Mechanism of Influence of High-Speed Self-Spin on Ignition Transients for a Solid Rocket Motor: a Numerical Simulation

High-speed self-spin is one of extreme working conditions that alters ignition internal ballistic performance and can induce ignition abnormalities. To demonstrate the studies on mechanism of interior ballistics as the results of acceleration loads imposed on spinning SRM, the modes of swirl dynamical flow and acceleration-induced combustion phenomena for igniter and propellant are developed and first taken into account in a new ignition model by user-defined sources (UDS). To verify the model, the heat transfer, added-mass and build-up pressure modes of this ignition model are verified by comparison with static ignition experimental data, second, the swirl flow field mode is validated through comparison between models and by analogy with experimental phenomena, then the numerical model is proved by grid-independent verification. Dimensionless analysis eliminates diversity in time scales at different periods. The influences of swirl flow, igniter, and propulsion acceleration-induced combustion on various stages of ignition are studied. It was found that: (1) Time scale in the ignition process of spinning SRM is mainly affected by the igniter‘s sensitivity to rotational acceleration (A_ig), whose change is approximately described as an empirical equation based on rotational overload (α) and ignition sensitivity coefficient limit A_ig,max; (2) The acceleration effect on propellant combustion is mainly manifested in the pressure peak and the pressure rate, however, it has little effect on the ignition delay; (3) Swirl flow factors are not the main factors affecting the ignition process for small SRMs with small-contraction nozzles.