Vortex-Induced Interfacial Instability As A Means to Improve Droplet Entrainment*

Modern laboratory experiments for hybrid rocket motors are concerned with increasing the fuel regression rate to improve the overall impulse of the engine. The simulations developed in this study demonstrate a novel method to promote droplet formation, atomization, and entrainment of liquid fuel into the gaseous oxidizer flow. A pair of two-dimensional isothermal cases, both with and without the ignition source for the combustion reaction, are conducted to compare its hydrodynamic influence on the oxidizer-fuel interactions. By exploiting the geometry of the ignition source upstream of the fuel, it has been found that the shedding vortices are capable of inducing instabilities at the fuel/oxidizer interface without increasing oxidizer flow rate. These investigations are performed using Volume of Fluid method and were inspired by a slab motor experiment conducted at CHREST at the University at Buffalo.  The results indicate that these vortex-induced instabilities are generated faster and cause improved fuel entrainment in the case where the ignition source is present. This vortex-induced method of improved fuel mixing can provide new avenues for the development of future hybrid rocket motors.