Overview of the European “Particulates” Project on the Characterization of Exhaust Particulate Emissions From Road Vehicles: Results for Light-Duty Vehicles 2004-01-1985

This paper presents an overview of the results on light duty vehicles collected in the “PARTICULATES” project which aimed at the characterization of exhaust particle emissions from road vehicles. A novel measurement protocol, developed to promote the production of nucleation mode particles over transient cycles, has been successfully employed in several labs to evaluate a wide range of particulate properties with a range of light duty vehicles and fuels. The measured properties included particle number, with focus separately on nucleation mode and solid particles, particle active surface and total mass. The vehicle sample consisted of 22 cars, including conventional diesels, particle filter equipped diesels, port fuel injected and direct injection spark ignition cars. Four diesel and three gasoline fuels were used, mainly differentiated with respect to their sulfur content which was ranging from 300 to below 10 mg/kg. All data (both real time and integrated) were collected in a common data base and centrally analyzed using common formats and methodologies, in order to eliminate inconsistencies and optimize comparability. Results show that particulate emissions are dramatically reduced by the combination of particulate traps and low sulfur fuels. However, particulate emissions patterns are also shown to differ between type approval and motorway driving conditions; this applying to both vehicle technology and fuel sulfur effects; the latter becoming more obvious under high temperature conditions. The relevance of the current emissions certification cycle should be considered with regard to next steps in vehicle emissions legislation and the various vehicle technologies that are expected to be introduced. The study provides evidence that both particle number and active surface measurements offer the potential for greater sensitivity in evaluating particulate emissions, without any significant increase in the variability of results. More importantly, the study revealed that the usage of a dedicated sampling procedure is in the position to yield sufficiently repeatable results of solid and total particle populations, especially over transient tests.