Numerical studies of charge mixture preparation for HCCI engines

This thesis presents detailed charge mixture preparation investigation on the set of conditions , leading to auto-ignition in a Homogenous Charge Compression Ignition (HCCI) engine. The emphasis of the study is placed on analysing the charge mixture composition, temperature and pressure conditions leading to auto-ignition, dependence on mixture properties and engine speed. To enable the HCCI technology to be a stand-alone production engine, understanding the fundamentals leading to auto-ignition will provide vital information to overcome the challenges limiting the HCCI engine, whilst providing good knowledge base for further studies. Increasingly stringent emissions legislation and more recent security of energy issues have motivated worldwide research into cleaner, more fuel efficient internal combustion engine. To this end, the HCCI combustion process has been identified as highly efficient alternative to conventional petrol/diesel engines. This is a new combustion process which has the potential to be both highly efficient and produce low emissions. Moreover; HCCI engines are suitable for use with a wide range of alternative fuels including natural gas or bio-diesel, Simultaneously while producing ultra-Iow emissions of NOx and particulate matter. However, one of the main considerations of HCCI is prediction of the occurrence of auto-ignition. Current published literature highlights the limited studies conducted to investigate the auto-ignition characteristics and the fundamentals of the HCCI process. The inspiration for this thesis is addressing the lack of studies/published work in those areas. Utilising two CFD codes (KIVA and Fluent) along with a number of HCCI specific sub-models, the HCCI process is investigated and correlated against experimental results with attention drawn to the mixture conditions leading auto-ignition. Combustion was not considered in this thesis. [Continues.]