Diesel engine performance using oxygenated fuels

Thesis (MSc)--Stellenbosch University, 2015.ENGLISH ABSTRACT: With worldwide emissions standards becoming more stringent over the last decade, the South African market seems set to follow suit. Older technology engines are however unable to attain these stringent standards and will require cleaner burning fuels. Biofuels like biodiesel and bioethanol-diesel blends are an attractive option as a result of their inherently oxygenated nature and renewable, low carbon footprint. Oxygenated fuels have been found to lower particulate and soot emissions without any significant increase in NOx, thus alleviating the usual particulate-NOx trade-off. In this study an existing diesel engine test facility has been upgraded to include emission equipment, and a low cost pressure indicating system. Fuel-to-fuel comparative testing was done with pump diesel and splash blended fuels consisting of pump diesel blended with varying amounts of ethanol and also biodiesel without including any cetane enhancing or blend stability additives. Emission analysis of the blended fuels showed a marked reduction in soot emission with little to no increase in NOx emission for all oxygenated fuels. This type of soot reduction without NOx increase is difficult to obtain through any other method. Blend stability was however a problem with the 15% ethanol-diesel blends.AFRIKAANSE OPSOMMING: Met wêreldwye uitlaatgas standaarde wat al hoe strenger geword het oor die laaste dekade, lyk dit asof dit net ‘n kwessie van tyd is voor Suid-Afrika dieselfde roete volg. Ouer tegnologie binnebrandenjins kan egter nie hierdie streng standaarde handhaaf nie en sal dus vereis dat die brandstof skoner brand. Biobrandstowwe, soos biodiesel en bio-etanol-diesel mengsels, blyk ‘n aantreklike opsie te wees vanweë hul natuurlike inhoud van suurstof en as hernubare hulpbron. Wanneer suurstof houdende brandstowwe soos hierdie verbrand word, word daar gevind dat daar ‘n daadwerklike afname in rook uitlaat is sonder enige merkbare toename in NOx uitlaatgasse. Dit is teenstrydig met die gewoonlike wisselwerking wat daar tussen hierdie twee uitlaatgas produkte is. In hierdie studie word die bestaande diesel enjin toetssel opgegradeer om uitlaatgas analiese toerusting asook ‘n lae-koste silinderdruk meettoestel te bevat. Brandstof-tot-brandstof vergelykings toetse word gedoen met gewone diesel asook toets diesel wat gemengde konsentrasies biodiesel of bio-etanol bevat. Die toets diesel bevat egter geen aanvullings om mengselstabiliteit of cetaan te verbeter nie. Toetsresultate toon dat daar merkbare vermindering in rook uitlaat is met min tot geen toename in NOx. Hierdie tipe van resultaat met produkte van ontbranding is moeilik om op enige ander manier te bewerkstellig. Daar word ook gevind dat diesel met 15 % bio-etanol nie ‘n stabiele mengsel is nie en dat fase skeiding plaasvind