A Preliminary Numerical Study on the Effect of High Freestream Turbulence on Anti-Vortex Film Cooling Design at High Blowing Ratio

Abstract

Researchers at NASA Glenn Research Center have developed and investigated a novel film cooling design, the anti-vortex hole (AVH), which has been shown to cancel or counter the vorticity generated by conventional holes and increase film effectiveness at high blowing ratios and low turbulence levels. This paper presents preliminary CFD results on the film effectiveness and net heat flux reduction at high blowing ratio and elevated freestream turbulence levels for the adjacent AVH. Baseline cases at low turbulence levels of 5% intensity and length scale of Λx/dm = 1 with a nominal blowing ratio of 2 and a density ratios of 1 and 2 were compared to previous results reported by Heidmann [1]. Higher freestream turbulence cases were investigated with a turbulence intensity and length scale of 10% and Λx/dm = 1 and 3, respectively. Results showed that higher freestream turbulence improves adiabatic effectiveness for the AVH design.

Flow Visualization of Multi-Hole Film-Cooling Flow under Varying Freestream Turbulence Levels

“…Figure 6 is shown to illustrate the typical coverage of a straight 30˚ inclination film cooling hole flow at high blowing ratio under varying turbulence conditions [9]. The hole diameter and Reynolds number and the plenum condition from this past study are consistent with the current work.…”

“…The control volume used was identical to the ones used in previous work [5]- [9], for the ease of direct comparison of the results. This control volume is determined such that the region of influence of a single hole is successfully encompassed.…”

“…A turbulence intensity of 1% and a length scale normalized by main cooling hole diameter of 1.0 was specified for the plenum. A Reynolds number based on the main film cooling hole diameter and mainstream flow conditions of 11,300 was matched to previous work [5] [8] [9].…”

基于des的叶片前缘气膜冷却的数值模拟

“…为了抑制肾形涡对, Hunley 等人 [17] 通过在主 冷却孔通道两侧加入两个倾斜一定角度的抑制涡较 小尺度冷却通道, 其初步 CFD 研究结果表明该方法 可提高冷却效率. 而 Kang [18] 提出了弯曲冷却孔几何 抑制肾形涡对的想法. 如图 1 所示, 弯曲冷却孔内产 生的通道涡对(PVP, Passage Vortex Pair)在离开冷却 孔后与肾形涡对旋向相反, 能够减小肾形涡对的尺 度和并削弱其强度, 从而促使冷却气流贴附在叶片 表面, 提高冷却效率.…”

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

“…The primary concern with the geometry is the influence elevated freestream turbulence intensity will have on the secondary holes effectiveness of mitigating the counter rotating vortex (CRV) pair of the main coolant hole. The AVH design used in this study had previously been investigated by Dhungel et al [13], Heidmann et al [11,12], Hunley et al [53], and Repko et al [36,37] and showed that there was a considerable improvement of film cooling effectiveness over the straight hole geometry. Hunley et al [53] and Repko et al [36,37] studied the effect of turbulence intensities of 5, 10, and 20% for a blowing ratio of 2.0 and found that elevated levels of freestream turbulence predicted improvements in the spanaveraged film cooling effectiveness.…”