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Real-world evaluation of PM and PN emissions from light-duty GDI vehicles using PEMS

Overview

For decades, dynamometer based measurements of vehicle and engine emissions during driving cycles have been the standard method of verifying vehicles and engines are meeting current federal regulations. These same emissions measurements and driving cycles have been used as the basis to estimate emission inventories or the total pollutant emissions in a particular area due to the use of a given population of vehicles at a defined time and set of conditions. However, use of a set of average or typical driving cycles that were designed more than 20 years ago does not necessarily give an accurate estimate of everyday vehicle use. Nor do they provide typical power demands on the vehicle’s engine [1-2]. Currently, there is an increased concern in both the US and EU about the degradation of the actual atmospheric pollution levels of nitrogen oxides (NOx) and particulate matter (PM) in spite of the stricter vehicle emission limits in recent years. Differences between conditions for chassis or engine test cycles defined by vehicle emission regulations and real driving can contribute to the differences between expected and actual pollution levels. Recent air quality studies show significant exceedances for NOx and PM emissions, mainly in urban areas with high populations where emissions are mainly contributed by transport sources. Portable emission measurement systems (PEMS) were introduced and have been used for the purpose of investigating and regulating real driving emissions (RDE) of vehicles. PEMS are becoming an important regulatory tool, as evidenced by recent developments in the US and EU. The California Air Resources Board (CARB) and the Environmental Protection Agency (EPA) are also conducting tests with PEMS here in the US with heavy duty on-road and light-duty vehicles to determine their viability to measure real world on-road emissions. This is in addition to the normal Federal Test Procedure (FTP-75), Highway Fuel Economy Test (HWFET), and US06 Supplemental Federal Test Procedures (SFTP) chassis dynamometer testing. The goal of this study is to investigate the PM mass and particle number emissions from current technology GDI vehicles during on-road testing. Testing will be conducted on 3 GDI vehicles of different technologies and model years using state-of-the-art PM and PN-PEMS units. Emissions will be measured over different driving conditions mimicking urban, rural, and highway driving patterns. For each vehicle and for each test route, on-road testing will be performed three times to validate tailpipe emissions

Lead Researcher: Dr. Georgios Karavalakis Co-researchers: Dr. Kent Johnson, Dr. Thomas Durbin