Extending the Lean Limit Operation of an SI Engine with a Multiple Electrode Spark Plug

The objective of this paper is to study the lean limit operation of a spark ignited internal combustion engine. The aim is to reduce the combustion duration and cyclic variation in lean mixtures; both of which are sensitive to the initial stage of combustion. This work involves increasing the burning rate in lean mixtures by minimizing the ignition delay through the use of a multiple electrode spark plug that has a total gap length of 10.2 mm.

The multiple electrode spark plug was tested on a single cylinder engine and its performance was compared with a conventional spark plug in the following areas: lean limit air-to-fuel ratio; CO, HC, and NO emissions: cyclic variations; and combustion duration.