The effects of direct injection of gaseous ammonia on the combustion characteristics and exhaust emissions of a spark-ignition engine were investigated. Port-injection gasoline was used to enhance the burning of ammonia that was directly injected into the engine cylinder. Appropriate direct injection strategies were developed to allow ammonia to be used in spark-ignition engines without sacrifice of volumetric efficiency.
Experimental results show that with gasoline providing the baseline power, total engine power increased as the injection timing of ammonia was advanced and the injection duration was increased. Engine performance with use of gasoline-ammonia was compared to that with gasoline alone. The brake specific energy consumption (BSEC) with gasoline-ammonia was very similar to that with gasoline alone. Ammonia direct injection caused slight reductions of BSCO2 and BSCO for all the loads studied but significantly increased brake specific hydrocarbon emissions (BSHC) because of the reduced combustion temperature of ammonia combustion. The use of ammonia resulted in increased NOx emissions because of formation of fuel NOx. Ammonia slip was also detected in the engine exhaust because of incomplete combustion.