Influence of Vortex-Shedding on Interfacial Instabilities in Hybrid Rocket Fuel Liquid Layers

With research in hybrid rocket motors becoming of interest due to their controllability and safety, the need has arisen for investigation into how to enhance the performance of these motors to become more comparable to current options. As regression rate is an area of hybrid rocket engine performance that needs to be improved, the introduction of vorticity in the oxidizer flow is a novel method to excite instability in the layer of melted paraffin-based fuel to increase mass entrainment which, in turn, would increase regression rate. In this paper, Volume of Fluid method was explored as a means to simulate the influence of an obstruction in the oxidizer flow, namely the glow plug ignition source used in experimental setups, in shedding vortices to trigger instabilities in the liquid interface. A two-dimensional simulation of cases with and without the glow plug were conducted for a cold-flow case to isolate its hydrodynamic influence on the oxidizer-fuel interactions. Results from these simulations of the slab burner experiment showed significant changes in vorticity generation between cases as well as an increase in mass entrainment by several orders of magnitude. As such, these observations open the door to investigation into the role of vorticity in combustion performance. As more is understood in this area, these insights can aid in prediction of new hybrid motor performance and guide future development.