Abstract: 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.

Key words: micro-nozzle, continuum-based model, Reynolds number, propulsive performance