エタノール予混合火炎の層洗および乱流燃焼速度に及ぼす圧力の影響

摘要

Spherically propagating laminar and turbulent flames at elevated pressures in a large volume chamber were studied for ethanol / air mixtures. The properties of the ethanol flame at elevated pressures, especially the burning velocity and the effects of the flame stretch acting upon it are quit important for the modeling of combustion in internal combustion engines. Experiments were carried out in the wide range of the equivalence ratio from 0.8 to 1.4 at two turbulence intensities of 0.80 and 1.59m/s varying the initial pressure from 0.10 to 0.50MPa. The unstretched laminar burning velocity decreased with increasing initial pressure. The ratio of turbulent burning velocity to unstretched laminar burning velocity increased with increasing the turbulence Karlovitz number. This ratio of the burning velocities was large for rich flames. Thermo-diffusive effects might be more influential to rich ethanol flames because of their small Lewis number. The ratio of turbulent to laminar burning velocity was also found to increase with increasing initial pressure.%近年，地球温暖化やエネルギー資源枯渇の観点から，温室効果ガスである二酸化炭素の排出量削減，石油代替燃料の利用や高効率燃焼法の開発が求められている。バイオエタノールはカーボンニュートラルな燃料であり，正味の二酸化炭素の排出量が少ないとされ，内燃機関の代替燃料として期待されている。これまでにエタノールの燃焼については，IsodaとKumagai による液滴燃焼に関する報告や，Gulderによる予混合燃焼に関する基礎燃焼特性の報告，またAgarwaによる実機における燃焼特性に関する報告がなされている。