A numerical simulation method for hydraulic transient process of a pressure regulating device

Abstract

The application discloses a kind of numerical simulation methods of hydraulic transient process of pressure regulating equipment, belong to the technical field of hydraulic transient process calculation of water conservancy and hydropower engineering, this method includes: system parameter input, calculation grid division and initial condition setting, pipe characteristic line method solution, impedance hole flow calculation, water level and air chamber state coupling calculation, gas dynamics calculation of air inlet hole, boundary simultaneous solution, time step and result output eight steps.The application realizes the high-precision numerical simulation of hydraulic transient process by establishing the dynamic mathematical model of impedance hole and air inlet hole and the boundary closed equation set of gas-liquid two-phase strong coupling, and provides an effective numerical analysis tool for the design optimization of new intelligent.

Description

Technical Field

[0001] This invention belongs to the field of hydraulic transition process calculation technology in water conservancy and hydropower engineering, and specifically relates to a numerical simulation method for the hydraulic transition process of pressure regulating equipment. Background Technology

[0002] In long-distance diversion hydropower stations, pumped storage power stations, and long-distance water conveyance projects, it is an important water hammer protection facility. When the unit load changes suddenly or valves are opened or closed, water hammer pressure fluctuations are generated in the pipeline. The rise and fall of the water level reflects the water hammer wave, absorbs or releases water, thereby reducing the amplitude of pressure fluctuations in the pipeline and ensuring the safe operation of the system.

[0003] Traditional calculations of hydraulic transient processes primarily target open systems, where the top is directly connected to the atmosphere and the air pressure is constant at atmospheric pressure. The calculation method typically employs the method of characteristics to solve for unsteady flow in the pipe, simultaneously solving the water level continuity equation and the impedance orifice head loss equation at the boundary.

[0004] However, existing technologies have the following shortcomings: First, traditional fixed structure decoupling algorithms use alternating weak coupling of hydraulic and gas processes to solve the problem, ignoring the bidirectional coupling effect between water and gas, and only support fixed orifice sizes, resulting in calculation errors of over 8% for water level and pressure under multiple operating conditions; Second, existing air cushion pressure regulating inlet orifices use piecewise functions to distinguish between subsonic and sonic airflow, with iterative oscillations at the flow critical point and a fixed constant for the polytropic exponent throughout the process, making it unable to match the two operating conditions of rapid compression with load shedding and long-term slow heat exchange; Third, there is currently no integrated time-series simulation mathematical model for two-stage water level feedback impedance and three-stage air pressure feedback inlet, lacking a multi-physics field simultaneous closed solution framework, which cannot support the optimization of intelligent structures and control strategies.

[0005] Therefore, there is an urgent need to develop a numerical method that can accurately simulate the hydraulic transient process of a pressure regulating device to support new designs and optimizations, and improve the accuracy and economy of engineering design. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing a numerical simulation method for the hydraulic transient process of pressure regulating equipment. This method fully reproduces the impedance and dynamic timing of the air inlet, enables strong coupling and simultaneous solution of multiple water and air fields, improves the simulation accuracy of surge waves and air chamber pressure, and provides a simulation tool for intelligent adjustable optimization.

[0007] To achieve the above objectives, the present invention provides a numerical simulation method for the hydraulic transient process of a pressure regulating device, comprising the following steps: S1. Collect all geometric dimensions, structural materials, and fluid properties of the upstream water diversion pipeline, downstream pressure pipeline, adjustable air cushion, water body, and air to construct a global parameter library, and output all parameters synchronously to S2, S3, S4, S5, and S6. S2. Based on the Courant stability criterion, divide the pipeline spatial step size and simulation time step size, discretize the upstream and downstream pipeline segments, assign initial head, rated steady-state flow rate, initial water level, initial air chamber pressure and volume to the pipeline, and output the discrete mesh and time step parameters to S3. S3. Use the C+ and C- characteristic line method to solve the instantaneous head and instantaneous flow rate of the pipeline node by node, extract the characteristic constants of the upstream and downstream boundaries and output them to S7; S4. Read the output water level of S5 in real time, dynamically update the instantaneous flow area of ​​the impedance based on the two-level water level threshold, distinguish between the two types of impedance coefficients of inlet and outlet water, calculate the instantaneous flow rate and head loss of the transect, and output the real-time flow rate of the impedance orifice to S5 and S7. S5. Simultaneously solve the continuous differential equation of water level, the geometric volume relationship of water level in air chamber, and the polytropic state equation of gas. Correct the polytropic index in real time according to the simulation heat exchange time, and output the real-time water level and absolute pressure of air chamber to S6 and S7. S6. Read the output chamber pressure of S5, update the inlet flow area according to the three-level pressure range, compare the internal and external pressure ratio with the critical pressure ratio to distinguish subsonic and sonic airflow, calculate the instantaneous mass flow rate of gas using the hyperbolic tangent smooth fusion method and output it to S7. S7 integrates the characteristic equations of the pipeline, the impedance orifice equation, the water level equation, the geometric equation of the air chamber, the gas polyvariate equation, and the intake airflow equation to construct a closed set of equations containing 8 independent unknowns; the Newton-Raphson iterative method is used to solve the unknowns of the global boundary, and dual convergence criteria of water level and pressure are set. If convergence is not achieved after reaching the maximum number of iterations, the time step is automatically halved and the solution is resolved; after the iteration converges, all state variables are updated and back to S4, S5, and S6 for iterative calculation. S8. After completing the single-time-step global coupling solution, update the pipeline and all state parameters, determine the termination condition of water level fluctuation, and after reaching the termination threshold, output the entire time history curve of pressure regulating water level, air chamber pressure, adjustable orifice area, and pipeline pressure envelope in batches.

[0008] Preferably, in S1, after collecting the pipe and fluid parameters, water hammer wave calculation is performed, and the corresponding standardized water hammer wave velocity calculation formula is: ; In the formula, The propagation speed of water hammer waves is expressed in m / s. Let be the bulk elastic modulus of water, in Pa; The density of water, in kg / m³ 3 ; The inner diameter of the pipe is in meters (m). This refers to the elastic modulus of the pipe wall, in Pa. The thickness is the pipe wall thickness, in meters (m).

[0009] Preferably, the Courant stability constraint in S2 is: ; In the formula, The time step for simulation calculation is expressed in seconds (s). This represents the spatial step length of a single section of the pipeline, in meters (m).

[0010] Preferably, the characteristic compatibility equations for C+ and C- in S3 are: The C+ feature line is represented as: ; ; In the formula, The instantaneous head at the current node; The constant of the C+ characteristic line is a single-time-step fixed value. This represents the instantaneous traffic flow of the current node. The characteristic impedance of the pipeline; The upstream characteristic node head is C+; For C+ upstream characteristic node traffic; The C-character line is represented as: ; ; In the formula, C is the characteristic line constant, a single-time-step fixed value; C - downstream characteristic node head; For C-downstream characteristic node traffic; The formula for calculating the characteristic impedance of a pipe is: ; In the formula, It is the acceleration due to gravity; This refers to the cross-sectional area of ​​the pipe for flow. The formula for calculating the pipe friction coefficient is: ; In the formula, This is the friction coefficient along the pipeline.

[0011] Preferably, in S4, the instantaneous flow area of ​​the impedance is dynamically updated based on the two-stage water level thresholds, and the instantaneous flow rate and head loss of the orifice are calculated by distinguishing between the two types of impedance coefficients: inlet and outlet. Specifically: The instantaneous flow area of ​​the impedance orifice is expressed as: ; In the formula, for Real-time flow area of ​​the impedance orifice; The initial area of ​​the impedance hole; Adjust the target area of ​​the impedance orifice; This is the trigger time for the water level threshold. The response time constant of the impedance orifice actuator; This is the curve shape coefficient; The instantaneous flow rate across the orifice is expressed as: ; In the formula, The instantaneous flow rate through the impedance orifice; The flow coefficient at the orifice of the impedance hole; The difference in water head before and after the impedance orifice; Head loss is expressed as: ; In the formula, For the head loss of the impedance orifice; Impedance coefficients for different operating conditions; If the water head difference between the upstream and downstream of the impedance orifice Water flows into the pressure regulator. If the head difference between the upstream and downstream sides of the impedance orifice Water flow out for pressure regulation ; The inlet water has a fixed impedance coefficient; This is the fixed impedance coefficient for the effluent.

[0012] Preferably, in S5, the simultaneous equations of water level continuity, the geometric volume relationship of water level in the gas chamber, and the polytropic equation of state of the gas are as follows: The water level continuity differential equation is expressed as: ; In the formula, The cross-sectional area of ​​the cylinder; The instantaneous rate of change of water level; Real-time water level; The geometric volume relationship between the air chamber water level and volume is expressed as: ; In the formula, This represents the real-time volume of the air chamber. This represents the initial volume of the air chamber; This represents the steady-state initial water level. The dynamic variability index is expressed as: ; In the formula, for The index of dynamic variability of gas at any given time; To rapidly compress the adiabatic index; The isothermal index is for slow heat transfer; This is the time constant for gas-liquid heat exchange; The polytropic equation of state for a gas is expressed as: ; In the formula, This refers to the absolute pressure within the gas chamber. This represents the initial absolute pressure of the air chamber.

[0013] Preferably, in S6, the subsonic and sonic airflows are distinguished by comparing the internal and external pressure ratios with the critical pressure ratio, using a hyperbolic tangent smoothing fusion calculation formula, specifically: The formula for calculating the critical pressure ratio is: ; In the formula, This refers to the critical pressure ratio for gas flow. The air insulation index; The formula for calculating subsonic flow rate is: ; In the formula, This refers to the subsonic gas mass flow rate; The inlet flow rate coefficient; for Real-time airflow area of ​​the air intake External atmospheric pressure; The gas constant of air; The thermodynamic temperature of the gas inside the chamber; The formula for calculating sound velocity flow rate is: ; In the formula, The mass flow rate of the gas at the speed of sound; The temperature of the gas in the gas chamber; The hyperbolic tangent smoothing fusion formula is: ; In the formula, The width of the transition interval is half the width. This refers to the mass flow rate of the gas at the air inlet. It is the hyperbolic tangent function.

[0014] Preferably, in S7, the closed system of equations contains 8 independent unknowns: Bottom water head Upstream pipeline flow Downstream pipeline flow Impedance orifice flow rate Water level Absolute pressure in the air chamber air chamber volume Inlet gas mass flow rate ; The criteria for determining iterative convergence are: ; ; The maximum number of iterations per time step is 30. If convergence is not achieved after exceeding this number of iterations, the simulation time step is halved. Solve again.

[0015] Preferably, the termination condition for determining water level fluctuation in S8 is: The peak value of water level fluctuation is reduced to less than 5% of the initial surge amplitude, or the total simulation time reaches 300~600s; The output data includes pressure regulating water level. air chamber pressure Impedance hole area Air intake area Maximum pressure envelope curve of the entire pipeline; minimum pressure envelope curve of the entire pipeline.

[0016] The present invention also provides a numerical simulation system for the hydraulic transient process of a pressure regulating device, comprising: The parameter input module is used to execute S1, input and store the geometric, material, and fluid setpoint parameters of the entire system, and synchronously distribute them to each calculation submodule. The mesh initialization module is used to execute S2, complete the pipe space discretization according to the Courant condition, and assign steady-state initial hydraulic parameters; The pipeline transient solution module is used to execute S3, solve for the instantaneous head and flow rate of the entire pipeline based on the C+ and C- characteristic line equations, and output the boundary characteristic constants; The adjustable impedance orifice calculation module is used to execute S4, read the real-time water level, dynamically update the instantaneous flow area of ​​the impedance orifice, and calculate the instantaneous flow rate across the orifice. The water-gas coupling calculation module is used to execute S5 and solve for real-time water level and gas pressure by combining water level, volume, dynamic polytropic index, and gas state equations. The adjustable air inlet airflow module is used to execute S6 and smoothly calculate the gas mass flow rate based on the instantaneous flow area of ​​the air inlet in the pressure classification. The multi-field coupling iteration module is used to execute S7, construct a closed system of equations containing 8 independent unknowns, and complete the Newton iteration to solve all boundary unknowns; The timing output module is used to execute S8, which continuously advances the simulation time and outputs all simulation timing results in batches when the termination condition is met.

[0017] Therefore, the present invention employs the above-mentioned numerical simulation method for the hydraulic transient process of a pressure regulating device. Compared with the prior art, the technical solution of the present invention has the following beneficial effects: (1) By establishing a dynamic mathematical model of the impedance hole and the air inlet hole, this invention has for the first time realized the numerical simulation of the hydraulic transition process, providing an effective numerical analysis tool for the design optimization of new intelligent systems and filling the gap in numerical simulation of existing technologies.

[0018] (2) By establishing a set of boundary closure equations with strong coupling between gas and liquid phases, this invention solves the pipe water flow, water body, gas chamber gas and air inlet gas flow simultaneously, which can accurately capture the interaction between various physical quantities and the calculation accuracy is significantly higher than that of traditional decoupling calculation methods. (3) The present invention uses a hyperbolic tangent smooth transition function to handle the flow state transformation problem of the inlet, which effectively avoids numerical oscillation caused by sudden changes in flow state and ensures the stability and convergence of numerical solution.

[0019] (4) This invention realizes gas-liquid coupling solution within the framework of traditional characteristic line method, maintains the computational efficiency of one-dimensional numerical method, and the computation time is comparable to that of traditional characteristic line method. It can meet the efficiency requirements of engineering design and has important engineering application value and economic benefits.

[0020] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0021] Figure 1 This is a flowchart of an embodiment of a numerical simulation method for the hydraulic transient process of a pressure regulating device according to the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical or scientific terms used in the present invention should have the ordinary meaning understood by those skilled in the art.

[0023] Example 1 like Figure 1 As shown, this embodiment provides a numerical simulation method for the hydraulic transient process of a pressure regulating device. It should be understood that the specific parameters, models and protocols mentioned in this embodiment are merely examples to help those skilled in the art understand the present invention, and are not intended to limit the present invention.

[0024] The present invention provides a numerical simulation method for the hydraulic transient process of a pressure regulating device, comprising the following steps: S1. Collect all geometric dimensions, structural materials, and fluid properties of upstream water diversion pipelines, downstream pressure pipelines, adjustable air cushions, water bodies, and air to construct a global parameter library and complete the conversion of basic fluid and pipeline parameters. In this step, the standardized water hammer wave velocity calculation formula is: ; In the formula, The propagation speed of water hammer waves is expressed in m / s. Let be the bulk elastic modulus of water, in Pa; The density of water, in kg / m³ 3 ; The inner diameter of the pipe is in meters (m). This refers to the elastic modulus of the pipe wall, in Pa. The thickness is the pipe wall thickness, in meters (m).

[0025] By substituting the complete set of geometric, material, and fluid properties parameters of the upstream water diversion tunnel, downstream pressure pipeline, adjustable air cushion, water body, and air into a standardized water hammer wave calculation model, the water hammer wave velocities of the two pipelines are calculated separately, and the wave velocity of the upstream tunnel is obtained. downstream pressure pipeline wave velocity All geometric, fluid, and wave velocity calculation values ​​are synchronously output to S2, S3, S4, S5, and S6.

[0026] S2. Based on the Courant fluid stability criterion, determine the spatial step size and simulation time step size, discretize the upstream and downstream pipelines into segments, assign values ​​to the steady-state head, rated flow rate, initial water level, initial pressure and volume of the air chamber, and output the discrete mesh and time step parameters.

[0027] In this step, the Courant stability constraint is: ; In the formula, The time step for simulation calculation is expressed in seconds (s). This represents the spatial step length of a single section of the pipeline, in meters (m).

[0028] Spatial discretization was performed using stability constraint formulas combined with wave velocity values ​​from two pipelines. The pipeline was divided into several calculation segments based on its total length, and a unified time step satisfying the stability conditions was selected based on the pipeline wave velocity. The initial head distribution and rated operating flow rate of the entire pipeline were given according to the system's steady-state operating conditions. All steady-state parameters, including the initial pressure regulating water level, initial gas chamber volume, and initial gas pressure, were simultaneously entered, and the discretized grid and time step parameters were transferred to S3.

[0029] S3. Construct two sets of characteristic compatibility equations, C+ and C-, solve for instantaneous head and instantaneous flow rate at each pipe node, extract upstream and downstream boundary characteristic constants, and output hydraulic boundary constraint parameters for coupling solution; In this step, the two sets of characteristic compatibility equations, C+ and C-, are specifically as follows: The C+ feature line is represented as: ; ; In the formula, The instantaneous head at the current node; The constant of the C+ characteristic line is a single-time-step fixed value. This represents the instantaneous traffic flow of the current node. The characteristic impedance of the pipeline; The upstream characteristic node head is C+; For C+ upstream characteristic node traffic; The C-character line is represented as: ; ; In the formula, C is the characteristic line constant, a single-time-step fixed value; C - downstream characteristic node head; For C-downstream characteristic node traffic; This refers to the pipe friction coefficient. The formula for calculating the characteristic impedance of a pipe is: ; In the formula, It is the acceleration due to gravity; This refers to the cross-sectional area of ​​the pipe for flow. The formula for calculating the pipe friction coefficient is: ; In the formula, This is the friction coefficient along the pipeline.

[0030] The transient head and flow rate are solved node by node using a set of double characteristic line compatibility equations; the characteristic impedances of the upstream and downstream pipelines are calculated by substituting the equations into the impedance and friction formulas respectively. With segmented friction coefficient Extracting upstream and downstream boundary characteristic constants Output the boundary hydraulic constraint parameters to S7.

[0031] S4. Read the real-time water level in real time, dynamically update the instantaneous flow area of ​​the impedance based on the two-level water level threshold, distinguish the inlet and outlet water conditions, select the corresponding impedance coefficient to calculate the instantaneous flow rate and head loss of the orifice, and transmit the real-time flow rate to S5 and S7. In this step, the instantaneous flow area of ​​the impedance orifice is expressed as: ; In the formula, for Real-time flow area of ​​the impedance orifice; The initial area of ​​the impedance hole; Adjust the target area of ​​the impedance orifice; This is the trigger time for the water level threshold. The response time constant of the impedance orifice actuator; This is the curve shape coefficient; The instantaneous flow rate across the orifice is expressed as: ; In the formula, The instantaneous flow rate through the impedance orifice; The flow coefficient at the orifice of the impedance hole; The difference in water head before and after the impedance orifice; Head loss is expressed as: ; In the formula, For the head loss of the impedance orifice; Impedance coefficients for different operating conditions; If the water head difference between the upstream and downstream of the impedance orifice Water flows into the pressure regulator. If the head difference between the upstream and downstream sides of the impedance orifice Water flow out for pressure regulation ; The inlet water has a fixed impedance coefficient; This is the fixed impedance coefficient for the effluent.

[0032] The system reads the water level at the current simulation moment in real time, compares it with the preset high and low water level thresholds, and dynamically updates the flow area of ​​the impedance orifice based on the two water level thresholds. The system distinguishes the inflow and outflow conditions according to the positive and negative water head before and after the orifice, selects the corresponding impedance coefficient to calculate the real-time flow rate, and transmits the flow rate data synchronously to S5 and S7.

[0033] S5. Simultaneously solve the continuous differential equation of water level, the geometric volume relationship of water level in the air chamber, the dynamic polyvariable exponential equation of heat exchange duration, and the polyvariable state equation of gas, and simultaneously solve the real-time water level and real-time absolute pressure of the air chamber, and output the real-time water level and air pressure to S6 and S7.

[0034] In this step, the water level continuity differential equation is expressed as: ; In the formula, The cross-sectional area of ​​the cylinder; The instantaneous rate of change of water level; This is the real-time water level.

[0035] The geometric volume relationship between the air chamber water level and volume is expressed as: ; In the formula, This represents the real-time volume of the air chamber. This represents the initial volume of the air chamber; This represents the initial steady-state water level.

[0036] The dynamic variability index is expressed as: ; In the formula, for The index of dynamic variability of gas at any given time; To rapidly compress the adiabatic index; The isothermal index is for slow heat transfer; is the time constant for gas-liquid heat exchange.

[0037] The polytropic equation of state for a gas is expressed as: ; In the formula, This refers to the absolute pressure within the gas chamber. This represents the initial absolute pressure of the air chamber.

[0038] By simultaneously solving four sets of equations—continuous water level, geometric water level in the air chamber, dynamic polytropic index, and polytropic state—the single-step water level change is obtained. The remaining volume of the air chamber is updated in real-time based on the water level, and the polytropic index is corrected in real-time according to the simulation duration. The current air chamber pressure is solved by simultaneously solving the polytropic state equations, and the water level and air pressure are synchronously transmitted to S6 and S7.

[0039] S6. Read the real-time air chamber pressure, adaptively update the air inlet flow area according to the three-level air pressure range, compare the internal and external pressures to distinguish between subsonic and sonic airflow, use the hyperbolic tangent function to smooth and fuse the two types of flow, calculate the instantaneous mass flow rate of the gas and output it to S7. In this step, the formula for calculating the critical pressure ratio is: ; In the formula, This refers to the critical pressure ratio for gas flow. The air insulation index; The formula for calculating subsonic flow rate is: ; In the formula, This refers to the subsonic gas mass flow rate; The inlet flow rate coefficient; for Real-time airflow area of ​​the air intake External atmospheric pressure; The gas constant of air; The thermodynamic temperature of the gas inside the chamber; The formula for calculating sound velocity flow rate is: ; In the formula, The temperature of the gas in the gas chamber; The mass flow rate of the gas at the speed of sound; The hyperbolic tangent smoothing fusion formula is: ; In the formula, The width of the transition interval is half the width. This refers to the mass flow rate of the gas at the air inlet. It is the hyperbolic tangent function.

[0040] The system reads the air pressure in the chamber in real time, matches the three-level ventilation area control range of low pressure, normal pressure and high pressure, and updates the instantaneous flow area of ​​the air inlet. It compares the ratio of internal and external air pressure with the critical pressure ratio to distinguish the two airflow states. It eliminates the numerical abrupt change in flow state switching through the hyperbolic tangent weighted formula and outputs the smoothed gas mass flow rate to S7.

[0041] S7. Integrate the characteristic equations of the pipeline, the impedance orifice equation, the water level equation, the geometric equation of the air chamber, the gas polymorphism equation, and the intake airflow equation to construct a closed set of equations with 8 independent unknowns. Set dual convergence criteria of water level and pressure, and a maximum number of iterations. Use the Newton-Raphson method for iteration. If it does not converge, halve the time step. After convergence, update all state variables and backfeed to S4, S5, and S6 for iterative calculation.

[0042] In this step, the closed system of equations contains 8 independent unknowns: Bottom water head Upstream pipeline flow Downstream pipeline flow Impedance orifice flow rate Water level Absolute pressure in the air chamber air chamber volume Inlet gas mass flow rate ; The criteria for determining iterative convergence are: ; ; The maximum number of iterations per time step is 30. If convergence is not achieved after exceeding this number of iterations, the simulation time step is halved. Solve again.

[0043] Once the convergence criteria are met, the bottom head and downstream flow rate are obtained. All eight state variables are updated, and the water level, pressure, and orifice area are transmitted back to S4, S5, and S6 to start the next time step cycle.

[0044] S8. After completing the single-time-step global coupling solution, update the pipeline and all state parameters, determine the termination condition of water level fluctuation, and after reaching the termination threshold, output the entire time history curve of pressure regulating water level, air chamber pressure, adjustable orifice area, and pipeline pressure envelope in batches.

[0045] In this step, the termination condition for water level fluctuation is determined as follows: The peak value of water level fluctuation is reduced to less than 5% of the initial surge amplitude, or the total simulation time reaches 300~600s; After the simulation is completed, batch export the time series data of the entire process: pressure regulating water level change curve, air chamber pressure change curve, impedance orifice area curve, air inlet area curve, and maximum and minimum pressure envelope curves of the entire pipeline.

[0046] Therefore, the present invention employs the above-mentioned numerical simulation method for the hydraulic transient process of a pressure regulating device, which can improve the calculation accuracy and provide an effective numerical analysis tool for design and optimization.

[0047] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A numerical simulation method for the hydraulic transient process of a pressure regulating device, characterized in that, Includes the following steps: S1. Collect all geometric dimensions, structural materials, and fluid properties of the upstream water diversion pipeline, downstream pressure pipeline, adjustable air cushion, water body, and air to construct a global parameter library, and output all parameters synchronously to S2, S3, S4, S5, and S6. S2. Based on the Courant stability criterion, divide the pipeline spatial step size and simulation time step size, discretize the upstream and downstream pipeline segments, assign initial head, rated steady-state flow rate, initial water level, initial air chamber pressure and volume to the pipeline, and output the discrete mesh and time step parameters to S3. S3. Use the C+ and C- characteristic line method to solve the instantaneous head and instantaneous flow rate of the pipeline node by node, extract the characteristic constants of the upstream and downstream boundaries and output them to S7; S4. Read the output water level of S5 in real time, dynamically update the instantaneous flow area of ​​the impedance based on the two-level water level threshold, distinguish between the two types of impedance coefficients of inlet and outlet water, calculate the instantaneous flow rate and head loss of the transect, and output the real-time flow rate of the impedance orifice to S5 and S7. S5. Simultaneously solve the continuous differential equation of water level, the geometric volume relationship of water level in air chamber, and the polytropic state equation of gas. Correct the polytropic index in real time according to the simulation heat exchange time, and output the real-time water level and absolute pressure of air chamber to S6 and S7. S6. Read the output chamber pressure of S5, update the inlet flow area according to the three-level pressure range, compare the internal and external pressure ratio with the critical pressure ratio to distinguish subsonic and sonic airflow, calculate the instantaneous mass flow rate of gas using the hyperbolic tangent smooth fusion method and output it to S7. S7 integrates the characteristic equations of the pipeline, the impedance orifice equation, the water level equation, the geometric equation of the air chamber, the gas polyvariate equation, and the intake airflow equation to construct a closed set of equations containing 8 independent unknowns; the Newton-Raphson iterative method is used to solve the unknowns of the global boundary, and dual convergence criteria of water level and pressure are set. If convergence is not achieved after reaching the maximum number of iterations, the time step is automatically halved and the solution is resolved; after the iteration converges, all state variables are updated and back to S4, S5, and S6 for iterative calculation. S8. After completing the single-time-step global coupling solution, update the pipeline and all state parameters, determine the termination condition of water level fluctuation, and after reaching the termination threshold, output the entire time history curve of pressure regulating water level, air chamber pressure, adjustable orifice area, and pipeline pressure envelope in batches.

2. The numerical simulation method for the hydraulic transient process of a pressure regulating device according to claim 1, characterized in that, In S1, after collecting pipe and fluid parameters, water hammer wave calculation is performed. The corresponding standardized water hammer wave velocity calculation formula is: ； In the formula, The propagation speed of water hammer waves is expressed in m / s. Let be the bulk elastic modulus of water, in Pa; The density of water, in kg / m³ 3 ; The inner diameter of the pipe is in meters (m). This is the elastic modulus of the pipe wall, in Pa. The thickness is the pipe wall thickness, in meters (m).

3. The numerical simulation method for the hydraulic transient process of a pressure regulating device according to claim 2, characterized in that, The Courant stability constraint in S2 is: ； In the formula, The time step for simulation calculation is expressed in seconds (s). This represents the spatial step length of a single section of the pipeline, in meters (m).

4. The numerical simulation method for the hydraulic transient process of a pressure regulating device according to claim 3, characterized in that, Characteristic compatibility equations for C+ and C- in S3: The C+ feature line is represented as: ； ； In the formula, The instantaneous head at the current node; The constant of the C+ characteristic line is a single-time-step fixed value. This represents the instantaneous traffic flow of the current node. The characteristic impedance of the pipeline; The upstream characteristic node head is C+; For C+ upstream characteristic node traffic; This refers to the pipe friction coefficient. The C-character line is represented as: ； ； In the formula, C is the characteristic line constant, a single-time-step fixed value; C - downstream characteristic node head; For C-downstream characteristic node traffic; The formula for calculating the characteristic impedance of a pipe is: ； In the formula, It is the acceleration due to gravity; This refers to the cross-sectional area of ​​the pipe for flow. The formula for calculating the pipe friction coefficient is: ； In the formula, This is the friction coefficient along the pipeline.

5. The numerical simulation method for the hydraulic transient process of a pressure regulating device according to claim 4, characterized in that, In S4, the instantaneous flow area of ​​the impedance is dynamically updated based on the two-stage water level thresholds. The instantaneous flow rate and head loss of the orifice are calculated by distinguishing between the inlet and outlet impedance coefficients. Specifically: The instantaneous flow area of ​​the impedance orifice is expressed as: ； In the formula, for Real-time flow area of ​​the impedance orifice; The initial area of ​​the impedance hole; Adjust the target area of ​​the impedance orifice; This is the trigger time for the water level threshold. The response time constant of the impedance orifice actuator; This is the curve shape coefficient; The instantaneous flow rate across the orifice is expressed as: ； In the formula, The instantaneous flow rate through the impedance orifice; The flow coefficient at the orifice of the impedance hole; The difference in water head before and after the impedance orifice; Head loss is expressed as: ； In the formula, For the head loss of the impedance orifice; Impedance coefficients for different operating conditions; If the water head difference between the upstream and downstream of the impedance orifice Water flows into the pressure regulator. If the head difference between the upstream and downstream sides of the impedance orifice Water flow out for pressure regulation ; The inlet water has a fixed impedance coefficient; This is the fixed impedance coefficient for the outlet water.

6. The numerical simulation method for the hydraulic transient process of a pressure regulating device according to claim 5, characterized in that, In S5, the simultaneous equations of continuity of water level, geometric volume relationship of water level in the gas chamber, and polytropic equation of state of the gas are as follows: The water level continuity differential equation is expressed as: ； In the formula, The cross-sectional area of ​​the cylinder; The instantaneous rate of change of water level; Real-time water level; The geometric volume relationship between the air chamber water level and the air chamber is expressed as: ； In the formula, This represents the real-time volume of the air chamber. This represents the initial volume of the air chamber; This represents the steady-state initial water level. The dynamic variability index is expressed as: ； In the formula, for The index of dynamic variability of gas at any given time; To rapidly compress the adiabatic index; The isothermal index is for slow heat transfer; This is the time constant for gas-liquid heat exchange; The polytropic equation of state for a gas is expressed as: ； In the formula, This refers to the absolute pressure within the gas chamber. This represents the initial absolute pressure of the air chamber.

7. The numerical simulation method for the hydraulic transient process of a pressure regulating device according to claim 6, characterized in that, In S6, the subsonic and sonic airflows are distinguished by comparing the internal and external pressure ratios with the critical pressure ratio. A hyperbolic tangent smoothing fusion calculation formula is used, specifically: The formula for calculating the critical pressure ratio is: ； In the formula, This refers to the critical pressure ratio for gas flow. The air insulation index; The formula for calculating subsonic flow rate is: ； In the formula, This refers to the subsonic gas mass flow rate; The inlet flow rate coefficient; for Real-time airflow area of ​​the air intake vent; External atmospheric pressure; The gas constant of air; The thermodynamic temperature of the gas inside the chamber; The formula for calculating sound velocity flow rate is: ； In the formula, The mass flow rate of the gas at the speed of sound; The temperature of the gas in the gas chamber; The hyperbolic tangent smoothing fusion formula is: ； In the formula, The width of the transition interval is half the width. This refers to the mass flow rate of the gas at the air inlet. It is the hyperbolic tangent function.

8. The numerical simulation method for the hydraulic transient process of a pressure regulating device according to claim 7, characterized in that, In S7, the closed system of equations contains 8 independent unknowns: Bottom water head Upstream pipeline flow Downstream pipeline flow Impedance orifice flow rate Water level Absolute pressure in the air chamber air chamber volume Inlet gas mass flow rate ; The criteria for determining iterative convergence are: ； ； The maximum number of iterations per time step is 30. If convergence is not achieved after exceeding this number of iterations, the simulation time step is halved. Solve again.

9. The numerical simulation method for the hydraulic transient process of a pressure regulating device according to claim 8, characterized in that, The termination condition for judging water level fluctuations in S8 is: The peak value of water level fluctuation is reduced to less than 5% of the initial surge amplitude, or the total simulation time reaches 300~600s; The output data includes pressure regulating water level. air chamber pressure Impedance hole area Air intake area Maximum pressure envelope curve of the entire pipeline; minimum pressure envelope curve of the entire pipeline.

10. A numerical simulation system for the hydraulic transient process of a pressure regulating device, applied to the numerical simulation method for the hydraulic transient process of a pressure regulating device as described in any one of claims 1-9, characterized in that, include: The parameter input module is used to execute S1, input and store the geometric, material, and fluid setpoint parameters of the entire system, and synchronously distribute them to each calculation submodule. The mesh initialization module is used to execute S2, complete the pipe space discretization according to the Courant condition, and assign steady-state initial hydraulic parameters; The pipeline transient solution module is used to execute S3, solve for the instantaneous head and flow rate of the entire pipeline based on the C+ and C- characteristic line equations, and output the boundary characteristic constants; The adjustable impedance orifice calculation module is used to execute S4, read the real-time water level, dynamically update the instantaneous flow area of ​​the impedance orifice, and calculate the instantaneous flow rate across the orifice. The water-gas coupling calculation module is used to execute S5 and solve for real-time water level and gas pressure by combining water level, volume, dynamic polytropic index, and gas state equations. The adjustable air inlet airflow module is used to execute S6 and smoothly calculate the gas mass flow rate based on the instantaneous flow area of ​​the air inlet in the pressure classification. The multi-field coupling iteration module is used to execute S7, construct a closed system of equations containing 8 independent unknowns, and complete the Newton iteration to solve all boundary unknowns; The timing output module is used to execute S8, which continuously advances the simulation time and outputs all simulation timing results in batches when the termination condition is met.

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