喷射压力对等离子体射流在液体中扩展的影响

在液体推进剂电热化学炮的内弹道过程中，等离子体射流的喷射压力对等离子体与液体之间的相互作用影响较大。为了研究喷射压力带来的影响，设计了等离子体射流在圆柱形充液室中扩展的观察试验，建立了等离子体射流在液体介质中扩展的二维轴对称非稳态数学物理模型，并进行了数值计算，计算结果和试验结果吻合较好。分析了喷射压力对等离子体射流扩展特性和流场分布特性的影响，结果表明：等离子体射流在液体介质中扩展，喷嘴附近出现了颈缩现象以及高低压相间分布结构，射流头部出现了局部高压区，侧面出现了局部低压区，等离子体射流的形状由椭圆形逐渐变为纺锤形，射流内部的主漩涡逐渐变大并向下游移动。喷射压力越大，Taylor空腔轴向扩展能力越强，轴向长度与破膜压力和时间呈指数关系；同时头部高压区移动越快，侧面低压区出现越晚，射流内部的主漩涡越大，温度波动越剧烈。增大喷射压力能够加强等离子体射流的扩展能力，但是不利于等离子体射流扩展的稳定性。

Effect of Injection Pressure on Propagation of Plasma Jet in Liquid

The injection pressure of plasma jet has a great effect on the plasma-liquid interaction during the interior ballistic process of liquid propellant electro-thermal chemical gun. An experiment of plasma jet propagating in cylindrical chamber filled with liquid was made, and a two-dimensional axisymmetric unsteady mathematical physics model of plasma-liquid interaction process is established. The numerical calculation was carried on. The calculated result is in good agreement with the experimental result. The effect of injection pressure on plasma expansion characteristics and flow field distribution characteristics is discussed. The results show that the necking phenomenon and the alternate distribution structure of the high and low pressures appear near the nozzle. A high pressure region is generated at the head of plasma jet, and a low pressure region is generated at the side of plasma jet. During expansion, the plasma jet gradually changes from oval shape to spindle-like shape. The main vortex in the plasma jet becomes larger and moves downstream. The higher the injection pressure is, the greater the axial expansion ability of Taylor cavity is, and the axial length is exponentially increased. At the same time, the faster does the high pressure region at the head of plasma jet move, the more later does the low pressure region at the side of plasma jet appear; the main vortex is bigger and the temperature fluctuation is stronger. Increasing the injection pressure of plasma jet can enhance the expanding ability of plasma jet, but it is not conducive to its expanding stability.