CVI反应器内部气体流场的有限元模拟及优化设计

采用有限元计算方法,研究了CVI反应器内部的流场特征.对于形状简单的构件,构件的放置方式和阵列对气体的流动状态具有显著的影响.与横向阵列相比,纵向阵列能充分保证构件沿其长度方向流场均匀性,减小回流现象;在反应器中,随着纵向阵列试样数量的增加和分布均匀性的提高,气体流动速度增大,流场均匀性提高.减少反应器内部的自由空间,是提高流场品质和化学气相沉积效果的关键.基于减少反应器内部的自由空间的原则,针对杯形复杂构件,提出了通过加入与其几何形状相适应的导流板工装,有效避免了在构件内部和外部形成回流区,实现流场的优化设计.

FEM Simulation and Optimization Design of Flow Field in CVI Reactor

Chemical vapor infiltration(CVI) is an essential process to manufacture the Continuous Fiber Reinforced Ceramic Matrix Composites.In order to optimize the manufacturing process,a systemic and in-depth study on simulating the flow field of CVI reactor is very important.The flow fields of CVI reactors were simulated by finite element method(FEM) based ANSYS-FLOTRAN of commercial software.For the simple shape component,the flow field is influenced evidently by the lay-mode and arrays of components.The boundary conditions of components are more uniformity and symmetry by parallel arrays of components than that of cross arrays,so the circumfluence in the CVI reactor was decreased.The velocity and pressure difference of the mixed gas were increased with the increase and uniformity of components in parallel arrays.It is key to improve the chemical vapor infiltration quality that reducing the free-space in the CVI reactor.Under the principle of reducing free spacing in CVI reactor,the flow field could be improved by the guide plates in CVI reactor with complex non-conventional shape components,and the circumfluence could be avoided around the components,so the flow fields were optimized.