EXPERIMENTAL STUDIES ON LOW PRESSURE SEMI-DIRECT FUEL INJECTION IN A TWO STROKE SPARK IGNITION ENGINE

摘要

In this work a two-stroke scooter engine was modified to work with semi-direct injection of gasoline at a pressure of 8 bar from an injector in the cylinder barrel pointed toward the cylinder head. The influence of injection timing, injection pressure, spark plugjocation and air-fuel ratio, on performance, emissions and combustion characteristics has been investigated. In addition, a comparison has been made with manifold injection of gasoline on the same engine at a given speed and various outputs. A significant reduction in HC emissions and fuel consumption with no adverse effects on NO{sub}x emissions and combustion stability was observed. A small drop in power and increase in CO emission were observed disadvantages of the new injection system. Injection timing was found to be the most important factor and a balance between reduction in short-circuited fuel by late injection, and time for mixture preparation by advancing the injection, was found to be essential.