Experimental and analytical characterization of a shear coaxial combusting GO2/GH2 flowfield

Abstract

Detailed measurements of the flow velocities and major species distributions downstream of a uni-element shear coaxial injector in a gaseous oxygen/hydrogen (GO2/GH2) rocket chamber are presented and compared with CFD predictions from a reacting Navier-Stokes solution. The velocity profiles are obtained by means of laser Doppler velocimetry, while the species (H2, O2, and H2O) are measured by Raman spectroscopy. The CFD predictions are in good agreement with the measurements, although they moderately overpredict the spreading rate of the reaction zone at the downstream location. Both experimental and numerical results indicate that the shear coaxial injector mixes slowly but that combustion is completed on a length scale representative of that tested in actual combustors. The experiments show high c* efficiency, and the computations show the flame combusts all the GO2, both suggesting complete combustion. Detailed CFD resolution shows that the base region behind the GO2 post tip acts as a flameholder for the GO2/GH2 flame. Overall, the results demonstrate that advanced diagnostics and CFD predictions can be used in concert as tools for gas/gas injector design. (Author)