Research On The Character Of Solid Rocket Motor Working Deep Underwater

The rocket floating mine is a kind of mine that deployed in the deep water inpeacetime, in wartime powered by solid rocket motor equipped on the mine to promotemine warhead fast floating actively attacking surface ships or water submarine target,exploding in the vicinity of the target. It has many advantages such as deep laying depth,covert performance and quick attack. After the solid rocket motor ignited to work in thedeep water, high temperature and high pressure gas in the combustion chamber gets intothe water through the nozzle to form a gas bubble in the first time. The bubble growthand change continue to occur by the gas-liquid interactions. Meanwhile, heat and masstransfer, phase transition, transfer of a complex wave phenomena occur between twophase of gas and liquid, the physical processes are extremely complex. Especially in thecase of large depth (underwater300~400m), the environment back pressure is up to3~4MPa, these factors will affect the performance of solid rocket motor, with importantvalue of research.In this paper, numerical simulation model of the solid rocket motor supersonic gasjet underwater based on VOF interface tracking method is established after the analysisand simplification of the procedure of the supersonic gas jet underwater. The model isverified to be feasible through the comparison with relevant experimental results. Onthis basis, the numerical simulation of unsteady two-dimensional axisymmetric greatdepth underwater solid rocket engine supersonic gas jet is carried out, gas bubblegrowth and change procedure is provided, the mechanism is revealed by analyzing thestructural changes of the jet flow field of gas-liquid two-phase. Through thecomparative analysis of the thrust performance and operating characteristics of thedifferent underwater depth and nozzle area-expansion ratio, the motor performance isresearched.The research results show that when the motor underwater over expanded work,gas bubble experienced “necking-expansion–necking” process in the initial stage, andflow field inside the motor nozzle varied severely, motor thrust rippled Then processentered the dynamic stabilization stage, by the aqueous medium oppression function, inthe nozzle expansion segment there is a normal shock wave oscillating back and forth inconsistent with the gas-liquid interface tremor near the nozzle. Deepening as theworking depth, motor thrust reduced and work performance degraded. When the motorworked at400m underwater, the thrust pulsed seriously, the motor worked as chokedand may worked failure. When the motor underwater fully expanded and underexpanded steady work, oppressed by water medium near the nozzle exit, the nozzle didnot form within the supersonic flow to subsonic jet emitted from the nozzle, but thethrust owned better stability.