Performance, combustion, and emissions in a diesel engine operated with fuel-in-water emulsions based on lignin

Dolanimi Ogunkoya, Shuai Li, Orlando J. Rojas and Tiegang Fang

Applied Energy, 2015, vol. 154, issue C, 861 pages

Abstract: We report for the first time on the use of water-continuous emulsions stabilized by a bio-based macromolecule in a compression-ignition diesel engine and compare their performance, combustion and emissions against the base fuels (diesel, biodiesel, and jet fuel). For this purpose, high internal phase ratio emulsions (70:30 fuel-to-water) were produced by mechanical emulsification using carboxymethylated wood lignin as stabilizer. Combusting experiments were performed with the engine operating at 2000rpm under three loads (0, 1.26 and 3.26bar brake mean effective pressure, BMEP). Engine performance, in-cylinder combustion, and exhaust emissions were monitored and compared for the fuels tested. At no load condition and when compared to the respective base (single phase) fuels, an increase in the indicated work was observed for diesel and biodiesel emulsions. Compared to the base fuels, the emulsions resulted in higher engine mechanical efficiency at 1.26 and 3.26bar BMEP except for jet fuel emulsion at 1.26bar. Additionally, they displayed a lower brake specific fuel consumption (BSFC), if calculated on the basis of effective fuel content discounting emulsion water, and higher brake thermal efficiency. Compared to the base fuel, the respective emulsions generally presented lower peak in-cylinder pressure, lower heat release rates, and longer ignition delays at 1.26bar and 3.26bar BMEP; the opposite effect was observed at no-load conditions. Remarkably, a large reduction of nitrogen oxides (NOx) emissions was noted in the combustion of the fuel emulsions, which was accompanied with a relatively higher carbon monoxide (CO) release at 1.26 and 3.26bar (at 0bar BMEP, the emulsions produced less CO emissions). The effect of emulsions on hydrocarbon emissions and smoke opacity depended on the fuel type and the engine load. Overall, it is concluded that while reports on fuel emulsions involve oil-continuous systems, the proposed water-continuous alternative represents an opportunity for diesel engines, whereby the fuel is dispersed as micrometric droplets for improved combustion and reduced emissions. At the same time, the fuel emulsion formulation takes advantage of the surface activity and high calorific value of widely available, inexpensive lignin stabilizers, making the proposed system a viable option towards cleaner or fully bio-based fuels.

Keywords: Fuel emulsions; Oil-in-water emulsion; Lignin; Stabilizer; Diesel engine combustion; Emissions (search for similar items in EconPapers)
Date: 2015
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Citations: View citations in EconPapers (20)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:appene:v:154:y:2015:i:c:p:851-861

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DOI: 10.1016/j.apenergy.2015.05.036

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