微喷管中稀薄流动时热力学非平衡现象研究

微喷管作为微推进系统中的重要部件,其工作性能的研究对于微推进系统的设计有着重要理论指导意义。采用求解带滑移边界条件的N-S方程和直接模拟蒙特卡洛(DSMC)方法,研究微喷管中的稀薄流动,通过设定气体分子转动松弛所需要的松弛碰撞数Zrot研究微喷管中的热力学非平衡现象。结果表明:Kn>0.1时,微喷管中流动开始变得稀薄,连续性假设失效,N-S方程求解结果出现误差;随着微喷管中流动稀薄程度增加,热力学非平衡现象逐渐明显;热力学非平衡现象使微喷管内气体内能转化为平动能的量减少,微喷管内速度和推力整体减小;热力学非平衡现象对微喷管流场影响大于对其工作性能的影响,考虑转动松弛对微喷管内温度场的影响大于速度场。

Study on thermodynamic non-equilibrium phenomenon of rarefied flow in micro-nozzle

As an important component in the micro-propulsion system,the study on the work performance of micro-nozzle has important theoretical guiding significance for the design of the micro-propulsion system.N-S equation with the slip boundary condition and direct simulated Monte Carlo(DSMC)method were used to study the rarefied flow in the micro-nozzle.The thermodynamic non-equilibrium phenomenon in the micro-nozzle was studied by setting the number of relaxation collision Z required for the rotational relaxation of the gas molecules.The results show that when Kn>0.1,the flow in the micro-nozzle begins to become rarefied,the continuity assumption fails,and the N-S equation results in errors.With the increase of the flow rarefaction in the micro-nozzle,the thermodynamic non-equilibrium phenomenon is gradually obvious.The thermodynamic non-equilibrium phenomenon reduces the amount of gas internal energy converted into translational kinetic energy in the micro-nozzle,which is followed by the velocity and thrust in the micro-nozzle decreasing.The thermodynamic non-equilibrium phenomenon has greater influence on the flow field of the micro-nozzle than on its working performance.The influence of considering the rotational relaxation on the temperature field is larger than the velocity field in the micro-nozzle.