|Title:||Study of combustion, performance and emissions of a diesel engine fueled with a ternary fuel (diesel-biodiesel-ethanol) in blended and fumigation modes|
|Advisors:||Cheung, Chun Shun (ME)|
Yung, Ka-fu (ABCT)
|Subject:||Hong Kong Polytechnic University -- Dissertations|
Diesel motor -- Alternative fuels
Motor vehicles -- Fuel systems
|Department:||Department of Mechanical Engineering|
|Pages:||xxiii, 211 pages : color illustrations|
|Abstract:||The use of renewable alternative fuels is a potential method to reduce emissions from diesel engines, in order to reduce air pollution and protect human health. Among all the alternative fuels, biofuel, including biodiesel and alcohols and their blend with diesel (especially diesel-biodiesel-ethanol blend (DBE)) is a great option as an alternative to diesel fuel for diesel engines. The effects of using DBE, diesel/biodiesel or diesel/ethanol on the combustion, performance and emissions of diesel engines in either the blended mode or the fumigation mode have been widely reported in the literature. However, there is not enough information about the differences between the effects of the blended mode and the fumigation mode on the performance, combustion and emissions and almost no information on the physicochemical properties of particulate matter (PM) of a diesel engine. Also, only alcohol fuels were utilized in the fumigation mode and the use of a mixture of biodiesel and alcohol as a fumigated fuel for comparison with the blended mode cannot be found. Therefore, this study aims at covering the above knowledge gaps through an experimental study to investigate the effects of different fueling modes of operation, including diesel, blended and fumigation modes, on the engine combustion, performance and emissions of a diesel engine fueled with a ternary fuel (DBE) under various engine speeds and loads. In addition, the present study introduced a combined fumigation and blended mode (F+B) of fueling to investigate its impact in comparison with the fumigation and blended modes. This study also includes an investigation on the effects of using different alcohols to form the ternary fuel. The alcohols considered include methanol, ethanol, propanol, butanol and pentanol. Each of the alcohol was mixed with diesel and biodiesel to form a ternary fuel with the same oxygen concentration and very close carbon, hydrogen and lower heating value for comparing their effects on the combustion, performance and emissions of the diesel engine. The results indicated that DBE is the most suitable ternary fuel for further investigation.|
The experiments were conducted on four fueling modes. In the diesel mode, pure diesel was injected into the engine cylinder. In the blended mode, 80% diesel, 5% biodiesel and 15% ethanol (D80B5E15), by volume, were mixed, and injected into the engine cylinder. In the fumigation mode, a mixture of biodiesel and ethanol (BE) was injected into the intake manifold; while diesel fuel was used as the main fuel. In the F+B mode, half of the BE mixture was injected into the intake manifold and another half of it was blended to form DBE and used as the main fuel. The experiments were conducted at a constant overall fuel composition of D80B5E15 for the three fueling modes to provide the same fuel composition for comparing their effects. The experiments were divided into three groups. The first and second groups were conducted to investigate the effects of using different fueling modes on the combustion, performance and emissions at five engine loads with a constant engine speed (1800 rpm) and five speeds with a constant load (142.5 Nm), respectively. The third group was conducted to study the physicochemical properties of PM sampled in the different fueling modes with four operating conditions. According to the average results, it is found that the blended mode has higher peak heat release rate, ignition delay, BTE, nitrogen monoxide (NO), nitrogen oxides (NOX), coefficient of variation (COV) in Max(dP/dθ), but lower duration of combustion, COVIMEP, BSFC, carbon dioxide (CO₂), carbon monoxide (CO), hydrocarbon (HC), nitrogen dioxide (NO₂), PM mass, total number concentration and geometric mean diameter, and similar peak in-cylinder pressure and exhaust gas temperature in comparison with those of the fumigation mode. In regard to the physicochemical properties of the PM, the blended mode has higher organic carbon (OC)/total carbon (TC), high-volatile substance (VS)/total-VS and low-VS/total-VS ratios and faster oxidization reactivity, but lower non-VS/total-VS ratio, TC, OC, elemental carbon (EC), EC/TC ratio, water-soluble organic carbon, polycyclic aromatic hydrocarbons, benzo[a]pyrene equivalent, n-alkanes, inorganic ions, metals and elements, primary particle size, fringe length, tortuosity and fringe separation distance compared to those of the fumigation mode. In addition, it is observed that the values of all the parameters in the F+B mode are between those of the fumigation mode and the blended mode, showing that the F+B mode has the effects between those of the fumigation and blended modes. It can be found from the results that the use of DBE has different effects on the engine combustion, performance and emissions by using the blended mode or the fumigation mode. It is because, in the blended mode, the lower cetane number and higher heat of evaporation of ethanol cause late combustion and affect other combustion, performance and emission parameters. In the fumigation mode, the combustion of diesel fuel in a homogeneous BE/air mixture inside the engine cylinder also affect combustion parameters, performance and emissions in a different manner than those in the blended mode. These relationships are investigated in this study by relating the performance and emissions to the combustion parameters in each fueling mode.
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