Measurement of Electrical Charge on Diesel Particles

Abstract

Nanoparticles (D p < 50 nm), which are formed as diesel engine exhaust cools and dilutes, constitute minority of total particle mass but majority of total particle number. There are several different theories to explain the nucleation of nanoparticles from diesel exhaust. The two main theories are homogeneous binary nucleation of sulfuric acid and water, and ion-induced nucleation. This study examined the ion-induced nucleation theory. In order to test the ionic nucleation theory, the charged fraction of the diesel particles were measured as a function of particle size using regular diesel fuel in this study. A very small amount of charge was found for the diesel nanoparticles in the nuclei mode, whereas there was a large charged fraction for the diesel particles in the accumulation mode. If ion-induced nucleation were the dominant mechanism for the nucleation of nanoparticles from diesel exhaust, one would expect a significant charge on the nuclei mode particles. The results from this study suggest that ion-induced binary nucleation is at least not a dominant mechanism for the nucleation of diesel exhaust when using regular diesel fuel.This study also examined the influence of metal additives on nucleation and particle charging. The metal additives examined are of the type used to enhance particle oxidation in diesel particulate filters. When used, the additives led to a large increase in the concentration of solid particles in the nuclei mode, and significantly raised the level of particle charge for particles of all sizes. When additives were used, some of the solid particles in the nuclei mode carried a charge. We believe that these metal related particles form early enough in the combustion process to be charged by ions present during and shortly after combustion.

Comparative Testing of a Miniature Diffusion Size Classifier to Assess Airborne Ultrafine Particles Under Field Conditions

“…Hence, the overload of the devices led to inaccurate measurements, characterized by a significant underestimation by the P-TRAK and a potential measurementerror in the miniDiSC. In theory, the charging efficiency of the miniDiSC could have been influenced by increased particle charge in proximity to exhaust pipes or due to specific fuel additives that increase charge of exhaust particles (Jung and Kittelson 2005). But neither the measurements during highway maintenance work nor the stationary measurements showed any indications of such an effect being of practical relevance.…”

Impacts of a Nanosized Ceria Additive on Diesel Engine Emissions of Particulate and Gaseous Pollutants

“…9 The above-mentioned study by Farfaletti and colleagues 8 found that the Ce catalyst was inefficient in the heavy-duty engine for all emissions except for B[a]P-TEQ (38% reduction), but markedly reduced all emissions except NO x (unchanged) in the light-duty engine. Another study by Jung and colleagues, 5 focusing on the kinetics of oxidation and combustion chemistry, reported a substantial increase of ultrafine particles emitted from a diesel engine combusting a fuel doped with a different commercial CeO 2 -based additive Eolys DPX-9 (Rhodia Electronics & Catalysis, La Rochelle, France).…”

MEMS for TPMS and exhaust of automobiles

“…PM emitted from diesel engine is charged particle [2]. Charge induced type PM sensor we designed can measure by real-time and it doesn't need particle collection apparatus.…”