推流器布置对氧化沟流场特性的影响

Effects of propeller layout position on flow characteristics in oxidation ditch

针对环形跑道式氧化沟污泥沉积现象,在池形结构不变的前提下,改变推流器的布置位置,以STARCCM+软件为仿真平台,采用多面体网格划分方式,调用标准k-ε湍流模型,对4台推流器同时开启状态下进行全流场模拟.分析流道各断面的速度分布、整体流场的流速分布以及流场死区率(速度低于某一值所占区域的比例),寻找适合于该池型结构的推流器最优布置方式.结果表明:推流器的安装位置对流速的分布至关重要,其与中间导流墙的间距偏大或偏小都会导致流场速度分布不均匀,死区率较高,而当其间距为环形导流墙半径与偏置距离之和的0.85倍时,整体的流速分布最为均匀,主要断面的平均流速较高,且均在0.35 m/s以上,死区率最低;在环形导流墙背后以及中间导流墙的两端不可避免地会出现脱流区域,但可以通过改变推流器位置进行改善;在氧化沟的弯道处受推流以及壁面阻碍作用有明显的涡旋现象.

To avoid sludge deposition in a running track type oxidation ditch, the layout position of four propellers was altered when the pool structure remained unchanged. The steady fluid flow field in the whole ditch is simulated by means of STARCCM ＋ software plus the standard k - e turbulence model when these propellers were in operation. The velocity distribution in each section in the ditch and the velocity distribution in the whole flow field as well as the dead water zone were analysed to specify the optimal propeller layout position for the pool. The results show that the propellers＇ position has a great influence on velocity distribution, and a too large or too small distance between a propeller and the middle baffle wall can lead to an uneven velocity distribution and an enlarged dead water zone. Especially, when the distance is about 0.85 times the sum of the circular baffle wall radius and the distance of the circular baffle wall centre to the middle baffle wall, the average fluid velocity is as high as 0.35 m/s in the major sections observed with the smallest dead water zone. Flow separation zones are inevitable at the back of the circular baffle wall and the two ends of middle baffle wall, but they can be diminished by changing propellers＇ position. In addition, there is an obvious vortex phenome-non in the corners of the ditch by virtue of the interaction between the propellers and the pitch walls.