AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Ultrafine Particle Infiltration to Passenger Vehicle Cabins: the Effects of Driving Speed and Ventilation Setting
EON LEE, Yifang Zhu, University of California, Los Angeles
Abstract Number: 149 Working Group: Urban Aerosols
Abstract Previous studies have found motor vehicle emissions leaking into vehicle cabins. However, few studies characterized location-specific infiltration and its contributions to in-cabin air quality. The present study examined ultrafine particle (UFP) infiltration in five passenger vehicles including a minivan and four sedans under different ventilation modes (i.e., off, outside air intake (OA), and recirculation (RC)) on both local and freeway routes. We observed high variability in mechanical ventilation fan settings among tested vehicles (i.e., 4 to 12 steps) and applied an equal measure of quartile fan settings to all the vehicles. This study first distinguished in-cabin UFP penetration by incursion routes: mechanical ventilation and infiltration through leakages. The primary leakage locations were identified at side-doors and rear-trunk by measuring UFP concentration gradients and differential pressure between in-cabin and across potential leakage areas. We found the infiltration amount through the leaks were different by leakage location, driving speed, ventilation modes, and fan settings. Increases in driving speed created differential pressure up to 300 Pa for passenger cars and 100 Pa for the minivan primarily because of aerodynamic changes on the moving vehicle. In contrast, the differential pressure between in-cabin and rear-trunk remained positive in the range of 10 to 60 Pa with respect to driving speeds. It suggests that no leakage would occur through side-doors and rear-trunk as a result of cabin pressurization driven by mechanical ventilation under OA mode. Under RC mode, however, we consistently observed a negative differential pressure between in-cabin and rear-trunk suggesting that on-road pollutants could infiltrate through rear-trunk in RC mode regardless of vehicle type or driving speed. Under RC mode, depending upon vehicle envelope aerodynamics, infiltration through side-doors was inconsistent in terms of leakage flow direction (i.e., into or out of the cabin) and the amount of infiltration.