等离子射流在模拟液体发射药中扩展特性的数值模拟

Simulation of Spreading Characteristics of Plasma Jet in Simulative Liquid Propellant

为了深入认识液体工质电热化学炮中等离子射流的点火过程,开展了等离子射流在液体发射药LP1846模拟工质中扩展特性的研究,建立了等离子射流在液体中扩展的二维轴对称非稳态数学模型,并基于液体工质为水的文献实验进行模型验证。在此基础上对等离子射流在LP1846液体发射药模拟工质中的扩展过程进行数值模拟,分析等离子射流在扩展过程中形态的变化以及射流场压力、速度和温度的分布特性。结果表明,扩展过程中由于Taylor-Helmholtz不稳定性,等离子射流和液体发射药模拟工质两相间存在湍流掺混现象,并随着扩展逐渐加剧,表现为射流头部凸出并逐渐轴向拉长形成尖头,同时射流卷吸液体发射药模拟工质在Taylor空腔中产生液滴,且数量逐渐增多。此外,等离子射流扩展过程中近喷孔处由于液体发射药模拟工质回流而出现颈缩现象。射流场由于膨胀波-压缩波交替作用而存在波动现象,且在近喷孔处尤为剧烈,表现为压力场呈现高低压相间分布,速度场也呈类似分布。

In order to understand the ignition process of plasma jet in the liquid propellant electrothermal chemical gun,the spreading characteristics of plasma jet in simulative liquid propellant LP1846 were studied.A two-dimensional axisymmetric un-steady mathematical model of plasma jet spreading in the liquid was established,and the model was validateded with the experi-ments based on the liquid working medium of water.On this basis,the spreading process of plasma jet in the simulative liquid propellant LP1846 was numerically simulated.The morphological changes of plasma jet and the distribution characteristics of pressure,velocity and temperature in the jet field were analyzed.Results show that when the plasma jet expands in the simula-tive liquid propellant LP1846,there is turbulent mixing phenomenon due to Taylor-Helmholtz instability,and it becomes more and more intense.It is manifested by the protruding head of the jet and the axial elongation to form a tip,and the jet entrains the simulative liquid propellant medium to produce droplets in Taylor cavity,and the number of droplets gradually increases.At the same time,the necking phenomenon occurs near the nozzle hole during the expansion of plasma jet due to the simulative liquid propellant backflow.The jet field fluctuates due to the alternating action of expansion and compression waves,especially near the nozzle hole.The pressure field shows alternating distribution of high and low pressures,and the velocity field also shows sim-ilar distribution.