Investigation of split injection in a single cylinder optical diesel engine

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Over the last decade, the diesel engine has made dramatic progress in its performance and market penetration. However, in order to meet future emissions legislations, Nitrogen Oxide (NOx) and particulate matter (PM) emissions will need to be reduced simultaneously. Nowadays researchers are focused on different combustion modes like homogeneous charge compression ignition (HCCI) combustion and premixed charge compression ignition (PCCI) which have a great potential for both low soot and low NOx. In order to achieve these combustion modes, different injection strategies have been investigated. This study investigates the effects of split injection strategies with high levels of Exhaust Gas Recirculation (EGR) on combustion performance and emissions in a high speed direct injection optical diesel engine. The investigation is focused on the effects of split injections at different injection pressures, injection timings and dwell angles using base diesel and biodiesel fuels. The effect of fuel properties has been also investigated as an attempt to reduce regulated exhaust emissions in diesel engines. Performance, emissions and combustion characteristics have been examined for two different biodiesel fuels, namely BTL 50 and BTL 46. A Ricardo Hydra single cylinder optical engine was used in which conventional experimental methods like cylinder pressure data, heat release analysis and exhaust emissions analysis were applied. Optical techniques like direct spray and combustion visualization were applied by means of a high speed imaging system with a copper vapour laser illumination system. A high-speed two-colour system has been developed and implemented to obtain in-cylinder diesel combustion temperature and soot measurements to gain better understanding of the mixture formation and combustion processes. This investigation concludes that the split injection strategies show potential to achieve low emissions combustion