Flowfield studies of a diamond-shaped fuel injector in a supersonic flow

Studies were performed to characterize the flow structure and the mixing characteristics of a diamond-port flush-wall fuel injector at Mach 2.0 airflow. The goals were to examine the flow structure in the near-field region of the diamond- and circular-port injectors and to quantify the effects of igniter torch flow on the near-field How structure with and without torch gas. Planar laser-induced fluorescence was used to document the flow trajectories and the injector-barrel shock shape for the injectors. For the inert mixing studies, the flow was seeded with a nitric-oxide-trace probe molecule, whereas for the reacting experiments, naturally occurring hydroxyl was used. The present experiments confirmed recent computation results that implied that under certain conditions, a diamond-shaped injector port could be tailored to improve mixing and produce an additional secondary flow structure with gasdynamic flame-holding potential. It was also shown that an igniter torch system could be incorporated without adversely affecting the tailored flow structure.