Author: Zhou, Quan
Title: Engine performance, combustion and emission characteristics of a diesel engine burning gaseous-diesel dual fuel
Advisors: Leung, C. W. (ME)
Degree: M.Sc.
Year: 2016
Subject: Diesel motor -- Alternative fuels.
Diesel motor -- Combustion.
Diesel motor exhaust gas
Hong Kong Polytechnic University -- Dissertations
Department: Department of Mechanical Engineering
Pages: xii, 93 pages : color illustrations
Language: English
Abstract: Experimental investigation performed to examine the engine performance, combustion and emission characteristics of a diesel engine burning LPG-diesel, methane-diesel or biogas-diesel dual fuel is presented. These three gaseous fuels are considered to be more environmental-friendly and clean fuels when compared to conventional diesel fuel. Thus, using LPG/methane/biogas as a supplement for part of the conventional diesel fuel is one promising way proposed to alleviate problems generated by using traditional diesel engines. Experimental investigations were conducted on a 4-cylinder diesel engine test-bed having a compression ratio of 19:1. The diesel engine was operated at 1800 rev/min under five different engine loads, whereas the gaseous fuel was added to replace some diesel fuel and was responsible to generate 10% to 20% of the total output power at each engine load, respectively. With 10% to 20% gaseous fuel power substitution, the effects of LPG/methane/biogas addition to the main diesel fuel are found to be closely related to the engine load. The in-cylinder pressure and heat release rate change significantly at high engine load under the dual fuel modes, while the variations are mild at low engine load. Comparing with the neat diesel mode, gaseous fuel-diesel dual fuel modes slightly deteriorate the engine performance at low to medium engine load, and the decline in brake thermal efficiency is within 11.4%. However, owing to the increase of injected pilot diesel fuel quantity and in-cylinder temperature at high engine load, the engine performance of all dual fuel modes can be recovered to that of the neat diesel mode. The best engine performance at 80% engine load is observed to be obtained under the 20% CH4-diesel dual fuel mode, and the BTE was increased by 6.9% compared to that of neat diesel mode.
In the present study, both gaseous emissions and particulate matter emissions were studied. Gaseous fuel-diesel dual fuel engine produces much higher brake specific carbon monoxide (BSCO) and hydrocarbon (BSHC) emissions, but lower brake specific particle mass concentration (BSPM) and nitrogen oxides (BSNOX) emissions. Regarding to the particle size distribution and number concentration, with the increase of engine load, the particle size distribution moves from small to large region. With gaseous fuel addition, the particle total number concentrations (TNC) and geometric mean diameters (GMD) of all dual fuel modes are decreased compared to that of neat diesel mode. In addition, the decreasing rate is increased with higher power substitution of gaseous fuel. Conclusively, the 20% methane-diesel dual fuel mode is observed to be the most effective operating mode that the BSNOX emissions and BSPM concentration reduced by 24.7% and 37.9% at the 80% engine load. In addition, it gives the best engine performance compared with other operating modes.
Rights: All rights reserved
Access: restricted access

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