module; the coupled digital twin simulation module incorporates multiple physical field parameters such as steam thermodynamics, flue gas heat exchange, structural stress, and thermal fatigue to construct a coupled simulation model of the turbine flow path and the boiler reheater; during the retrofit design phase, it simulates the coordinated operation under pure condensing rated conditions, maximum heating conditions, minimum heating conditions, and low-load heating conditions, and automatically iteratively verifies the flow path adjustment parameters and reheater retrofit parameters; The iterative convergence condition is that the reheater outlet steam temperature deviation, the efficiency reduction of the flow stage group, and the flow resistance increment of the reheater tube group all meet the preset limits. Iterative convergence is determined when all three indicators are met simultaneously. The three indicators correspond to the three core operating dimensions of steam temperature quality, flow efficiency, and fan energy consumption, respectively, which can comprehensively verify the overall performance of the modification scheme.

[0014] Compared with existing technologies, this turbine flow path and boiler reheater co-modification system adapted to high-pressure heating upgrades has the following advantages: I. This invention establishes a bidirectional coupling mapping relationship between the enthalpy drop distribution of the flow stage group and the thermal impedance of the reheater heating surface. It uses a bidirectional iterative approach to complete the coordinated matching of the modification parameters on both sides, replacing the traditional single-direction parameter docking modification design mode of separate disciplines. Parameter adaptation can be achieved in the design stage across the entire operating range, ensuring that the reheater is in a reasonable heat exchange range under different heating steam extraction rates. This reduces unnecessary expansion of the heating surface and replacement of flow components, thereby reducing the amount of engineering work and investment costs of the modification, and also reducing the fluctuation range of reheat steam temperature under all operating conditions.

[0015] Second, this invention covers the entire process from retrofit design to operation control by setting up a series of collaborative mechanisms such as graded extraction steam flow distribution, thermal stress collaborative management and control, and multi-physics field coupling simulation. It can adapt to various operating scenarios such as dynamic fluctuations in heating load and switching between pure condensing and heating modes. While maintaining stable reheat steam temperature, it reduces the thermal stress impact on equipment caused by sudden changes in extraction steam volume. It can also avoid the problem of single-condition compliance but other condition parameters exceeding limits through full-condition simulation verification, making the retrofitted unit operate more smoothly and maintain good economic performance in long-term operation.

[0016] Other advantages, objectives and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from an examination of the following, or may be learned from the practice of the invention. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0018] Figure 1 This is a schematic diagram of the overall module architecture and data flow of the collaborative transformation system of the present invention; Figure 2 This is a schematic diagram of the bidirectional iterative calculation process of the collaborative matching solution module of the present invention; Figure 3 This is a schematic diagram of the collaborative management and control process for unit operation after the modification of this invention. Detailed Implementation

[0019] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0020] This embodiment selects a high-pressure heating upgrade project of a 300MW subcritical coal-fired unit as a practical case study, such as... Figure 1As shown, the entire system consists of four core units: a flow parameter modeling module, a reheater thermodynamic impedance calculation module, a collaborative matching solution module, and a modification scheme output module. It is also equipped with a staged extraction steam collaborative allocation module, a thermal stress collaborative control module, and a coupled digital twin simulation module to complete the supporting control on the operation side. The entire system breaks away from the conventional practice of designing and modifying the turbine and boiler separately. It completes the bidirectional matching of parameters on both sides of the turbine flow and boiler reheater during the design stage, reducing the workload of on-site modification, and at the same time keeping the reheat steam temperature stable under various heating conditions of the unit.

[0021] After the entire system is started, the flow parameter modeling module is run first. This module needs to collect two types of basic data. The first type is the original design data of the flow path at each stage of the unit's high-pressure cylinder, including the flow area of ​​each stage, the stationary vane installation angle, the single-stage design enthalpy drop, the rated operating condition exhaust pressure, and the rated operating condition exhaust temperature. The second type is the actual operating records of the unit over the past 12 months, filtering out abnormal data during unit start-up and shutdown periods and equipment failures, and extracting the measured values ​​of pressure, temperature, and flow efficiency at each stage under stable operating conditions. This modification requires the addition of two types of heating steam extraction, with extraction pressures of 2.5 MPa and 1.0 MPa respectively, and a maximum total steam supply flow rate of 180 t / h for the unit. The module uses the Vlugel stage variable operating condition calculation method to build a flow stage variable operating condition calculation model. It selects four extraction steam flow rates of 0t / h, 60t / h, 120t / h and 180t / h to carry out step-by-step calculations, covering the entire range from pure condensing operation to full load heating of the unit. It calculates the range of high-pressure cylinder exhaust parameters and the adjustable range of enthalpy drop at each stage corresponding to different extraction steam flow rates.

[0022] The calculations yielded a high-pressure cylinder exhaust temperature range of 315℃ to 345℃ and an exhaust pressure range of 3.8MPa to 4.6MPa. The adjustable range of the enthalpy drop in the last four stages of the high-pressure cylinder flow path is 3% to 8%. The reason for prioritizing the adjustment of the last four stages of the high-pressure cylinder is that this enthalpy drop accounts for a higher proportion of the overall system performance. Modification can quickly change the steam state at the cylinder outlet, and the modification will not significantly reduce the overall flow path efficiency. This is a lower-cost adjustment area for on-site modification. The above numerical range will be used as the flow path boundary conditions for subsequent collaborative matching calculations.

[0023] While the flow parameter modeling module is running, the reheater thermodynamic impedance calculation module is simultaneously activated. This module collects structural data for all tube groups in both the low-temperature and high-temperature reheaters, including the inner diameter of individual pipes, wall thickness, total number of tubes in the overall tube bank, transverse pitch, longitudinal pitch, and total area of ​​the heating surface in a single section. Simultaneously, it retrieves measured data from the unit's historical operating records, including inlet and outlet pressure differences and outlet steam temperatures corresponding to different inlet steam flow rates and temperatures, to calibrate the module's internal calculation model. The module combines the in-tube convection heat transfer formula and the pipe friction resistance calculation formula to build a reheater thermodynamic characteristic calculation model. It calculates the flow resistance, in-tube convection heat transfer coefficient, and outlet steam temperature variation patterns for each tube section under different inlet steam conditions. Through fitting multiple sets of operating conditions, it derives the in-tube mass flow velocity range corresponding to the optimal heat transfer effect of the reheater.

[0024] The optimal in-tube mass flow velocity range was calculated to be 280 kg / (m²·s) to 360 kg / (m²·s). This range was derived by fitting the erosion resistance and convective heat transfer characteristics of the reheater tubes, taking into account both heat transfer efficiency and tube wall wear rate. It represents a universally optimal flow velocity range for reheaters of the same parameter class. If the in-tube flow velocity exceeds the upper limit of the range, the pipe resistance will increase rapidly, increasing fan power consumption; if the flow velocity is below the lower limit of the range, the heat transfer coefficient will decrease significantly, and the reheated steam temperature will fail to meet design standards. This flow velocity range serves as the reheater side boundary condition for the collaborative matching calculation.

[0025] After both modules complete their data output, all calculated data is sent to the collaborative matching solution module for bidirectional matching calculations. The collaborative matching solution module establishes a bidirectional coupling mapping relationship between the enthalpy drop distribution of the flow stage group and the thermal impedance of the reheater heating surface. Unlike traditional methods that only perform unidirectional parameter docking, this module uses the cylinder outlet steam flow rate, temperature, and pressure calculated from the flow stage as the input for reheater calculations. At the same time, it transmits the reasonable resistance range required by the reheater back to the flow stage calculation. The parameters on both sides are adjusted synchronously and mutually constrained. Through multiple iterations, the modification parameters suitable for all operating conditions are calculated.

[0026] The bidirectional iterative operation within the collaborative matching solution module is divided into four fixed steps, such as... Figure 2 As shown: The first step is to select the rated heating condition as the initial benchmark for iterative calculations, adjust the enthalpy drop distribution scheme of the last stage group of the high-pressure cylinder, and calculate the corresponding exhaust parameters of the high-pressure cylinder. The rated heating condition is chosen as the starting point because the unit operates under this condition for the longest time throughout the year. Using this as the starting point can reduce the overall number of iterations and shorten the calculation time.

[0027] The second step is to import the exhaust steam parameters calculated in the first step into the reheater thermodynamic characteristic calculation model to calculate the reheater heat transfer coefficient, outlet steam temperature, and pipeline flow resistance under the corresponding operating conditions, and simultaneously check whether the current mass flow rate in the pipe falls within the optimal range.

[0028] The third step is to compare the difference between the result calculated in the second step and the preset optimization target. If the difference exceeds the allowable range, two adjustments are performed simultaneously: one is to modify the thermal impedance of the corresponding tube group of the reheater, and the adjustment method includes locally changing the transverse pitch of the tube bank and slightly adding or removing heat exchange pipes; the other is to correct the enthalpy drop distribution of each stage of the high-pressure cylinder flow, and the adjustment method includes fine-tuning the stationary vane installation angle and slightly changing the local flow area.

[0029] Fourth, repeat steps two and three until all operating parameters reach the preset threshold for matching, and output the final flow modification parameters and reheater modification parameters.

[0030] The iterative calculation process sets an upper limit for the adjustment range per cycle. The single adjustment of the enthalpy of the flow path cannot exceed 5% of the value of the previous cycle, and the single adjustment of the reheater thermal impedance cannot exceed 8% of the value of the previous cycle. This ratio is determined by the balance between iterative stability and computational efficiency. Too large a step size can easily lead to oscillations and divergence in the iteration results, while too small a step size will significantly increase the number of iterations. This range is a general empirical value for the optimization iteration of thermal systems, which is suitable for the bidirectional coupled calculation in this scenario. Setting an upper limit for the range is to prevent the single change value from being too large, which would cause the iterative calculation to fail to converge, and to ensure that the calculation results change smoothly in each cycle.

[0031] The optimization direction is determined entirely by the overall objective function of collaborative optimization, as shown in the following expression: In the formula, The total objective function value; This represents the maximum deviation between the reheater outlet steam temperature and the rated value under all operating conditions. The percentage decrease in efficiency after the modification of the flow stage group; This represents the percentage increase in flow resistance after the reheater modification. , , These are the weighting coefficients corresponding to steam temperature deviation, flow efficiency, and flow resistance increment, which are preset according to the focus of the modification requirements.

[0032] The weighting coefficients typically range from 0.2 to 0.5, with the sum of the three values ​​being 1. These values ​​are derived from statistical data and engineering experience of similar unit retrofits and can be flexibly adjusted based on the core retrofit objectives. If the retrofit prioritizes steam temperature stability, the weighting coefficients can be increased. If more attention is paid to flow efficiency loss, it can be improved. In this case, the priority is to ensure stable steam temperature, and the following settings are implemented. =0.4, =0.35, =0.25, the sum of the three values ​​equals 1.

[0033] After each iteration, the degree of parameter matching between the flow-reheater and the reheater is determined by the following formula: In the formula, The parameter matching degree between the flow path and the reheater is 0 to 1; The total number of typical operating conditions participating in the verification; For the first A typical working condition; For the first Under each operating condition, the reheater tube mass flow rate corresponding to the current flow and exhaust parameters; For the first The design value of the in-tube mass flow rate corresponding to the optimal heat exchange efficiency of the reheater under each operating condition.

[0034] Four typical operating conditions were selected for verification, with a matching degree threshold set at 0.95. This threshold was determined based on the acceptable range of heat exchange efficiency deviation in engineering applications. When the matching degree reaches 0.95, the deviation between the actual heat exchange efficiency of the reheater and the optimal value under all operating conditions can be controlled within 3%, meeting engineering requirements and falling under the general design criteria in the field of thermal power retrofitting. Calculated values ​​higher than this threshold indicate that the parameter adaptation meets engineering requirements.

[0035] This case study completed 12 rounds of iterative calculations, achieving a final matching degree of 0.962, reaching the preset threshold. The determined modifications and adjustments were: the installation angle of the ninth to twelfth stage stator vanes in the high-pressure cylinder was adjusted from -2° to +3°, and the enthalpy drop of each stage was adjusted by 4% to 7%; the transverse pitch of the third to fifth rows of pipes in the cryogenic reheater was increased by 5%. The entire adjustment scheme did not require replacing all flow vanes or the entire reheater tube bank, significantly reducing the on-site modification workload.

[0036] After all matching calculations are completed, the data is transferred to the modification scheme output module. The modification scheme output module integrates all adjustment values ​​to generate a complete collaborative modification technical document, which is divided into two parts: flow path modification data and reheater modification data. The flow path modification data includes adjustment values ​​for the installation angles of each stage of stationary blades, the dimensions of the heating extraction steam outlet positions, and a comparison table of enthalpy drop adjustments for each stage. The reheater modification data includes the tube pitch adjustment scheme, bypass piping layout drawings, and a checklist of thermal parameters for each operating condition. The parameters in the two documents correspond one-to-one, allowing on-site construction personnel to directly carry out modification work according to the documents.

[0037] After the unit's retrofit was completed and put into operation, the staged extraction steam coordinated distribution module, the thermal stress coordinated control module, and the coupled digital twin simulation module were simultaneously put into operation and control. The entire set of operation-side coordinated logic forms a complete closed loop, such as... Figure 3 As shown.

[0038] The staged steam extraction and distribution module is equipped with independent bypass pipelines for the 2.5MPa and 1.0MPa steam extraction ports. The 2.5MPa extraction steam is taken from the pipeline after the fifth stage of the high-pressure cylinder and bypassed to the medium-temperature section of the reheater; the 1.0MPa extraction steam is taken from the pipeline after the seventh stage of the high-pressure cylinder and bypassed to the low-temperature section of the reheater. The bypass connection location and extraction steam pressure are kept close to each other to reduce energy loss caused by steam throttling. The module continuously collects the real-time flow rate of the two heating steam sources. When the flow rate of either source changes, the opening of the bypass pipeline valve is adjusted proportionally according to the extraction steam enthalpy value. As the extraction steam flow rate increases, the bypass supplementary steam flow rate increases synchronously. The logical principle is that after the extraction steam rate increases, less steam enters the main pipeline of the reheater, and the flow velocity in the pipe decreases. By relying on the bypass supplementary steam, the flow velocity in each section of the pipeline can be maintained within a reasonable range.

[0039] In this case study, a reasonable flow velocity range for the pipeline was set at 15 m / s to 25 m / s. This range was determined based on the balance between pipeline wear rate and resistance loss. Excessive flow velocity would exacerbate pipe wall erosion and wear, while insufficient flow velocity would result in inadequate heat exchange. This range falls within the standard design flow velocity range for power plant steam pipelines. Synchronous valve adjustment prevents the occurrence of two problems: excessively high flow velocities causing pipe wall erosion in certain areas, and excessively low flow velocities leading to poor heat exchange.

[0040] The thermal stress collaborative management module is equipped with a coupled thermal stress calculation model for flow-through components and reheater tube walls. Input data includes the metal materials of the two types of equipment, tube wall thickness, unit operating time, and maintenance records over the years. When there are short-term and significant changes in the steam extraction flow rate, the module will not instantly open or close the extraction valves completely. Instead, it adopts a gradient valve opening adjustment method to control the heating and cooling rates of the flow-through metals and the reheater tube walls to maintain a match. At the same time, it simultaneously fine-tunes the desuperheating water flow rate at the reheater inlet to offset the additional pipeline stress caused by the inconsistent thermal expansion of the two types of equipment.

[0041] The entire adjustment process needs to satisfy the thermal stress synergistic constraint inequality, as follows: In the formula, The temperature change rate of the flow stage components; This represents the allowable rate of temperature change of the reheater tube wall; This is a safety matching coefficient, ranging from 0.8 to 1.0, set according to the equipment's material and service life. =0.9 Reserve a 10% safety margin to control the rate of change of flow temperature to not exceed 90% of the reheater's allowable rate, thereby reducing the probability of cracking caused by long-term alternating stress in the pipe weld.

[0042] The coupled digital twin simulation module integrates four types of parameters—steam thermodynamics, flue gas heat exchange, structural stress, and thermal fatigue—to build coupled simulation models of the turbine and boiler. Before all modification parameters are finalized, four typical operating conditions are simulated: pure condensing rated operating condition, maximum heating condition, minimum heating condition, and low-load heating condition. The system automatically verifies the operational effects of the modification parameters under each condition. Model iteration convergence requires simultaneous satisfaction of three criteria: the maximum deviation of the reheater outlet steam temperature does not exceed ±3℃, the efficiency decrease after flow path modification does not exceed 1%, and the increase in pipeline resistance after reheater modification does not exceed 5%. Only when all three criteria are met is the modification parameter considered qualified. These three limits are taken from the conventional acceptance indicators for heating system modifications of units of the same capacity, balancing modification effectiveness with equipment safety margins. In this case, all four simulated operating conditions met the convergence criteria, and there were no instances of excessively high steam temperature in the pure condensing condition or insufficient steam temperature in the heating condition.

[0043] This case study demonstrates how a complete system integrates parameters on both the turbine and boiler sides from the design stage, eliminating operational problems arising from separate modifications relying solely on individual rated parameter connections. Actual measurement data after the unit's modification showed an average increase of over 8% in reheater heat exchange efficiency across all heating extraction sections, with reheat steam temperature fluctuations controlled within ±3℃, and a decrease in coal consumption for power generation under heating conditions. This system is not limited to 300MW subcritical units; it can be used in conjunction with various coal-fired units of different capacities and steam parameters for cogeneration modifications and boiler heating surface optimization.

[0044] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A turbine flow path and boiler reheater co-modification system adapted to high-pressure heating upgrades, characterized in that, The system includes a flow parameter modeling module, a reheater thermodynamic impedance calculation module, a collaborative matching solution module, and a modification scheme output module; The flow parameter modeling module is used to collect the original design parameters and historical operating data of each stage of the high-pressure cylinder of the unit to be modified. Combined with the parameter level and flow range of the newly added heating steam extraction, it constructs a variable operating condition calculation model of the flow stage group and outputs the high-pressure cylinder exhaust parameter range and the adjustable range of enthalpy drop of each stage under different heating steam extraction volumes. The reheater thermal impedance calculation module is used to collect the tube group structural parameters and historical operating data of the boiler reheater, construct a reheater thermal characteristic calculation model, and output the tube group flow resistance, heat transfer coefficient and outlet steam temperature variation law under different inlet steam parameters. The collaborative matching solution module is used to establish a two-way coupled mapping relationship between the enthalpy drop distribution of the flow stage group and the thermodynamic impedance of the reheater heating surface. With the optimization goal of the optimal heat exchange efficiency of the reheater and the minimum outlet steam temperature deviation under all operating conditions, the module iteratively adjusts the enthalpy drop distribution scheme of the flow stage group and the thermodynamic impedance parameters of the reheater tube group in both directions until the parameter matching degree of the two meets the preset threshold. The modification scheme output module is used to generate a collaborative modification technical document that includes modification parameters for the flow side and modification parameters for the reheater side.

2. The turbine flow path and boiler reheater coordinated retrofit system for high-pressure heating upgrades according to claim 1, characterized in that, The bidirectional iterative adjustment of the collaborative matching solution module is performed according to the following steps: The first step is to adjust the enthalpy drop distribution scheme of the last stage group of the high-pressure cylinder based on the rated heating conditions as the initial benchmark, and output the corresponding exhaust parameters of the high-pressure cylinder. The second step is to input the exhaust steam parameters into the reheater thermodynamic characteristic calculation model to calculate the reheater heat transfer coefficient, outlet steam temperature and flow resistance values ​​under the corresponding operating conditions. The third step is to compare the deviation between the calculation results and the optimization target. If the deviation exceeds the allowable range, the thermodynamic impedance parameters of the corresponding tube group of the reheater are adjusted in reverse, and the enthalpy drop distribution scheme on the flow side is corrected at the same time. Fourth, repeat steps two and three until the parameter matching degree under all operating conditions reaches the preset threshold, and output the final flow adjustment parameters and reheater adjustment parameters.

3. The turbine flow path and boiler reheater coordinated retrofit system for high-pressure heating upgrades according to claim 2, characterized in that, The bidirectional iteration of the collaborative matching solution module takes the overall collaborative optimization objective function as the iteration direction. The overall collaborative optimization objective function is: In the formula, The total objective function value; This represents the maximum deviation between the reheater outlet steam temperature and the rated value under all operating conditions. The percentage decrease in efficiency after the modification of the flow stage group; This represents the percentage increase in flow resistance after the reheater modification. , , These are the weighting coefficients corresponding to steam temperature deviation, flow efficiency, and flow resistance increment, which are preset according to the focus of the modification requirements.

4. The turbine flow path and boiler reheater coordinated retrofit system for high-pressure heating upgrades according to claim 2, characterized in that, During the bidirectional iteration of the collaborative matching solution module, the adjustment range of the flow enthalpy drop in a single iteration does not exceed the preset proportion corresponding to the enthalpy drop value of the previous round, and the adjustment range of the reheater thermal impedance in a single iteration does not exceed the preset proportion corresponding to the impedance value of the previous round.

5. A turbine flow path and boiler reheater co-modification system adapted to high-pressure heating upgrades, as described in claim 2, is characterized in that... The parameter matching degree of the collaborative matching solution module is quantitatively determined by the flow-reheater parameter matching degree calculation formula, which is: In the formula, The parameter matching degree between the flow path and the reheater is 0 to 1; The total number of typical operating conditions participating in the verification; For the first A typical working condition; For the first Under each operating condition, the reheater tube mass flow rate corresponding to the current flow and exhaust parameters; For the first The design value of the in-tube mass flow rate corresponding to the optimal heat exchange efficiency of the reheater under each operating condition.

6. A turbine flow path and boiler reheater co-modification system adapted to high-pressure heating upgrades, as described in claim 1, is characterized in that... The system also includes a staged steam extraction and coordinated distribution module; the staged steam extraction and coordinated distribution module is equipped with bypass pipe groups connected to the corresponding temperature section of the reheater for heating steam extraction ports of different pressure levels; the module collects the flow rate data of heating steam extraction at each level in real time, and when the steam extraction volume of a certain level changes, it adjusts the steam flow compensation amount of the corresponding bypass pipe group according to the steam extraction enthalpy value ratio. The larger the steam extraction volume, the larger the flow compensation amount of the corresponding pipe group, so as to control the steam flow rate of each pipe section of the reheater to be within the preset design range.

7. A turbine flow path and boiler reheater co-modification system adapted to high-pressure heating upgrades, as described in claim 1, is characterized in that... The system also includes a thermal stress collaborative management module; the thermal stress collaborative management module has a built-in coupled thermal stress calculation model of the flow path components and the reheater tube wall. When the heating extraction steam rate changes abruptly, a gradient extraction steam valve opening adjustment strategy is adopted to control the temperature change rate of the flow path to match the temperature rise or fall rate of the reheater tube wall; at the same time, the desuperheating water flow rate at the reheater inlet is adjusted synchronously to compensate for the thermal expansion difference between the two.

8. A turbine flow path and boiler reheater co-modification system adapted to high-pressure heating upgrades, as described in claim 7, is characterized in that... The adjustment process of the thermal stress collaborative control module satisfies the thermal stress collaborative constraint inequality, which is: In the formula, The temperature change rate of the flow stage components; This represents the allowable rate of temperature change of the reheater tube wall; The safety matching coefficient ranges from 0.8 to 1.0, and is set according to the equipment material and service life.

9. A turbine flow path and boiler reheater co-modification system adapted to high-pressure heating upgrades, as described in claim 1, is characterized in that... The system also includes a coupled digital twin simulation module; the coupled digital twin simulation module incorporates multiple physical field parameters such as steam thermodynamics, flue gas heat exchange, structural stress, and thermal fatigue to construct a coupled simulation model of the turbine flow path and the boiler reheater; during the retrofit design phase, it simulates the coordinated operation under pure condensing rated conditions, maximum heating conditions, minimum heating conditions, and low-load heating conditions, and automatically iteratively verifies the flow path adjustment parameters and reheater retrofit parameters; The iterative convergence condition is that the reheater outlet steam temperature deviation, the efficiency reduction of the flow stage group, and the flow resistance increment of the reheater tube group all meet the preset limits. Iterative convergence is determined when all three indicators are met simultaneously.

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