Abstract
This paper presents the feasibility to apply scavenging-port injection of a compressed natural gas (CNG) to a two-stroke spark-ignition engine. A two-cylinder production engine for boat racing is used as a test engine. Through a preliminary experiment with several methods of CNG flow-rate measurement, a reliable procedure could be established. The engine was run at a constant speed of 3000 rpm and WOT condition. Comparing with the operation with a gas-mixer, by applying scavenging-port injection BSFC was decreased by 20 % and HC emission by 47 % at the best condition. Three methods of injector installation and three types of fuel pipe attached to the injector tip were included in the optimization process. A mechanism to explain the optimizing was also proposed on the basis of the consideration on the interaction between the flow of CNG jet and the scavenging flow.
