Investigation of Flame Propagation under High Pressure Conditions in a Rapid Compression Facility using High-Speed Optical and Pressure Diagnostics

摘要

Fundamental studies on the initiation and propagation of reaction fronts or flames into premixed fuel/air mixtures are important to developing new strategies to improve combustion efficiencies, particularly at conditions that are the emphasis of modern engine design. This study focuses on supplementing the limited experimental data on flame propagation into premixed gases at high-pressure and moderate temperature conditions. Experiments were conducted in a spark plug equipped rapid compression facility (RCF) using high-speed optical and pressure diagnostics. Fast image processing algorithms were coupled with pressure measurements to determine key quantitative metrics of reaction fronts initiated by the spark discharge, and propagated into premixed iso-octane and air. Initial reaction front results for P ≌ 8 atm and T ≌ 950 K indicate that the lean flammability limit is Φ ＝ 0.4. Flame speeds/reaction front propagation rates were measured in the range of 1.3-1.6 m/s. The presence of reaction fronts reduced the ignition delay time compared to conditions when no reaction fronts are initiated.