Laminar Burning Characteristics of 2-Methylfuran Compared with 2,5-Dimethylfuran and Isooctane

The gasoline alternative 2-methylfuran (MF) has attracted the attention of fuel researchers, because of a breakthrough in its production technology. Both 2,5-dimethylfuran (DMF) and 2-methylfuran can be produced by dehydration and the hydrogenolysis of fructose. Little is known about the laminar burning characteristics of MF, although its combustion performance in spark ignition (SI) engines has been proved to be attractive by previous studies. Using high-speed Schlieren photography, this work examines the laminar burning characteristics of MF–air mixtures with varying temperatures (60, 90, and 120 °C) and equivalence ratios (0.6–1.1) at an initial pressure of 0.1 MPa in a constant-volume vessel. The stretched flame speeds are determined by the outwardly spherical flame method. The unstretched flame speed, Markstein length, laminar burning velocity, flame thickness, density ratio, Markstein number, and laminar burning flux of MF combustion at different equivalence ratios and temperatures are then deduced and compared to those of DMF and isooctane. The results show that the stretched flame propagation speed of MF decreases as the stretch rate increases. The unstretched flame speed of MF is 10%–30% faster than that of DMF and 10%–50% faster than that of isooctane. The maximum unstretched flame speed of MF under the three temperatures tested occurs at an equivalence ratio (Φ) of 1.1, whereas the maximum unstretched flame speeds of DMF and isooctane occur at Φ = 1.1 and 1.2. The Markstein lengths for the three fuels decrease as Φ increases and the Markstein length of MF is generally smaller than that of DMF and isooctane. The burning velocity of MF is the fastest among the three fuels at all temperatures and Φ tested. The flame thickness of MF is the smallest at all test conditions compared to DMF and isooctane. The laminar burning flux of MF increases as the initial temperature increases and exhibits peak values between Φ = 1.1 and Φ = 1.2.