Analysis of the Impact of 2-Methylfuran on Mixture Formation and Combustion in a Direct-Injection Spark-Ignition Engine

Within the Cluster of Excellence “Tailor-Made Fuels from Biomass”, a new reaction sequence to transform biomass into 2-methylfuran has been developed. In the present study, the influence of this potential biofuel on in-cylinder spray formation and evaporation as well as engine performance is studied experimentally using a direct-injection spark-ignition single-cylinder research engine. The results obtained for 2-methylfuran are benchmarked against investigation on the same engine using conventional research octane number (RON) 95 fuel and ethanol. The in-cylinder spray formation and evaporation process is characterized by high-speed Mie scattering visualizations, indicating quicker evaporation of 2-methylfuran compared to ethanol. Engine experiments support the findings of the optical measurements by revealing excellent combustion stability, especially in cold conditions, combined with a hydrocarbon emission reduction of at least 61 % in the relevant spark timing range compared to conventional fuel. The enleanment capability was also found to be higher by 0.16 units of relative air/fuel ratio. A noticeable drawback resulting from the combustion of 2-methylfuran is higher emissions of nitrogen oxides. The knock resistance of 2-methylfuran at full load is significantly better compared to RON 95, however, worse than ethanol. It allows for a compression ratio increase of more than 3.5 units compared to RON 95. The measured efficiency benefits with a compression ratio increase of 3.5 units range up to 9.9 % at full load.