Evaluating heavy-duty diesel engine aftertreatment devices with a split exhaust configuration.

摘要

West Virginia University evaluated diesel oxidation catalysts (DOC) and lean-NO_x catalysts as part of the Diesel Emissions Control-Sulfur Effects (DECSE) program. In order to perform thermal aging of the DOC and lean-NO_x catalysts simultaneously and economically, each catalyst was sized to accommodate half of the engine exhaust flow. Simultaneous catalyst aging was then achieved by splitting the engine exhaust into two streams such that approximately half of the total exhaust flowed through the DOC and half through the lean-NO_x catalyst. This necessitated splitting the engine exhaust into two streams during emissions measurements. The fraction of exhaust entering the measurement system was calculated based on a comparison of measured CO₂ concentrations taken during a full flow exhaust run and a partial flow exhaust run. Emissions sampled from the partial exhaust stream were then corrected based on these measured CO₂ concentrations to reflect the original full flow levels. Integrated engine-out emissions measured in the split exhaust streams during transient operation generally agreed well with emissions measured using the full exhaust stream. Measured emissions in the partial exhaust configuration remained within 5% of a 50/50 split except at idle or low power operation. When these results from a split flow test were corrected back to full flow levels, all measured emissions were within 11% of the full exhaust case for transient tests and 13% for steady state tests. Split exhaust emissions levels were hard to quantify at low exhaust flow rates.