AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
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Advanced Emission Reduction Devices and Particle Number Emissions: Knowledge from a California On-road HD-truck Testing
TIANYANG WANG, David Quiros, Arvind Thiruvengadam, Shaohua Hu, Tao Huai, Yifang Zhu, University of California, Los Angeles
Abstract Number: 83 Working Group: Control and Mitigation Technology
Abstract Particle emissions from heavy-duty vehicles (HDVs) have significant environmental and public health impacts. Currently, the air quality standards for PM have all been set on a mass basis; however, numerous studies have suggested that PM-related health hazards are correlated with the particle number concentration, which primarily indicates the concentration of ultrafine particles (UFPs, d <= 100 nm). Previous research found that particle number emission from HDVs could be highly elevated by sulfur oxidation and the nucleation mode particle formation dependent on vehicle on-road status, engine technology and emission controls. In this study, we measured real-time particle emissions from six modern HDVs powered by diesel and compressed natural gas over six route types totaling over 6,800 miles of on-road operation in California to investigate the particle number emissions from HDVs. The distance-based particle number emission factors (PNEFs) of the five tested diesel HDVs equipped with diesel particulate filters (DPFs) were between 2.94×1011 and 2.99×1013 particles/mile, which were 50 to 5000 times lower than a 1998 HDV not originally equipped but retrofitted with a DPF. PNEFs significantly increased due to passive regeneration when the DPF outlet temperature reached a critical value, usually between 250 and 340 °C, which was commonly exceeded when HDVs were traveling at speeds over 45 mph. Compared with passive regeneration, active DPF regeneration events produced higher PNEFs in a 2013 model year diesel HDV. No directly relationship was found between distance-based PNEF and vehicle speed. However, linear changes in vehicle speed result in logarithm changes in an alternative parameter, particle number emission rate (particles/s), indicating that vehicle speed may be used as an indicator of particle number emissions from modern HDVs.