Computational Modeling and Sensitivity Evaluation of Liquid Rocket Injector Flow

A three-dimensional computational model of an experimental rectangular combustion chamber was developed to explore the wall heat transfer of a GO2/GH2 shear coaxial single element injector. The CFD model allowed for the direct analysis of heat transfer effects due to flow dynamics—an analysis that would be very difficult using experimental studies alone. The use of a 3-D CFD model revealed heat transfer effects due to flow streamlines and eddy conductivity, and provided insight into the two-dimensional nature of the wall heat flux. A grid sensitivity study was conducted to determine the effects of grid resolution on the combustion chamber length and heat flux. The results of a grid sensitivity study were inconclusive, as a grid-independent solution could not be reached. However, it was found that the predicted heat flux was largely independent of the grid resolution, as long as the near-wall region was well resolved. Finally, a single-element injector model was constructed to explore the sensitivity of the peak heat flux and combustion chamber length to the circumferential and radial spacing of injector elements in the outer row of a multi-element injector. Many cases, including the baseline case, had a recirculation region that was oriented such that the outer shear layer was directed at the combustion chamber wall, resulting in a large peak heat flux near the injector face. It was found that by increasing the spacing between injector elements of the outer row while reducing the distance of the outer row to the wall, a relatively flat heat flux profile could be obtained.