Experimental and kinetic modeling studies of laminar flame speed of n-butanol/ethanol blends

The use of n-butanol and ethanol as biofuels has been intensively studied in the last decades. At the commercial level, ethanol is used as a blending agent for gasoline or in pure form in flex engines. In the future, n-butanol could also be used in blends with ethanol, due to its combustion properties. This work presents experimental and kinetic modeling studies of laminar flame speed (S-L) of n-butanol/ethanol blends. Experimentally, these blends are estimated for a fresh fuel/air mixture at 400 K and 1 bar using a constant volume reactor. Numerically, 11 available chemical kinetics models are tested for a wide range of operating conditions (temperature, equivalence ratio, and pressure) for the alcohols and their blends. A comparison between the numerical and experimental results of the S-L for n-butanol, ethanol, and the blends was performed, using the measured and available experimental data at different pressures and temperatures. Finally, a comprehensive sensitivity analysis of the S-L of these fuels with respect to the reaction rate constants was performed using the models. Concerning B20 and B40 blends, it was observed that the promoting and degrading reactions of both blends flames are very similar to those of ethanol flames. Whereas concerning B60 and B80 blends, as the addition of n-butanol increases in the blend, the promoting and degrading reactions in the blends S-L become closer to those of n-butanol flames.