Modeling of a sinusoidal lobed injector: Vorticity and concentration fields for a cold flow

In this report, we present a simple and somewhat preliminary numerical model of a sinusoidal lobed injector. The lobed (corrugated) injector is being considered by several investigators as a potentially efficient device to mix fuel and air for combustion purposes. In this configuration, air flows parallel to the troughs and valleys of corrugations which grow in amplitude in the stream-wise direction. These ramped corrugations produce stream-wise vortices which enhance the downstream mixing. For the lobed injector, the corrugations are actually double walled which allows one to inject fuel through the space between them into the flow downstream of the ramp. The simulation model presented herein is based on a vorticity formulation of the Navier-Stokes equations and is solved using an unsteady viscous vortex method. In order to demonstrate the utility of this method we have simulated the three-dimensional cold mixing process for injection of methane gas into air. The vorticity and fuel concentration field downstream of the injector are simulated for two different injector geometries. We observe from these two simulations that variation of the amplitude of the corrugations can be used to achieve considerably different mixing patterns downstream of the injector