Influence of injection timing on the exhaust emissions of a dual-fuel CI engine

Environmental concerns and limited amount of petroleum fuels have caused interests in the development of alternative fuels for internal combustion (IC) engines. As an alternative, biodegradable, and renewable fuel, ethanol is receiving increasing attention. Therefore, in this study, influence of injection timing on the exhaust emission of a single cylinder, four stroke, direct injection, naturally aspirated diesel engine has been experimentally investigated using ethanol blended diesel fuel from 0% to 15% with an increment of 5%. The engine has an original injection timing 27° CA BTDC. The tests were performed at five different injection timings (21°, 24°, 27°, 30°, and 33° CA BTDC) by changing the thickness of advance shim. The experimental test results showed that NO_x and CO₂ emissions increased as CO and HC emissions decreased with increasing amount of ethanol in the fuel mixture. When compared to the results of original injection timing, at the retarded injection timings (21° and 24° CA BTDC), NO_x and CO₂ emissions increased, and unburned HC and CO emissions decreased for all test conditions. On the other hand, with the advanced injection timings (30° and 33° CA BTDC), HC and CO emissions diminished, and NO_x and CO₂ emissions boosted for all test conditions.