||Edwards Air Force Base, CA 93524
The objectives of this research are to develop mathematical models for ignition of composite solid propellants and then to implement them in computational codes and verify their applicability. Currently, modeling of the internal flow of solid rocket motors using computational fluid dynamics (CFD) assumes immediate ignition of the exposed propellant grain, with the igniter acting as a mass flow or mass flux inlet. The resulting simulations are adequate for thrust profile determination but fail to model the actual ignition transient. This short period is important because this is when catastrophic grain failures occur. These types of failures (for example, grain slump and bore choking) require a multiphysics approach for their prediction. Any such multiphysics approaches to modeling the ignition transient will benefit from modeling of propellant ignition. Various factors may influence the time to ignition of the propellant surface, such as combustion gas temperature, exposure time, gas velocity, and boundary layer depth. In this project, mathematical models for ignition of composite propellants will be studied and tested for applicability using simple combustion experiments. The most appropriate ones will be selected for use in computational fluids models, and incorporated using a user defined function (UDF). The researcher will use the relevant CFD variables as inputs to the UDF, with the output being both time to ignition and subsequent mass flux rate. Following this, CFD models will be used with the UDF to simulate verification experiments that validate the models and test the limits of their applicability.
 Li, Q., Liu, P., and He, G., “Fluid-solid coupled simulation of the ignition transient of solid rocket motor,” Acta Astronautica, Vol. 110, 2015; doi: 10.1016/j.actaastro.2015.01.017.
 Charlery, R., Renouf, M., Saulot, A., Daly, N., and Berthier, Y., “Experimental and numerical modelling of the ignition of solid propellant,” Tribology International, 2015; doi: 10.1016/j.triboint.2014.07.012.
 Hu, B., and Wang, B., “Numerical Modeling and Studies of Ignition Transients in End-Burning-Grain Solid Rocket Motors,” J. Propul. Power, Vol. 32, No. 6, 2016, pp. 1333–1343. doi: 10.2514/1.B36024.
solid propellant; ignition transient; rocket motor; finite element analysis; computational fluid dynamics