热水循环加热厌氧反应器的稳态数值模拟分析

Research Progress of Computational Model for Rotating Turbulent Flow in Fluid Machinery

对于厌氧发酵系统,温度分布是否均匀是影响产气效率的关键因素。本研究通过在10L厌氧反应器中分别对水和TS为12.4%（质量分数）的发酵料液进行加热的热平衡试验,运用Fluent软件对厌氧污泥传热特性进行仿真模拟,通过传感器监测温度变化,得出水的温度分布与高TS料液有很大差异,而且在没有搅拌装置的情况下进行高TS料液的传热仿真,不能将其物性参数默认为水。在对水进行传热仿真时发现,对于低TS料液进行仿真要考虑料液间的对流换热,因此需调用Boussinesq假设,调用该假设后,模拟与试验最大误差仅为4.2%。对换热管壁面厚度设置作出分析并得出：在Fluent中设置虚拟壁面与在Gambit中直接绘制壁面模型两种方法具有相同效果,而前者可以简化模型并减少计算时间。此外,在进行高TS仿真时发现最适合这种热水循环加热系统的湍流模型为可实现k-ε模型（Realizable k-ε）。

Rotating turbulent flows are widely existed in pumps, turbines, compressors and other fluid machinery. The three-dimensional stochastic fluctuations are very strong in this kind of flow. The high adverse pressure gradient, large streamline curvature and complex wall surface in rotating turbulent flow have significant effects on the performance of fluid machinery. Although a lot of turbulence models have been developed, there is no universal turbulence model that could be used to simulate rotating turbulent flow in fluid machinery. Each turbulence model has its own applicable scope. The prediction performance of the existing turbulence models either in physical or numerical aspects has not yet met the actual need of fluid machinery. Aiming at strong rotating and large curvature turbulent flow, the turbulence models were reviewed. From three aspects of the high Reynolds number flow in turbulent core area, the low Reynolds number flow near wall and the transition flow from laminar to turbulent areas, the applicability of existing turbulence models for fluid machinery was analyzed. The problems of two series turbulence models, including Reynolds-averaged Navier-Stokes models and scale-resolving simulation models used in solving rotating turbulent flow were compared. The typical Reynolds-averaged Navier-Stokes models introduced included Spalart-Allmaras, k-ε, k-ω, V2F and RSM models. The typical scale-resolving simulation models included LES, SAS, DES and ELES models. The effective methods to use the suitable turbulence model for different problems and different targets were investigated. The development trend of turbulence model and the application of turbulence model in fluid machinery were discussed.