Homogeneous charge compression ignition (HCCI) engine fuelled with ethanol, iso-octane and products of in-cylinder reformation in an IDI-type engine

The major focus of this research is to analyze the individual parameters, such as, fuel chemistry, EGR, intake air temperature and engine speed that affect the HCCI combustion on-set and to utilize in-cylinder reformation as means of controlling the HCCI combustion on-set. A new in-cylinder reformation system to control the on-set of combustion has been designed and fabricated with direct injection capabilities to examine the proposed in-cylinder reformation process. The proposed reformation strategy has the advantage of temporarily varying the compression ratio during the compression stroke and controlling the HCCI combustion on-set, in addition to the effects of fuel reformation products. The methodology adopted in this thesis to identify these parameters is mostly experimental. However, there is a smaller computational component which involves HCCI cycle calculations with fuel reformation using a single-zone model. The computational part is primarily used to analyze the advantages of a proposed in-cylinder reformation strategy on HCCI combustion before implementation in the experimental set-up.;The experimental engine used for the study is a four-stroke, three cylinder In-Direct Injection (IDI) type compression ignition engine which was converted to single cylinder operation for HCCI combustion. The HCCI engine was fuelled with a lean mixture of air and fuel (ethanol, iso-octane, mixture of ethanol/iso-octane or ethanol with products of in-cylinder reformation). Based on cycle-resolved in-cylinder pressure measurements, the experimental results demonstrate that the addition of iso-octane to ethanol retards the onset of combustion and subsequently leads to a reduction of the IMEP and thermal efficiency. The addition of EGR retards the on-set of HCCI combustion and the study indicates that ethanol allows for the use of higher percentage of EGR when compared to iso-octane. The proposed in-cylinder reformation strategy is an effective method for controlling HCCI combustion on-set (SOC) and reduces the regulated engine-out emissions. The temporary change in compression ratio that results from utilizing the proposed pre-chamber methodology has a stronger influence in controlling the HCCI combustion on-set (SOC) compared to the effects of fuel reformation products alone.