Experimental and theoretical study of particulate re-entrainment from the combustion chamber walls of a diesel engine

Abstract

The purpose of this research was to investigate the influence of the in-cylinder surfaces on the net emission of the particulate matter in the exhaust of a single cylinder, diesel engine. In order to obtain this information, time-resolved sampling was done to characterize the particulate matter emitted in the engine exhaust. A rotating probe sampled the free exhaust plume once each engine cycle. The rotation of the probe was synchronized with the engine cycle in such a way that the samples could be taken at any predetermined crank angle degree window. The sampling probe was designed for isokinetic sampling in order to obtain reliable results. To characterize the exhaust particulate in real time, a filter for mass concentration measurements was used. The results showed about 45 per cent higher mass concentrations as well as particles of larger diameter emitted during blowdown than late in the displacement phase of the exhaust stroke. This suggests that high in-cylinder shear rates and velocities which are associated with the blowdown process, cause the deposited soot to be re-entrained from the surfaces of the combustion chamber, where re-entrainment is favoured by conditions of high surface shear.A mathematical model to predict the amount of soot re-entrained from the cylinder walls is presented. This model is based on information presented in the literature along with the results of the time-resolved measurements of mass concentration. This model supported the hypothesis of soot deposition during the combustion process, with subsequent re-entrainment during the blowdown process of the exhaust stroke.

Alternatives to the Gravimetric Method for Quantification of Diesel Particulate Matter near the Lower Level of Detection

“…A particle preclassifier was added to reduce the variability of the measurement because previous studies showed that very large particles were spontaneously re-entrained in the exhaust during transient test cycles and that re-entrainment was influenced by preconditioning the exhaust system. [37][38][39][40] In addition, greater stability of the environmental conditions in the filter weighing room and better balance precision/resolution were required. The procedure for weighing each filter was well defined with added requirements for charge neutralization, stabilization time, and repeat weighings of sample filters.…”

Diesel Quality in Jordan: Impacts of Vehicular and Industrial Emissions on Urban Air Quality

“…This high rate demand of diesel fuel may due to the recent large increase in the numbers of diesel-powered vehicles, lower price than other fuels, notable market penetration of diesel-fueled gas turbines to assure electricity demand during peak-load, diesel fuel has 40% higher efficiency than gasoline-engine vehicles along with lower production of CO 2 and lower national energy bills (Jaber et al, 1997;Oak Ridge National Laboratory Review, 2000). Therefore, diesel engines present an attractive major transporter for many applications despite their high emissions of sulfur dioxide (SO 2 ), nitrous oxides (NO x ), carbone monoxide (CO), O 3 , hydrocarbons (HCs), total suspended particulates (TSP), particulate matters (PM 10 ), and noise compared to gasoline engines (Abu-Qudais and Kittelson, 1997). Emissions from high sulfur diesel fuel contribute to the deteriorating of air quality, which in turn, affects human health, damaging crops, forming acid rain, and lowering visibility in addition to its negative impact on the biodiversity and ecosystems (Oak Ridge National Laboratory Review, 2000).…”

Sampling Method for Particle Measurements of Vehicle Exhaust

“…In addition to hydrocarbons, soot particles can be lost in sampling lines by deposition. These deposited particles may re-entrain and cause an unexpected coarse particle mode in particle size distribution [7,8]. The origin of the coarse particles may be in the exhaust system of the vehicle or in the sampling lines.…”