共轴反转型生物反应器内流场数值模拟与性能分析

使用生物可降解塑料是解决白色污染的有效手段,然而在生物反应器中生产可降解塑料过程中会面临气体传质能力不足和能耗过大等问题,导致生产成本居高不下。为解决这些问题,提出了一种共轴反转型机械搅拌式生物反应器,并通过数值模拟对新型反应器内两相流场进行了仿真及定量分析。通过模拟气泡羽流、鼓泡塔及搅拌器系统内流场,并与实验结果对比,在双流体模型中引入了曳力、升力及湍流扩散力以及基于TroshkoHassan模型的两相湍流模型,验证了双流体模型在该问题中的有效性。对新设计的反应器内流场模拟结果表明,两相作用力模型对模拟准确性影响较大,而共轴反转能够在流场中形成更好的剪切效应,增强气体分散能力,从而提高整体气含率及相对功率准数。

Numerical simulation and performance analysis of flow field in coaxial contra-rotating bioreactor

The use of biodegradable plastics is an effective means of solving white pollution. However, the production of degradable plastics in bioreactors will face problems such as insufficient gas mass transfer capacity and excessive energy consumption, resulting in high production costs. To solve these problems, a new design of bioreactor with coaxial contra-rotating propellers is proposed as well as according flow analysis based on numerical simulation. To verify our numerical models, three different benchmarks including bubble plume, bubble column and stirred tank are performed. Drag force, lift force and turbulent dispersion force are included in our two-phase model. Standard k-\epsilon method is modified via Troshko-Hassan model to consider bubble induced turbulence. Additionally, sliding grid method is employed to simulated rotating turbine. The results show that phase interactions in two-fluid method have a significant influence on accuracy of simulation. Our final result agrees well with experiments and previous literature. As for new bioreactor, it is shown that shear force is enhanced between two turbines. Gas hold-up, dispersion capabilities and RPD(relative power demand) are improved in new bioreactor compared with traditional design.