Browse Publications Technical Papers 2001-01-3538

Ammonia Emissions from the EPA's Light Duty Test Vehicle 2001-01-3538

Ammonia (NH3) emissions were measured from the EPA's Light Duty Test Vehicle while operated on a chassis dynamometer. The vehicle's (1993 Chevrolet equipped with a three-way catalyst) emissions were measured for three transient (urban driving, highway fuel economy, and hard acceleration) cycles and steady state operation. Previous research1, 2 has shown that NH3 is predominately emitted from vehicles with a catalyst (three-way or dual-bed). The vehicle's catalyst is designed to reduce nitrogen oxides (NOx) to nitrogen (N2) and oxygen (O2) during normal operation. The reduction of NOx to NH3 occurs during periods of reducing conditions when insufficient O2 is available. NH3 emissions were measured during fuel-rich/reduced-O2 conditions (open-loop control scheme). The results demonstrate that NH3 production is correlated to combustion conditions3. The results also show that the amount of NH3 produced correlates with the amount of time that the vehicle remains in the open-loop control scheme. The significance of this finding is that NH3 production can be predicted for a fleet based on the frequency of enrichment of vehicles equipped with a three-way catalyst. The results also provide a means of determining the location of roadway links and/or specific locations where NH3 production can be anticipated based on predicted engine power.


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