Numerical Modeling and Studies of Ignition Transients in End-Burning-Grain Solid Rocket Motors

Abstract

The ignition-transient process in the end-burning-grain solid rocket motor has been studied. Simplified numerical models for 1) a mass-added ignitor, 2) a grain-propellant combustion, 3) the opening of nozzle closure, and 4) the enhancement of heat transfer on the surface of the solid propellant have been developed. The individual influence of the input of ignitors (energy strength and input time), the physical and chemical properties of propellants (critical burning temperature, burning rate, thermal conductivity, and initial temperature), and the breaking pressure of closure on the ignition transient have been systemically compared. The three stages of the ignition-transient process, namely, ignition induction, flame spreading, and chamber charging, have been successfully reproduced. The interior ballistics agrees with the ground-experimental data. The rapid generation of the initial flame and the creation of the “second peak” of the chamber pressure both contribute to a successful ignition. The results show that the factors that may accelerate the ignition transient do not always increase the second peak of the chamber pressure. The energy input of the ignition gas has greater influence on the ignition transient than do the enhancement of the heating and ignition process of the propellants. The breaking pressure of the nozzle closure has a very weak influence on the chamber pressure’s second peak, but considerably increases the ignition overpressure of the initial flame.