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Bioethanol is an established biofuel used today in sparked-ignited (SI) engines, however with limited fuel efficiency and stringent requirements on the ethanol purity (water content). In this paper, we will present the operation of a compression-ignition (CI) engine fuelled with upgraded hydrous ethanol. A specific fuel upgrade operation (excluding additives) converts a fraction of the hydrous ethanol to diethyl-ether, hence increases the cetane number up to adequate levels. The resulting upgraded fuel is tested in a commercial diesel engine (light-duty common-rail EURO IV model). In particular, the compression ratio is kept unchanged and only the injection timing is modified to ensure compression-ignition operation, securing the peak pressure at 8-12 degrees after top dead center.

Partially Premixed Combustion (PPC) is a combustion concept by which it is possible to get low smoke and NOx emissions simultaneously. PPC requires high EGR levels to extend the ignition delay so that air and fuel mix prior to combustion to a larger extent than with conventional diesel combustion. This paper investigates the operating region of single injection PPC for three different fuels; Diesel, low octane gasoline with similar characteristics as diesel and higher octane standard gasoline. Limits in emissions are defined and the highest load that fulfills these requirements is determined. The investigation shows the benefits of using high octane number fuel for Multi-Cylinder PPC. With high octane fuel the ignition delay is made longer and the operating region of single injection PPC can be extended significantly. Experiments are carried out on a multi-cylinder heavy-duty engine at low, medium and high speed.