Experimental and numerical investigation of combustion characteristics on GO2/GH2 shear coaxial injector

This study presents the results of a visualization investigation of the gas–gas injection combustion characteristics using a shear coaxial injector of non-premixed gaseous oxygen and gaseous hydrogen (GO2/GH2) under elevated ambient pressures. Advanced optical diagnostic approaches, including hydroxyl (OH) planar laser-induced fluorescence (PLIF) and high-speed imaging, are employed to capture the spatial distribution of the OH radical and the instantaneous flame dynamics near the faceplate. Experimental results indicate that an instantaneous reaction zone represents an apparent local extinction and re-ignition phenomenon, but does not affect the overall time-averaged reaction distribution. In addition, this study adopts the same ignition device and sequence used in a previous study; however, a different ignition process occurs. The reasons for this difference may be attributed to the fact that the exorbitant pressure peak disturbs the originally stable, downstream, cold-flow fields near the axis, which radically change the initial ignition and flame propagation processes. In order to demonstrate the feasibility and effectiveness of the applicability of computational fluid dynamics (CFD), several different associations of Reynolds averaged Navier–Stokes (RANS) approaches are compared with each other and with the experimental results. This proves that the turbulent model plays a dominant role in affecting the flow field structure. Based on the comparison with optical diagnostic results, a numerically-aided approach using RANS simulation is proposed to quantify the experimental results. This study is a first attempt to establish a standard corresponding relation between the simulation results and the optical diagnosis results.