Abstract: 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. Key

Key words: electro-thermalchemicalpropulsion, injectionpressure, Taylorcavity, plasmajet, liquidmedium