噴射条件ならびに燃焼室形状が天然ガスデュアルフュエル過給機関の性能・排気特性に及ぼす影響

Abstract

This study aims to obtain a strategy for optimizing the combination of diesel-fuel injection conditions and combustion chamber geometry to achieve high thermal efficiency with low exhaust emissions in a natural-gas/diesel dual fuel engine. Experiments were performed using a single-cylinder test engine with a common-rail injection system varying injection timings of two-stage pilot injection and piston bowl diameter. The pilot spray development was calculated using CFD simulation to understand the mechanism of experimental results. The experimental results showed that a smaller bowl diameter reduces THC and NOx emissions under a condition of high equivalence ratio, and the CFD results showed that the smaller bowl diameter provides a richer mixture of 1st pilot injection and a leaner mixture of 2nd pilot injection than a larger bowl diameter.