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

超声速流化学氧碘激光器（S-COIL）工业应用的障碍之一是排气压力低，这就需要一个巨大的压力回收系统来实现废工作混合物的排放。为了使系统小型化，应采用高总压的活性氧碘增益介质来提高废气的滞止压力。然而，引入混合室的氧气流的停滞压力不能提高，因为目前可用的单线态氧气发生器在低压下运行。另一方面，碘流可以被提升到更高的压力。通过将高压碘流与低压氧流混合，我们可以提高增益介质的总压强。为了在不引起冲击波或其他不良影响的情况下做到这一点，碘流应该扩大到足够的规模，使两股流的压力在它们加入时匹配。换句话说，高马赫数的碘流应与低马赫数的氧流混合。因此，在本研究中，对具有不同马赫数的两种流动之间的混合特性进行了数值研究。采用斜喷管阵列超音速平行混合系统。研究了三种类型的喷嘴，即(a)坡道喷嘴，(b)对称坡道喷嘴和(c)对称横扫坡道喷嘴。每个喷嘴阵列都有一个不均匀的堆积形状，目的是产生涡流，增强混合。氧和碘两种流动分别在喷嘴内膨胀，单重态δ氧在低滞止压力下的流动加速到单位马赫数，碘经氮稀释后在高滞止压力下的流动加速到较高马赫数（= 4.8）。通过对等效一维流动的检验，确定了喷嘴尺寸和流动的充气条件。为了提高超声速流盘管废气的压力回收，对不同马赫数的氧和碘两种气流的混合特性进行了数值研究。计算了三种喷管的流场，分别是斜坡喷管、对称斜坡喷管和对称后掠斜坡喷管。结果表明，与其他两种喷管相比，对称后掠斜喷管的增益显著提高，排气压力降低，但可以忽略不计。少

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