二维喷嘴内稠密气固射流稳定性实验

Experimental on the stability of dense gas-solid jet in two-dimensional nozzle

利用高速摄像仪对二维喷嘴内稠密气固射流稳定性进行了实验研究,考察了颗粒粒径、料仓压力以及喷嘴收缩角等因素对射流流动模式及稳定性的影响。结果表明:对于颗粒粒径为78μm的气固射流,随着料仓压力的增大,射流出口速度增大,射流固含率降低,在料仓压力≥0.03MPa、射流速度≥4.82m/s、射流固含率≤0.168时,喷嘴内稠密气固射流出现气泡型的不稳定流动模式;随着颗粒粒径的增大,气固射流固含率降低,喷嘴内稠密气固射流从气泡模式转变为颗粒团不稳定流动模式;改变喷嘴收缩角对射流不稳定模式影响不大。利用微型压力传感器对喷嘴直管不同位置压力进行测量,结果表明压力脉动主要是由于气固射流中气泡及颗粒团的产生及演变导致的。研究表明,随着料仓压力增大,颗粒在喷嘴内向下运动过程中压降增加,渗透进颗粒流的气体分率增加,将导致喷嘴内气固相互作用增强,进而引起气固射流不稳定。

The stability of dense gas-solid jet in two-dimensional nozzle was studied by using a highspeed camera.Effects of particle diameter,hopper pressure and nozzle convergence angle on the jet flow pattern and stability were investigated.Results showed that for the gas-solid jet with a particle diameter of 78μm,the velocity of gas-solid jet increases with the hopper pressure,and the solid fraction of gas-solid jet decreases.An unsteady bubble-type flow pattern appeared when the hopper pressure was equal or greater than 0.03MPa,the velocity of gas-solid jet was equal or greater than 4.82m/s,and the solid fraction of gas-solid jet was equal or less than 0.168.With the increase of particle diameter,solid fraction of gas-solid jet decreases,and dense gas-solid jet transforms from bubble-type to particle cluster unsteady flow pattern.There is little effect on the jet flow of unsteady pattern when the nozzle convergence angles change.Micro pressure sensors were used to measure the pressure at different positions in the nozzle,and results revealed that the pressure pulsation is mainly caused by the formation and evolution of bubbles and particle clusters.Current study shows that with the increase of the hopper pressure,the fraction of gas permeating into the gas-solid jet increases during the downward movement of the particles in the nozzle,which will lead to the enhancement of the gas-solid interaction in the nozzle,and then cause the instability of the gas-solid jet.