氧碘化学激光器射流数值模拟方法研究

Numerical simulation of COIL injection

为了研究氧碘化学激光器喷流流场流动情况,采用数值方法求解二维可压缩非定常Navier-Stokes方程及组分连续方程,空间离散格式为AUSM+up格式,用四步龙格-库塔方法作显式时间推进,湍流粘性系数使用k-ε两方程湍流模型进行求解。假设混合气体为热力学完全而热值非完全气体,化学反应模型采用有限速率反应模型。使用一种松弛迭代的方法来处理化学源项的刚性问题。计算了一个标准算例,结果与美国GASP程序计算结果符合良好。对氧碘化学激光器流场进行了二维数值模拟,研究了该激光器中激发态氧初始产额、水蒸气含量以及不同喷管数目对增益分布的影响。结果表明,除水和增加激发态氧初始产额都可使小信号平均增益增大,采用两个碘喷管比采用一个碘喷管能够获得更大的小信号平均增益。

In order to study the injection field of a chemical oxygen iodine laser（COIL） ,the injection flows in supersonic COIL were simulated by solving the Reynolds averaged Navier-Stokes equations and species continuity equations based on fourstage Runge-Kutta time-stepping scheme on structured viscous mesh. The simulations were carried out with AUSM ＋ up scheme employing the k-ε turbulence model. The finite-rate reaction model was employed with thermodynamic perfect gas properties for chemical reaction. The stiffness problem of chemical source was overcome by a relaxation iterative scheme. Transverse He-I2 injection test case was simulated with this method. The results were in good agreement with the result of AeroSoft＇s GASP. The supersonic COIL flows with He-I2 injection were also simulated. The distribution of the mass fraction and averaged small signal gain were calculated. The results showed that the averaged small signal gain increased with the increasing of O2 （ ^1△ ） yields or with the decreasing of the water vapor. The averaged small signal gain of a COIL with two spouts is bigger than that of a COIL with one spout.