Mixing of oxygen and iodine in a subsonic coil

The objective of the study is to experimentally investigate the mixing of transversely injected stream of a carrier gas carrying iodine with an oxygen cross-flow in a subsonic Chemical oxygen iodine Laser (COIL). The investigation was performed non-intrusively, using iodine planar laser induced fluorescence (PLIF). A frequency doubled Nd:YAG laser was used as the light source, and the images were acquired using a CCD camera. Injectant mole fraction data was reduced from these images using digital image processing. Experiments were performed for different cross-flow and injected flow rates. A parameter called degree of unmixedness, which was defined as the ratio between the standard deviation of the image intensities and the average intensity, was used to quantify the mixing. A mixing distance was defined as the location downstream of which the degree of unmixedness did not change by 10%. It is seen from the images that for the same injected flow rates, the mixing distance is higher for higher crossflow rates. It is also observed that for a given crossflow rate, higher injected flow rates lead to lower mixing distances. The mixing distances obtained were correlated using the ratio between the momentum flow rates of the injected jets and the cross-flow. The mixing distances were found to decrease with increasing momentum ratios.