Quantitative Mixing Measurements of a Supersonic Injection COIL Nozzle with Trip Jets

摘要

A supersonic nozzle with supersonic iodine injection was designed and studied with Planar Laser-Induced Fluorescence (PLIF). The nozzle simulates Chemical Oxygen Iodine Laser (COIL) flow conditions with non-reacting, cold flows. A laser sheet near 565 nm excited the iodine, and the fluorescence was imaged with an intensified and gated CCD camera. Streamwise and semi-spanwise (oblique-view) images were taken, where the presence of injected flow was highlighted. With these images, the flow structures were identifiable and the mixing quality between the primary and injected flow was quantitatively measured with histograms, structure size measurements, and jet penetration. Four different injection scenarios are investigated. The first scenario includes a single injector positioned downstream of the nozzle throat. To enhance the mixing between the flows, trip jets were placed in the wake of the single jet. The trip jets, significantly smaller than the primary iodine jet, are intended to destabilize the counter-rotating vortex pair (CRVP) of the primary jet. Three different trip jet configurations are compared for their ability to enhance mixing between the oxygen and iodine flows. While the mixedness between the injected and primary flows was not optimized, the comparison between the four different injection scenarios may aid in future nozzle design and mixing optimization.