Spray Ignition of Primary Reference Fuels Blended with Ethanol and 2,5-Dimethylfuran

Engine knocking poses a significant challenge for downsizing and boosting strategies in spark-ignition (SI) engines. In the event of knock, the unburnt fuel-oxidizer mixture auto-ignites after being compressed by the flame front and piston of an SI engine. Conventional knock is influenced by combustion chemistry and physical properties of the fuel. In this work, we present auto-ignition characteristics of primary reference fuel (PRF75), ethanol, 2,5-dimethylfuran, and their blends in Advanced Fuel Ignition Delay Analyzer (AFIDA). Three different pressures, i.e. 10, 15, and 20 atm and four different temperatures, i.e. 450, 500, 550, and 600 ⁰C have been used as initial conditions. A weak negative temperature coefficient (NTC) behavior has been observed for PRF75 ignition in AFIDA in this work. Moreover, for PRF75, the ignition delay times at low temperatures have been observed to show weaker dependence on pressure in comparison to the high temperature cases. For ethanol and 2,5-dimethylfuran, the effect of pressure on ignition has been observed to be minimal. For the blends of PRF75 and ethanol (or 2,5-dimethylfuran), the ethanol (or 2,5-dimethylfuran) chemistry starts to dominate when ethanol (or 2,5-dimethylfuran) quantity reaches 20 % in the fuel blend. The present comparative study provides an idea about the total resistance to auto-ignition considering both physical and chemical properties of the fuel blends.