Development of exhaust gas pressure recovery system for supersonic-flow chemical oxygen-iodine lasers

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One of the hindrances in industrial applications of supersonic-flow chemical oxygen-iodine laser (S-COIL) is the lowness of the exhaust gas pressure, due to which a massive pressure-recovery system is required to implement the discharge of the spent working mixture. In order to downsize the system, the stagnation pressure of the exhaust gas should be improved by means of utilizing an active oxygen-iodine gain medium at a higher total-pressure. However, the stagnation pressure of the oxygen flow, which is introduced to the mixing chamber, cannot be raised since singlet oxygen generators available today operate at a low pressure. The iodine flow, on the other hand, can be boosted to higher pressure. By mixing this high-pressured iodine flow with the low-pressured oxygen flow, we can raise the total pressure of the gain medium. In order to do this without causing shockwave or other undesirable effects, the iodine flow should be expanded enough so that the pressures of both flows match whe … More n they join. In other words, the iodine flow having higher Mach number should be mixed with the oxygen flow having lower Mach number. Thus, in this study, the mixing characteristics between two flows having different Mach numbers are numerically examined. A supersonic, parallel mixing system with ramp nozzle array is adopted.Three types of nozzles, namely, (a) ramp nozzle, (b) symmetric ramp nozzle, and (c) symmetric swept-ramp nozzle are examined. Each of the nozzle arrays has an unevenly-piled shape with the intention of causing vortex and enhancing mixing. The two flows of oxygen and iodine expand separately in the nozzle : The flow of singlet-delta oxygen at a low stagnation pressure accelerates to unit Mach number, while the flow of iodine, which is diluted with nitrogen, at high stagnation pressure does to a higher Mach number (= 4.8). The nozzle dimensions and plenum conditions of the flows are determined based on the examination of an equivalent one-dimensional flow.The characteristics of mixing between two flows of oxygen and iodine, having different Mach numbers, are numerically examined with the intention of improving the pressure recovery of the exhaust gas of supersonic-flow COIL. The flow fields are calculated for three types of nozzles, namely, ramp nozzle, symmetric ramp nozzle, and symmetric swept-ramp nozzle. The results indicate that the symmetric swept-ramp nozzle has significantly higher gain and negligibly lower exhaust gas pressure than other two. Less