Experimental and numerical studies of diamond-shaped injector in a supersonic flow
Reacting and nonreacting flowfields around a diamond-shaped fuel injector were investigated in a Mach 2.0 freestream, experimentally and numerically. The goals of the inert mixing studies were to (1) compare the flow structure around a diamond injector between two leading-edge injection angles (45 and 90 degree) and (2) investigate the flow features with dual-port torch injection. The goal of the reacting studies, on the other hand, was to examine the reactivity in the lateral counter-rotating vortex pair (LCVP) under the high temperature test conditions. NO- and OH- planar laser-induced fluorescence (PLIF) diagnostics were used to accomplish these goals, and some complementary 1-D and 3-D numerical simulations were performed. The plume penetration of the diamond port with 90-deg. leading-edge injection was found to be slightly higher than that with 45-deg. leading-edge injection. The NO-PLIF images captured the 3-D structure of the LCVP for the first time, and it agreed well with the 3-D numerical simulations. OH consumption in the LCVP was clearly observed when ethylene was injected from the diamond port and the fuel-lean upstream torch was applied, but intensive combustion was not attained. Even when oxygen was injected from the diamond port and the fuel-rich upstream torch was applied, the reaction in the LCVP was still insufficient. The 3-D simulation estimated the mole fraction of the diamond gas and torch gas in the LCVP as 70% and 5%, respectively. The 1-D reaction calculation explained the phenomena observed in combustion tests and predicted that autoignition and flameholding are possible when the total temperature of airflow is ~2600 K and fuel is hydrogen. Copyright 2009 by the American Institute of Aeronautics and Astronautics, Inc.