Experiments in Stratified Combustion with a Rapid Compression Machine

Abstract

High-speed movies and analysis of rapid compression machine experiments were used to study mechanisms that control combustion rates in the Texaco Controlled Combustion System. The Texaco system is a spark-ignited, direct injection, stratified charge engine with a deep cup in the piston, relatively high swirl in the combustion chamber, and injection-controlled timing. The fuel injection nozzle is directed at spark plug electrodes. Air swirl is oriented to carry fuel from the injector to the spark plug. The Texaco stratified charge engine has demonstrated good fuel economy, relatively low emissions, and a wide fuel tolerance. A rapid compression machine was employed to obtain performance data and high-speed combustion photographs with the Texaco geometry. Experimental results were analyzed to describe the combustion process, particularly physical mechanisms that control mixing and combustion rates. Air motion in the combustion chamber appeared to be dominated by air swirl, and simple mass and momentum arguments could be used to calculate air swirl at top dead center. Fuel jet motion for the injector to the spark plug could be computed with a single jet mixing model. A similar model also appeared to be appropriate for calculating the motion of unburned fuel-air mixture in the wake of spark plug electrodes.