High Freestream Turbulence Simulation in a Scaled-Up Turbine Vane Passage

Abstract

Quantifying high freestream turbulence effects on surface heat transfer and on blade boundary layer development is important for improving predictions of the thermal loading and aerodynamic losses for gas turbine blades, vanes, and endwalls. To improve our physical understanding as well as improve CFD capabilities, detailed flow and thermal field data is needed in addition to surface data. This paper discusses the development of a turbulence generator that is capable of generating turbulence intensities as high as 20% and yet allow an independent control on the turbulent length scale. The integral length scale at a turbulence intensity of TI = 20% ranged from 2.1 cm to 5.5 cm. The development of the turbulence generator took place in a wind tunnel having a large, constant area, test section. After this development, the turbulence generator was placed upstream of a scaled-up turbine vane. This paper also describes the development of the turbine vane test section that has a central first stage stator vane that was scaled up by a factor of nine. Finally, turbulence measurements, turbulent length scales, and energy spectra measured inside the turbine vane passage are presented and compared to measurements that were made in the constant area test section. The results indicate that in the first 40% of the stator vane passage, the turbulence levels rapidly decrease by a factor of four with the integral length scales having a rapid growth.