Experimental optimization of transverse jet injector geometries for mixing into a supersonic flow

Preliminary experiments were performed in a supersonic wind tunnel at a Mach number of 3.0 in which transverse injection into a crossflow was optimized. The method is used to find the locations of circular cross section holes which provide optimum mixing. The holes were located on injector disks which could be fabricated on a rapid prototyping stereolithography system. The injected gas, seeded with ethanol vapor, is illuminated at various locations downstream using an ND: YAG pulsed laser providing spanwise images of the injected plume. From these images, quantities such as cross sectional area, penetration depth, and growth rate could be found. This allowed for optimization of two holes using a simulated annealing method which produced improvements in cross sectional area and penetration depth of 83%and 8% respectively from the baseline case consisting of a single, equivalent area injector. Similarly, when optimization of three holes was performed, improvements in cross-sectional area and penetration depth of 65% and 2%, respectively, were found. Also, a figure of merit was calculated which combined these parameters and gave improvements of 43% and 5% for the two and three hole injector scenarios, respectively.