Date of Award
Mechanical, Automotive, and Materials Engineering
Applied sciences; Ethanol; Homogeneous charge compression ignition; In-cylinder reformation, Iso-octane
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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.
Gnanam, Gnanaprakash, "Homogeneous charge compression ignition (HCCI) engine fuelled with ethanol, iso -octane and products of in -cylinder reformation in an IDI-type engine" (2008). Electronic Theses and Dissertations. 8082.