Fundamental studies on direct conversion from thermalenergy to photo energy using unsfeady exciled state ofmolecales

本研究是为了发展利用碳氢化合物燃烧产生的非稳态作为热能-光能转换器的CO_2气体动力激光器而进行的。在这项研究中，甲烷/空气燃烧室的基本特性在常压和加压条件下进行了实验研究。结果表明，该燃烧室具有宽调节比，可达48位。这意味着燃烧室可以在宽负荷下进行控制。从理论上研究了高浓度H_2O共存对CO_2（001）和CO_2（100）能级间粒子数平衡的影响。结果表明，当甲烷/空气为化学计量比的燃气通过超声速喷管膨胀到马赫数为5.0时，可以实现粒子数在其能级之间的反转，从而获得激光发射。当H_2O浓度为0.4时，数密度比达到最大值，且峰值位置随H_2O浓度的增加而向上游移动。在N_2浓度一定的情况下，粒子数反转的幅度随燃料C/H的增大而增大。在实验和理论研究的基础上，通过增益测量证实了粒子数反转的存在。结果表明，输入激光功率通过激光腔被放大。这意味着人口反转的出现。

This study was done in order to develop CO_2 gas dynamic laser using unsteady states generated by combustion of hydrocarbons as a converter of thermal energy to photo energy An unsteady flame propagation combustor was developed applicable to the driving gas generator. In this study, the fundamental characteristics of the combustor using methane/air at normal pressure and pressurized condition were experimentally investigated. It was found that the combustor has the wide turn-down ratio up to 48 digit. It means the combustor can be controlled in the wide load. The combustion of methane/air was well promoted because combustion is occurred through the whole combustion chamber.The effect of coexisting H_2O with high concentration on the population balance between CO_2 (001) and CO_2 (100) levels was theoretically investigated. It was found that the populations inversion between their levels enough to obtain laser emission can be realized when the combustion gas with the methane/air at stoichiometric ratio is adiabatically expanded so as to achieve the Mach number 5.0 through the supersonic nozzle. The ratio of the number densities becomes maximum at 0.4 of H_2O in concentration, and the location where the peak appears shifts upstream with increasing H_2O concentration. The magnitude of the population inversion increases with increasing C/H of fuel in constant concentration of N_2. But the width in the streamline keeping the population inversion becomes narrow in high concentration of H_2O.Based on the experimental and theoretical studies above, the gain measurements to confirm an existence of a population inversion were done. The results obtained showed that input laser power was amplified through a laser cavity. It meant the appearance of the population inversion.