高孔隙率多孔氮化硅构件较高马赫数下流-热-固耦合力学特性分析

Analyzing the Fluid-Solid-Heat Coupled Mechanical Properties of Highly Porous Silicon Nitride Member Under High Mach Number

以凝胶注模技术制备的固相含量为40%、45%、50%(质量分数,下同),孔隙率高达65.24%、63.26%、61.19%的多孔氮化硅天线罩材料作为研究对象。将测得的材料性能参数作为有限元分析模拟的数据支撑,构件模型载体选择正切尖拱形,使用FLUENT模拟流场,结构场采用ANSYS软件,热力耦合得到不同固相含量的材料在不同马赫数下流-热-固耦合后的热应力强度,对其力学特性进行分析。结果表明,较高马赫数下的飞行构件的尾部连接端是受热应力最大的部位,也是失稳较为严重的部位。飞行构件的结构稳定性需通过加固尾部连接端来提高;气动热是引起天线罩构件失稳的首要问题,解决结构失稳的关键在于解决气动热,可通过在天线罩构件外增加耐热隔层,使其免受气动热;多孔氮化硅材料的孔隙率与失稳时对应的马赫数成正比,热导率是影响多孔氮化硅天线罩构件在较高马赫数下受到热应力大小的关键因素。

The 40%, 45% and 50% （mass fractionm） solid content porous silicon nitrides with porosity of 65.24%, 63.26% and 61.19%, respectively, were successfully fabricated by gel-casting. And the gel-cast porous silicon nitride flight member with tangent pointed arch model was investigated by finite element analysis, using the property parameters as calculating data. The flow field was simulated by FLUENT software, and the fluid-solid-heat coupling analysis under different Maeh number was conducted by ANSYS calculation. It was found that the tail connection end of the component was subjected to the maximum stress and exhibited serious instability. The stability of the component needed to be enhanced by strengthening the tail connection end. The pneumatic heat was the key to the instability of the component. It was revealed that an outside heat insulation layer was needed to protect the member under high Mach number. The porosity of porous silicon nitride material was in direct proportion to that of the Mach number at unstable situation. The thermal conductivity of porous silicon nitride was the key to the value of thermal stress under high Mach number.