Gas Mixtures Effects in SRM Ignition Transient

The internal ballistic of a solid rocket motor is characterized by a complex flow-field determined by the injection of the combustion products into the chamber and the rapid mixing with the cold pressurizing gas. This work presents and discusses three different gasdynamics models of inert ideal gas mixture. All the three models, adapted to a quasi one-dimensional unsteady model, are able to consider the variation with pressure of thermo-physical properties of the gas mixture inside the combustion chamber. The ignition transient of Zefiro 9 motor, the third solid stage of VEGA launcher, has been selected as test case. The results, compared with the constant property mixtures case and with the experimental data, show consistent variations with the mixture property variation ranges. The numerical simulations quantify the small but present effects due to the variation of gas mixture thermo-physical properties with pressure on the SRM IT internal ballistics.