Study On Premixed Laminar Combustion Of Hydrogen Blended Ethanol Fuels

The diversification of energy and vehicle fuels in the 21st century, developments and applications of bio-energy and other renewable and clean alternative fuels are the inevitable trends towards purifying air, protecting the environment and solving the problem of mineral fuel shortage. As being good alternative fuels, both ethanol and hydrogen can improve effectively the performance of combustion and reduce emissions. The mixture of ethanol with small quantities of hydrogen can achieve good complementary actions.Based on the reformed hydrated alcohol fuels containing ethanol and hydrogen, this paper has studied the premixed laminar combustion properties of ethanol-hydrogen mixtures through experiment and numerical calculation and integrated the chemical reaction mechanism of ethanol-hydrogen mixtures.The flame speed,laminar burning velocity,Markstein length,flame thickness,flame front surface structure and the burning flux are obtained by the experimental study of ethanol-hydrogen mixtures at different equivalent ratios and hydrogen proportions on the constant volume combustion bomb. The results show that:with the increase of the hydrogen proportion, the flame speed (stretched and unstretched),laminar burning velocity(stretched and unstretched) and the burning flux increase gradually (the increase rate of the burning flux is slightly less than the laminar burning velocity), Markstein length decreases. While the flame speed and the laminar burning velocity achieve peaks at an equivalent ratio equal to 1.2 and decrease after deviating from this value. Markstein length decreases with the increase of the equivalent ratio in low hydrogen proportions (less than 40%) and the opposite happens when hydrogen proportion is more than 60%. The generation rate of combustion products increases with the increase of the stretched ratio whereas the gas consumption rate decreases when the stretched ratio is increased. Besides the change of the pressure shows that the combustion in the constant volume combustion bomb is carried out under conditions similar to adiabatic conditions. Three kinds of flame instabilities are observed in flame pictures. Meanwhile fit the empirical formula of the unstretched laminar burning velocities of ethanol-hydrogen mixtures. Explore the lean burn limit of ethanol-hydrogen mixtures, and hydrogen enhancement in ethanol can extend the lean burn limit.Through adding the basic element reaction H2O2+O2=HO2+HO2 and thermodynamic datum of O and O2 which are contained in the hydrogen mechanism to the ethanol mechanism, the chemical reaction mechanism of ethanol-hydrogen is integrated. By the methods of sensitivity and ROP, the consumption rates of ethanol and hydrogen are analyzed in details. Meanwhile in order to predict NO emissions, Zeldovich mechanism is added to the new ethanol-hydrogen mechanism. Based on the above mechanism, the flame speed,laminar burning velocity,adiabatic flame temperature,CO/NO emissions and the flame structure of ethanol-hydrogen mixtures in different initial conductions are calculated using CHEMKIN software, and this calculation plays a key role in the experimental study.Comparison shows good agreements between numerical calculation and experimental results of burning velocity and flame speed, and this means that the integrated mechanism of this paper can be used to calculate the combustion process of ethanol-hydrogen mixtures with different hydrogen proportions at conditions which are stoichiometric ratio and lean mixture.