Experimental study of horizontally lifted high-speed nonpremixed flame jets

Abstract

This paper presents an experimental study on horizontally jet flames with rather high velocities (58 m/s-167 m/s, Reynolds number up to 3.0 × 105), which mainly fall in the momentum-controlled region. Both high-speed schlieren and color imaging techniques have been adopted to obtain the time-resolved images, based on which the flame and flow dynamics has been discussed comprehensively. Under the test conditions, all the flames have shown lift-off characteristics. The dynamic mode decomposition (DMD) and proper orthogonal decomposition (POD) analysis has been performed to reveal the flame and flow fluctuating frequency and the corresponding spatial distribution. The results have shown two high frequency modes at 269 Hz and 537 Hz in the lifted-off jet region, which may come from the test bench vibration. The statistics of flame length, height and lift-off distance have been presented, which have been compared with previously reported data at lower velocities. The comparison indicates that the flame behaviors have shown quite dramatic differences in the buoyancy and momentum-controlled regions. The present experiments have extended the research of horizontally placed jet flames to a wider velocity range, which has greatly broadened our knowledge of the lift-off jet flame behaviors under high velocity conditions.