Combustion of Biodiesel- and Ethanol-Diesel Intake Injection Mixtures with 2007-01-4011
Seven biofuel-diesel fuel configurations were tested in a single-cylinder research diesel CFR engine that allowed variable injection timing. These seven configurations included three biodiesel-diesel blends (20% and 100%); two ethanol-diesel blends (15% and 20%), and two cases in which ethanol was injected into the intake air flow (20% and 33%). Combustion characteristics, NOx emissions, and soot emissions were compared with diesel operation across a range of injection timings. The effect of fuel compressibility affected the timing of injection, with biodiesel-diesel blends having advanced injection and ethanol-diesel blends having delayed injection. Biodiesel-diesel blends showed reduced ignition delay with only modest changes in combustion duration, while ethanol-diesel mixtures showed longer ignition delay but much shorter combustion duration and earlier phasing. In general, all the biofuel-diesel configurations improved thermal efficiency (∼3% relative) but increased fuel consumption to a greater extent due to lower energy content. None of the seven configurations had a large effect on NOx emissions. Soot was slightly lower for both biodiesel-diesel and blended ethanol-diesel. However, premixing ethanol with intake air using a port-fuel injector lowered soot by approximately 50%.