Comprehensive analysis of particle emissions from both exhaust and non-exhaust sources: a methodological approach

Particle emissions from engines have long been topic of research studies because of their detrimental impact on human health and environment. Light duty vehicles represent the main contributor of particles in the congested urban areas and in the next future thought there will be a drastic reduction of fossil fuels, an increasing of the electric vehicles and an improvement of battery technology, a good control of exhaust particle emissions must be yet guaranteed using accurate and effective measurements for their characterization. This paper is an excursus of commercial and innovative techniques used for the evaluation of the particle emissions due to the engine exhaust. The effect of the main parameters on the soot formation and particle emissions were analyzed and described such as the influence of the injection strategies, the fuel type including commercial and not commercial fuels, and the lubricant oil. The particulate matter was characterized at the exhaust by means of the measure of number and size. Moreover, non-conventional diagnostics based on the optical detection of the natural flame chemiluminescence was applied to follow the combustion evolution and to evaluate the in-cylinder soot concentration. The correlation between the formation mechanisms of soot in the combustion chamber and the particle emissions at exhaust allows a comprehensive analysis. Particular attention was payed to the particles smaller than 23 nm that will be object of the next European emission regulation. The difficulties correlated to their measurement caused by the large fraction of volatiles in the 10 - 23 nm range that can nucleate or condense on existing particles was highlighted. In this regard a methodological approach consisting in the sampling and conditioning of the particles at two different temperature settings was defined within the project Sureal-23 to evaluate the volatile organic fraction of these particles. The knowledge developed within the exhaust particle emissions allowed to develop an experimental layout and a methodology for the sampling and measurement of non-exhaust particles.