Fumigation of a diesel engine with low Btu gas

A 0.5 liter single-cylinder, indirect-injection diesel engine has been fumigated with producer gas, a mixture of principally H₂, CO, and N₂ with a heating value of about 160 Btu/ft³. Producer gas is produced by air-blown gasification of coal or biomass. Measurements of power, efficiency, cylinder pressure, and emissions were made. At each operating condition, engine load was held constant, and the gas-to-diesel fuel ratio was increased until abnormal combustion (severe efficiency loss, missfire, knock, or preignition) was encountered. This determined the maximum fraction of the input energy supplied by the gas, E_max, which was found to be dependent upon injection timing and load. At light loads, E_max was limited by severe efficiency loss and missfire, while at heavy loads it was limited by knock or preignition. The highest value of E_max that could be obtained at full load was 48% at a timing of 2 CAD BTDC, while the highest overall value of E_max, 72%, was obtained at 20% load, at a timing of 11 CAD BTDC. Fumigation generally increased ignition delay and heat release rates, but peak pressures were not strongly influenced. Efficiency was slightly decreased by fumigation as were NO_x and particle emissions while CO emissions were increased.