A study of the physical and chemical properties of exhaust emissions from heavy-duty diesel engines.

摘要

This dissertation presents for the first time, on-road measurements of the emission rates of regulated and non-regulated species from heavy-duty diesel (HDD) engines using CE-CERT's Mobile Emissions Laboratory (MEL). The work presented here begins with a description of the MEL and the Secondary Dilution System for particulate matter (PM) sampling and then presents emission rates of regulated pollutants from on-road HDD vehicles as well as back-up generators. It was determined that the emission rates of regulated pollutants differ from those currently used in regulatory inventory models such as EMFAC. Investigations of the variation of the chemical nature of diesel PM with various operating modes showed that organic carbon emission rates from HDD vehicles in congested conditions are 8 times those during freeway cruising, while elemental carbon emissions can vary by as much as 3 times. Chemical speciation of the organic fraction of diesel PM yielded insight into the variation of emission rates with different modes of operation, although overall source profiles were fairly constant. Calculations of the relative risk associated with the target compounds quantified in this work, demonstrated the importance of semi-volatile species (such as naphthalene) in health risk assessments. A newly developed, fast-Scanning Electrical Mobility Spectrometer enabled the identification of variations in particulate size distribution and number concentration due to various vehicle-operating modes and identified modes of operation yielding high concentrations of nano-particles. These results give insight into methods of reducing and controlling HDD emissions, the effects of vehicle activity on emission inventory models and variations in risk associated with emissions. The use of these data to make informed community planning decisions, identify areas where traffic regulation may significantly reduce HDD emissions, and increase the accuracy of atmospheric modeling as it pertains to diesel sources are discussed.