High turbulence combustion chamber for lean-burn heavy-duty CNG engines

Alternative fuels may enable vehicles to realize a low environmental impact, making them particularly suited for use in urban areas. Among alternative fuels, the most viable appears to be Compressed Natural Gas (CNG). In fact, due to its gaseous state, its high Octane Number, and its low toxicity, natural gas is an excellent fuel for low emission Otto cycle engines. Previous works on a natural gas spark ignition engine for urban bus suggested the possibility to meet the new European emission limits by using very lean air-fuel mixture. In order to achieve this goal a new high turbulence combustion chamber suitable for lean burn operation was realized. the chamber was used on a six cylinder engine derived from a Diesel one. Pollutant emission (NMHC, CO, NOx) met the current limits of the European ECER49 regulation.