厌氧发酵液中平行气泡间相互作用的数值模拟

Numerical simulation of parallel bubbles interaction in anaerobic fermentation slurry

在Fluent软件中采用SIMPLE算法,对具有剪切变稀性的厌氧发酵液中平行双气泡间的相互作用进行了数值模拟。探讨了气泡间距、尺寸、流变性质对气泡间相互作用的影响。结果发现:当两气泡间距较大时,气泡相互排斥,直到互相不影响;当两气泡间距较小时,气泡间液相的惯性力起作用,气泡互相吸引、接触进而聚并。临界聚并的距离随着两气泡的体积增大而减小。发酵液的剪切变稀性越高,两气泡之间稳定上升过程中气泡最终达到稳定时速度越低,相互作用的临界距离越小。研究结果可以为生物质及市政垃圾厌氧发酵过程的优化设计提供理论依据。

The commercial CFD software ANSYS FLUENT 16.0 and SIMPLE method were used to simulate of parallel bubbles interaction in anaerobic fermentation slurry which has complex rheological property. The effects of bubbles distance, bubble diameter and shear thinning property on parallel bubbles interaction was discussed. The simulation result shows that, when the bubbles distance is larger than critical distance, the two bubbles are mutually exclusive; when the two bubbles distance smaller than critical distance, the two bubbles are mutually attract, and then coalescence. The critical distance of coalescence is decreased with the increase of bubble diameter. The higher the shear thinning property of anaerobic fermentation slurry, the lower viscosity of liquid around bubble, and the lower the velocity as the bubble reach to the steady motion, which result in the smaller critical distance of bubble coalescence. Therefore, the simulation of parallel bubbles interaction in anaerobic fermentation slurry is an essential prerequisite and could provide useful information for biomass and civil sludge anaerobic fermentation process design and optimization.