Simulation Of The Transient Internal Flow Of SRM With The Grain Surface Regression Based On Level-set Method

Precise internal ballistic calculation of Solid Rocket Motor(SRM) is important to predict the working process of SRM. At present, most SRM internal ballistics is calculated by zero-dimensional or two-dimensional internal ballistic theory solely. Although some scholars have accomplished the zero-dimensional or one-dimensional internal ballistic calculation coupling with burning surfaces regression of solid grains, there are just a few scholars who had accomplished the three-dimensional flow calculation couping with surfaces regression.Dynamic mesh method can be used to accomplish the three-dimensional flow calculation coupling with grain surface regression, but when the grain geometry is complicated, it is difficult to accomplish the flow calculation by using dynamic mesh method.Based on the secondary development of Fluent by using User Defined Function(UDF), a method that can be used to accomplish the precise three-dimensional transient flow calculation coupling with grain surface burnback is developed in this paper. The work of this paper can be summarized as follow:1. Level-set method coupling with Minimum Distance Function (MDF) can be used to calculate solid grain surface regression, no matter what kinds of surface the grain has, for example, plane surfaces, convex surfaces, concave surfaces, parts of surfaces with no regression or with different regression velocity.2. A method based on contour is used to segment the cell geometry and reconstruct rest of cell geometry, and a method can be used to calculate the interface surface and volume of rest of the cell for any convex polyhedron mesh is developed, it is easy to be understood and to be accomplished by program, and it has high precision What is most important is that it provides an interface for the flow calculation coupling with surface regression.3. When the flow with mass addition and surface regression is calculated, the result calculated by using the combination method of level-set and porous media model is similar with the one calculated by using typical dynamic mesh method, it proves that the combination method can be used to calculate the flow with mass addition and surface regression.4. The combinatio in method of level-set and porous media model is used to calculate the flow of a SRM whose grain is a short tube and burning surfaces located on inner cylinder and both end sides, and the chamber pressure and grain surface area are agree with the result of zero-dimensional internal ballistic calculation. It proves that the combination method can be used to calculate the flow in SRM with grain surface burnback.5. The flow of a SRM chamber which has a finocyl grain is calculated by using the combination method of level-set and porous media model, and its transient result considering surface regression is compared with its steady ones and its transient ones not considering surface regression, the influence of grain surface burnback and historical state of chamber flow is analyzed.The work done imply that the combination method of level-set and porous media can be used to calculate the transient flow with grain surface regression precisely, it proves a foundation for the flow with erosion combustion or flawed grain.