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Queen Mary University of LondonQueen Mary University of London
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School of Engineering and Materials Science
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PhD Thesis: Soot formation and oxidation in a high-pressure spray flame

Author: DEMOSTHENOUS, A

Year: 2005

Supervisor(s): Roy Crookes

This research is focused on a better understanding of the diesel soot formation and oxidization mechanisms at elevated pressure and how these behave at different operating conditions. For the experimental set-up a steady-state high-pressure combustion chamber has been used.

Soot samples were collected using water cooled probes at the exhaust, at a pressure range between 0.6-1.5MPa and with input equivalence ratio of 0.8-1.2, also various parameters were recorded such as temperature, pressure, flow measurement and exhaust gas analysis, were presented together.

The combustion process within the combustion chamber was simulated using a commercially available CFD code (Star-CD), the species analysis, velocity etc. were presented at 10 bars pressure and at three equivalent ratios: lean (.08), Stoichiometric (1.0) and rich (1.2).

For prediction of soot formation and oxidation inside the high-pressure combustion chamber a numerical code has been used which was already developed in the university, three different soot formation models have been examined (Narasimham, Hiroyasu and Moss). Several cases were run using the above models from 5-15 bars in step of 1bar and five equivalent rations (0.8, 0.9, 1.0, 1.1, 1.2).

Soot samples collected at the exhaust were examined under the TEM (Transmission Electron Microscope) showing the structures of diesel soot agglomerates, high magnification images were presented along with EDS (Energy Dispersive Spectroscopy) analysis at different magnification, the crystallites inter-layer spacing was measured using a diffraction pattern from the specimen.