レーザー誘起ブレイクダウンを用いた着火における予混合気初期温度の影響

摘要

現在環境負荷低減や高効率な燃焼器の設計開発が求rnめられており，希薄予混合燃焼はその方策の一つとしてrn重要視されている．実用燃焼器における，希薄予混合燃rn焼に対しては，確実な着火が求められており，プラグをrn用いた火花点火方式に代わる新しい着火手法として，レrnーザー誘起ブレイクダウンを用いた着火（以後　レーザrnー着火とする）が提案・検討されている．%Laser-induced ignition gathers attention as the relatively new technique of ignition owing to its flexibility of ignition point that could be of benefit for stability and combustion efficiency in the lean premixed combustion. In this study, the laser-induced ignition phenomena have been investigated experimentally, especially on the relation between the initial temperature of the premixed gas and the minimum ignition energy. Methane/air mixture is used as the premixed gas. The initial temperature of premixed gas is varied from 300 K to 450 K under the constant molar density. Results clearly show that the absorption energy to the plasma is not affected by the increase of the initial temperature of premixed gas. In addition, the minimum incident energy for ignition decreases with the increase of initial temperature of premixed gas. Eventually, the increase of the initial temperature improves the ignitability of premixed gas by the laser-induced ignition.