Study of the knocking propensity of 2,5-dimethylfuran-gasoline and ethanol-gasoline blends

Measurements of the knocking propensity of two biofuels blended at low levels with a gasoline fuel were performed in a single-cylinder direction-injection research engine at three load conditions. Blends tested included three blends containing 2,5-dimethylfuran (DMF) blended by volume with gasoline at concentrations of 5%, 10%, and 15%. A blend of 10% DMF/10% ethanol with a balance of gasoline was also tested. The knocking propensity of the blends using the potential advanced biofuel were compared to the performance of E10 and gasoline. Knocking intensity was quantified using in-cylinder pressure measurements. A comparison of the improvement in the knock-limited spark advance (KLSA) relative to the baseline gasoline was performed for the fuels tested, where the knock limit was defined as the spark crank angle where more than 10% of the cycles knock with a knocking intensity greater than 100 kPa. All of the blends using either DMF or ethanol showed improvement in the KLSA relative to the baseline gasoline fuel. The blend with 10% ethanol and 10% DMF showed the best performance for the fuels tested and gave an improvement in the KLSA of 7 crank angle degrees at the full load condition. Ethanol showed a greater ability to reduce knocking tendency than DMF for the same volumetric blend percentage. The higher autoignition resistance of the ethanol blends is hypothesized to be due at least in part to the higher latent heat of vaporization reducing the in-cylinder temperature. (C) 2012 Elsevier Ltd. All rights reserved.