Study of Pre-chamber Jet Combustion Behavior using a Small Two-stroke Optically Accessible Engine

A small 2-stroke engine can be an effective power source for an electric generator mounted on a series hybrid electric vehicle. In recent years, a technology referred to as pre-chamber jet combustion has attracted attention as a means of enhancing thermal efficiency by improving mixture ignitability. In this study, experiments were conducted to investigate differences in combustion behavior between the application of spark-ignited (SI) combustion and pre-chamber jet combustion to a small, two-stroke engine. The experimental equipment used was a two-stroke, single-cylinder, optically accessible engine with a displacement of 63.3 cm3. Differences between conventional SI combustion and pre-chamber jet combustion were examined by means of in-cylinder pressure analysis, in-cylinder combustion visualization and image processing software. The diameter of the connecting orifice of the pre-chamber was varied between two types. The results revealed that the combustion time and indicated mean effective pressure obtained with pre-chamber jet combustion were more stable compared with conventional combustion. It was also found that a linear jet combustion flow was formed with a smaller connecting orifice diameter and the combustion time was shortened, but combustion was not stable. In addition, it was found that the maximum pressure decreased with a higher jet flow velocity.