Performance and Emissions of a Natural Gas Fueled Two-Stroke SI Engine

This paper presents the results of an experimental activity carried out on a two-stroke SI engine for moped (with a displacement 50 cm3) fueled alternatively by gasoline and natural gas. The effect of the fuel on engine performance and efficiency was evaluated comparing both instantaneous (pressure signal in the crankcase, cylinder and exhaust pipe) and overall data (torque, power, fuel consumption, emissions). Cylinder pressure was measured in order to evaluate the effect of fuel on the optimum ignition timing angle and on cyclic dispersion. Engine emissions were measured by means of a gas analyzer and a gas-chromatograph. Moreover this experimental analysis has been carried out also to validate the 1D-3D numerical model for the simulation of the scavenging and combustion processes in a small-size spark-ignition two-stroke engine.