Volatile organic compound emissions from an engine fueled with an ethanol-biodiesel-diesel blend

With the advent of energy crisis, vehicle engines need alternative energy sources eagerly to supply power. Ethanol-biodiesel-diesel blends are considered to be effective solutions. One way is diesel engines burning blended fuels. Diesel engines exhaust many kinds of volatile organic compounds (VOCs) when mixed fuels burn in them. Extremely poisonous as these VOCs are, they can cause severe damage to the natural environment as well as human health. To explore the characteristics of the unregulated emissions produced by diesel engines and then to limit them, research and studies should be conducted. The research in this paper used a single-cylinder diesel engine and a chromatograph mass spectrometer to investigate 9 kinds of VOCs (benzene, toluene, n-butyl acetate, ethylbenzene, p-xylene, m-xylene, styrene, o-xylene, n-undecane) emissions of ethanol-biodiesel-diesel (EBD) and diesel (D). The solid phase adsorption-thermal desorption-gas chromatography mass spectrometry (GC/MS) had an advantage in measuring and analyzing VOC emissions, so it was used for investigating the total emissions of 9 kinds of VOCs. Based on the standard curves of VOCs, the GC/MS computed the peak area of each VOC and realized the quantitative analysis of target compounds. By the calculating equation of VOC specific emissions and other test parameters (exhaust flow, engine power, dilution ratio, test time), the test got VOC specific emissions of two different fuels under different operating conditions. The test selected five typical conditions to collect exhaust when burning EBD and D. EBD contained 10 vol. % ethanol, 30 vol. % biodiesel, 55 vol. % diesel, 2.5 vol. % n-butyl alcohol and 2.5 vol. % iso-octyl alcohol, which had strong stabilities and good economy. From the analysis of the test results of VOC emissions, it was found that EBD increased total emissions by 84.2% at rated power but decreased by 14.85% at 10% load and by 20.39% at 50% load compared with diesel. But under other test conditions, VOC emissions with EBD were lower than diesel. VOC emissions of the two fuels were mainly benzene and toluene at medium and high load, which increased up to 47.4%. Emissions of other components increased at low load. In general, it was possible to decrease VOC emissions at medium or low loads when the diesel engine was fueled with EBD. The ozone specific reactivities (SR) of the engine exhaust for the two test fuels were approximately the same for the selected operating conditions. The SRs of EBD were a bit lower than D at medium and low loads. EBD had an advantage relative to VOC emissions which was found mainly at medium and low loads. This study is valuable for contributing to the building of a VOC emissions standard and for demonstrating the potential benefit of substitute fuels in reducing VOCs.