Ammonia Emissions from the EPA's Light Duty Test Vehicle

Abstract

<div class="htmlview paragraph">Ammonia (NH<sub>3</sub>) 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 research<sup><span class="xref">1</span>, <span class="xref">2</span></sup> has shown that NH<sub>3</sub> is predominately emitted from vehicles with a catalyst (three-way or dual-bed). The vehicle's catalyst is designed to reduce nitrogen oxides (NO<sub>x</sub>) to nitrogen (N<sub>2</sub>) and oxygen (O<sub>2</sub>) during normal operation. The reduction of NO<sub>x</sub> to NH<sub>3</sub> occurs during periods of reducing conditions when insufficient O<sub>2</sub> is available. NH<sub>3</sub> emissions were measured during fuel-rich/reduced-O<sub>2</sub> conditions (open-loop control scheme). The results demonstrate that NH<sub>3</sub> production is correlated to combustion conditions<span class="xref"><sup>3</sup></span>. The results also show that the amount of NH<sub>3</sub> produced correlates with the amount of time that the vehicle remains in the open-loop control scheme. The significance of this finding is that NH<sub>3</sub> 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 NH<sub>3</sub> production can be anticipated based on predicted engine power.</div>