微喷管内声速点位置及临界压比

Sonic point position and critical pressure ratio in micro nozzles

关键词:  微喷管+  声速点+  尺度效应

Key words:  Micro nozzle~+  Sonic point~+  Scale effect

摘要:

为提高微型空间推进器和微型气体涡轮机等微型器件的性能,利用有限体积法求解二维可压缩N-S方程模拟了扩张比为1.7的收缩-扩张微喷管内部的流场结构和温度分布,研究了尺度效应对微喷管内部流场结构的影响,计算中微喷管的喉部宽度为1~200μm。数值结果表明:在扩张比和进出口压力相同的条件下,微喷管出口马赫数随着微喷管尺度的减小而减小。微喷管内首次出现声速点的位置随着喷管尺度的缩小从喷管喉部逐渐移向喷管出口,临界压比值随着喷管尺度的减小而减小。

Abstract:

This research is aimed at improving the performance of micro-space propulsions and micro gas turbine generators.The gas flow characteristics in 2D convergent-divergent micro nozzle were analyzed by numerical simulation based on finitevolume method.The throat width of micro nozzle is 1~200μm and the expansion area ratio is 1.7.The numerical results indicate that the outlet March number and critical pressure ratio decreases with the decreasing of the throat width.The numerical results also show that the first sonic point position moves away from the throat to the outlet of the micro nozzle with decrease of the throat width. These particular behaviors are attributed to the increased surface-to-volume ratio leads to high viscosity dissipation in the micro nozzle.