ABSTRACT

Flow distortions from upstream combustors generate various and significant changes to the patterns of endwall heat transfer for an aircraft engine. In this study, to model engine-representative oncoming flows into the high-pressure turbine, turbulence and swirl generators are carefully designed at the inlet of a linear turbine cascade. Detailed heat transfer characteristics over the endwall are measured by using a steady thermochromic liquid crystal (TLC) method for various Reynolds numbers. Comparisons with a baseline case that has no upstream turbulence or swirl generators show that both turbulence and inlet swirl alter the heat transfer levels and distribution patterns, but their mechanism of action differs from one another. The turbulence alters the heat transfer by thinning the inlet boundary layer, while the inlet swirl generates the changed heat transfer due to the sweep effects of the swirl on the endwall, resulting in a much higher heat transfer enhancement than that by the turbulence. Additionally, the highest enhancement for both cases is found at the low Reynolds number of 1.0 × 10⁵ and higher Reynolds numbers yield to a reduced enhancement. Specially, compared to the turbulence case, the enhancement by the inlet swirl drops much more rapidly, indicating that the inlet swirl effects have stronger links to the Reynolds number.

摘要

来自上游燃烧器的流动变形会对飞机发动机的端壁传热模式产生各种显着的变化。在这项研究中，为了模拟进入高压涡轮的具有发动机代表性的迎面流，在线性涡轮叶栅的入口处精心设计了湍流和涡流发生器。通过使用稳定的热致变色液晶 (TLC) 方法测量各种雷诺数的端壁上的详细传热特性。与没有上游湍流或涡流发生器的基线情况进行比较表明，湍流和入口涡流都改变了传热水平和分布模式，但它们的作用机制彼此不同。湍流通过变薄入口边界层来改变热传递，而入口涡流由于涡流对端壁的扫掠效应产生了改变的传热，导致比湍流的传热增强更高。此外，在 1.0 × 10 的低雷诺数下，发现这两种情况的最高增强⁵和更高的雷诺数产生降低的增强。特别地，与湍流情况相比，入口涡流的增强下降得更快，表明入口涡流效应与雷诺数有更强的联系。