Effect of Engine Specifications on In-Cylinder Flow Field in a Spark-Ignited Natural Gas Engine

Abstract

An experimental study was made to investigate the effects of engine specifications on in-cylinder flow field in a spark-ignited natural gas engine. The instantaneous two-dimentional flow field in a single-cylinder visualization engine was measured by using the PTV method over the wide range of piston combustion chamber configuration, top clearance, and nominal swirl ratio. The results showed that swirl is more shifted to the outward radial direction in expansion stroke as piston cavity diameter decreases. In compression stroke, however, the extent of swirl shift is almost constant even if piston cavity diameter varies. Reverse squish is more accelerated than swirl as piston cavity diameter decreases. Smaller piston cavity diameter resulted in larger squish velocity and actual swirl ratio. Top clearance had little effect on flow field. Swirl is more shifted to the outward radial direction in expansion stroke as nominal swirl ratio decreases. Higher nominal swirl ratio resulted in larger actual swirl ratio, while it had little effect on squish velocity.