Temperature Dependence of the Laminar Burning Velocity of Methanol Flames

Abstract

To better understand and predict the combustion behavior of methanol in engines, sound knowledge of the effect of the pressure, unburned mixture temperature, and composition on the laminar burning velocity is required. Because many of the existing experimental data for this property are compromised by the effects of flame stretch and instabilities, this study was aimed at obtaining new, accurate data for the laminar burning velocity of methanol−air mixtures. Non-stretched flames were stabilized on a perforated plate burner at 1 atm. The heat flux method was used to determine burning velocities under conditions when the net heat loss from the flame to the burner is zero. Equivalence ratios and initial temperatures of the unburned mixture ranged from 0.7 to 1.5 and from 298 to 358 K, respectively. Uncertainties of the measurements were analyzed and assessed experimentally. The overall accuracy of the burning velocities was estimated to be better than ±1 cm/s. In lean conditions, the correspondence with recent literature data was very good, whereas for rich mixtures, the deviation was larger. The present study supports the higher burning velocities at rich conditions, as predicted by several chemical kinetic mechanisms. The effects of the unburned mixture temperature on the laminar burning velocity of methanol were analyzed using the correlation u L = u L0 (T u /T u0 ) α . Several published expressions for the variation of the power exponent α with the equivalence ratio were compared against the present experimental results and calculations using a detailed oxidation kinetic model. Whereas most existing expressions assume a linear decrease of α with an increasing equivalence ratio, the modeling results produce a minimum in α for slightly rich mixtures. Experimental determination of α was only possible for lean to stoichiometric mixtures and a single data point at ϕ = 1.5. For these conditions, the measurement data agree with the modeling results.

A detailed chemical kinetic modeling, ignition delay time and jet-stirred reactor study of methanol oxidation

“…Liao et al [20] reported laminar burning velocities using the spherical combustion bomb technique for methanol/'air' mixtures at 358 K. Veloo et al [21] experimentally determined the laminar flame speed of methanol using the counter-flow configuration technique at atmospheric pressure and at an unburned mixture temperature of 343 K. Vancoillie et al [22] reported laminar flame speed measurements at atmospheric pressure for methanol/'air' mixtures at unburned gas temperatures of 298-358 K using the heat flux method. What is absent for the most part in the previous studies is validation data for engine relevant conditions at pressures in the range 10-150 atm in the temperature range 800-1600 K. This study provides a comprehensive set of data in this regime and covers low-to high-temperature chemistry by coupling ST, RCM and JSR measurements.…”

Development and validation of a quasi-dimensional model for methanol and ethanol fueled SI engines

“…Laminar burning 150 velocity correlations for methanol and ethanol have been determined based on chemical kinetics calculations [31]. These correlations have been extensively validated against measurements obtained on two different fundamental combustion research setups [5,32,33]. Figure 1 shows that, compared to the older correlations of Metghalchi & Keck and Gülder, the methanol u l correlation developed by the current authors places the peak laminar burning velocity at a richer equivalence ratio and predicts a less steep decrease in u l for rich mixtures.…”

“…They offer the potential of CO 2 neutral transport and increased energy security, while ameliorating engine performance and efficiency compared to fossil fuels thanks to a number of interesting properties [5,6]. The most significant interesting properties of light alcohols include: 35 • High heat of vaporization, which causes considerable charge cooling as the injected fuel evaporates.…”

“…The current authors have worked on the laminar burning velocity of methanol and ethanol mixtures, compiling data from the literature [31] and looking at numerical [31] as well as experimental [5,32,33] means to determine a suitable laminar burning velocity correlation. Laminar burning 150 velocity correlations for methanol and ethanol have been determined based on chemical kinetics calculations [31].…”

Development and Validation of a Quasi-Dimensional Model for (M)Ethanol-Fuelled SI Engines

“…The authors have worked on the laminar burning velocity of methanol and ethanol mixtures, compiling data from the literature [21] and looking at numerical [21] as well as experimental [22] means to determine a suitable laminar burning velocity correlation. A laminar burning velocity correlation has been determined based on chemical kinetics calculations [21].…”