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An experimental investigation on the effects of freestream turbulence intensity on film cooling effectiveness and heat transfer coefficient for an anti-vortex hole.

机译：自由流湍流强度对反涡流孔膜冷却效率和传热系数影响的实验研究。

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摘要

Film cooling is used to thermally protect combustor and turbine components by creating a layer of relatively cooler air than the freestream air to insulate the components from the hot freestream gases. This relatively cooler air is taken from upstream in the high-pressure compressor section at a loss to the engine efficiency, and therefore must be used as effectively as possible. The efficiency gained from increasing the turbine inlet temperature outweighs the loss due to extracting air from the compressor section if the cooling air is used effectively. A novel anti-vortex hole (AVH) geometry has been investigated experimentally through a transient infrared thermography technique to study the film cooling effectiveness and surface convective heat transfer coefficients for varying blowing ratio and freestream turbulence intensity. A major concern with the AVH will be how the secondary jets counteract the main counter rotating vortex (CRV) pair at increased freestream turbulence levels. This is the first experimental facility to study the effects of higher freestream turbulence levels on an AVH geometry. Furthermore, this is the first experimental investigation to report centerline film cooling effectiveness and the convective heat transfer coefficient that had not been reported in prior studies. The AVH geometry is designed with two secondary holes stemming from a main cooling hole; these holes attempt to diffuse the coolant jet and mitigate the vorticity produced by conventional straight holes. This geometry shows improved results at low turbulence intensities compared to conventional straight holes. Three freestream turbulence intensities of 1, 7.5, and 11.7% were investigated at blowing ratios of 0.5, 1.0, 1.5, and 2.0 to form a test matrix of twelve different test conditions. Results showed that the higher freestream turbulence conditions were beneficial in the performance of the AVH. Increasing the blowing ratio at all turbulence levels also improved film cooling effectiveness both span-averaged and on the centerline. The highest performing case was at a turbulence intensity of 7.5% and a blowing ratio of 2.0. The 11.7% cases outperformed the 1% cases, but it appears that at 11.7% cases that the higher freestream turbulence reduces the performance of the secondary holes compared to the 7.5% cases. Increasing the blowing ratio and turbulence intensity will result in a higher heat transfer coefficient, and thus must be taken into account for future designs.
机译：薄膜冷却用于通过产生一层比自由流空气相对凉爽的空气来热保护燃烧室和涡轮机部件，以使部件与热的自由流气体隔离。这种相对较冷的空气是从高压压缩机段的上游吸入的，这会降低发动机的效率，因此必须尽可能有效地利用。如果有效利用冷却空气，提高涡轮机入口温度所获得的效率将超过因从压缩机部分抽取空气而造成的损失。通过瞬态红外热成像技术，实验研究了一种新型的抗涡孔（AVH）几何形状，以研究膜的冷却效率和表面对流换热系数，以改变吹塑比和自由流湍流强度。 AVH的一个主要问题是次级射流如何在增加的自由流湍流水平下抵消主反向旋转涡流（CRV）对。这是研究高自由流湍流水平对AVH几何形状影响的第一个实验设施。此外，这是第一个报告中心线薄膜冷却效果和对流传热系数的实验研究，而先前的研究尚未对此进行报道。 AVH几何设计有两个从主冷却孔引出的辅助孔。这些孔试图扩散冷却剂射流并减轻常规直孔产生的涡旋。与传统的直孔相比，这种几何形状在低湍流强度下显示出改进的结果。在吹塑比为0.5、1.0、1.5和2.0的情况下，研究了三种自由流湍流强度分别为1、7.5和11.7％，以形成十二种不同测试条件的测试矩阵。结果表明，较高的自由流湍流条件有利于AVH的性能。在所有湍流水平下提高吹塑比也可以改善跨距平均和中心线的薄膜冷却效率。性能最高的情况是湍流强度为7.5％，吹风比为2.0。 11.7％的情况优于1％的情况，但似乎在11.7％的情况下，与7.5％的情况相比，较高的自由流湍流会降低次级孔的性能。增加吹风比和湍流强度将导致更高的传热系数，因此在将来的设计中必须考虑到这一点。

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  • 作者

    Hayes, Stephen Andrew.;

  • 作者单位

    West Virginia University.;

  • 授予单位 West Virginia University.;
  • 学科 Mechanical engineering.;Aerospace engineering.
  • 学位 M.S.
  • 年度 2014
  • 页码 124 p.
  • 总页数 124
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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