ADN基推力器热回浸对毛细管微尺度流动特性影响的数值模拟研究

小推力ADN基推力器在工作中,其毛细管内的推进剂容易在壁面传热作用下发生相变,进而影响推力器的正常工作。为了深入理解推进剂在毛细管内的相变和流动特性,采用三维数值模拟方法对毛细管微尺度流动和相变特性进行计算。计算考虑了毛细管与喷注器内的流固耦合传热、推进剂相变过程。推进剂相变采用Lee模型,气液体积分数的求解和气液界面捕捉重构采用VOF-CSF方法。本文首次采用VOF模型耦合Lee相变模型计算了ADN基推进剂在毛细管内的相变过程,并结合气泡空间分布仿真结果得到了质量流量和热回浸温度对流动特性的影响规律。计算结果显示,受到ADN基推进剂的冷却作用,毛细管内壁面温度要略低于外表面。毛细管内的气泡形成于弯管处,其体积沿着毛细管轴向下游逐渐增加,采取散热措施可减少并推迟气泡的形成。随着ADN基推进剂质量流量的降低或下游热回浸温度的增加,毛细管内的气泡均显著增加,且形成区域更接近上游区域。当热回浸温度从800K增加至1100K时,毛细管内的气泡体积从25.6mm~3增加至58.7mm~3。

Numerical Simulation of Effects of Heat Soak-Back onMicro-Scale Flow Through a Capillary inADN-Based Thruster

During working of a small thrust force ADN based thruster, liquid ADN based propellant flowing through a metal capillary commonly undergoes phase change due to the heat transfer between solid wall and fluid, which can affect the normal operation of the thruster. In this study, 3D CFD method was used to understand the issue. The detailed model and methods involved a coupled method for solid/fluid steady heat transfer calculations, the Lee model for liquid-vapor phase transitions, VOF-CSF model for the two-phase volume fraction calculations and surface capture and reconstruction. The results revealed that the vapor bubbles formed at the curved section of the capillary, transported and grew along the downstream direction of the capillary. The formation processes of bubbles could be impeded and delayed by using the copper cooling method. With decreasing of the mass flow rate of ADN based propellant or increasing of the temperature due to heat reflux, the bubble in the capillary increased significantly, and the forming region of bubbles was closer to the inlet.