Valve Timing for Control of Oxides of Nitrogen (NOx)

Freeman, Max A.; Nicholson, Roy C.

doi:10.4271/720121

Cited by 18 publications

(1 citation statement)

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“…Exhaust-gas recirculation is an important technique utilized for emission control in SI engines [7], [8], [25]- [27]. The exhaust gas recirculated back to the combustion chamber increases the proportion of inert gas in the cylinder charge mixture and also increases the heat capacity of the mixture.…”

Section: Increasing Engine Out No X Through Changes In Spark Timingmentioning

confidence: 99%

Passive SCR for lean gasoline NOX control: Engine-based strategies to minimize fuel penalty associated with catalytic NH3 generation

et al. 2016

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Lean gasoline engines offer greater fuel economy than common stoichiometric gasoline engines. However, excess oxygen prevents the use of the current three-way catalyst (TWC) to control nitrogen oxide (NO X) emissions in lean exhaust. A passive SCR concept, introduced by General Motors Global R&D, makes use of a TWC that is already onboard to generate NH 3 under slightly rich conditions, which is stored on the downstream SCR. The stored NH 3 is then used to reduce NO X emissions when the engine switches to lean operation. In this work, the effect of engine parameters, such as air-fuel equivalence ratio and spark timing, on NH 3 generation over a commercial Pd-only TWC with no dedicated oxygen storage component was evaluated on a 2.0-liter BMW lean burn gasoline direct injection engine. NO X reduction, NH 3 formation, and reductant utilization processes were evaluated, and fuel efficiency was assessed and compared to the stoichiometric engine operation case. Air-fuel equivalence ratio was found to be one of the most important parameters in controlling the NH 3 production; however, the rich operation necessary for NH 3 production results in a fuel consumption penalty. The fuel penalty can be minimized by adjusting spark timing to increase rich-phase engine out NO X emissions and, thereby, NH 3 levels. Additionally, higher engine out NO X during engine load increase to simulate acceleration resulted in additional fuel savings. A 10% fuel consumption benefit was achieved with the passive SCR approach by optimizing rich air-fuel equivalence ratio and spark timing while also utilizing acceleration load conditions.

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Section: Increasing Engine Out No X Through Changes In Spark Timingmentioning

confidence: 99%