Characterization of laminar premixed methanol–air flames

This study focuses on the effects of initial temperature and pressure on the propagation characteristics of laminar premixed flame of methanol–air mixtures. Spherically expanding laminar premixed flames, freely propagating from spark ignition sources in initially quiescent methanol–air mixtures, are continuously recorded by a high-speed CCD at various equivalence ratios and temperatures. The flames are then analyzed to deduce the flame speed. The stretch imposed on the spherical flame front is explored experimentally; as a consequence, the unstretched laminar burning velocities of methanol–air flames have been derived. The present measurements are compared with the experimental data reported previously, and good agreements are obtained. Combined previous results, a correlation in the form of ul=ulo(Tu/Tu0)αT(Pu/Pu0)βpul=ulo(Tu/Tu0)αT(Pu/Pu0)βp has been developed to describe the dependences of initial temperature and pressure on the burning velocities of methanol–air flames. The global activation temperatures are determined in terms of the burning mass flux. And then, the Zeldovich numbers for methanol–air flames are estimated as a function of equivalence ratio. On the basis of the mass burning flux, an alternative correlation of laminar burning velocities has been proposed, and agreements can still be found in the comparison between this alternative forms and the power law correlation above.