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Furans such as 2-Methylfuran (2-MF) and 2,5-Dimethylfuran (DMF) can be produced from biomass sugars and offer superior properties for use in SI engines. This paper describes the study of the auto-ignition characteristics of furans and other biofuels using a rapid compression machine. Blending with PRF90 and RG, the auto-ignition suppression of 2-MF was almost equal to that of ethanol and larger than toluene, although the auto-ignition delay of pure 2-MF was shorter than that of ethanol and toluene. This was because 2-MF suppresses the cool flame reaction. Knock evaluation using a single-cylinder research engine also indicated that the addition of 2-MF improved the anti-knock properties as well as ethanol.

Occurrence of knock in spark ignition (SI) engines is usually suppressed by inhibiting auto-ignition of the fuel-air mixture. A steep increase in pressure by auto-ignition of the local mixture is thought to initiate the pressure oscillation, which results in knock. Therefore, in order to prevent knock, the strength of the pressure oscillation would be decreased by reducing the local heat release of the end gas. In this study, the oxidation reaction rate of the auto-ignition was attempted to be reduced by dilution of the mixture. The effect of mixture dilution on the strength of pressure oscillation, that is knock intensity, was examined using a rapid compression machine (RCM) and a single cylinder SI engine. The test result of compression ignition of homogeneous mixture using RCM showed that increase in dilution ratio could decrease the knock intensity even if the input heat increased and the auto-ignition timing advanced.