Overview of the european "particulates" project on the characterization of exhaust particulate emissions from road vehicles:Results for heavy duty engines

This paper presents an overview of the results on heavy duty engines collected in the "PARTICULATES" project, which aimed at the characterization of exhaust particle emissions from road vehicles. The same exhaust gas sampling and measurement system as employed for the measurements on light duty vehicles [1] was used. Measurements were made in three labs to evaluate a wide range of particulate properties with a range of heavy duty engines and fuels. The measured properties included particle number, with focus separately on nucleation mode and solid particles, particle active surface and total mass. The sample consisted of 10 engines, ranging from Euro-I to prototype Euro-V technologies. The same core diesel fuels were used as in the light duty programme, mainly differentiated with respect to their sulphur content. Additional fuels were tested by some partners to extend the knowledge base. Engine tests were mainly conducted over the standard European regulatory cycles (ESC and ETC), although additional steady state conditions, including some off-cycle points, were also assessed. All data (both real time and integrated) were collected in a common data base and centrally analyzed, using common formats andmethodologies in order to eliminate inconsistencies and optimize comparability. As for light duty vehicles, the results show that particulate emissions from heavy duty engines are markedly reduced by advanced technologies, most notably by the combination of particulate traps and sulphur-free fuels. However, particulate emissions patterns are also shown to be influenced by operating conditions; in particular fuel sulphur effects are most obvious under high temperature operation. The study provides evidence that particulate number measurement offers the potential for greater sensitivity in evaluating particulate emissions. It demonstrates that the "PARTICULATES" dedicated sampling procedure is capable of delivering repeatable results even in the case of the unstable nucleation mode, also for heavy duty engines. The data provide a first step towards emission factors based on particle size and number for heavy duty engines. However it should not be forgotten that nucleation mode particles are highly dependent on sampling conditions. Further research continues to be needed on the health relevance of measurements of "nucleation" mode particles, their chemical composition and their fate in the atmosphere.