后缘下锉对离心式叶轮表观滑移系数的影响

O. Litfin, A. Delgado
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引用次数: 0

摘要

离心式叶轮的尾缘流动非常重要,因为它决定了出口流速三角形,从而决定了传递给流体的功。本文研究了后缘下锉对叶轮出口流动的影响以及由此产生的滑移系数。采用数值模拟的方法研究了不同的下尾缘形状。在大范围的叶片角度下进行了2D-RANS模拟。对于默认的切断尾缘配置,可以区分叶片尾缘周围的附流区和分离流区,这主要取决于叶片出口角度。分离流型的出现与性能的显著变化有关,这主要是由于叶轮出口流动偏转的减少。欠锉的后缘导致较少明显滑移的叶片角度高达40度。这可以归因于这样一个事实,即在默认后缘的情况下,下锉防止了附加流型的发生。额外的DES模拟提供了对这一现象所涉及的详细流动结构的更深入的了解,并揭示了尾缘和尾流中的湍流结构。所得结果提供了对离心泵叶轮尾缘流动的深入了解,并有助于更好地理解所涉及的现象。此外,该结果还可以解释通常观测到的叶轮表观滑移与滑移因子模型预测的理论滑移之间的偏差。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
On the Effect of Trailing Edge Under-Filing on the Apparent Slip Factor of Centrifugal Impellers
The trailing edge flow in a centrifugal impeller is of great importance as it determines the exit flow velocity triangle and therefore the work transferred to the fluid. The present study deals with the impact of trailing edge under-filing on the impeller exit flow and the resulting slip factor. Different under-filed trailing edge shapes are investigated by means of numerical simulations. 2D-RANS simulations are performed for a wide range of blade angles. For the default cut-off trailing edge configuration an attached and a separated flow regime around the blade trailing edge can be distinguished, mainly depending on the blade exit angle. The occurrence of the separated flow regime is associated with a significant change in performance, mainly due to the reduced flow deflection at the impeller exit. Under-filing of the trailing edge leads to less apparent slip for blade angles up to 40 degrees. This can be attributed to the fact that under-filing prevents the attached flow regime occurring in case of the default trailing edge. Additional DES simulations provide deeper insight into the detailed flow structures involved in this phenomena and reveal the turbulent flow structures in the trailing edge and wake flow. The obtained results provide a deep insight into trailing edge flows in centrifugal pump impellers and help to get a better understanding of the phenomena involved. Moreover, the results can provide an explanation to the often observed deviation of the apparent impeller slip from the theoretical slip predicted by slip factor models.
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