Experimental Study On New Ignition System And Gain Generator With Gaseous Film Cooling For Combustion-driven HF/DF Lasers

Continuous running time is one of the key parameters of the lasers, and to improve the reliability of long operational combustion-driven continuous wave(CW) HF/DF lasers is a major research content. The gain generator of the combustion-driven chemical laser runs in harsh environment with high temperature, high pressure and strong oxidizing, wherefore the ablation problems turn to be the main limitation for the long operational reliability of the lasers. As for the ablation, the most serious problems appear at the spark-plug ignition and the throat of the nozzle banks. A new ignition system with F2 gas generator and a new type of gain generator with film cooling were designed and tested in experiments. The feasibility and ablation resistance of the new ignition system and film cooling gain generator were verified.For the reliable ignition requirements of combustion-driven CW HF/DF lasers, a F2 gas generator and its supporting experimental system were designed and built. Self-ignition experiments were carried out under atmospheric and vacuum conditions to verify the F2 gas generator`s own stability and reliability, and the regular pattern that molar ratios of F/F2 and equilibrium temperature of the products change along with the different proportions of the oxidant(NF3) and fuel(H2) in the F2 gas generator was investigated. New ignition system with F2 gas generator were tested for nearly one hundred times in the real ignition experiments and all these experiments got succeed through reasonable timing control which fully verify the stability and reliability of the new ignition system. The new ignition system with a F2 gas generator provides an alternative to the conventional spark-plug ignition.A new type of He-gaseous film cooling gain generator and its experimental systems were designed and built for the ablated problems in the throat of the combustion-driven chemical lasers` nozzle banks. Ablative verification experiments which last for 1s/5s/10s/30s/60 s were carried out under specific conditions of combustion gas mass flow. The total pressure in the combustionn chamber remained stable in the experiments, and the cooling water`s temperature tends to be balanced at about 46℃ in the exit of the nozzles` convergence segment and at about 36℃ in sidewalls of the chamber. Ablation phenomenon did not occur in the nozzle throat. Ablation experiments at different cooling gaseous film mass flow were launched and all the experiments fully confirmed the protective effect of the gas film for the nozzle throat. The film cooling gain generator is proved to be a technological approach to solve the ablation problem in the gain generator of combustion-driven chemical lasers.