气流化学激光理论研究的若干进展

以超声速HF/DF化学激光和超声速氧碘化学激光(COIL)为代表的气流化学激光(GCL), 因其科学意义、军事和工业应用价值，近30多年来得到了突飞猛进的发展.由于超声速膨胀混合流在控制强放热反应动力学和热力学过程方面的特殊本领，使气体动力学在高功率GCL的发展中起着关键性的作用.高功率GCL性能的分析计算自然也沿用非平衡气体动力学的方法，假定气流(包括激光能级分子和原子)为连续介质，谱线为均匀加宽，并联立求解气体动力学方程组，增益动力学和基于光强迭加原则的辐射传输诸方程，称为速率方程(RE)模型.20世纪70年代后期又提出和发展了GCL性能计算的半气体动理学(SGK)模型，在SGK模型中仍假定气流为连续介质，但同时考虑了激光能级分子微观热运动的贡献，谱线加宽的非均匀加宽效应，并用双参数摄动法求解激光能级分子速度分布函数方程组(即广义Boltzmann方程组), 因此SGK模型是一个同时考虑宏观和微观尺度运动的跨尺度模型.本文综述RE模型和SGK模型以及用它们预测GCL性能的若干研究进展，同时简评等增益模型和腔模(模图样)理论研究的一些进展.最后从气体动力学的角度提出一些值得 进一步研究的课题.

RESEARCH PROGRESS ON GAS FLOW-CHEMICAL LASER THEORIES

Gas flow and chemical lasers, with supersonic CW HF/DF chemical laser and supersonic chemical oxygen-iodine laser(COIL) as their chief representatives, are making a great progress owing to their scientific significance, and military and industrial applications in recent thirty years. Because the supersonic mixing flow has a special capacity to control the strong- release-energy reaction dynamics and thermodynamic processes, nonequilibrium gas dynamics play a key role in developing gas flow and chemical lasers. The analysis and calculation for high power GCL performances continue to use methods of nonequilibrium gas dynamics, i.e., to assume the gas flow (including laser gas compositions) to be a continuous medium and the line profile to be broadened homogeneously and to solve simultaneously the gas dynamics equations, gain dynamics and radiation transfer equations, which was called the rate equations(RE) model. A semi-gas kinetics(SGK) model for predicting GCL's performance was presented in the late 1970s. In the SGK model, the gas flow is still assumed as a continuous medium, however, the influence of thermal random motions of lasing molecules on the GCL's performance and the inhomogeneous broadening effects are considered, a double-parameters perturbational method is used to solve the generalized Boltzmann equation describing the change of the velocity distribution function of lasing energy-level molecules. Therefore, the SGK-model considers both the macroscopic and microscopic scales. Some research progress on the RE- and SGK-models and their applications in predicting GCL's performances are presented in this paper. Some advances on the equal-gain model and the cavity-mode (or mode pattern)theory are discussed briefly. In view of gas dynamics, we present some topics worthy of further studies.