微喷管流的连续介质模型及其适用性

基于无滑移和有滑移的连续介质模型,对微喷管内的超声速冷态气体流场进行了二维和三维数值模拟,利用DSMC方法验证微喷管流中的连续介质模型,并重点分析微喷管流的低雷诺数效应、三维端面效应及其推进性能.研究表明,局部流场的模拟对模型和边界条件的要求要高于推进性能的估算,在努森数小于0.03时,可以使用无滑移的N-S方程预测推进性能;雷诺数是表征低雷诺数效应和推进性能的特征参数,提高工作压力可以改善微喷管的粘性损失和推进性能;在雷诺数大于1000时,若蚀刻深度和喉部宽度的比值超过13,微喷管具备很好的二维特性.

Continuum-based Model and Its Validity for Micro-nozzle Flows

Two-dimensional and three-dimensional simulations are performed to investigate supersonic cold gas flows in micro-nozzles using continuum-based no-slip and slip models,respectively.The validity of continuum-based models is examined by DSMC method.The study focuses on low Reynolds number effects,three-dimensional effect and propulsive performance of the micro-nozzle flow.It shows that compared to the prediction of propulsive performance,the simulation of local flow fields needs a more stringent model.The no slip N-S equations are able to predict propulsive performance of micro-nozzles with Kn<0.03.Reynolds number is a key parameter in governing low Reynolds number effect and propulsive performance.The strong viscous losses can be mitigated and better propulsive performance can be achieved at higher chamber pressures.The micro-nozzle with the ratio of etch depth to throat width more than 13 has a good 2D characteristic as Re>1000.