LDV测试技术在测量稀相气固并流上行和下行循环流化床两相速度中的应用

利用后向散射光纤激光多普勒测速仪（LDV），同时测量了内径为140mm的并流上行和下行循环流化床中稀相区局部气体和颗粒速度分布，并对实验结果进行了无固次处理和分析，对比了上行床与下行床内两相速度以及它们随表现气速和固体循环量的变化规律。研究发现对于顺重力场的并流下行床和逆重力场的并流上行床，床内两相速度分布存在明显差异，这主要是由于气固流动机理不同引起的。研究还表明在下行床中速度分布在形状上呈现明显的相似性。

THE APPLICATION OF LDV TECHNIQUE TO MEASURE TWO-PHASE FLOW IN A GAS-SOLIDS CONCURRENT UPFLOW AND DOWNFLOW CFB

The experiments are conducted in a gas-solids concurrent upflow and downflow CFB that is 140 mm in ID. A feasible Laser Doppler Velocimetry technique based on amplitude discrimination has been used to determine the local gas and solids velocities of the dilute phase simultaneously. Through dimensionless treatment and analysis of the experimental data,the two-phase velocities in the riser and downcomer are compared and their variances with the superficial gas velocity and solids circulating rate are also examined. The experimental results show that the two-phase velocities in the concurrent downflow bed,in which directions of gas and gravity are same,are greatly different with that in the concurrent upflow bed,in which gas flow is opposite dlrection of gravity. This difference is chiefly caused by mechanism of gas solids interaction. The research also shows that in the downcomer the velocity profiles of gas and solids display great similar1ty in the shape. They vary little with the operation conditions.