Optical characterization of hydrogen-air laminar combustion under cellularity conditions

Abstract

Abstract In this work, an optical characterization of the hydrogen-air laminar combustions is presented in order to investigate the onset of cellular instabilities and quantify their intensity. Different combustion experiments of hydrogen-air have been developed in a cylindrical constant volume combustion bomb with centered ignition and transparent windows. The development of the flame and the wrinkling of its surface are recorded with a Schlieren technique. A cellularity density index (cell#/cm2) is used to quantify the phenomenon. The pressure during the combustion is registered with a piezoelectric transducer and its signal is treated by means of a two-zone diagnosis model. A parametrical study has been made by varying the fuel/air equivalence ratio, initial pressure and initial temperature during the combustions. In agreement with other published works, the present results show that hydrogen-air flames are more cellular as the mixture is leaner, with increasing values of the cellularity density. Similar trends are obtained as the initial pressure or the initial temperature increases.