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UBC Theses and Dissertations

Particulate emissions by H.P.D.I. engines using thermophoretic sampling and electron microscopy Nair, Anil Kumar

Abstract

A particulate sampler was designed and built for sampling particulate material from engines, on to the Transmission Electron Microscope (TEM) grids. It was designed taking into account all the challenges from different points of view of fluid mechanics, heat transfer, emission statistics, aerosol mechanics and practicability. Several instruments like temperature controller, temperature indicator, heating wire, flowmeter, valves, thermocouples and suitable conduits and other accessories for the passage of hot exhaust gas from engines were connected to the sampler to set up a thermophoretic sampling system. The intended application of the sampling system was to help in getting a good idea about parameters of interest in aerosol behaviour like particle size range, particle number concentration on the grid, particle shapes, spherule dimensions and chemical composition for the exhaust particulate material from the High Pressure Direct Injection (HPDI) engines - the compression ignition engines using natural gas as the fuel. Sampling tests were conducted in HPDI engines at different load conditions, different speed conditions and different conditions of pilot pulse-width. The particles in the grids were examined carefully with the TEM and measurements were taken. The results have been compiled and reported in this thesis. The particle average number concentration as deposited on the grid increased with increasing load conditions and increasing quantities of pilot diesel fuel consumption. Particle size ranged from about 15 nm to about 20 microns in some cases. Due to the presence of enormous number of tiny particles and single independent spherules, their number concentration could not be accurately measured using visual assessments. However, the number concentrations of particles larger than 500 nm could be found out in all cases except at 85% load condition in an engine. The spherules were of different sizes and their sizes ranged from about 15 nm to 1.5 microns in some cases. Generally, the single independent spherules were smaller in size compared to those in the agglomerates of particles. Several notable features of the particles, were found during the analyses and they are reported in the results. Some assumptions were made in designing the sampler and in computing its deposition efficiency. Actual deposition was 10-20% of predicted values. The major sources of error are also mentioned. Descriptions of some notable micrographs are presented. The data collected during the analyses were thoroughly analyzed to reach conclusions regarding the performance of the sampler and particulate emission by HPDI engines. The research project has brought to light many aspects of particulate emission by HPDI engines and has helped in preparing a database on it.

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