Experimental investigation on different injection strategies for ethanol Partially Premixed Combustion

Partially Premixed Combustion (PPC) is a combustion concept which aims to provide combustion with low smoke and NOx with high efficiency. Extending the ignition delay to enhance the premixing, avoiding spray-driven combustion and controlling the combustion temperature to optimum levels through use of suitable lambda and EGR levels, have been recognized as key factors to achieve such combustion. Fuels with high ignitability resistance have been proven to be a good mean to extend the ignition delay. In this work pure ethanol has been used as a PPC fuel. The objective of this research was to investigate a suitable injection strategy for PPC combustion fueled with ethanol. Extensive experimental investigations were performed on a single-cylinder heavy-duty engine. The number of injections for each cycle, timing of the injections and the ratio between different injection pulses was varied one at a time and the combustion behavior was investigated at medium and low loads. The engine performance was evaluated in terms of controllability, stability, combustion noise, emissions and different efficiencies. Additionally, a comparison between single and double-injection strategies was performed. The results indicated that the double injection strategy should be prefered for PPC fueled with ethanol as double injection strategy offers good combustion controllability and combustion performance (i.e. low emissions and high efficiency) while keeping the combustion noise at very low levels.