comparative evaluation of the effect of partial substitution of diesel fuel by natural gas on performance and emissions of a fumigated dual fuel diesel engine

reduction of exhaust emissions is a major research task in diesel engine development in view of increasing concerns regarding environmental protection and stringent exhaust gas regulations. simultaneousreduction of nox emissions and particulate matter is quite difficult due to the soot/nox trade-off and isoften accompanied by fuel consumption penalties. towards this aim, automotive engineers have proposedvarious solutions, one of which is the use of alternative gaseous fuels as a supplement for the commercial liquid diesel fuel. this type of engine, which operates fuelled simultaneously with conventional diesel oiland gaseous fuel, is called “dual fuel” diesel engine. majority of the dual fuel diesel engines operate on the fumigation principle where the liquid diesel fuel is partially replaced by gaseous one fumigated intothe intake air. one of the gaseous fuels used commonly in compression ignition engine is natural gas, which has a relatively high auto-ignition temperature and moreover is an economical and clean burningfuel. the high auto-ignition temperature of natural gas is a serious advantage against other gaseous fuels since the compression ratio of most conventional di diesel engines can be maintained. moreover thecombustion of natural gas produces practically no particulates since natural gas contains less dissolved impurities (e.g. sulphur compounds). the present contribution is mainly concerned, with an experimentalinvestigation of the characteristics of dual fuel operation when liquid diesel is partially replaced with natural gas under ambient intake temperature in a di diesel engine. in the present work the results from thisinvestigation concerning data are given for performance and exhaust emissions. furthermore, through this experimental work the effect of liquid fuel percentage replacement by natural gas i.e. various values ofgaseous fuel / total fuel mass ratios are examined. the conclusions of this study may be proven to be consid