摘要
对于地下电站高大厂房气流组织的研究目前有三种方法:射流公式法、CFD方法、模型实验法。CFD方法以其易于适用复杂几何形状,不依赖经验参数,易实现多工况模拟等诸多优点而倍受青睐,因此,本文采用CFD方法对某一实际工程进行了气流组织研究。
1.湍流模型的选取 模拟结果的正确性十分依赖于所选择模型是否能准确地描述现象。在水电站工程实际应用中以往多采用的是标准的k-ε两方程模型,而本文采用了在标准k-ε模型基础上变形的重整化群k-ε模型(RNG-k-ε模型)。RNG模型相比于标准k-ε模型对瞬变流和流线弯曲的影响能作出更好的反应。本文选择此模型对含强热源的电站厂房高大空间速度、温度场进行了模拟,取得了合理的结果。
2.问题简化及网格划分 在数值模拟中合理的简化物理模型既能反应问题物理本质又能使模拟得以顺利实现。由于本电站厂房空间高大,尺寸为53m×15.4m×15.5m,粗略划分网格数超过百万,现有计算机资源很难满足计算要求。本文采用计算区域的简化处理,根据射流对称特点,将整个计算区域简化为原来的1/3,计算网格数大大减少,计算时间亦大大缩短,有效地解决计算机资源不足的问题。
3.不同送风方式的数值模拟 本文运用FLUENT软件对地下水电站高大厂房三维温度场和速度场的模拟,通过研究比较,认为分层空调方式比中送上回送风方式空调效果好,在大空间应采用分层空调,而下送上回送风方式温度效率较大,可实现较大温差送风,是一种值得考虑的气流组织方式。
本文通过运用CFD软件,实现了地下电站高大厂房几种送回风方式的数值模拟,可为此类高大空间建筑气流组织的优化研究提供参考。
Currently, there are three methods for predicting air distribution in underground hydropower station. They are jet formula method, CFD method and model experiment method Considering the great many merits of CFD method such as easily applying to complex geometric, independent of experiential parameters and easily simulate for many conditions and so on, this thesis use CFD method to study of the air distribution of certain pratical project.
Choosing the turbulence model The correctness of the simulation are strongly dependent on the turbulent model you choose. More often, the standard k- ε turbulent model is used. But there are some disadvantages of it. In this article , the KNG- k-
ε turbulent model is used which can make good result on transient flow and bend flow. A satisfying result is made though using this model.
Simplify the problem and divide the mesh In numerical simulation, proper simplification of the physical problem can make the simulation simple. The object studying in this article is too large. The dimension is 53mX 15.4nX 15. 5m and the total mesh number is over one million which cannot be calculated by current personal computer. According the symmetry principle, minimize the model one third the size of the former model. The mesh number is greatly decreased which successfully solve the
problem of lacking of computer resource.
Simulation for different types of air distributions The 3-D distributions of airflow and tenperature fields in large space are numerically calculated using the software of FLUENT. Through comparing the result of simulation, thinks that the delaminated air conditioning is better than the one of middle supply-up return air distribution. The air supply of low sidewall has large temperature efficiency and can supply the air with low temperature, as is a considerable type of air distribution.
This thesis uses the CFD soft ware-FLUENT, realizes the simulation of air
distribution. The simulation offers guidance to the optional design of the air distribution of this type of problem.
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