Comparative Evaluation of the Effect of Partial Subs- titution 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 in-creasing concerns regarding environmental protection and stringent exhaust gas regulations. Simultaneous reduction of NOx emissions and particulate matter is quite difficult due to the soot/NOx trade-off and is often accompanied by fuel consumption penalties. Towards this aim, automotive engineers have proposed various 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 oil and 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 into the 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 burning fuel. 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 the combustion 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 experimenta