Brunel University School of Engineering and Design PhD Theses
Abstract
This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Controlled auto-ignition (CAI) combustion in the gasoline engine has been extensively studied in the last several years due to its potential for simultaneous improvement in fuel consumption and exhaust emissions. At the same time, there has been increasing interest in the use of alternative fuels in order to reduce reliance on conventional fossil fuels. Therefore, this study has been carried out to investigate the effect of alcohol fuels on the combustion characteristics and in-cylinder processes of CAI combustion in a single cylinder gasoline engine.
In order to study the effect of alcohol fuels, combustion characteristics were
investigated by heat releases analysis in the first part. The combustion process was
studied through flame structure and excited molecule by chemiluminescence imaging.
Furthermore, in-cylinder gas composition was analysis by GC-MS to identify the auto-ignition reactions involved in the CAI combustion. In addition, the influence of
spark-assisted ignition and injection timings were also studied.
Alcohol fuels, in particular methanol, resulted in advanced auto-ignition and faster
combustion than that of gasoline. In addition, their use could lead to substantially lower HC, NOX and CO exhaust emissions. Spark-assisted ignition assisted gasoline combustion by advancing ignition timing and initiating flame kernel at the centre of combustion chamber but it had marginal effect on alcohol fuels. Auto-ignition always took place at the perimeter of the chamber and occurred earlier with alcohol fuels. Fuel reforming reactions during the NVO period were observed and they had significant effect on alcohol combustion