Nozzle Trans-regime Flow Simulation Based On N-S/DSMC Coupling Algorithm

With the development trend of our military and aerospace missions,there is an increasing demand for all types of spacecraft tominiature thrustersthatcan provide very low thrust.The micro-nozzle as a key component of micro-thrusters,it mainly controls the flow to realize orbital maneuver and special attitude control of the spacecraft.According to the different levels of gas flow,the flow area is divided into: high-density continuum regime,very low density of free-molecular regime and the transitional regime between the two regimes.Under normal circumstances,the internal nozzle flow will not only be incontinuum regime,there will be a clear thinning effect on the partial flow process.In addition,due to the small size of the micro-propulsion device,the viscous effect of gas has a great influence on the performance and propulsion efficiency of the micro-nozzle.Therefore,the research of the flow characteristics of the micro-nozzle is of great significance to the design and performance improvement of the MEMS power system,and also conducive to the development of micro-space propeller.In this paper,the Navier-Stokes equations based on continuum method and direct simulation Monte Carlo method based on molecular dynamics are used to simulate the internal flow field and external plume of the micro-nozzle.The N-S method based on finite volume methodand the DSMC Computation Program Based on Patch Grid are developed.Combined with flux-based weakly coupled information transfer mechanism,we develop the core functional modules of hybrid algorithms: continuous failure judgment module,grid region division module,information transmission module and data storage module,the bidirectional coupling algorithm of N-S/DSMC based on skin-grid is implemented.On the basis of ensuring the accuracy of the calculation of the lean flow,hybrid algorithm improves the computational efficiency of the algorithm.This article successfully applied to the inter-basin micro-nozzle flow calculation.In this paper,we study the micro-nozzlebased on the MEMS one-component propeller developed by the NASA / Goddard Space Flight Center,Maintaining the nozzle area ratio unchanged,we study the effects of small-scale viscous effects and lean effects on the performance and propulsion efficiency of the micro-nozzle at different inlet flows,wall temperatures,divergence angles and propellant types.And we also simulate the external plume of the micro-nozzle,the distribution of plume outside the micro-nozzle under thin conditions was found,it will be ready for the further research on force-heat coupling effect of plumes.