偏置出口循环流化床内颗粒体积分数分布的测试

Experimental investigation on local particle volume fractions distribution in offset-exit circulating fluidized bed

为了研究不同床体布置结构对循环流化床内气固流动特性的影响,在截面为0.35m×0.48m、高4.9m的循环流化床实验台上,以平均粒径为366.2μm的玻璃珠为床料,采用PC6D反射式光纤探针对不同轴向高度截面上不同径向位置处的局部颗粒体积分数分布进行实验测量.采用数值插值和时序分析的方法对测量结果进行分析后发现:床内结构的布置对炉内气固两相流动的影响明显,底部炉膛单侧渐扩结造成颗粒体积分数的径向分布不均,后墙侧颗粒体积分数明显高于前墙侧;受炉膛矩形截面的影响,炉膛截面长边处的颗粒体积分数明显低于短边处的颗粒体积分数;稀相区偏置炉膛出口的布置破坏了炉内气固流动的环核结构,在炉膛左墙和后墙侧形成了颗粒的局部高体积分数分布.利用时序分析的方法对颗粒体积分数瞬时信号进行分析.结果表明,在该工况条件下炉膛底部的气固流动在微观结构上为不稳定的两相结构,在过渡段环核结构的交界位置气固作用最剧烈,颗粒体积分数波动较大.

The local solid-particle volume fraction distributions were studied in a plexiglas rectangular CFB cold model with the size of 0.35 m ×0.48 m×4.9 m by using a reflective-type fiber-optic particle concentration probe（PC6D） in order to analyze the effects of the geometry structure on the gas-solid flow properties.The transparent glass bead with 366.2 μm diameter was used as bed materials during the experiment.Time series analysis and numerical interpolation methods were adopted to analyze the experimental data.Results showed that： in transition region,the expanding cross-section of wear wall structure significantly affected the gas-solid flow and the radial distribution of solid volume fraction was asymmetry;the local solid volume fraction near the wear wall was higher than the solid volume fraction near the front wall.In the dilute region,the offset-exit and the corner effect induced the defluxion of the particles movement and the core-annular distribution was broken.Time series analysis of the transient signals indicated that the two-phase structure in the bottom was unstable,and in the transition region the solids fluctuation was acute near the boundary between the core and annular section.