Quantitative assessment of in-use emissions from on-road diesel vehicles

The control of emissions of oxides of nitrogen (NOx) and particulate matter (PM) from diesel engines has lagged far behind that of gasoline engines. Recently the Environmental Protection Agency (EPA) has promulgated the toughest regulations to control emissions from diesel engines. These new regulations require the use of diesel particulate filters (DPF) which reduce PM mass, but under some situations increase the number of nano-sized particles. Additionally, EPA is regulating in-use diesel emissions rather than simply in a laboratory where it became essential to be able to measure in-use diesel emissions.;Traditional laboratory methods are not suited for in-use measurements; thus new methods and tools were needed. One of the accomplishments of this research was to complete the development of an on-road heavy duty mobile emission laboratory (MEL). Since only one MEL exists, another key element for this research was the development of portable emissions monitoring systems (PEMS) and the design of tests matrix to validate their measurements against the MEL. A careful statistical design considered a progression from few to many degrees of freedom. Another key aspect of this research was the development and evaluation of a particle number measurement method to assess the regulation of particle number of DPF equipped diesel engines.;With a focus on emission inventory and certification of the existing fleet, all of the heavy duty trucks tested were model year (MY) vehicles newer than 1998. In order to analyze PEMS under new emission controlled conditions, two MY 2008 heavy duty vehicles were selected and tested in their original "as is" condition. The two 2008 vehicles' emissions controls systems were also redesigned in order to exercise the PEMS measurement systems over a broader range of NOx and PM emissions.;The findings from this research discovered that the PEMS instruments are not suitable for post-2010 on-highway emission standards and the mass based PEMS are not suitable for in-use measurements on 1994 on-highway technology. PEMS improvements should continue to be developed and re-evaluated. The particle number measurement method worked well during prescribed driving schedules, but it was found to be unreliable during in-use operation.