Assessing Emission and Power Tradeoffs of Biodiesel and n-Butanol Diesel Blends for Fuel Sustainability
Citation:
Liang, M. Assessing Emission and Power Tradeoffs of Biodiesel and n-Butanol Diesel Blends for Fuel Sustainability. FUEL. Elsevier Science BV, Amsterdam, Netherlands, 283:118861, (2020). https://doi.org/10.1016/j.fuel.2020.118861
Impact/Purpose:
The use of biodiesel in the transportation sector is the need for energy security. Although biodiesel combustion can decrease the diesel particulate matter (PM) pollutant on a mass basis, the shift of PM size distribution to a smaller peak size arose concerns to the roadside and near raod exposure and human health concerns. This because biodiesel PMs can disperse to further distance and absrob more harmful organic compounds than diesel PMs due to the smaller size and greater prosity providing more space. In addition, the tradeoff between decreasing PM and increasing dramaticly NOx is another concern for biodiesel usage in transportation. The purpose of this study is to find a possible solution that can compromise in the emisison of PM and NOx tradeoff and provide science data and informantion for future research and decision making. In this study, we tested biodiesel blends (with or without n-butanol additive) and neat No.2 diesel (D100); compared the size districtuion of PM and NOx concentration emitted from different fuel combustions; quantified the changes of black carbon in various PMs in term of the OC/EC ratio and the morphology. The results have shown that the binary diesel-biodiesel blend (D80B20) offers reduced PM and black carbon emission, but higher NOx in engine exhaust. Comparatively the tertiary diesel-biodiesel-butanol blend with 5 v/v% n-butanol (D80B15Bu5) offers superior environmental tradeoff in the black carbon and NOx emission than D80B20. In specific, the peak size of PM from D80B20 and D80B15Bu5 is 0.20-0.32 ¿m, significantly smaller than >0.40 ¿m dpmax for D100 and 0.30 ¿m cut-off size of regular diesel particulate filters (DPF). A 5% butanol substitution for methyl ester in D80B15Bu5 led to a reduction of NOx emission by 4.8% to a concentration level close to that of the No.2 diesel. Our study will provide scinticfic data and foundations to further research on pollutation prevention through fuel optimization. Out experiments have shown that undesired trade-off in NOx formation can be managed through adding a small amount of additive (such as n-butonal in our experiments). This is just one of the possible measures to achieve the compromise of the PM-NOx tradeoff associated with biodiesel combustion. In addition, the results of this study have a practical implication on environmental impacts on fuel sustainability and urban air quality management.
Description:
The use of renewable biodiesel and additives diversifies transportation fuel supply. Combustion tests on neat ultra-low sulfur No.2 diesel (D100) and its blends with biodiesel and the n-butanol additive were conducted to investigate environmental impacts and tradeoffs in engine emission and power output. The testing results show measurable changes in power output and engine emission, particularly in diesel particulate matter (DPM) size distribution and black carbon compositions. The binary diesel-biodiesel blend D80B20 (80% D100 and 20%B100 by volume) offers reduced PM and black carbon emission, but higher NOx in engine exhaust. Comparatively the tertiary diesel-biodiesel-butanol blend B15Bu5 (80% D100, 15% B100, and 5% Bu100 by volume) shows superior environmental tradeoff in the black carbon and NOx emission than D80B20. Both fuel blends suffer a 3.0–5.6% increase in brake-specific fuel consumption. At higher combustion temperature, the butanol-oxygenated diesel fuel produces DPMs of smaller size, higher number concentrations, greater OC fractions, and more amorphous black carbon particles. The peak DPM aerodynamic size dpmax for D80B20 and B15Bu5 blends is 0.20–0.32 μm, smaller than >0.40 μm dpmax for D100 and the 0.30 μm cut-off size of regular DPM filters. For an internal combustion engine capable of accommodating biodiesel and water fraction in the fuel mixture, the B15Bu5 blend offers a viable fuel alternative according to the comparative testing results. The use of biodiesel and butanol additive in petroleum diesel can decrease the DPM emission, while the undesired NOx formation in tradeoff can be managed through optimizing the tertiary composition of petroleum diesel, biodiesel, and fuel additives.
URLs/Downloads:
DOI: Assessing Emission and Power Tradeoffs of Biodiesel and n-Butanol Diesel Blends for Fuel Sustainability