- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Combined effects of unsteady wake and free-stream turbulence on turbine blade film cooling with laid-back fan-shaped holes using PSP technique
摘要： Detailed film cooling effectiveness distribution for a gas turbine blade under the effects of unsteady wakes and oncoming free-stream turbulence intensities was obtained using pressure sensitive paint (PSP) technique. Tests were performed on a linear cascade at Reynolds number of 3.85 × 10^5 based on the blade chord at cascade exit. Upstream unsteady wakes were simulated using a spoke-wheel type wake generator. The test blade has three rows of compound angled cylindrical film holes at the leading edge, five rows of laid-back fan-shaped holes on the pressure surface and three rows of laid-back fan-shaped holes on the suction surface. The wake Strouhal number was varied from 0 to 0.36 and three mass flux ratios were determined. The oncoming free-stream turbulence intensities are 2.7% and 26.9%, respectively. Results show that the effect of the mass flux ratio on the film cooling effectiveness decreases under the high turbulence intensity and unsteady wake conditions. In most regions of the blade surface, the film cooling effectiveness decreases with the increase of wake Strouhal number, and the free-stream turbulence superimposed on the unsteady wake reduces the film cooling effectiveness further. The effect of the unsteady wake decreases under the high free-stream turbulence conditions.
关键词： Turbulence intensity,Film cooling effectiveness,PSP,Wake,Mass flux ratio,Turbine blade,Strouhal number,Laid-back fan-shaped hole
更新于2025-09-23 15:23:52
-
Lidar arc scan uncertainty reduction through scanning geometry optimization
摘要： Doppler lidars are frequently operated in a mode referred to as arc scans, wherein the lidar beam scans across a sector with a ?xed elevation angle and the resulting measurements are used to derive an estimate of the n minute horizontal mean wind velocity (speed and direction). Previous studies have shown that the uncertainty in the measured wind speed originates from turbulent wind ?uctuations and depends on the scan geometry (the arc span and the arc orientation). This paper is designed to provide guidance on optimal scan geometries for two key applications in the wind energy industry: wind turbine power performance analysis and annual energy production prediction. We present a quantitative analysis of the retrieved wind speed uncertainty derived using a theoretical model with the assumption of isotropic and frozen turbulence, and observations from three sites that are onshore with ?at terrain, onshore with complex terrain and offshore, respectively. The results from both the theoretical model and observations show that the uncertainty is scaled with the turbulence intensity such that the relative standard error on the 10 min mean wind speed is about 30 % of the turbulence intensity. The uncertainty in both retrieved wind speeds and derived wind energy production estimates can be reduced by aligning lidar beams with the dominant wind direction, increasing the arc span and lowering the number of beams per arc scan. Large arc spans should be used at sites with high turbulence intensity and/or large wind direction variation.
关键词： arc scans,wind energy,Doppler lidar,scan geometry optimization,turbulence intensity
更新于2025-09-04 15:30:14