Partially premixed combustion in an optically accessible compression ignition engine
File(s)
Author(s)
Touloupis, Dimitris Panagiotis
Type
Thesis
Abstract
This thesis sets out the high-speed imaging and Laser Induced Incandescence (LII) work carried out on the Ricardo Hydra and the Volvo D5 single cylinder optical light duty diesel engines at Imperial College London. A literature review was presented on diesel engine operation strategies along with a review on the optical diagnostic techniques used for the purpose of the present thesis.
The experimental work on the Ricardo Hydra optical engine comprises three different experimental campaigns, which investigate three major engine operation strategies, commonly employed by engine manufacturers, namely inlet air dilution, pilot injection and post injection. The analysis identifies combustion patterns and characteristics and describes how these were affected when different operation strategies were employed. The investigation focused on soot emissions formation and their evolution throughout the combustion event. Most importantly, the employed operation strategies were evaluated in regard to their efficiency in reducing engine-out soot emissions.
The experimental work on the Volvo D5 optical engine focused on the effect of injection timing and of a close-coupled pilot injection on combustion stratification and soot formation at operating conditions that promote PPC operation.
Findings were analysed via means of pressure trace and apparent rate of heat transfer analyses, as well as a series of optical diagnostics techniques, namely high-speed flame natural luminosity imaging, CH* and C2* line-of-sight chemiluminescence, as well as planar Laser Induced Incandescence (pLII).
Overall, results suggest that longer ignition delay is a key parameter in lower engine-out soot emissions, which can be achieved by several operating techniques. Longer ignition delay leads to enhanced in-cylinder mixing, which facilitates operation in the Partially Premixed Combustion regime, where fuel-rich areas can be eliminated, and soot formation weakens.
The experimental work on the Ricardo Hydra optical engine comprises three different experimental campaigns, which investigate three major engine operation strategies, commonly employed by engine manufacturers, namely inlet air dilution, pilot injection and post injection. The analysis identifies combustion patterns and characteristics and describes how these were affected when different operation strategies were employed. The investigation focused on soot emissions formation and their evolution throughout the combustion event. Most importantly, the employed operation strategies were evaluated in regard to their efficiency in reducing engine-out soot emissions.
The experimental work on the Volvo D5 optical engine focused on the effect of injection timing and of a close-coupled pilot injection on combustion stratification and soot formation at operating conditions that promote PPC operation.
Findings were analysed via means of pressure trace and apparent rate of heat transfer analyses, as well as a series of optical diagnostics techniques, namely high-speed flame natural luminosity imaging, CH* and C2* line-of-sight chemiluminescence, as well as planar Laser Induced Incandescence (pLII).
Overall, results suggest that longer ignition delay is a key parameter in lower engine-out soot emissions, which can be achieved by several operating techniques. Longer ignition delay leads to enhanced in-cylinder mixing, which facilitates operation in the Partially Premixed Combustion regime, where fuel-rich areas can be eliminated, and soot formation weakens.
Version
Open Access
Date Issued
2018-06
Date Awarded
2018-12
Copyright Statement
Creative Commons Attribution NonCommercial No Derivatives Licence
Advisor
Taylor, Alex
Jones, William
Sponsor
European Commission
Grant Number
607214/FP7-PEOPLE-2013-ITN
Publisher Department
Mechanical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)