Combustion and emissions of a diesel engine with pentanol addition

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Combustion and emissions of a diesel engine with pentanol addition


Author: Xiao, Yao
Title: Combustion and emissions of a diesel engine with pentanol addition
Degree: M.Sc.
Year: 2015
Subject: Diesel motor -- Combustion.
Diesel motor exhaust gas.
Diesel motor -- Alternative fuels.
Motor fuels.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Mechanical Engineering
Pages: xi, 100 leaves : illustrations ; 30 cm
Language: English
InnoPac Record:
Abstract: Experimental investigations were conducted on a 4-cylinder natural-aspirated direct-injection diesel engine, focusing on the effects of pentanol addition on engine combustion, performance, and regulated emissions under five engine loads at 1800rpm. Compared pentanol-biodiesel with pure diesel, there were gradual increases in in-cylinder pressure, heat release rate and brake specific fuel consumption (BSFC) from low to high engine load, which were due to higher oxygen content, higher burning velocity and lower energy density. Meanwhile, the peak in-cylinder pressure and peak heat release rate sharply increased, because ignition delay of pentanol-biodiesel was longer than biodiesel and diesel. Regulated gaseous emissions including CO₂/CO, HC, NOX and smoke opacity were investigated. Compared pentanol-biodiesel with diesel, the lower energy density of pentanol-biodiesel decided that more carbon contents were consumed to generate the same power. Correspondingly pentanol addition increased CO₂ emission. The higher oxygen content improved oxygenated fuel combustion and oxidation, therefore lower HC emission, CO emission and smoke opacity were observed. Due to higher oxygen content and combustion temperature, all the oxygenated fuels except BP20 increased NOx emissions. Particular attentions were paid on the effect of pentanol addition on the particle emission and the physico-chemical properties of the diesel particulates. And particulates were analyzed with the aid of TEM and TGA facilities. Pentanol addition performed superior reduction capacity of PM mass emission. It indicated that pentanol inhibited the chemical kinetic of particle formation by substituting biodiesel or diesel with pentanol. At the same time, results from SMPS exhibited that pentanol addition can reduce GMD and TNC of diesel particulate at all tested operating conditions. Comparing the physical structures of pentanol-biodiesel with diesel particles, larger sized primary particles were emitted at high engine load which was affected by the equivalence ratio. Pentanol addition lowered particle diameter due to cooling effect reducing exhaust temperature. With pentanol-biodiesel operation, smaller radius of gyration and less spherical aggregate particle were found. Because the pentanol inhibited the formation of soot nuclei and decreased its volume density. For nano-structure, pentanol addition obviously increased fringe length and decreased tortuosity of primary particles. For chemical properties, increasing of engine load lowered the percentage of volatile substances in particulates, due to high in-cylinder temperature promoting the oxidation of volatile substances. On the other hand, compared oxygenated fuels with diesel, higher oxygen content strengthened oxidation of volatile substances obviously. Therefore, compared with diesel, the percentages of non-volatile substances were higher, with the increasing of pentanol volume fraction.

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