Abstract
The time-dependent unsteady flow at midspan of an axial-flow turbine rotor was investigated experimentally using a laser Doppler velocimetry (LDV) system, focusing on the influence of free-stream turbulence intensity at very low Reynolds number (Re_<out, RT>=3.6×(10)^4). The free-stream turbulence intensity at nozzle inlet was elevated from 0.5% to 9.4% by setting a turbulence-generating sheet. The time-averaged and time-dependent flows were analyzed and the effects of nozzle wake on the flow field inside the rotor were determined qualitatively and quantitatively. The flow separation occurred at the rotor suction surface even under the high turbulence intensity condition because of the low Reynolds number flow. However, the decrease in flow fluctuation was observed at the higher turbulence intensity. The turbulence in the wake region was anisotropy and it exhibited strong Reynolds stress at both the low and high free-stream turbulence intensities.
