E. Sukjit

Finding synergies in fuels properties for the design of renewable fuels - hydroxylated biodiesel effects on butanol-diesel blends.

This article describes the effects of hydroxylated biodiesel (castor oil methyl ester - COME) on the properties, combustion, and emissions of butanol-diesel blends used within compression ignition engines. The study was conducted to investigate the influence of COME as a means of increasing the butanol concentration in a stable butanol-diesel blend. Tests were compared with baseline experiments using rapeseed methyl esters (RME). A clear benefit in terms of the trade-off between NOX and soot emissions with respect to ULSD and biodiesel-diesel blends with the same oxygen content was obtained from the combination of biodiesel and butanol, while there was no penalty in regulated gaseous carbonaceous emissions. From the comparison between the biodiesel fuels used in this work, COME improved some of the properties (for example lubricity, density and viscosity) of butanol-diesel blends with respect to RME. The existence of hydroxyl group in COME also reduced further soot emissions and decreased soot activation energy.

Interrogating the surface: the effect of blended diesel fuels on lubricity

The lubricating properties of two sustainable alternative diesels blended with ultra low sulphur diesel (ULSD) were investigated. The candidate fuels were a biodiesel consisting of fatty acid methyl esters derived from rapeseed (RME) and gas-to-liquid (GTL). Lubricity tests were conducted on a high frequency reciprocating rig (HFRR). The mating specimen surfaces were analysed using optical microscopy and profilometery for wear scar diameters and profiles respectively. Microscopic surface topography and deposit composition was evaluated using a scanning electronic microscope (SEM) with an energy dispersive spectrometer (EDS). Like all modern zero sulphur diesel fuel (ZSD), GTL fuels need a lubricity agent to meet modern lubricity specifications. It has been proven that GTL responds well to typical lubricity additives in the marketplace. The lubricity of ULSD, GTL and blends of these fuels were significantly improved with the addition of as little as 10% volume of RME, inducing more stable hydrodynamic conditions. Topography measurements showed the formation of a residue when RME was blended in the base fuels and composition analysis indicated a predominately carbon formation on the worn surfaces that correlated with wear scar diameters. On the other hand, the test disc under GTL lubrication showed the smooth and residue free surface. The optimal proportion of blended fuel that created the smallest wear scar diameter was 70% GTL, 20% ULSD and 10% RME.