Laminar burning characteristics of 2-MTHF compared with ethanol and isooctane

- Laminar flame characteristics of 2-MTHF were studied.
- Laminar flame speed of 2-MTHF was compared with ethanol and isooctane.
- The peaks of un-stretched flame speeds occur in a range of Φ 1.1-1.2.
- Laminar burning velocity of 2-MTHF is ∼0.56 m/s at stoichiometric ratio, 393 K.

2-Methyl tetrahydrofuran (2-MTHF) is one of the promising second-generation biofuel candidates, raising increasing interest because of the recent breakthrough in producing 2-MTHF from biomass. As a potential gasoline extender and renewable oxygenate, its high energy density and avoidance of competing with food make it attractive compared with ethanol. In the current work, the laminar burning characteristics of 2-MTHF-air mixtures are studied with varying equivalent ratios (0.88-1.43) and initial temperatures (333 K, 363 K and 393 K) at ambient pressure in a constant-volume vessel. The results are compared with ethanol and isooctane, a representative component in gasoline. The stretched flame speed, un-stretched flame speed, Markstein length, flame thickness, Markstein number, laminar burning velocity and burning flux are calculated and analyzed. The result shows that for most tests, the ranking of un-stretched flame propagation speed is ethanol, 2-MTHF and isooctane. The peaks of un-stretched flame speeds against varying equivalent ratios appear at Φ = 1.1-1.2 for three tested fuels. The Markstein length indicates that generally isooctane has the most diffusion-thermal stable flame than 2-MTHF and ethanol when Φ < 1.2 at 393 K. Ethanol shows the smallest flame thickness in most of the test points. The laminar burning velocity of 2-MTHF is much faster than isooctane and is comparative with ethanol, indicating its fast-burning property and potential of improving engine thermal efficiency.