多级挡板对横流鼓泡床颗粒停留时间分布影响的数值模拟

基于欧拉双流体模型耦合组分输运方程对三维横流矩形鼓泡流化床内气固两相流动行为进行了数值模拟,在挡板数1~13范围内探究了挡板形式(溢流板、底流板和侧流板)对颗粒流动状态及停留时间分布的影响规律。使用颗粒再循环率R-评估了流化床内腔室间的颗粒输运行为。结果表明,三种挡板形式均能提高床内颗粒停留时间的均一性,减弱颗粒返混,且颗粒流动随挡板数量增加趋于平推流,增加挡板数量有利于延长颗粒平均停留时间;采用侧流板可使床内形成横向固含率梯度,而底流板则使各腔室内出现“左低右高”的局部固含率梯度,表明挡板形式影响了颗粒输运行为的驱动力;此外,溢流床具有更高的颗粒再循环率,颗粒逆流现象严重,侧流板和底流板则能更好调节腔室间的颗粒输运行为,三种挡板形式下的颗粒再循环率均随挡板数量增加呈现降低趋势,而挡板数量对底流床的颗粒再循环率影响更大。

Efficient Design of Multi-stage Cascade Waveband Separator

We propose a cascade system of filters for realizing a non-uniform waveband separation for optical networks. The use of such separation is required at the DEMUX stage in a optical OXC switching wavebands. The design of the system is based on optimized balanced tree, which minimizes the overall optical loss.