Combustion characterization of natural gas in a lean burn spark-ignition engine

Lean burn natural gas fuelled spark-ignition engines are particularly attra ctive regarding environmental performance. Nevertheless, few data exist con cerning lean combustion in gas engines in terms of ignition delay, combusti on duration and combustion rate. Such data are necessary when using thermod ynamic models to predict energy and environmental performance. The present study proposes a contribution to such combustion characterization as a func tion of spark timing, air excess and engine load. This work is based on exp erimental cylinder pressure measurements in an open chamber engine on the o ne hand, and on a one-zone thermodynamic model used as a heat release analy sis tool on the other hand. Results obtained, such as mass fraction burned, ignition delay and combustion duration, allow identification of the parame ters used in the Wiebe function, a semi-empirical law that is frequently us ed to describe the combustion in predictive models.