| In this thesis, based on the background of coal-water slurry gasification technology, the influence of surfactant on droplets breakup regime was studied experimentally with high-speed camera. Surfactant solution and air were used as experimental medium. Main research contents were summarized as follows:For bag breakup regime, the influence of surfactant on critical Weber number, deformation characteristics, time characteristics, mean diameter and droplets size distribution were discussed. The results showed that, the critical Weber number of liquid drop breakup and atomization was found to be nonlinear in the presence of surfactant. We have found that critical Weber number first increases and then decreases with the increase of surfactant concentration. The surfactant concentration when critical Weber number reaches the turning point was found to be close to critical micelle concentration (CMC). Except the unchanged maximum deformation diameter df,m/d0, all deformation parameters like maximum dimensionless rim diameters dr,m/d0, radial length lm/d0, axial length wm/d0, length-width ratio lm/wm, of bag changed fast when concentration was below the CMC, however, the variation of these parameters turned to steady when concentration exceeded the CMC. Besides, there was little influence on characteric deformation time Tf, however, characteric breakup time Ta increased when surfactant solution concentration increased. What’s more, with the concentration increasng, the Sauter diameter (SMD) significantly decreased, and drops size distribution became more uniform.As a result, it can remarkablely improve atomization effect.For shear breakup regime, the effect of surfactant on deformation characteristics, time characteristics, core drop velocity, mean drop drag coefficients and shear breakup critical Weber number were studied. The results showed that, the surfactant had a small impact on shear breakup regime. All above parameters stayed steady when surfactant solution concentration changed. |
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