Effects of High Freestream Turbulence Levels and Length Scales on Stator Vane Heat Transfer

Abstract

Gaining a good understanding of how high freestream turbulence augments heat transfer is important for predicting thermal loadings for turbine blades and vanes. This study was aimed at documenting the surface heat transfer and the highly turbulent flowfield around a stator vane. The effects of turbulence levels between 11% and 24% were studied. At the highest turbulence level, two different Reynolds numbers (Reex = 6 × 105 and 1.2 × 106) and two different length scales were also studied. Three-component laser Doppler velocimeter measurements of the velocity fluctuations indicated that downstream of the active grid there was an initial decay of the turbulent kinetic energy which then leveled off at about one leading edge radius upstream of the vane. Inside the vane passage the turbulent kinetic energy increased slightly and then decayed through the passage. The surface heat transfer showed the largest augmentations on the pressure side of the vane with higher augmentations at higher turbulence levels, smaller length scales, and higher Reynolds numbers.

Effects of High Intensity, Large-Scale Freestream Combustor Turbulence on Heat Transfer in Transonic Turbine Blades

“…However, as pointed out earlier, the approaching turbulence intensity and scale are much higher in this work. The low speed turbine vane turbulence data from Radomsky and Thole (1998) also demonstrated that the turbulence levels on the pressure surface were higher than those measured on the suction surface.…”

“…The effect of freestream turbulence intensity and length scale on turbine vane heat transfer in a low speed facility was studied in detail by Radomsky and Thole (1998) …”

“…Turbulence was generated in the facility using a passive turbulence grid placed (2002) and Radomsky and Thole (1998). Van Fossen and Bunker (2002) used a 60° section of a GE 90 dual-annular combustor in a wind tunnel to model the exit flow of a combustor, including inlet swirl vanes, film cooling holes and dilution holes.…”

“…Radomsky and Thole (1998 documented surface heat transfer and the turbulent flowfield around a scaled up stator vane. Several different turbulence levels as high as 25% were generated.…”

“…Observations of heat transfer augmentation were consistent with results reported by Ames (1995), with heat transfer augmentation being greatest on the pressure surface and in the stagnation region and suction surface transition shifting toward the leading edge at elevated freestream turbulence levels. In Radomsky and Thole (1998), detailed measurements of unsteady velocity upstream of the vane passage and along a streamline in the center of the vane passage were used to document the levels of turbulence kinetic energy and all three unsteady components of velocity through the vane passage. The turbulent kinetic energy was shown to increase through most of the blade passage.…”