激光器中压气体风冷系统的实验研究

本文通过模拟传热模型,建立起激光器风冷系统的换热基本方程式.分析指出:仅当热阻主要集中于光泵浦——冷却质一侧时,增加循环工作物质密度才有提高换热效果、减小流动阻力、降低风机耗功的明显效果.在此基础上研制成功重复率为10c/s,热耗散功率200W的激光器中压气体封闭循环风冷系统.实验研究所用气体压力P、流速W、壳体外壁侧热阻等诸因素对冷却效能影响的结果亦与分析结论一致.     

Highly efficient CW laser operation in 4 at. % Tm~(3+) and 4 at. % Y~(3+) codoped CaF_2 crystals

Tm:CaF_2 and Tm;Y:CaF_2 single crystals were prepared by the temperature gradient technique. The spectral properties of Tm;Y:CaF_2 single crystals were investigated and compared with those of Tm:CaF_2. It was demonstrated that codoping with Y~(3+) ions could efficiently improve the spectroscopic properties. Tm;Y:CaF_2 crystals have larger absorption cross-sections at the pumping wavelength, larger mid-infrared stimulated emission cross-sections, and much longer fluorescence lifetimes of the upper laser level(Tm~(3+):~3H_4 level) than Tm:CaF_2 crystals. Continuous-wave(CW) lasers around 1.97 μm were demonstrated in 4.0 at. % Tm,4.0 at. % Y:CaF_2 single crystals under 792 nm laser diode(LD) pumping. The best laser performance has been demonstrated with a low threshold of 0.368 W, a high slope efficiency of 54.8%, and a maximum output power of 1.013 W.     

向心透平稳态全工况性能预测及其实验研究

将向心透平膨胀机喷咀入口至叶轮后扩压管出口模拟为单喷管,通过理论分析,推导出向心透平稳态全工况特性通用模型框架。基于实测数据,应用广义最小二乘法,获得通流特性和效率特性二个模型。用该模型预测其它两台透平膨胀机的特性,结果表明:模型实用范围和精度都较好。因此,在设计向心透平时,它可作为典型特性模型,为全工况优化设计提供依据。     

高重复频率中压氮气风冷固体激光器

一般风冷无法对高重复频率的光泵浦实施有效冷却;水冷却液虽换热系数高,但体积庞杂,水冷液产生的锈蚀和光耗还将引起激光器稳定性极大下降.本文的分析表明:激光棒表面平均温度t_(wim)与环境大气温度t_a之差主要取决于激光棒单位长度上耗散的热功率q_l、冷却质密度ρ及流速w.