Tetra CFD Applications
Solid Rocket Motor Ignition Using Loci/CHEM
Solid rocket ignition involves complex processes of propellant heating, gasification, and surface and gas phase chemical reactions that take place over brief very period of time before the burning becomes self-sustaining. We do not simulate the detailed physics of the ignition process but rather replicate the ignition behavior through mathematical models of varying complexity. The simplest model uses a temperature switch that turns on the surface burning boundary condition when the surface temperature reaches the specified value. For many problems, this actually works reasonably well, with the exception that it underestimates the temporal delay due to combustion initiation and propellant heating. A more complex model, which is the subject of an ongoing STTR Phase I research project ( Advanced Flow Analysis Tools for Transient Solid Rocket Motor Simulations), considers the thermal soak of the propellant, surface and gas phase reactions, and physical burn back of the grain with mesh recession to more realistically simulate the transient ignition process. The tools being developed are available in Loci/CHEM by special arrangement.
The above example shows the temperature contours in a solid rocket motor ignition simulation using the thermal soak model with gas and condensed phase reactions contributing to the propellant heat flux.