High Free-Steam Turbulence Effects on Endwall Heat Transfer for a Gas Turbine Stator Vane

Radomsky, R. W.; Thole, Karen A.

doi:10.1115/1.1312807

Cited by 57 publications

(16 citation statements)

References 20 publications

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“…It has been well-recognized that the high inflow turbulence enhances the heat transfer on various locations of the turbine blade, such as blade surface [6,7], end wall [8,9], and trailing edge [10]. Up to 50% increase in blade leading edge heat transfer was reported by a high inflow turbulence by Mehendale et al [11].…”

Section: Introductionmentioning

confidence: 96%

Effects of Inlet Turbulence and End-Wall Boundary Layer on Aerothermal Performance of a Transonic Turbine Blade Tip

Zhang

Rawlinson

2014

Journal of Engineering for Gas Turbines and Power

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Most of the previous researches of inlet turbulence effects on blade tip have been carried out for low speed situations. Recent work has indicated that for a transonic turbine tip, turbulent diffusion tends to have a distinctively different impact on tip heat transfer than for its subsonic counterpart. It is hence of interest to examine how inlet turbulence flow conditioning would affect heat transfer characteristics for a transonic tip. The present work is aimed to identify and understand the effects of both inlet freestream turbulence and end wall boundary layer on a transonic turbine blade tip aerothermal performance. Spatially-resolved heat transfer data are obtained at aerodynamic conditions representative of a high-pressure turbine, using the transient infrared thermógraphy technique with the Oxford High-Speed Linear Cascade research facility. With and without turbulence grids, the turbulence levels achieved are 7%-9% and 1%, respectively. On the blade tip surface, no apparent change in heat transfer was observed with high and low inlet turbulence intensity levels investigated. On the blade suction suiface, however, substantially different local heat transfer distributions for the suction side near tip surface have been observed, indicating a strong local dependence of the local vortical flow structure on the freestream turbulence. These experimentally observed trends have also been confirmed by CFD examinations using the Rolls-Royce HYDRA. A further CFD analysis suggests that the level of inflow turbulence alters the balance between the passage vortex associated secondaiy flow and the over tip leakage (OTL) flow. Consequently, an enhanced inertia of near wall fluid at a higher inflow turbulence weakens the cross-passage flow. As such, the weaker passage vortex leads the tip leakage vortex to move further into the mid passage, with the less spanwise coverage on the suction surface, as consistently indicated by the heat transfer signature. Different inlet end wall boundary layer profiles are employed in the computational study with HYDRA. All CFD results indicate the inlet boundary layer thickness has little impact on the heat transfer over the tip surface as well as the pressure side near-tip suiface. However, noticeable changes in heat transfer are obsei-vedfor the suction side near-tip surface. Similar to the inlet turbulence effect, such changes can be attributed to the interaction between the passage vortex and the OTL flow.

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Section: Introductionmentioning

confidence: 96%

Effects of Inlet Turbulence and End-Wall Boundary Layer on Aerothermal Performance of a Transonic Turbine Blade Tip

Zhang

Rawlinson

2014

Journal of Engineering for Gas Turbines and Power

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“…Therefore, particularly in low aspect ratio blading, common isotropic turbulence models validated in simple geometry may not be suitable. Several investigations were performed on turbine blading focusing on the effect of turbulence intensity on the heat transfer [1,2], secondary flows development and transition [3][4][5][6]. Ristic et al [7] and Xiao and Lakshminarayana [8] performed detailed measurements using LDA inside a turbine rotor where a high level of anisotropy has been reported in the wake and secondary flow region.…”

mentioning

confidence: 98%

Turbulence Measurements and Analysis in a Multistage Axial Turbine

Porreca

Hollenstein

Kalfas

et al. 2007

Journal of Propulsion and Power

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This paper presents turbulence measurements and detailed flow analysis in an axial turbine stage. Fast response aerodynamic probes were used to resolve aperiodic fluctuations along the three directions. Assuming incompressible flow, the effective turbulence level and Reynolds stress are retrieved by evaluating the stochastic velocity component out of the measured time-resolved pressure and flow angle fluctuations along the streamwise, radial, and circumferential direction. A comparison between turbulence intensity and measured total pressure shows that flow structures with higher turbulence level are identified in the region of loss cores at the exit of the second stator passage. Turbulence intensity is evaluated under isotropic and nonisotropic assumption in order to quantify the departure from isotropic conditions. The measurements show that locally the streamwise fluctuating component can be twice bigger than the radial and tangential component. The current analysis shows that multisensor fast response aerodynamic probes can be used to provide information about the mean turbulence levels in the flow and the Reynolds stress tensor, in addition to the measurements of unsteady total pressure loss. Nomenclature c = absolute velocity vector e = mean unit vector in the secondary flow definition p = static pressure p d = dynamic head s, , r = streamwise, circumferential, and radial directions T=T 0 = blade passing period fraction t = time u = streamwise velocity component u,ṽ,w = periodic velocity component: phase-lock averaged u 0 , v 0 , w 0 = stochastic (aperiodic) velocity components v = circumferential velocity component w = radial velocity component = yaw angle = pitch angle x = absolute uncertainty of quantity x = density Subscripts/superscripts 1 = probe position 1 iso = isotropic assumption NS = nonsimultaneous sec = secondary flow vector

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“…Also, that the effects of turbulence are localized to the endwall near the leading edge of the vane. In another study Radmonski and Thole[24] performed endwall heat transfer tests based on Stanton number…”

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confidence: 99%

Experimental Heat Transfer Distributions Over an Aft Loaded Vane With a Large Leading Edge at Very High Turbulence Levels

Varty

Ames

2016

Volume 8: Heat Transfer and Thermal Engineering

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Vane heat transfer distributions have been acquired on an aft loaded vane with a large leading edge over a range of turbulence conditions and across a range of Reynolds numbers. The large leading edge was designed to reduce heat transfer levels around the vane stagnation region and provide an opportunity to internally cool the region using a double wall cooling method. Heat transfer measurements were acquired in a linear cascade using a constant heat flux technique. The cascade was designed in a four vane, three full passage configuration with inlet bleeds flows and exit tailboards shaped along streamlines. Heat transfer measurements were acquired at exit chord Reynolds numbers of 500,000, 1,000,000, and 2,000,000 over seven turbulence conditions. The turbulence conditions included a low turbulence condition (Tu ≈ 0.7%), a small grid (M = 3.175 cm) at far and near locations (Tu ≈ 3.5% & 7.9%), a larger grid (Tu ≈ 8.0%), an aero-combustor closely coupled to the cascade and with a decay spool in between (Tu ≈ 13.5% and 9.3%) as well as with a new very high turbulence generator (Tu ≈ 17.4%). Heat transfer levels in the stagnation region are correlated in terms of approach flow Reynolds number and turbulence conditions and compared with recent large cylindrical leading edge test surface data using the TRL parameter. The surface heat transfer measurements are presented at different Reynolds numbers in terms of Stanton number based on exit conditions. These comparisons provide useful information on the level of turbulence augmentation in laminar regions of the flow as well as the onset location and length of transition. Midspan surface static pressure distributions were acquired at all the conditions and were used as a basis to determine experimental isentropic Mach number distributions. These data are reported in part but were also used to help generate the free-stream boundary condition for a boundary layer calculation. Predictive comparisons generated from boundary layer calculations (STAN7) using an algebraic turbulence model (ATM) and a well-known transition model (Mayle) are provided. At low turbulence levels the close comparisons provide confidence in the experimental technique. At higher turbulence levels the comparisons may provide a better indication of the physics of response of vane heat transfer to the external turbulence. These data are expected to help clarify the physics of vane heat transfer at very high turbulence levels.

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High Free-Steam Turbulence Effects on Endwall Heat Transfer for a Gas Turbine Stator Vane

Cited by 57 publications

References 20 publications

Effects of Inlet Turbulence and End-Wall Boundary Layer on Aerothermal Performance of a Transonic Turbine Blade Tip

Effects of Inlet Turbulence and End-Wall Boundary Layer on Aerothermal Performance of a Transonic Turbine Blade Tip

Turbulence Measurements and Analysis in a Multistage Axial Turbine

Experimental Heat Transfer Distributions Over an Aft Loaded Vane With a Large Leading Edge at Very High Turbulence Levels

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