Browse Publications Technical Papers 2009-01-0909
2009-04-20

Emissions of NO x , NH 3 and Fuel Consumption Using High and Low Engine-Out NO x Calibrations to Meet 2010 Heavy Duty Diesel Engine Emission Standards 2009-01-0909

For engine operations involving low load conditions for an extended amount of time, the exhaust temperature may be lower than that necessary to initiate the urea hydrolyzation. This would necessitate that the controller interrupt the urea supply to prevent catalyst fouling by products of ammonia decomposition. Therefore, it is necessary for the engine controller to have multiple calibrations available in regions of engine operation where the aftertreatment does not perform well, so that optimal exhaust conditions are guaranteed during the wide variety of engine operations.
In this study the test engine was equipped with a catalyzed diesel particulate filter (DPF) and a selective catalytic reduction system (SCR), and programmed with two different engine calibrations, namely the low-NOx and the low fuel consumption (low-FC). The low-NOx calibration, to be used in case of insufficient heat in the exhaust stream, was developed to meet the 2010 emission standards for heavy-duty diesel engines. The two engine calibrations produced different exhaust conditions, and their interaction with the exhaust aftertreatment was investigated under transient and steady state cycles.
Variable urea injection points and several mixing devices were also employed to further improve the SCR conversion efficiency. The optimal configuration resulted in an additional 20% NOx reduction over the ESC cycle.

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