Investigation Of The Ignition Transient In Large Aspect Ratio Solid Rocket Motors

This dissertation integrates theoretical analysis and numerical simulation method to investigate the ignition transient process of large aspect ratio solid rocket motors.Theoretical analysis emphasizes on heat transfer both inside propellant and between igniter exhaust and internal grain surface. For igniter device with side holes, by adopting Manglar Transform and with achievements in heat transfer study on jet impinging on plane, formula of heat transfer coefficient for igniter exhaust impinging on internal grain surface is obtained.Mathematic analysis demonstrates that classic Fourier heat transfer formula can not properly describe such wave propagation phenomena as transient heat transfer inside propellant. After affirming the existence of non-Fourier effect, the hyperbolic equation suited for describing rapidity heat transfer process inside propellant is obtained. Experiment is designed to measure heat relaxation time. Comparison with heat action time validates above analysis.To found basis of numerical simulation, the igniter mass flow rate predication model is first modified to consider such effect as ignition delay and burning process occurred in igniter device for large aspect ratio solid rocket motors.The mathematical models suited for 1-D,2-D and 3-D unsteady flow simulation during ignite transient process of large aspect ratio solid rocket motors are constructed repectively. Corresponding software is accomplished. Comparison between simulation and experiment result verify the correctness of both mathematical model and simulation program.1-D simulation results are adopted to construct the relationship between pressure rise rate and flame spreading process along propellant surface; Appropriate step to enhance efficiency of ignition charge is discussed based on 2-D simulation results and flame spreading process in fin slots is analyzed with 3-D simulation results. The study indicates that the end of flame spread over grain surface corresponds to max value of pressure rise rate and the flame is not continuous in fin slots.Response characteristic of solid propellant to sudden load is studied based on differential nonlinear viscoelasticity constructural equation during ignition transient process. Structure integrity of propellant is also analyzed.Monte Carlo method is adopted to study performance dispersion of igniter device. After introducing Uniformity Design Method, the performance dispersion during ignition transient process is investigated. Measures to depress dispersion band are also discussed.The research work of this dissertation not only brings forward new viewpoint for theoretic study such as heat transfer analysis, but also provides foundation for solving such engineering problem as ignite device design, ignite performance dispersion control and ignite characteristic analysis. The achievements will have significant effect on both theoretic study and engineering practice.