Comparison of Standard Particulate Matter Measurement Techniques to Real-World Wind Tunnel Measurements of Heavy-Duty Diesel Trucks

摘要

Particulate Matter (PM) is one of the most sought-after exhaust emissions from Heavy-Duty Diesel Engines (HDDEs) to reduce. Several regulations in Europe and North America have led the way in drastically reducing PM of both on-road and off-road engines through stringent adoption of Diesel Particulate Filters (DPFs) and advanced combustion techniques. The effects of these advanced aftertreatment systems were studied using standardized testing procedures and equipment. While PM is defined as a "single" criteria pollutant, its complex structure entails several chemical compounds and molecules, displaying a whole spectrum of particle sizes. In addition, the morphology of some volatile compounds is shown to be affected by the interaction with background air during exhaust dilution and cooling. Although a variety of studies have attempted to fully capture dilution conditions taking place in the wake of a vehicle and reproduce those in a laboratory environment, a gap still exists in the understanding of the formation and maturation of diesel exhaust aerosols once the exhaust is emitted into the atmosphere. This work aims to contribute to bridging the gap by offering particle characterizations obtained by both artificial dilution and direct sampling from the exhaust plume developing in the wake of a vehicle in a wind tunnel. Three heavy-duty trucks were selected for this study representing three different states of engine technologies. Results suggest that laboratory techniques commonly used in diesel exhaust particle characterization work may not fully capture the evolution of PM particles once they leave the tailpipe. This appears to be especially true for particles in the nucleation mode size range in the case of vehicles equipped with DPFs.