Abstract of PhD Thesis

Evaluation of Options for Reducing Irish Diesel Particulate Emissions – Utilising Measurement and Modelling Methods

Shane O'Sullivan (2005), University College Dublin

Diesel engines produce several exhaust constituents that are considered to be harmful air pollutants. Of these, Diesel Particulate Matter (DPM) is currently under close scrutiny due to its adverse health and environmental effects. The objectives of this research project were (i) to quantify real-world DPM emissions from in-use vehicles, (ii) to model the dispersion and dynamic composition of DPM, and (iii) to determine suitable DPM reduction strategies for Ireland.

The design and measurement issues associated with the quantification of particulate emissions from a moving diesel vehicle, as it undergoes normal driving transients, were examined, and addressed, during the development of a new on-road DPM measurement system. The devised system works by continuously drawing off a fixed percentage of the exhaust gases, filtering this sample and storing the collected particulate matter for eventual weighing. The merits and limitations of the new DPM measurement system were investigated during testing under real-world, urban and motorway driving conditions.

A Computational Fluid Dynamics program was used to model the dispersion of the exhaust plumes from several different diesel vehicles. The growth of the exhaust plumes from the tailpipes was analysed, and values for the instantaneous pollution levels that a passer-by would be exposed to from a passing vehicle were calculated. Surface adsorption and nucleation models were also used to determine the effects of adsorption, nucleation and aging on the exhaust particle composition.

 In the final section of this project, Irish DPM emissions were examined. Information regarding the size, and emissions characteristics, of the Irish Diesel fleet was collated, and current DPM emissions were calculated. DPM reduction strategies in use elsewhere were identified, and subsequently examined in the Irish context. Recommendations were made regarding the more beneficial strategies that should be pursued by the Irish government in order to reduce DPM emissions.