Ammonia and nitrous oxide emissions of a stoichiometric natural gas engine operating with high caloric value and low caloric value fuels.

• NH 3 and N 2 O emissions were investigated at both steady and transient conditions. • NH 3 and N 2 O are high when using high caloric value fuel during steady test cycle. • N 2 O emissions are mainly emitted during the engine cold starting process. • N 2 O emissions of low caloric fuel are higher in cold WHTC while lower in hot WHTC. With the implement of the increasingly stringent emission standards, natural gas engines feature stoichiometric operation with three way catalyst (TWC) have been put into focus due to their low-cost and high-efficient aftertreatment system. In this paper, the ammonia and nitrous oxide emissions during both steady-state and transient test cycles are analyzed with the aid of the regulated emission values and the temperatures in the TWC system. The results indicated that in the steady-state test cycle, NH 3 are highest at low-speed high-load condition and N 2 O emissions are at extremely low levels during the whole test cycle. At most operating modes of the steady-state test cycle, NH 3 and N 2 O emissions exhibit higher values when operated with high caloric value fuel. In both cold and hot start world harmonized transient cycle(WHTC) tests, motorway sub-cycle has the highest average NH 3 emissions and adopting low caloric value fuel could reduce the tendency of NH 3 formation; N 2 O emissions are mainly generated in the engine starting period. In the cold start WHTC tests, adopting fuel with high caloric value is favorable for the abatement of N 2 O emissions while in the hot start WHTC tests, using fuel with low caloric value would be a better choice for the control of N 2 O emissions. [ABSTRACT FROM AUTHOR]