Natural gas is a cleaner fuel source alternative for heavy duty engines. This study discusses the conversion of a single-cylinder diesel research engine to a natural-gas spark-ignited engine with port fuel injection. The conversion to spark-ignited natural-gas operation may be performed with small modifications to the engine. The piston bowl geometry of the converted engine was shown to have a substantial effect on the apparent heat-release rate, showing a double peak for certain spark timings. Peak indicated efficiency was reported at 36 percent for spark timing of -10 CA ATDC, with peak IMEP of 8 bar occurring at -15 CA ATDC. The end of combustion characteristics for the bowl-in-piston engine geometry were strongly influenced by the final flame propagation in the squish band region.
Keywords Natural gas engine; spark ignition; stoichiometric operation; combustion characteristics; flat engine head and bowl-in-piston chamber