Erosive Effects and Melt Layer Stability in Solid Fuel Scramjets

One of the most fundamental issues of hypersonic vehicle design is the requirement for propulsion, engine-airframe integration: systems are so tightly coupled the aero and propulsion cannot be separated from each other. The tight integration of engine and airframe in scramjets can be facilitated by solid fuel walls that reduce the heat losses of the highly integrated combustion chamber and provide a simple valve-free mechanism to produce thrust. The main drawback of solid fuels wall is the change in geometry during flight that leads to variations of the combustion efficiency. The present computational investigation aims at improving the state of the understanding of the interactions between solid fuel walls and working fluid with emphasis on the processes that control pyrolization and wall regression. The most important issue in modelling the regression rate is to approximate the effect of the shear stress on the fuel burn rate laws. This is known as erosive burning in solid propellant literature. In the present work, we evaluate the effect of shear stress on the burn rate and propose a computational model of its physics based mixing length damping near the wall.