The Temperature and Pressure Dependencies of Propagation Characteristics for Premixed Laminar Ethanol-Air Flames

Laminar burning velocity is strongly dependent on mixture characteristics, e.g. initial temperature, pressure and equivalence ratio. In this work, spherically expanding laminar premixed flames, freely propagating from a spark ignition source in initially quiescent ethanol-air mixtures, have been imaged and then the laminar burning velocities were obtained at initial temperatures of 358 K to 500K, pressure of 0.1 to 0.2 MPa and equivalence ratio of 0.7 to 1.4. The measured results and literature data on ethanol laminar burning velocities were accumulated, to analyze the effects of initial temperature and pressure on the propagation characteristics of laminar ethanol-air flames. A correlation in the form of ( ) ( ) 0 0 p T u u T T P P u u u u l lo    was proposed, and validated over much wide temperature, pressure and equivalence ratio ranges. The global activation temperatures were determined in terms of the laminar burning mass flux for ethanol-air flames. And the Zel’dovich numbers were estimated as well. The dependencies of global activation temperature and Zel’dovich number on initial mixture pressure, temperature and equivalence ratio were explored. Additionally, an alternative correlation of laminar burning velocities, from the view of theoretical arguments, was proposed on the basis of the determined ethanol-air laminar mass burning flux. Good agreements were obtained in its comparison with the literature data.