Combustion and emissions of a glycerol-biodiesel emulsion fuel in a medium-speed engine

Emulsion fuels are one option currently being explored to reduce powerplant and maritime emissions. Emulsification enables hydrophilic, typically low-value, molecules to be incorporated into traditional hydrocarbon fuels. Energetic oxygenated molecules, such as glycerol, are biorenewable and have the potential to reduce refueling costs and carbon emissions. When properly formulated, emulsions improve diesel combustion characteristics and reduce particulate matter (PM) and oxides of nitrogen (NOx). This paper explores the utilisation of glycerol-biodiesel emulsion (23 wt% glycerol) in a one-megawatt, six-cylinder, medium-speed diesel engine at constant speed to determine impacts on combustion dynamics, emissions and overall suitability. Fuel performance is compared to ultra-low-sulphur diesel (ULSD) and 380 cSt. heavy fuel oil (RMG 380). Idle emissions are shown to be comparatively poor due to low combustion stability and longer combustion delay. As load is increased to 25% of peak output, reductions in carbon monoxide (CO) and PM are observed. The lower energy density, however, restricts peak engine power which achieved 90% of full load at maximum fuel consumption. Despite engine maximum power derating, glycerol emulsion fuels require no engine modification and show promise as a powerplant fuel with a low-carbon footprint.