In the present work, measured laminar burning velocities of methyl formate (MF)–air mixtures at atmospheric pressure are presented for high mixture temperatures (up to 500 K) using an externally heated mesoscale diverging channel method. The experiments were performed for equivalence ratios ranging from Φ = 0.6 to Φ = 1.4 with an unburnt mixture temperature range from 350 to 500 K. The results reported in the literature and mechanism predictions of Aramco 2.0 (2016), Dievart (2013), and Dooley (2010) using PREMIX code are then compared with the data obtained from the existing experimental setup. The progressive change of temperature exponent and laminar burning velocity with equivalence ratios is akin to the other gaseous and liquid fuels outlined in the literature. The maxima and minima associated with the laminar burning velocity and temperature exponent (α) respectively is observed at Φ ≈ 1.1 or a slightly richer side. The mechanism predictions of the Aramco 2.0 (2016) detailed kinetic model is used for a detailed analysis of the mixture oxidation to account for the sensitivity of the key reactions on the laminar burning velocity. The overall effect of H-abstraction of methyl formate enhances the laminar burning velocity at 500 K. From reaction pathway analysis, it is observed that the global combustion rate rises when the unburnt mixture temperature changes from 348 to 500 K.

Experimental measurements of laminar burning velocity are presented for mixture temperatures above the autoignition temperature of premixed n-heptane + air mixtures using an externally heated mesoscale diverging channel method. Direct measurements of laminar burning velocity are carried out at 1 atm of pressure for an unburnt mixture temperature range (350−600 K) with the mixture equivalence ratio varying from ϕ = 0.6 to 1.5. Nonlinear power-law correlation is proposed to delineate the effect of change in the mixture temperature on the burning velocity variation at various equivalence ratios. A minimum value for the temperature exponent is observed for stoichiometric n-heptane + air mixtures. The maximum value of laminar burning velocity is measured for ϕ ≈ 1.1 at all mixture temperatures. The reported data sets are compared with the available experimental results and the predictions of various detailed kinetic models, i.e., LLNL V3.1 (2011), JetSurF 2.0 (2010), and Poli Mi (2014). Good agreement of the present data is observed with the predictions of the LLNL V3.1 reaction mechanism at all unburnt mixture temperatures. The predictions of other kinetic models show slight under-prediction at higher mixture temperatures. Sensitivity analysis using the LLNL V3.1 mechanism is reported to highlight the contribution of key reactions enhancing/reducing the laminar burning velocity at 470 and 600 K mixture temperatures. With an increase in the mixture temperature from 470 to 600 K, the influence of the chain branching reaction (H + O 2 ↔ O + OH) on laminar burning velocity increases nearly 63.5%. Formation of a vinyloxy radical (CH 2 CHO) from the oxidation of a vinyl radical (C 2 H 3 ) enhances the burning velocity at a 470 K temperature. Oxidation of C 2 H 3 (at 600 K) becomes crucial in governing engine knocking in low-temperature oxidation of n-heptane. It is deduced from the reaction pathway diagram that the production of a highly reactive compound, C 2 H 2 , at 600 K plays a significant role and governs the overall reaction rate of the mixture.

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