A Preliminary Investigation of a Hydrogen Injection Wedge Strut for a Scramject Combustor Application

This M.Eng Report is a preliminary investigation of the strut geometry in a strut-based hydrogen scramjet combustor and assesses flow characteristics in an inviscid and viscid flow with no hydrogen injection, a viscid flow with hydrogen injection, and a viscid flow with hydrogen injection and combustion model. This investigation is performed using ANSYS Fluent. The viscid cases utilize the Shear Stress Transport (SST) k-omega model for turbulence, with the volumetric eddy dissipation model for combustion case. Results in this study are validated against the same wedge strut geometry and results from the Deutsches Zentrum für Luftund Raumfahrt (DLR) scramjet, by Waidmann [1], and a grid independence study is conducted for completeness. Performance of the different geometries are quantified by mixing efficiency, combustion efficiency, and total pressure recovery. The 2-dimensional results of this paper are comparable to the Schlieren images (shadow graphs) of the DLR combustor. 

The viscid case with no hydrogen injection is compared to the inviscid case with no hydrogen stream, resulting in the presence of boundary layers and shear layers. This increased the strength and quantity of shock/expansion wave reflections downstream of the strut. The addition of the hydrogen stream increased the thickness of the central wake region along the combustor, further increasing strength of the shock reflections, as well as creating a symmetric recirculation region downstream of the strut. The eddy-dissipation combustion model is applied, resulting in a larger, non-symmetric recirculation region. The combustion efficiency reached 78.42% with complete mixing at 245 mm along the combustor, whereas the non-combusting case achieved complete mixing at 225 mm along the combustor. The high entropy caused by the irreversible processes across several strong shocks in the combustion case attributed to a total pressure loss of 46%.