Unburnt THC and its Compositions in Diesel Exhaust Gas under Transient Operations

Unburnt HC and its components including 1, 3 butadiene and benzene from a DI diesel engine during both start up to warm up" and "increasing load" operations were investigated. At start-up with a high equivalence ratio the THC gradually increased with elapsed cycles, and then decreased sharply with a rapid decrease in equivalence ratio at warm-up operation. Coolant temperature strongly influenced on the THC concentrations and the THC with lower coolant temperature are remarkably higher throughout the "start-up to warm-up". Reducing the equivalence ratio and shortening the duration of high equivalence ratio operation at start-up are effective to reduce THC emission. The lower hydrocarbon components determined the THC behavior for both "start-up to warm-up" and "increasing load" operations, while the proportion of each HC component was not significantly changed. Of the components, ethylene comprised the larger portion of the low hydrocarbon components, 1, 3 butadiene and benzene are slightly detected for both transient operations.