平直出口段对微喷管性能的影响

Impact on of Straight Outlet Section to Micro-Nozzle Performance

以Fluent 6.3为工具,进行数值模拟求解二维稳态可压缩N-S方程,分析了喷管有无平直出口段以及平直出口段长度对扩张比为5.4的收缩-扩张微喷管内压力和速度分布影响,进而分析了对微喷管的流量系数和推力效率影响;计算结果表明:喷管有无平直出口段以及平直出口段长度l,将会影响微喷管出口区域流体压力分布和速度分布;与喷管出口无平直出口段相比,当喷管出口有平直出口段时,流体压力最低值和速度最大值靠近喷管出口中心区域,并且影响区域增加;当喉部特征雷诺数Re较小时,流量系数Cd和推力系数ηF随l的增加先增大再减小;随着Re的增加,流量系数Cd和推力系数ηF的变化变小。

The Fluent 6. 3 software was applied to simulate the supersonic flow in micro nozzle. The simulation was complemented by computing steady 2-D Navies-stokes equations to analyze the pressure contour and velocity contour inside the micro nozzle which has straight exit section and the length of straight exit section l. Also the performances of flow coefficients and thrust force efficiencies were studied. The numerical results show that whether the nozzle has straight exit section or not and the section length l will affect the pressure contour and velocity contour inside the thruster. Compared to the nozzle that has no straight exit section,the increased minimum pressure region and the maximum velocity region are close to the center of exit in the nozzle that has straight exit section. When the throat Reynolds number Re is small,the flow coefficient Cdand thrust coefficient ηFfirstly increase then decrease with the increase of l. With the increase of Re,the variation of the flow coefficient Cdand thrust coefficient ηFfor higher Re are smaller than for lower Re.