Simulation of Liquefying Propellants with Swirl

The goal of this research is to numerically investigate the behavior of the liquid layer in hybrid rocket fuels in the presence of swirl. Converge, a commercial computational fluid dynamics (CFD) code, is used to simulate the flow in a cylindrical port hybrid grain. Of particular interest is the effect of the swirling flow on droplet entrainment, which enhances the mass flow rate and increases performance in hybrid rockets. It is found that low levels of swirl, seem to inhibit the formation of the instabilities that lead to droplet entrainment; however, this effect is less noticeable at higher levels of swirl. This may be partially attributed to the nature of the swirling flow in the chamber as the magnitude of the swirl velocity is reduced in the outer portion of the chamber near the liquid layer. This is due to the free vortex structure that has been observed in these flows, with the swirl velocity decreasing with the inverse of the radius.