Parametric Modeling And 1D-3D Coupling Method Research On Multi-branch Pipe

The function of the main steam system is to transfer the saturated steam from steam generators (SG) to other equipment in nuclear power plant. The steam from different SG was pooled to the main steam pipe, and then assigned to the turbine, MSR and other equipment in the process. The main steam system is composed of the main steam pipe, the branch pipe connected to the SG or the steam-using equipment and valves along the pipes. The security and economy of the second-loop system operation is mainly dependent on the rationality and accuracy of steam flow distribution in nuclear power plant. Therefore, it's very important to control the system steam flow distribution during the VV&A.The traditional research methods to the main steam system include experimental research,1D system simulation and CFD numerical simulation. The experimental research requires large amounts of resources and long experimental period. In addition, the experimental result of the internal flow and pressure field distribution and transient characteristic is difficult to display. The application of CFD numerical simulation solves the problem of traditional experimental research. However, the large number of system grid requires high performance of computer, which is hard to achieve in most cases. Compared to the CFD numerical simulation, the 1D system simulation can significantly reduce the complexity of the model and simulation time. But the distribution of internal flow field can't be shown by the system simulation. And the simulation accuracy of elbow or T-shaped pipe is not high enough. In order to solve the above problems, a more effective solution is to use the 1D-3D coupling calculation method. By this way, the key equipment, such as the multi-branch pipe, was simulated with CFD software in 3D. And the other equipment were simulated with 1D system simulation software. The coupling calculation was achieved by the boundary data transmission of the interface program.This thesis develop the interface program in C# language to realize the two-way coupling calculation between 1D Flowmaster (FM) and 3D Fluent software. The flow and pressure field distribution of main steam system in steady condition, as well as the coupled characteristics between different branch pipes in given transient condition was researched. In order to assure the accuracy and efficiency of coupling calculation, the factors which may influence the coupling calculation, such as the initial boundary condition setting, the coupling factors and the length of branch joints,would be researched.The 3D parametric modeling software of multi-branch pipe was developed to establish different multi-branch pipe models and complete structured mesh generation automatically.According to the principle of control variable, multi-branch pipes of different structure were simulated and compared to research the main pipe length, diameter and the branch pipe arrangement on the influence of the steam system flow and pressure field. The optimization design principle of multi-branch pipe structure model was summed up for the scheme design.