Initial parameter generation method based on numap steady-state calculation

Abstract

The application belongs to the technical field of thermal hydraulic analysis in nuclear reactors, and proposes an initial parameter generation method based on NUMAP steady-state calculation, which comprises: obtaining a thermal hydraulic simulation system model to be initialized in NUMAP, and decomposing the model into multiple single-flow single-pressure boundary chain structure sub-models; for each single-flow single-pressure boundary chain structure sub-model, setting the gas mass fraction of each in-line component and the non-condensable gas mass fraction to 0, and setting the flow to a constant value at the flow boundary; setting the temperature of each in-line component to the average of the inlet and outlet temperatures, or linearly filling the temperature of each in-line component according to the length of the component with the inlet and outlet temperatures as the endpoints; obtaining the total friction pressure drop along the line by subtracting the total gravity pressure drop along the line from the total pressure drop along the line, linearly dividing the total friction pressure drop along the line according to the parameters, and sequentially assigning the initial pressure of the in-line component from the inlet boundary. The application can make NUMAP reach steady state as soon as possible.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal hydraulic analysis in nuclear reactors, and in particular to an initial parameter generation method based on NUMAP steady-state calculation. Background Art

[0002] Thermal-hydraulic analysis of nuclear reactors is a crucial aspect of nuclear energy engineering. Nuclear reactors involve complex thermodynamic and kinetic processes, such as heat generation, transfer, and distribution, as well as coolant flow patterns. These processes directly impact reactor safety, operational efficiency, and lifespan. Therefore, thermal-hydraulic analysis of nuclear reactors is a critical step in ensuring their safe and efficient operation. Efficient and reliable thermal analysis provides a scientific basis for reactor design, operation, and safety, improving reactor efficiency, ensuring reactor safety, and promoting the continuous development of nuclear energy technology.

[0003] Over the past few decades of nuclear power plant development, a number of thermal-hydraulic analysis programs have been developed for light water reactor design, dynamic analysis, and simulation. Among the more prominent are RELAP (USA), CATHARE (France), and ATHLET (Germany). The Nuclear Reactor Unified Modeling and Analysis Platform (NUMAP) is China's first large-scale unified modeling and simulation platform based on Modelica for the nuclear power sector. The platform adopts Modelica, the core language standard of MBSE and CPS. Under the multi-domain unified modeling framework based on Modelica, it innovatively breaks through key technologies such as the model expression and compilation and solution technology of complex thermal-hydraulic systems, and the coupled solution of multi-disciplinary heterogeneous equation systems. It solves the international difficult problem of unified compilation and solution of two-phase flow partial differential equations and differential algebraic equations. It can be used as a powerful tool for high-precision simulation of the multi-condition operating characteristics of the entire system of nuclear power plants under complex conditions such as strong coupling of multiple disciplines, strong correlation at multiple levels, and strong correlation of multiple systems. It can be applied to multiple application scenarios such as scheme design verification, system integration verification, virtual experimental simulation, monitoring and troubleshooting, operation training, twin operation, etc. of nuclear power plants and related experimental equipment.

[0004] Thermal-hydraulic simulation systems are designed to replicate and predict the behavior and performance of thermal-hydraulic systems under diverse operating conditions. For the same model, different boundary conditions are set to correspond to different operating conditions. Boundary condition parameters are typically user-defined based on actual operating conditions and may be missing or inaccurate. However, completing and verifying the self-consistency of boundary conditions is a complex and difficult challenge that is beyond the scope of this project.

[0005] Generally speaking, steady-state calculations in thermal-hydraulic simulation systems require iterative calculations starting from a given set of initial parameters until a steady state is reached. These initial parameters describe the system's state at the start of the simulation, such as the initial temperature distribution and whether the fluid is stationary or flowing. Theoretically, using steady-state values ​​as initial parameters allows the system to quickly reach stability, meaning that the ideal initial parameters are the steady-state values. However, real-time simulation systems for complex thermal-hydraulic circuits are typically hyperbolic equation systems, whose coefficients are often infused with numerous empirical engineering models. Due to their poor robustness, it is often difficult to convert these equations into elliptic equations to solve for their corresponding steady-state values ​​under specific boundary conditions.

[0006] Traditional thermal-hydraulic simulation systems perform steady-state calculations by assigning initial parameters to components along the process, or using default values. These parameters are then adjusted during operation to ensure the model operates properly. However, for complex models, adjusting the initial parameters of hundreds or even thousands of control volumes is tedious and highly dependent on user experience. Even a single incorrect parameter can cause the system to malfunction. Therefore, a method is needed to calculate a set of initial parameters based on the user-provided boundary parameters, ensuring proper software operation and rapid stabilization. Summary of the Invention

[0007] The purpose of the present invention is to provide an initial parameter generation method based on NUMAP steady-state calculation, which can calculate a set of initial parameters based on the boundary parameters filled in by the user, so that NUMAP can operate normally and reach a steady state as soon as possible, facilitating the system to perform subsequent transient simulation based on this steady state.

[0008] The present invention solves the technical problem and adopts the following technical solution:

[0009] The initial parameter generation method based on NUMAP steady-state calculation includes the following steps:

[0010] Obtain the thermal-hydraulic simulation system model to be initialized in NUMAP and decompose it into multiple single-flow single-pressure boundary chain structure sub-models;

[0011] For each single-flow single-pressure boundary chain structure sub-model, the mass gas content of each component along the process and the mass gas content of non-condensable gas are set to 0, and the flow rate is set to a constant value at the flow boundary;

[0012] Set the temperature of each component along the process to the average of the inlet and outlet temperatures, or use the inlet and outlet temperatures as endpoints and fill them linearly according to the component length as the temperature of each component along the process;

[0013] The total friction pressure drop along the path is obtained by subtracting the total gravity pressure drop along the path from the total pressure drop along the path. This pressure drop is linearly divided according to each group of parameters, and the initial pressures of the components along the path are assigned sequentially starting from the inlet boundary.

[0014] As a further optimization, after obtaining the thermal-hydraulic simulation system model to be initialized in NUMAP and decomposing it into multiple single-flow single-pressure boundary chain structure sub-models, the coolant in the first stage of the single-flow single-pressure boundary chain structure sub-model is a single-phase fluid in each component along the process and is not heated.

[0015] As a further optimization, in the single-flow single-pressure boundary chain structure sub-model, the components from the inlet to the outlet are connected in sequence, with one side being the flow boundary and the other side being the pressure boundary.

[0016] As a further optimization, the total friction pressure drop along the path is obtained by subtracting the total gravity pressure drop along the path from the total pressure drop along the path, and is linearly divided according to each group of parameters. The initial pressure of the components along the path is assigned in sequence starting from the inlet boundary, where:

[0017] The total pressure drop along the process is expressed as , the total gravity pressure drop along the way is expressed as , the total friction pressure drop along the way is expressed as ;

[0018] The total friction pressure drop along the process is ;

[0019] The total pressure drop along the is the outlet pressure value Subtract the inlet pressure value ,Right now ;

[0020] The total gravity pressure drop along the The calculation formula is: ,in , is the outlet height of the single flow and single pressure boundary chain structure sub-model, is the inlet height of the single flow and single pressure boundary chain structure sub-model;

[0021] The total friction pressure drop along the The calculation formula is: ;

[0022] in, L is the length of the flow channel; D is the diameter of the flow channel; is the coolant density; is the average flow rate of coolant; f is the friction coefficient;

[0023] Assuming coolant flow m remains unchanged, assuming that the component flow channels are all circular, the coolant flow rate , at this time the total friction pressure drop along the ,in, K is the friction pressure drop proportional coefficient.

[0024] As a further optimization, the coolant density is calculated during the calculation of the total gravity pressure drop along the process. Obtained by consulting the thermophysical properties table of water.

[0025] As a further optimization, the total friction pressure drop along the and Proportional to the total friction pressure drop along the way, that is, according to the parameters of each component Perform linear allocation.

[0026] As a further optimization, assume that there are N components along the way starting from the entry boundary. Respectively represent the number of segments, diameter, length and height of each component,

[0027] The friction pressure drop proportionality coefficient At this time, the outlet pressure of each component Set to ;

[0028] For a single component , its inlet pressure is the outlet pressure of the previous component, and the pressure inside a single component is linearly distributed with the length. , the distance from the component entrance The pressure value is .

[0029] As a further optimization, the initial pressure and temperature of each segment of each component represent the average pressure and temperature of the corresponding segment. When generating the initial parameters, the pressure and temperature at the midpoint of each segment are used instead, that is, Pick .

[0030] The beneficial effects of the present invention are: through the above-mentioned initial parameter generation method based on NUMAP steady-state calculation, first, the thermal-hydraulic simulation system model to be initialized in NUMAP is obtained, and it is decomposed into multiple single-flow single-pressure boundary chain structure sub-models; secondly, for each single-flow single-pressure boundary chain structure sub-model, the mass gas content and the mass gas content of non-condensable gas of each along-the-process component are set to 0, and the flow rate is set to a constant value at the flow boundary; then, the temperature of each along-the-process component is set to the average of the inlet and outlet temperatures, or the inlet and outlet temperatures are used as endpoints, and linear filling is performed according to the component length as the temperature of each along-the-process component; finally, the total friction pressure drop along the process is obtained by subtracting the total gravity pressure drop along the process from the total pressure drop along the process, and it is linearly divided according to each group of parameters, and the initial pressure of the along-the-process components is assigned in sequence starting from the inlet boundary. The method of the present invention can be used only when the initial steady state can be decomposed and simplified into a model with a single flow and single pressure boundary chain structure, that is, when step S1 can be implemented. Therefore, the present invention can provide reasonable and effective initial parameters, so that NUMAP can operate normally and reach a steady state as soon as possible, which facilitates the system to perform subsequent transient simulation based on this steady state. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Flowchart of the method for generating initial parameters based on NUMAP steady-state calculation in Example 1 of the present invention;

[0032] Figure 2 Schematic diagram of the steam exhaust system in Example 2 of the present invention;

[0033] Figure 3 This is a schematic diagram of the inlet flow boundary in Example 2 of the present invention;

[0034] Figure 4 Schematic diagram of the outlet pressure boundary in Example 2 of the present invention;

[0035] Figure 5 Schematic diagram of default initial parameters of the steam generator heating section in Example 2 of the present invention;

[0036] Figure 6 This is a schematic diagram of the default parameter operation results in Example 2 of the present invention;

[0037] Figure 7 This is a schematic diagram of unified filling parameters in Example 2 of the present invention;

[0038] Figure 8 This is a schematic diagram of the operation results of unified filling parameters in Example 2 of the present invention;

[0039] Figure 9 This is a schematic diagram of the operation of unified filling parameter pressure in Example 2 of the present invention;

[0040] Figure 10 This is a schematic diagram of the unified springtail parameter temperature operation in Example 2 of the present invention;

[0041] Figure 11 Schematic diagram of optimal initial parameters of the steam generator heating section in Example 2 of the present invention;

[0042] Figure 12 Schematic diagram of the operating results of the optimal initial parameters in Example 2 of the present invention;

[0043] Figure 13 This is a schematic diagram of the optimal initial parameter fluid pressure operation in Example 2 of the present invention;

[0044] Figure 14 This is a schematic diagram of the optimal initial parameter fluid temperature operation in Example 2 of the present invention;

[0045] Figure 15 This is a schematic diagram of initial parameters of a steam generation section heater generated by the initial parameter generation method based on NUMAP steady-state calculation in Example 2 of the present invention;

[0046] Figure 16 Schematic diagram of the operating results of the parameters of the initial parameter generation method based on NUMAP steady-state calculation in Example 2 of the present invention;

[0047] Figure 17 Schematic diagram of the parameter fluid pressure operation of the initial parameter generation method based on NUMAP steady-state calculation in Example 2 of the present invention;

[0048] Figure 18 Schematic diagram of the fluid temperature operation of the initial parameter generation method based on NUMAP steady-state calculation in Example 2 of the present invention. DETAILED DESCRIPTION

[0049] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations. Example 1

[0050] This embodiment provides a method for generating initial parameters based on NUMAP steady-state calculations. The flowchart is shown in Figure 1 , wherein the method comprises the following steps:

[0051] S1. Obtain the thermal-hydraulic simulation system model to be initialized in NUMAP and decompose it into multiple single-flow single-pressure boundary chain structure sub-models;

[0052] S2. For each single-flow single-pressure boundary chain structure sub-model, set the mass gas content of each component along the process and the mass gas content of non-condensable gas to 0, and set the flow rate to a constant value at the flow boundary;

[0053] S3. Set the temperature of each component along the process to the average of the inlet and outlet temperatures, or use the inlet and outlet temperatures as endpoints and fill them linearly according to the component length as the temperature of each component along the process;

[0054] S4. The total friction pressure drop along the path is obtained by subtracting the total gravity pressure drop along the path from the total pressure drop along the path. The total friction pressure drop along the path is linearly divided according to each group of parameters, and the initial pressure of the components along the path is assigned in sequence starting from the inlet boundary.

[0055] In this embodiment, based on the NUMAP built-in example Case07_PRS, the following assumptions can be made about the usage scenario of the initial parameter generation method:

[0056] 1) In the first stage of the model, the coolant in each component along the process is a single-phase (liquid) fluid, that is, no heating is performed. Complex working condition simulations are all performed from a simple single-phase (liquid) steady state through a transient transition;

[0057] 2) The first stage of the model can be simplified as a "single flow and single pressure boundary chain structure", that is, the components are connected in sequence from the inlet to the outlet, with one side being the flow boundary and the other side being the pressure boundary;

[0058] 3) The given parameters at each boundary condition must be self-consistent and accurate. For example, the pressure and temperature parameters at the flow boundary must also be close to the ideal steady-state values.

[0059] Therefore, after obtaining the thermal-hydraulic simulation system model to be initialized in NUMAP and decomposing it into multiple single-flow single-pressure boundary chain structure sub-models, the coolant in the steady state of the first stage of the single-flow single-pressure boundary chain structure sub-model is a single-phase fluid in each component along the process and is not heated; and in the single-flow single-pressure boundary chain structure sub-model, the components from the inlet to the outlet are connected in sequence, with one side being the flow boundary and the other side being the pressure boundary.

[0060] It should be pointed out that in this embodiment, based on the single-phase assumption, for the initial parameters of the along-line components, their mass gas content and the mass gas content of non-condensable gas are both set to 0. Since there is no heating and it is a single pressure boundary, the temperature and flow rate (Kg / s) in the components do not change drastically. The temperature of the along-line components can be taken as the average of the inlet and outlet temperatures or linearly filled according to the length of the component with the inlet and outlet temperatures as endpoints. The flow parameters use the constant value at the flow boundary.

[0061] Therefore, in this embodiment, it is necessary to focus on the initial pressure setting of the components along the way.

[0062] It should be pointed out that in a stable single-phase flow system, the pressure drop between any two cross sections is composed of friction pressure drop, lifting pressure drop (gravity pressure drop) and acceleration pressure drop, namely The acceleration pressure drop can be ignored compared with the other two pressure drops, so only the friction pressure drop is considered. Gravity pressure drop .

[0063] For single-phase flow, the gravity pressure drop , the calculation is relatively easy. The friction pressure drop is calculated by Darcy's formula: ;in, L is the length of the flow channel (m); D is the diameter of the flow channel (m); is the coolant density (Kg / m 3 ); is the average flow velocity of the coolant (m / s); f is the coefficient of friction, which is difficult to determine.

[0064] Here, based on the model assumption, it can be assumed that the coolant flow rate m remains unchanged, assuming that the component flow channels are all circular, then the coolant flow rate , at this time the friction pressure drop , that is, the friction pressure drop and Directly proportional.

[0065] Therefore, the pressure values ​​at the inlet and outlet are known , , that is, the total pressure drop along the way is The total gravity pressure drop along the model can be calculated from the height difference between the inlet and outlet of the model , after ignoring the acceleration pressure drop, the total friction pressure drop along the path is , then naturally, the total friction pressure drop along the way can be calculated according to the parameters of each component Perform linear allocation.

[0066] Specifically, assuming there are N components along the way starting from the entry boundary, They represent the number of segments, diameter (m), length (m), and height (m) of each component, where the height is the difference between the outlet elevation and the inlet elevation of the component (may be a negative value), and the pressure values ​​at the inlet and outlet are , , then the friction pressure drop proportional coefficient is , and then, the outlet pressure of each component Should be set to ; For a single component , its inlet pressure is the outlet pressure of the previous component, and it can be considered that the pressure in a single component is linearly distributed with the length, so for the component , the distance from the component entrance The pressure value is .

[0067] Here, the initial pressure and temperature of each segment of each component represent the average pressure and temperature of the corresponding segment. When generating the initial parameters, the pressure and temperature at the midpoint of each segment are used as substitutes, i.e. Pick In addition, in the calculation of gravity pressure drop, the coolant density (liquid water density) This can be obtained by consulting the thermophysical properties table of water. Example 2

[0068] In Example 1, all test cases were conducted using the NUMAP development version 1.2. Given ideal boundary conditions, the Case 07_PRS example, based on NUMAP's built-in secondary-side passive residual heat removal system, compared the steady-state simulation results and stabilization times under different initial parameter settings. This example simulated three steady states: the unheated steam exhaust system steady state, the heated steam exhaust system steady state, and the steam-water natural circulation system steady state.

[0069] This embodiment focuses on the steady-state initialization before all transient operations, that is, the first steady-state: the unheated steady-state of the steam exhaust system. To this end, we establish Figure 2 Simplified model (steam exhaust system). In the subsequent experiments, the inlet flow boundary and outlet pressure boundary of the simplified model are set as follows Figure 3 and Figure 4 , where the inlet flow boundary is a constant value of 0.0262405 Kg / s, the outlet pressure boundary is 10.0717 MPa, and other boundary parameters are the steady-state values ​​that are stable under this boundary, that is, subsequent experiments are carried out under ideal boundary conditions.

[0070] For the secondary side passive residual heat removal system case Case07_PRS, the algorithm for generating initial parameters of the components along the process under ideal boundary conditions includes the following steps:

[0071] S1: Simplify the secondary side passive residual heat removal system case Case07_PRS to Figure 2 Simplified structure, i.e. steam exhaust system, which satisfies the single flow single pressure boundary chain structure model;

[0072] S2: Set the mass gas holdup and non-condensable gas holdup of components Pipe 1, Multi-way 1, Steam Generator Heating Section, Pipe 2, Multi-way 2, Pipe 3, and Pipe 4 to 0 in sequence, and set the flow rate to a constant value at the flow boundary, i.e., 0.0262405 kg / s.

[0073] S3: Linearly fill the pipes in the order of pipe 1, multi-way 1, steam generator heating section, pipe 2, multi-way 2, pipe 3, and pipe 4, taking the inlet and outlet temperatures as endpoints according to the length of each component.

[0074] In this example, the total length of the component is 6.8m, the inlet boundary temperature is 502.15K, and the outlet boundary temperature is 502.137K. The temperature difference per unit length is (502.137-502.15) / 6.8=-0.001911764705879K. For example, the length of pipe 1 is 1.2m and it is divided into 3 sections. Its inlet temperature is the inlet boundary temperature, and its outlet temperature is

[0075] 502.15-0.001911764705879*1.2=502.1477058823529K, so the three temperature values ​​are initialized to

[0076] 502.15+(502.1477058823529-502.15)*((1.2 / 3)*1 / 2 / 1.2)=502.1496176470588K

[0077] 502.15+(502.1477058823529-502.15)*((1.2 / 3)*3 / 2 / 1.2)=502.1488529411764K

[0078] 502.15+(502.1477058823529-502.15)*((1.2 / 3)*5 / 2 / 1.2)=502.1480882352941K.

[0079] S4: The total friction pressure drop along the path is obtained by subtracting the total gravity pressure drop along the path from the total pressure drop along the path. Then, according to the parameters of each component, It is linearly divided, and then the initial pressures are assigned in sequence from the inlet boundary in the order of pipe 1, multi-way 1, steam generator heating section, pipe 2, multi-way 2, pipe 3, and pipe 4.

[0080] In this example, there are 7 components to be initialized. The inlet boundary pressure is 10.1194*10^6Pa, and the outlet pressure is 10.0717*10^6Pa. By consulting the thermophysical property table of water, it can be seen that at 502.15k and 10MPa, the density of water is approximately 834.2Kg / m3 , the acceleration due to gravity is g=9.8m / s 2 , the total height of the device is 5.6m, the parameters of each component The sum of is 1.87756*10^9, so the friction pressure drop per unit length is

[0081] (10.0717*10^6-10.1194*10^6+834.2*9.8*5.6) / (1.87756*10^9)=-1.022126589829353*10^-6Pa.

[0082] For example, the length of pipe 1 is 1.2m, the diameter is 0.02m, the height is 0m, and it is divided into 3 sections. Its inlet pressure is the inlet boundary pressure, and the outlet pressure is

[0083] 10.1194*10^6-834.2*9.8*0-1.022126589829353*10^-6*(1.2 / 0.02^5)=10.11901670252881*10^6Pa, so the three temperature values ​​are initialized to

[0084] 10.1194*10^6+(10.11901670252881*10^6-10.1194*10^6)*(1.2 / 3*1 / 2 / 1.2)=10.11933611708814*10^6Pa

[0085] 10.1194*10^6+(10.11901670252881*10^6-10.1194*10^6)*(1.2 / 3*3 / 2 / 1.2)=10.11920835126441*10^6Pa

[0086] 10.1194*10^6+(10.11901670252881*10^6-10.1194*10^6)*(1.2 / 3*5 / 2 / 1.2)=10.11908058544068*10^6Pa.

[0087] Note that for a single component, its inlet temperature and pressure are the same as the outlet temperature and pressure of the previous component. For example, the inlet temperature and pressure of Multi-channel 1 are the outlet temperature and pressure of Pipe 1, which are 502.1477058823529K and 10.11901670252881*10^6Pa, respectively.

[0088] In this embodiment, the initial parameters of the components along the process are all set to the default values ​​of the software. For example, the initial parameters of the steam generator heating section are as follows: Figure 5 When all components along the process use default parameters, the software cannot run normally, and the error message is as follows Figure 6 As shown, it can be seen that in order to ensure the normal simulation of NUMAP software, it is very necessary to design a reasonable and effective initial parameter generation algorithm.

[0089] Next, in this embodiment, the initial temperature of all pipes is uniformly set to 500k, the initial pressure is uniformly set to 10MPa, and the initial inlet flow rate is uniformly set to 0Kg / s. Taking the steam generator heating section as an example, its initial parameters are as follows: Figure 7 When the components along the process use the above initial parameters, the steady-state monitoring module of the software is turned on, and the model simulation will be judged to be stable at 135.9 seconds. The running results are as follows Figure 8 shown.

[0090] Taking the steam generator heating section as an example, the pressure and temperature changes of its four sections are as follows: Figure 9 and Figure 10 As shown, from Figure 9 and Figure 10 It can be seen that although the use of unified initial parameters for all components can make the software run normally, its stabilization time is too long, which may result in failure to stabilize when transients occur, affecting further simulation of the system.

[0091] Generally speaking, the optimal method for selecting initial parameters is to use the parameters when the model reaches stability as the initial parameters. Taking the steam generator heating section as an example, the optimal initial parameters can be found in Figure 11 When the components along the process use the above optimal initial parameters and the steady-state monitoring module of the software is turned on, the model simulation will be judged to be stable at 9.18 seconds. The running results are as follows: Figure 12 As shown,

[0092] Taking the steam generator heating section as an example, the pressure and temperature changes of its four sections are as follows: Figure 13 and Figure 14 As shown by Figure 13 and Figure 14 It can be seen that under the optimal initial parameters, the time it takes for the model simulation to reach stability is extremely short, indicating that good initial parameters can indeed greatly shorten the time it takes for the model simulation to reach stability.

[0093] Therefore, in this embodiment, by consulting the thermophysical property table of water, it can be seen that at 502.15k and 10MPa, the density of water is approximately 834.2Kg / m 3 , the acceleration due to gravity is g=9.8m / s 2 , the total height of the device is 5.6m, so the total gravity pressure drop is -0.0457809MPa, and the total friction pressure drop is -0.0019191MPa. Taking the steam generator heating section as an example, the initial parameters generated by the method proposed in this embodiment are shown in Figure 15When the components along the process use the initial parameters generated by the algorithm mentioned above, the model simulation reaches stability at 9.18 seconds. The running results are as follows: Figure 16 As shown, taking the steam generator heating section as an example, the pressure and temperature changes of its four sections are as follows Figure 17 and Figure 18 shown.

[0094] Depend on Figure 17 and Figure 18 It can be seen that although the initial parameters generated using the method proposed in this embodiment do not completely match the ideal steady-state initial parameters in terms of numerical value, the changing trends of the various parameter values ​​along the process are generally consistent. Furthermore, the model simulation using the initial parameters generated in this embodiment achieves the same stabilization time as that achieved using the ideal steady-state initial parameter settings. The simulated pressure and temperature values ​​for each section of the key components closely match those obtained using the ideal steady-state initial parameter settings, demonstrating that this embodiment effectively addresses the steady-state initialization issue for this model.

[0095] It should be added that, for a model whose initial steady state can be simplified to a single-flow single-pressure boundary chain structure, the method of this embodiment can also provide reasonable and effective initial parameters.

[0096] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. The initial parameter generation method based on NUMAP steady-state calculation is characterized by: The steps include: Obtain the thermal-hydraulic simulation system model to be initialized in NUMAP and decompose it into multiple single-flow single-pressure boundary chain structure sub-models; For each single-flow single-pressure boundary chain structure sub-model, the mass gas content of each component along the process and the mass gas content of non-condensable gas are set to 0, and the flow rate is set to a constant value at the flow boundary; Set the temperature of each component along the process to the average of the inlet and outlet temperatures, or use the inlet and outlet temperatures as endpoints and fill them linearly according to the component length as the temperature of each component along the process; The total friction pressure drop along the path is obtained by subtracting the total gravity pressure drop along the path from the total pressure drop along the path. This pressure drop is linearly divided according to each group of parameters, and the initial pressure of the components along the path is assigned sequentially starting from the inlet boundary. The total friction pressure drop along the path is obtained by subtracting the total gravity pressure drop along the path from the total pressure drop along the path, and is linearly divided according to each group of parameters. The initial pressure of the components along the path is assigned in sequence starting from the inlet boundary, where: The total pressure drop along the process is expressed as , the total gravity pressure drop along the way is expressed as , the total friction pressure drop along the way is expressed as ; The total friction pressure drop along the process is ; The total pressure drop along the is the outlet pressure value Subtract the inlet pressure value ,Right now ; The total gravity pressure drop along the The calculation formula is: ,in , is the outlet height of the single flow and single pressure boundary chain structure sub-model, is the inlet height of the single flow and single pressure boundary chain structure sub-model; The total friction pressure drop along the The calculation formula is: ; in, L is the length of the flow channel; D is the diameter of the flow channel; is the coolant density; is the average flow rate of coolant; f is the friction coefficient; Assuming coolant flow m remains unchanged, assuming that the component flow channels are all circular, the coolant flow rate , at this time the total friction pressure drop along the ,in, K is the friction pressure drop proportional coefficient; Assume that there are N components along the way starting from the entry boundary. Respectively represent the number of segments, diameter, length and height of each component, The friction pressure drop proportionality coefficient At this time, the outlet pressure of each component Set to ; For a single component , its inlet pressure is the outlet pressure of the previous component, and the pressure inside a single component is linearly distributed with the length. , the distance from the component entrance The pressure value is ; The initial pressure and temperature of each segment of each component represent the average pressure and temperature of the corresponding segment. When generating the initial parameters, the pressure and temperature at the midpoint of each segment are used as substitutes, i.e. Pick .

2. The method for generating initial parameters based on NUMAP steady-state calculation according to claim 1, characterized in that: After obtaining the thermal-hydraulic simulation system model to be initialized in NUMAP and decomposing it into multiple single-flow single-pressure boundary chain structure sub-models, the coolant in the first stage of the single-flow single-pressure boundary chain structure sub-model is a single-phase fluid in each component along the process and is not heated.

3. The method for generating initial parameters based on NUMAP steady-state calculation according to claim 1, characterized in that: In the single-flow single-pressure boundary chain structure sub-model, the components from the inlet to the outlet are connected in sequence, with one side being the flow boundary and the other side being the pressure boundary.

4. The method for generating initial parameters based on NUMAP steady-state calculation according to claim 1, characterized in that: In the calculation of the total gravity pressure drop along the coolant, the coolant density Obtained by consulting the thermophysical properties table of water.

5. The method for generating initial parameters based on NUMAP steady-state calculation according to claim 1, characterized in that: The total friction pressure drop along the and Proportional to the total friction pressure drop along the way, that is, according to the parameters of each component Perform linear allocation.

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