Mathematical Modelling of Nonstationary Physico Chemical Processes in Large Sized SPRM Pyrotechnical Ignition System

Abstract

In this paper, the laws of the unstable wave processes accompanying the combustion abnormal mode in the large-sized solid propellant rocket motor {SPRM) pyrotechnical ignition system {IS) are investigated by numerical method. The IS contains the main {cylindrical) channel (MC) having uniform perforation over the lateral surface, The left MC boundary is blocked and the right boundary is uniformly perforated. The whole perforation is hermetically sealed from outside. The additional {cylindrical) channel {AC) {an initial impulse amplifier) with uniform perforation over the lateral surface is installed into the MC cavity, coaxially to MC. The right AC boundary is blocked, and the time-varying high-temperature gas flow, containing incandescent 'particles is supplied from initiator, equipped with a fast burning compound, through AC left perforated boundary. To imitate the exploitation conditions, the IS is placed in cylindrical imitation chamber {imitative SPRM). In a number of cases, before the beginning of the IS operation, a situation can be realised when the pelletised solid propellant {PSP) mass is non-uniformly distributed along the IS AC length, and the greater part of the AC lateral perforation is blocked by the PSP inserted in the IS MC. Under these conditions, the effect of abnormal strengthening of the pressure waves at the AC boundaries is possible. For describing the abnormal nonstationary physico-chemical processes, a mathematical model is developed. For the check-up of this complex model, the numerical calculation results have been compared with the results of the fire stand tests for the regular IS and the engine. The numerical analysis of the unstable wave process development in the AC has shown that the rise of the pressure with an ever increasing amplitude is realised at the moment, when a shock wave reflects alternately, on the left and on the right AC boundaries. The effect of the pressure waves' abnormal strengthening can result in the destruction of the AC and other elements of the IS structure and exert undesirable influence on the development of the ignition process of the SPRM charge, On the basis of the numerical analysis results, a modified design of the pyrotechnical IS construction having increase operational reliability is suggested.