Effects of CNG quantity on combustion characteristics and emissions of a dual fuelled automotive diesel engine

The paper reveals some experimental aspects of compressed natural gas (CNG) use in dual fuel mode at an automotive diesel engine. Brake specific energetic consumption, incylinder pressure, emissions and variability of indicated mean effective pressure are analysed at operating regime of 2000 rpm and 40% load. Using CNG as an alternative fuel reduces brake specific energetic consumption by 50%, the CO2 emission by 10% and sets the in-cylinder maximum pressure 13 bar higher comparative to diesel fuel fuelling. The smoke and hydrocarbons emissions and the variability of indicated mean effective pressure are affected by the injection of compressed natural gas into intake manifold: HC emission grows 24 times, the smoke number and the coefficient of variability of IMEP double their values. The use of compressed natural gas at an automotive diesel engine improves its energetic performances and combustion process, having positive effects on CO2 emission and fuel consumption.