Stratified and Buoyancy-Induced Flow in Closed Compressor Rotors
Stratified and Buoyancy-Induced Flow in Closed Compressor Rotors
复制标题
封闭式压缩机转子中的分层流和浮力诱导流
DOI：
10.1115/1.4055448
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Lock G
中科院分区：
文献类型：
--
作者：
Lock G
压气机盘径向生长受同向旋转盘内导热和盘间旋转流核内浮力驱动对流的共轭换热的强烈影响。准确预测这些阀瓣的金属温度是热机械设计中的一个重要问题，在热机械设计中，必须仔细控制叶尖间隙，以确保在所有操作条件下的安全和效率。本文对封闭旋转空腔内的流体力学和换热进行了实验研究，并将结果与理论模型进行了比较，并引入了一个新的压缩参数χ。当χ值较大时，当可压缩性影响很大时，空气温度接近裹尸布的温度；这样的条件抑制了浮力效应，旋转空腔中的流动变得分层，流体核心内的对流被传导所取代。分层对压气机盘片内部的温度分布和应力有很大的影响，具有重要的实际意义。文中还给出了χ对圆盘径向温度分布和护罩换热关联式的影响，并与以前发表的可压缩性影响较小的数据进行了定性比较。实验表明，χ存在一个临界值，在该临界值处，对流热通量为零。圆盘温度的径向分布与圆柱体的纯导热情况一致。提出了一种新的基于实测热流密度和理论核心温度的换热关联式。还研究了空腔内的非定常流动特性，确定了实验条件范围内的相干旋转结构。这些气旋/反气旋涡旋对产生无因次周向压差，这是通过旋转核心径向流出(冷流体)和流入(热流体)所必需的。实验表明，这些压力变化的大小可以与χ数相关联，当GR值较高时，这种结构是不存在的。实验和理论相结合的结果将对发动机设计者和计算模型的验证具有实际意义。
The radial growth of compressor discs is strongly influenced by conjugate heat transfer between conduction in the co-rotating discs and buoyancy-driven convection in the rotating fluid core between the discs. An accurate prediction of metal temperatures of these discs is an important issue in thermo-mechanical design, where blade-tip clearances must be controlled carefully to ensure safety and efficiency under all operating conditions. This paper presents an experimental study of the fluid dynamics and heat transfer in a closed rotating cavity, comparing results with theoretical models and introducing a new compressibility parameter χ. At large values of χ, where compressibility effects are significant, the air temperature approaches that of the shroud; such conditions suppress buoyancy effects and the flow in the rotating cavity becomes stratified, with convection replaced by conduction inside the fluid core. There are important practical consequences of stratification with significant differences in temperature distributions and stresses inside compressor discs. The influence of χ is also shown on the radial temperature distributions for the discs and on the shroud heat transfer correlations, which are compared qualitatively with previously published data collected where the effects of compressibility are relatively small. The experiments reveal that there is a critical value of χ where the convective heat flux to the shroud is zero. The radial distribution of disc temperature was that expected from pure conduction in a cylinder. A new heat transfer correlation based on measured shroud heat flux and the theoretical core temperature is presented. The unsteady flow characteristics in the cavity were also investigated, identifying coherent rotating structures across a range of experimental conditions. These cyclonic/anti-cyclonic vortex pairs generate the nondimensional circumferential pressure difference necessary for the radial outflow (of cold fluid) and inflow (of hot fluid) through the rotating core. The experiments show that the magnitude of these pressure variations can be correlated against Grashof number and at high values of χ the structures do not exist. The combined experimental and theoretical results will be of practical interest to engine designers and for the validation of computational models.