Effects of Piston Design and Inlet Gas flow on the Performance and Exhaust Emissions in a Natural Gas Fueled Spark Ignition Engine

Abstract

An experimental study was made on a natural gas fueled spark ignition engine to improve its thermal efficiency and exhaust emissions by the lean burn operation. A multi-cylinder engine was tested for purposes of practical application. Investigated were the effects of the piston design and the gas motion induced by a shrouded inlet valve on the combustion process, the thermal efficiency, exhaust emissions and the lean limit of stable operation. It was found that a bowl-in-piston resulted in higher thermal efficiency and extended lean limit as compared with a flat piston. A shrouded inlet valve generally resulted in shorter duration of combustion, lower NO_x emissions and lower thermal efficiency than a conventional valve. When a shrouded inlet valve was set so as to direct the mixture flow toward the prechamber throat, the lean limit was extended with low exhaust emissions and relatively high thermal efficiency.