Concentrations and Size Distributions of Particulate Matter Emissions from a Class-8 Heavy-duty Diesel Truck Tested in a Wind Tunnel

In an effort to develop engine/vehicle test methods that will reflect real-world emission characteristics, West Virginia University (WVU) designed and conducted a study on a Class-8 tractor with an electronically controlled diesel engine that was mounted on a chassis dynamometer in the Old Dominion University Langley full-scale wind tunnel. With wind speeds set at 88 km/hr in the tunnel, and the tractor operating at 88 km/hr on the chassis dynamometer, a Scanning Mobility Particle Sizer (SMPS) was employed for measuring PM size distributions and concentrations. The SMPS was housed in a container that was attached to a three-axis gantry in the wind tunnel. Background PM size-distributions were measured with another SMPS unit that was located upstream of the truck plume. Ambient temperatures were recorded at each of the sampling locations. The truck was also operated through transient tests with vehicle speeds varying from 65 to 88 km/hr, with a wind speed of 76 km/hr. Sampling of the plume with the truck operating at 88 km/hr revealed uni-modal distributions with geometric mean diameter (GMD) values ranging from 55 to 80 nm. When size distributions from five locations in the plume were corrected for concentration with respect to dilution, they were found to be similar. Size distributions and concentrations of PM emissions from the tractor operating at 88 km/hr were found to agree with those from few other heavy-duty diesel vehicles that this team of researchers had previously tested in the field using the WVU Transportable Heavy-duty Vehicle Emissions Testing Laboratory. Under idle operation a distinct nuclei mode was detected with GMD varying from 14 to 24 nm.