Diesel Exhaust Heat Recovery to Promote HCCI of Wet Ethanol on Dedicated Cylinders

Wet ethanol is a low cost renewable fuel which often shows challenging ignition in spark-ignited engines. This can be tackled by using non-flame propagating combustion modes like HCCI. This paper shows experimental results of a diesel fueled generator set which recovers exhaust heat from one of the diesel cylinders to promote HCCI of ethanol on other cylinders. Experimental tests provided results of heat release, energy efficiency and a thorough combustion analysis that demonstrate the possibility of this concept which requires minimal changes on the original engine, making possible to retrofit existing units. A three-cylinder four-stroke engine originally fueled with diesel was used. The diesel injection system in one of the cylinders was replaced by an ethanol electronic fuel injection. Inlet heat for achieving HCCI was provided by complete exhaust recycling from one of the diesel cylinders. Stable HCCI combustion was achieved in the ethanol cylinder. Very low cycle-to-cycle combustion variation was observed and indicated efficiency was at the same levels of the original diesel cylinder.