Magnetohydrodynamic Modeling And Simulation Of The Working Process Of The Discharge Rod Plasma Generator

In order to study the behavior characteristics and motion law of plasma in the working process of discharge rod plasma generator,this paper used the method of describing magnetic field based on magnetic vector potential,deduced the electromagnetic field equations again,and established a relatively complete theoretical model of MHD combined with capillary ablation model and plasma physical parameter model.The software Fluent was redeveloped by using the macro function written in C language,the electromagnetic field equations and hydrodynamic equations were coupled in parallel,the plasma expansion process in the discharge rod plasma generator was numerically simulated,and the general variation law of plasma expansion characteristics was obtained;By changing the characteristic parameters such as jet pressure,nozzle diameter and discharge voltage,the influence of characteristic parameters on the plasma expansion process was obtained.During the working process of the discharge rod plasma generator,the plasma expansion is mainly radial,and its expansion displacement and expansion volume increase gradually with the expansion time.The variation law of plasma at the nozzle with time is as follows: the pressure decreases monotonically,the temperature first increases significantly,then decreases slightly,and then continues to increase,the velocity first increases rapidly,reaches the maximum velocity,and then decreases slowly,the density first increases briefly and then continues to decline,and the lorentz force,joule heat and conductivity increase.In the plasma phase,the distribution law with the radial position is as follows: the pressure decreases first and then increases,the temperature decreases little,the velocity increases first and then decreases rapidly,the density decreases gradually,the lorentz force increases first and then decreases,the joule heat fluctuation decreases,and the conductivity fluctuation rises;The distribution law with the axial position is that the pressure,velocity,lorentz force,joule heat and conductivity are symmetrically distributed,which is larger near the positive-negative electrode and smaller at the symmetry axis,and there are differences on both sides of the symmetry axis.The whole electromagnetic field is unsteady,and the temperature and density change sharply at the interface between plasma phase and air phase.The increase of jet pressure mainly increases the expansion displacement,expansion volume and pressure in the flow field.The pressure peak after the shock increases,the pressure difference before and after the shock also increases,and the shock position is closer to the front;The decrease of nozzle diameter mainly increases the velocity and Mach number in the plasma phase,but the time of its occurrence is slightly delayed,and the whole expansion time also decreases;The increase of discharge voltage mainly increases the temperature in the plasma phase and the ablation rate of polyethylene wall.They increase obviously in the later stage of expansion,but the whole expansion time decreases to a certain extent.This is helpful to judge the state of plasma at different times and positions,so as to obtain the plasma with corresponding performance by selecting appropriate characteristic parameters,which has important guiding significance for the design of discharge rod plasma generator suitable for different conditions.