A method for coupling CFD and system program of a nuclear power system

Abstract

The application discloses a kind of nuclear power system CFD and system program coupling method, steps are as follows:1. for steam generator U-shaped section heat transfer tube in reactor respectively establish three-dimensional geometric model belonging to CFD program OpenFOAM and one-dimensional simplified model belonging to system program RELAP5;2, using RELAP5 program input card sets initial boundary condition and initial state of calculation domain of geometric model;3, RELAP5 program is calculated to the responsible area model, obtains calculation result, realizes data conversion using intermediate program and passes calculation result to OpenFOAM, as the boundary condition of OpenFOAM this time step;4, OpenFOAM is calculated to the responsible area model, obtains calculation result, realizes data conversion using intermediate program and passes calculation result to RELAP5 program, as the boundary condition when RELAP5 program next time step calculation;5, repeat step 3, step 4, until the region to be solved completes full time period calculation.Complete to the region to be solved multi-dimension, high-fidelity coupling analysis.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of nuclear reactor system program application, and particularly relates to a system-level program and a three-dimensional computational fluid dynamics software external coupling calculation method. BACKGROUND

[0002] The steam generator is an important device in the nuclear reactor system, and the built-in U-shaped section heat transfer pipe can transmit the heat of the primary loop to the secondary loop. However, the U-shaped section heat transfer pipe has a relatively long length, has a straight pipe section and a bend pipe section, and is in a relatively complex heat exchange environment, so that the primary loop coolant leakage and other transient accidents are prone to occur in the use process, and the generated three-dimensional thermal hydraulic phenomenon has an important influence on the thermal safety characteristics of the reactor. The analysis method for the part of the device can adopt two kinds of system-level analysis program and computational fluid dynamics program. The system-level analysis program such as RELAP5, TRACE and ATHLET usually assumes that the fluid flow is one-dimensional flow in the pipe and other components, and adopts the lumped parameter method to quickly analyze the thermal hydraulic characteristics of the reactor system. The system-level analysis program has small calculation cost, fast calculation speed, and can quickly evaluate the thermal characteristics of the components. However, when facing the complex three-dimensional thermal hydraulic phenomenon, the analysis ability of the system-level analysis program is relatively limited. The CFD (computational fluid dynamics) program such as OPENFOAM, FLUENT and CFX is increasingly widely used in the thermal hydraulic design link of the reactor. The above program can obtain high-precision three-dimensional thermal hydraulic analysis results by developing fine modeling for the region to be studied and solving the basic control equation of fluid mechanics. However, due to the limitation of calculation resources and calculation time, the current three-dimensional computational fluid program is still limited to the study of the local region of the reactor. It is difficult to realize the analysis work of the full system scale for the three-dimensional computational fluid program.

[0003] In summary, by feeding back the required calculation conditions of the system-level analysis program and the CFD program two different scale programs to each other in the process of simulation, the fine three-dimensional thermal hydraulic phenomenon of the local region can be obtained, and the results of the full system simulation can be more accurate and detailed. Therefore, the application has important reference value and guiding significance for the system-level thermal hydraulic analysis of the nuclear reactor. SUMMARY

[0004] In order to overcome the problems existing in the prior art, the purpose of the application is to provide a nuclear power system CFD and system program coupling method. When the CFD (computational fluid dynamics) program OpenFOAM and the system program RELAP5 program are used for thermal hydraulic phenomenon analysis of the U-shaped section heat transfer pipe of the steam generator in the nuclear reactor, the method combines the characteristics of high calculation efficiency of the system analysis program and accurate calculation of the computational fluid dynamics software, and can complete the multi-dimensional, full-system high-fidelity coupling analysis of the reactor system.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] A method for coupling CFD and system program in a nuclear power system, when using the CFD program OpenFOAM and the system program RELAP5 to analyze the thermal-hydraulic characteristics of the U-shaped heat transfer tube of a steam generator, employs a domain separation method for modeling. An intermediate program compiled using shell and Python languages ​​enables data transfer between OpenFOAM and RELAP5 at the connection points between their respective computational domains, achieving multi-scale coupling. This method can account for the influence of OpenFOAM's three-dimensional thermal-hydraulic calculation results on the RELAP5 program's calculation results. The method includes the following steps:

[0007] Step 1: Establish a geometric model for the U-shaped heat transfer tube of the steam generator in the reactor, which is divided into the RELAP5 program calculation area and the OpenFOAM calculation area. The outlet of the RELAP5 program calculation area is connected to the inlet of the OpenFOAM calculation area, and the inlet of the OpenFOAM program calculation area is connected to the outlet of the RELAP5 program calculation area.

[0008] Step 2: Input the RELAP5 program card according to the design conditions to set the boundary conditions and initial state of the computational domain of the RELAP5 program at time T0, i.e., the initial time. Select the solver corresponding to OpenFOAM and use the initialization program compiled with shell and Python languages ​​to initialize OpenFOAM, including zeroing all the boundary conditions in the "0" folder that comes with OpenFOAM and zeroing the calculation start time in the "controlDict" file that comes with OpenFOAM.

[0009] Step 3: The REALP5 program is based on T n The boundary conditions at each time step are used to calculate the computational domain for one time step, where n = 0, 1, 2, 3... The calculation results are output to an external text file and passed to the storage T calculated by OpenFOAM via an intermediate program compiled from shell and Python languages. n The file containing time-mapping information and boundary conditions is used as a T in OpenFOAM. n The boundary conditions at each time step include passing the temperature, pressure, and liquid or gas flow rate at the exit and inlet of the RELAP5 computational domain to the inlet and outlet of the OpenFOAM computational domain, respectively.

[0010] Step 4: The OpenFOAM program reads the stored T nThe file contains time grid information and boundary conditions. Based on these boundary conditions, it performs a time-step calculation on the computational domain, outputs the results to an external text file, and then passes them to the RELAP5 program via an intermediate program compiled from shell and Python languages. n+1 Boundary conditions at each time step include passing the temperature, pressure, and liquid or gas flow rate from the OpenFOAM computational region's outlet and inlet to the RELAP5 computational region's inlet and outlet, respectively.

[0011] Step 5: Repeat steps 3 and 4 until the RELAP5 program and the OpenFOAM computation area complete the full-time computation, thus completing the multi-scale coupling of the RELAP5 program and the OpenFOAM program.

[0012] The coupling method proposed in this invention is suitable for simultaneously considering the impact of system-level safety analysis and detailed thermal-hydraulic phenomenon analysis on the analysis of local areas of nuclear reactors. Compared with existing analysis methods, this invention has the following advantages:

[0013] 1. This invention uses the RELAP5 system analysis program and the OpenFOAM computational fluid dynamics program to model and calculate the U-shaped heat transfer tube components separately. While ensuring computational efficiency, it provides more accurate boundary conditions for the two inlets and two outlets in each region, which is beneficial for accurately analyzing the impact of local thermal-hydraulic phenomena on the reactor system.

[0014] 2. The present invention uses the region overlap method for region partitioning to establish the system model. The model has a complete loop and exhibits good convergence in the calculation of transient conditions.

[0015] 3. This invention uses the OpenFOAM computational fluid dynamics program for three-dimensional modeling, which enables detailed analysis of the heat transfer characteristics of the region for which OpenFOAM is responsible for calculation, thereby improving the accuracy of reactor safety analysis;

[0016] 4. This invention achieves external coupling by using an intermediate program control-driven approach while maintaining the integrity of the program in different dimensions. It can carry out coupling work for most existing thermal hydraulic programs, and at the same time facilitates later program maintenance and upgrades. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a specific coupling process of the coupling method of the present invention.

[0018] Figure 2 This is a schematic diagram of the control body model constructed using the OpenFOAM-RELAP5 coupling program in this invention, showing the control unit, control body number, and the transmission paths of each physical quantity.

[0019] Figure 3 The three-dimensional model of the U-shaped heat transfer tube, calculated by OpenFOAM. Detailed Implementation

[0020] The following example uses intermediate program-driven, controlled OpenFOAM and RELAP5 interactive data to implement coupled analysis. It selects an explicit coupling method and a region-overlapping partitioning method, combined with... Figure 1 Schematic diagram of coupling process and Figure 2 , Figure 3 The modeling diagram will be further described below:

[0021] This invention provides a method for coupling CFD (Computational Fluid Dynamics) with system programs in nuclear power systems. This method uses the CFD program OpenFOAM and the system program RELAP5 to analyze the thermal-hydraulic phenomena of the U-shaped heat transfer tubes in the steam generator of a nuclear reactor. Figure 1 A schematic diagram of the coupling process is provided. Figure 2 and Figure 3 A schematic diagram of U-shaped heat transfer pipe modeling using OpenFOAM and RELAP5 is provided. The intermediate bend section of the pipe is calculated using OpenFOAM, while the remaining area is calculated using RELAP5. The specific coupling method is as follows:

[0022] Step 1: Establish a geometric model for the U-shaped heat transfer tube of the steam generator in the reactor, which is divided into the RELAP5 program calculation area and the OpenFOAM calculation area. The outlet of the RELAP5 program calculation area is connected to the inlet of the OpenFOAM calculation area, and the inlet of the OpenFOAM program calculation area is connected to the outlet of the RELAP5 program calculation area.

[0023] Step 2: Input the RELAP5 program card according to the design conditions to set the boundary conditions and initial state of the computational domain of the RELAP5 program at time T0, i.e., the initial time. Select the solver corresponding to OpenFOAM and use the initialization program compiled with shell and Python languages ​​to initialize OpenFOAM, including zeroing all the boundary conditions in the "0" folder that comes with OpenFOAM and zeroing the calculation start time in the "controlDict" file that comes with OpenFOAM.

[0024] Step 3: The REALP5 program is based on T n The boundary conditions at each time step are used to calculate the computational domain for one time step, where n = 0, 1, 2, 3... The calculation results are output to an external text file and passed to the storage T calculated by OpenFOAM via an intermediate program compiled from shell and Python languages.n The file containing time-mapping information and boundary conditions is used as a T in OpenFOAM. n The boundary conditions at each time step include passing the temperature, pressure, and liquid or gas flow rate at the exit and inlet of the RELAP5 computational domain to the inlet and outlet of the OpenFOAM computational domain, respectively.

[0025] Step 4: The OpenFOAM program reads the stored T n The file contains time grid information and boundary conditions. Based on these boundary conditions, it performs a time-step calculation on the computational domain, outputs the results to an external text file, and then passes them to the RELAP5 program via an intermediate program compiled from shell and Python languages. n+1 Boundary conditions at each time step include passing the temperature, pressure, and liquid or gas flow rate from the OpenFOAM computational region's outlet and inlet to the RELAP5 computational region's inlet and outlet, respectively.

[0026] Step 5: Repeat steps 3 and 4 until the RELAP5 program and the OpenFOAM computational domain complete the full-time computation, thus completing the multi-scale coupling of the RELAP5 and OpenFOAM programs. The above content further elaborates on the coupling method for a specific scheme; parts not detailed in detail are common knowledge to those skilled in the art.

Claims

1. A method for coupling CFD and system program in a nuclear power system, characterized in that: When using the CFD program OpenFOAM and the system program RELAP5 to analyze the thermal-hydraulic characteristics of the U-shaped heat transfer tube of a steam generator, the domain separation method is used for modeling. The intermediate program compiled by shell and Python languages ​​enables OpenFOAM and RELAP5 to transfer data at the connection between their respective computational domains, realizing multi-scale coupling and taking into account the influence of OpenFOAM's three-dimensional thermal-hydraulic calculation results on RELAP5's calculation results. The method includes the following steps: Step 1: Establish a geometric model for the U-shaped heat transfer tube of the steam generator in the reactor, which is divided into the RELAP5 program calculation area and the OpenFOAM calculation area. The outlet of the RELAP5 program calculation area is connected to the inlet of the OpenFOAM calculation area, and the inlet of the OpenFOAM program calculation area is connected to the outlet of the RELAP5 program calculation area. Step 2: Input the RELAP5 program card according to the design conditions to set the boundary conditions and initial state of the computational domain of the RELAP5 program at time T0, i.e., the initial time. Select the solver corresponding to OpenFOAM and use the initialization program compiled with shell and Python languages ​​to initialize OpenFOAM, including zeroing all the boundary conditions in the "0" folder that comes with OpenFOAM and zeroing the calculation start time in the "controlDict" file that comes with OpenFOAM. Step 3: The REALP5 program is based on T n The boundary conditions at each time step are used to calculate the computational domain for one time step, where n = 0, 1, 2, 3... The calculation results are output to an external text file and passed to the storage T calculated by OpenFOAM via an intermediate program compiled from shell and Python languages. n The file containing time-mapping information and boundary conditions is used as a T in OpenFOAM. n The boundary conditions at each time step include passing the temperature, pressure, and liquid or gas flow rate at the exit and inlet of the RELAP5 computational domain to the inlet and outlet of the OpenFOAM computational domain, respectively. Step 4: The OpenFOAM program reads the stored T n The file contains time grid information and boundary conditions. Based on these boundary conditions, it performs a time-step calculation on the computational domain, outputs the results to an external text file, and then passes them to the RELAP5 program via an intermediate program compiled from shell and Python languages. n+1 The boundary conditions at each time step include passing the temperature, pressure, and liquid or gas flow rate at the outlet and inlet of the OpenFOAM computational region to the inlet and outlet of the RELAP5 computational region, respectively. Step 5: Repeat steps 3 and 4 until the RELAP5 program and the OpenFOAM computation area complete the full-time computation, thus completing the multi-scale coupling of the RELAP5 program and the OpenFOAM program.

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