An Experimental Study of Turbine Vane Heat Transfer With Leading Edge and Downstream Film Cooling

1990 ◽  
Vol 112 (3) ◽  
pp. 477-487 ◽  
Author(s):  
N. V. Nirmalan ◽  
L. D. Hylton
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Film Cooling ◽  
Pressure Ratio ◽  
Leading Edge ◽  
External Heat ◽  
Gas Temperature ◽  
Temperature Ratio ◽  
External Heat Transfer ◽  
Turbine Vane

This paper presents the effects of downstream film cooling, with and without leading edge showerhead film cooling, on turbine vane external heat transfer. Steady-state experimental measurements were made in a three-vane, linear, two-dimensional cascade. The principal independent parameters—Mach number, Reynolds number, turbulence, wall-to-gas temperature ratio, coolant-to-gas temperature ratio, and coolant-to-gas pressure ratio—were maintained over ranges consistent with actual engine conditions. The test matrix was structured to provide an assessment of the independent influence of parameters of interest, namely, exit Mach number, exit Reynolds number, coolant-to-gas temperature ratio, and coolant-to-gas pressure ratio. The vane external heat transfer data obtained in this program indicate that considerable cooling benefits can be achieved by utilizing downstream film cooling. The downstream film cooling process was shown to be a complex interaction of two competing mechanisms. The thermal dilution effect, associated with the injection of relatively cold fluid, results in a decrease in the heat transfer to the airfoil. Conversely, the turbulence augmentation, produced by the injection process, results in increased heat transfer to the airfoil. The data presented in this paper illustrate the interaction of these variables and should provide the airfoil designer and computational analyst with the information required to improve heat transfer design capabilities for film-cooled turbine airfoils.

An Experimental Study of Turbine Vane Heat Transfer With Leading Edge and Downstream Film Cooling

1989 ◽  
Author(s):  
V. Nirmalan ◽  
L. D. Hylton
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Film Cooling ◽  
Pressure Ratio ◽  
Leading Edge ◽  
External Heat ◽  
Gas Temperature ◽  
Temperature Ratio ◽  
External Heat Transfer ◽  
Turbine Vane

This paper presents the effects of downstream film cooling, with and without leading edge showerhead film cooling, on turbine vane external heat transfer. Steady state experimental measurements were made in a three-vane, linear, two-dimensional cascade. The principal independent parameters — Mach number, Reynolds number, turbulence, wall-to-gas temperature ratio, coolant-to-gas temperature ratio, and coolant-to-gas pressure ratio — were maintained over ranges consistent with actual engine conditions. The test matrix was structured to provide an assessment of the independent influence of parameters of interest, namely, exit Mach number, exit Reynolds number, coolant-to-gas temperature ratio, and coolant-to-gas pressure ratio. The vane external heat transfer data obtained in this program indicate that considerable cooling benefits can be achieved by utilizing downstream film cooling. The downstream film cooling process was shown to be a complex interaction of two competing mechanisms. The thermal dilution effect, associated with the injection of relatively cold fluid, results in a decrease in the heat transfer to the airfoil. Conversely, the turbulence augmentation, produced by the injection process, results in increased heat transfer to the airfoil. The data presented in this paper illustrate the interaction of these variables and should provide the airfoil designer and computational analyst the information required to improve heat transfer design capabilities for film cooled turbine airfoils.

scholarly journals Effect of Discrete Surface Disturbances on Vane External Heat Transfer

1997 ◽  
Author(s):  
R. S. Bunker
Keyword(s):  
Heat Transfer ◽  
Turbulence Intensity ◽  
Pressure Ratio ◽  
Leading Edge ◽  
Suction Side ◽  
External Heat ◽  
Freestream Turbulence ◽  
External Heat Transfer ◽  
Enhancement Factors ◽  
Surface Disturbances

A transonic linear vane cascade has been utilized to assess the effects of localized surface disturbances on airfoil external heat transfer coefficient distributions, such as those which may be created by the spallation of thermal barrier coatings. The cascade operates at an overall pressure ratio of 1.86, with an inlet total pressure of about 5 atm. Cascade Reynolds numbers based on axial chord length and exit velocity range from 2.2 to 4.8 · 106. Surface disturbances are modeled with the use of narrow trip strips glued onto the surface at selected locations, such that sharp forward facing steps are presented to the boundary layer. Surface locations investigated include the near leading edge region on either side of the stagnation point, the midchord region of the pressure side, and the high curvature region of the suction side. Heat transfer enhancement factors are obtained for disturbances with engine representative height-to-momentum thickness ratios, as a function of Reynolds number. Enhancement factors are compared for both smooth and rough airfoil surfaces with added disturbances, as well as low and high freestream turbulence intensity. Results show that leading edge heat transfer is dominated by freestream turbulence intensity effects, such that enhancements of nearly 50% at low turbulence levels are reduced to about 10% at elevated turbulence levels. Both pressure and suction side enhancement factors are dominated by surface roughness caused effects, with large enhancements for smooth surfaces being drastically reduced for roughened surfaces.

scholarly journals Highly Resolved Distribution of Heat Transfer for Turbine Leading Edge Film Cooling Including Reynolds Number and Blowing Rate Effects

1998 ◽  
Author(s):  
K. Jung ◽  
D. K. Hennecke
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Film Cooling ◽  
Heat Mass Transfer ◽  
Leading Edge ◽  
Transfer Coefficients ◽  
Complex Flow ◽  
Long Distance ◽  
Naphthalene Sublimation Technique

The effect of leading edge film cooling on heat transfer was experimentally investigated using the naphthalene sublimation technique. The experiments were performed on a symmetrical model of the leading edge suction side region of a high pressure turbine blade with one row of film cooling holes on each side. Two different lateral inclinations of the injection holes were studied: 0° and 45°. In order to build a data base for the validation and improvement of numerical computations, highly resolved distributions of the heat/mass transfer coefficients were measured. Reynolds numbers (based on hole diameter) were varied from 4000 to 8000 and blowing rate from 0.0 to 1.5. For better interpretation, the results were compared with injection-flow visualizations. Increasing the blowing rate causes more interaction between the jets and the mainstream, which creates higher jet turbulence at the exit of the holes resulting in a higher relative heat transfer. This increase remains constant over quite a long distance dependent on the Reynolds number. Increasing the Reynolds number keeps the jets closer to the wall resulting in higher relative heat transfer. The highly resolved heat/mass transfer distribution shows the influence of the complex flow field in the near hole region on the heat transfer values along the surface.

Evaluation of CFD Simulations of Film Cooling Performance in the Showerhead Region of a Turbine Vane Including Conjugate Effects

2012 ◽  
Author(s):  
Thomas E. Dyson ◽  
David G. Bogard ◽  
Sean D. Bradshaw
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Leading Edge ◽  
External Boundary ◽  
Experimental Measurements ◽  
Impingement Cooling ◽  
Heat Transfer Augmentation ◽  
Turbine Vane ◽  
Sst Turbulence Model ◽  
Investigate Heat Transfer

Computational simulations using RANS and the k-ω SST turbulence model were performed to complement experimental measurements of overall cooling effectiveness and adiabatic film effectiveness for a film cooled turbine vane airfoil. Particular attention was placed on the showerhead. The design made use of five rows of showerhead holes and a single gill row on both pressure and suction sides. The simulated geometry also included the internal impingement cooling configuration. Internal and external boundary conditions were matched to experiments using the same vane model. To correctly simulate conjugate heat transfer effects, the experimental vane model was constructed to match the Biot number for engine conditions. Computational predictions of the overall and adiabatic effectiveness were compared to experimental measurements from both the conducting vane and a model constructed from low conductivity foam. The results show that the k-ω SST RANS model over-predicts both adiabatic and overall effectiveness due in part to limited jet diffusion. The simulations were also used to investigate heat transfer augmentation, which is difficult to measure experimentally in the showerhead region. The results showed substantial augmentation of 1.5 or more over large portions of the leading edge, with many areas exceeding 2.0. However, the simulations also showed a reduction in heat transfer (i.e., hf/h0 < 1) for locations beneath the coolant jets. This result was likely due to Taw being an inappropriate driving temperature for separated jets.

scholarly journals Full Coverage Shaped-Hole Film Cooling in an Accelerating Boundary Layer With High Freestream Turbulence

2016 ◽  
Vol 138 (7) ◽  
Author(s):  
J. E. Kingery ◽  
F. E. Ames
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Film Cooling ◽  
Density Ratio ◽  
Leading Edge ◽  
Test Surface ◽  
Turbulence Level ◽  
Full Coverage ◽  
Lower Reynolds Number ◽  
Shaped Hole

Full coverage shaped-hole film cooling and downstream heat transfer measurements have been acquired in the accelerating flows over a large cylindrical leading edge test surface. The shaped holes had an 8 deg lateral expansion angled at 30 deg to the surface with spanwise and streamwise spacings of 3 diameters. Measurements were conducted at four blowing ratios, two Reynolds numbers, and six well documented turbulence conditions. Film cooling measurements were acquired over a four to one range in blowing ratio at the lower Reynolds number and at the two lower blowing ratios for the higher Reynolds number. The film cooling measurements were acquired at a coolant to free-stream density ratio of approximately 1.04. The flows were subjected to a low turbulence (LT) condition (Tu = 0.7%), two levels of turbulence for a smaller sized grid (Tu = 3.5% and 7.9%), one turbulence level for a larger grid (8.1%), and two levels of turbulence generated using a mock aerocombustor (AC) (Tu = 9.3% and 13.7%). Turbulence level is shown to have a significant influence in mixing away film cooling coverage progressively as the flow develops in the streamwise direction. Effectiveness levels for the AC turbulence condition are reduced to as low as 20% of LT values by the furthest downstream region. The film cooling discharge is located close to the leading edge with very thin and accelerating upstream boundary layers. Film cooling data at the lower Reynolds number show that transitional flows have significantly improved effectiveness levels compared with turbulent flows. Downstream effectiveness levels are very similar to slot film cooling data taken at the same coolant flow rates over the same cylindrical test surface. However, slots perform significantly better in the near discharge region. These data are expected to be very useful in grounding computational predictions of full coverage shaped-hole film cooling with elevated turbulence levels and acceleration. Infrared (IR) measurements were performed for the two lowest turbulence levels to document the spanwise variation in film cooling effectiveness and heat transfer.

Surface Roughness Effects on External Heat Transfer of a HP Turbine Vane

2005 ◽  
Vol 127 (1) ◽  
pp. 200-208 ◽  
Author(s):  
M. Stripf ◽  
A. Schulz ◽  
S. Wittig
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Surface Roughness ◽  
Turbulent Boundary Layer ◽  
Full Range ◽  
Reynolds Numbers ◽  
External Heat ◽  
Reference Surface ◽  
External Heat Transfer ◽  
Turbine Vane

External heat transfer measurements on a highly loaded turbine vane with varying surface roughness are presented. The investigation comprises nine different roughness configurations and a smooth reference surface. The rough surfaces consist of evenly spaced truncated cones with varying height, diameter, and distance, thus covering the full range of roughness Reynolds numbers in the transitionally and fully rough regimes. Measurements for each type of roughness are conducted at several freestream turbulence levels (Tu1=4% to 8.8%) and Reynolds numbers, hereby quantifying their combined effect on heat transfer and laminar-turbulent transition. In complementary studies a trip wire is used on the suction side in order to fix the transition location close to the stagnation point, thereby allowing a deeper insight into the effect of roughness on the turbulent boundary layer. The results presented show a strong influence of roughness on the onset of transition even for the smallest roughness Reynolds numbers. Heat transfer coefficients in the turbulent boundary layer are increased by up to 50% when compared to the smooth reference surface.

Numerical Study on Flow and Heat Transfer Characteristics of Swirl Cooling on Leading Edge Model of Gas Turbine Blade

2011 ◽  
Author(s):  
Zhao Liu ◽  
Zhenping Feng ◽  
Liming Song
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Wall Temperature ◽  
Leading Edge ◽  
Circular Pipe ◽  
Temperature Ratio ◽  
Cooling Passage ◽  
Tangential Inlet

In this paper a numerical simulation is performed to predict the swirl cooling on internal leading edge cooling passage model. The relative performances of four kinds of turbulence models including the standard κ-ε model, the RNG κ-ε model, the standard κ-ω model and the SST κ-ω model in the simulation of the swirl flow by tangential inlet jets in a circular pipe are compared with available experimental data. The results show that SST κ-ω model is the best one based on simulation accuracy. Then the SST κ-ω model is adopted for the present simulation. A circular pipe with a single rectangular tangential inlet jet or with two rectangular tangential inlet jets is adopted to investigate the swirl cooling and its effectiveness. The influence of the Reynolds number and the inlet to wall temperature ratio are investigated. The results indicate that the heat transfer coefficient on the swirl chamber increases with the increase of Reynolds number, and increases with the decrease of the inlet to wall temperature ratio. The swirl pipe with two tangential inlets could get a heat transfer enhancement of about three times to that of the nonswirling pipe, while swirl pipe with one tangential inlet could get a heat transfer coefficient 38% higher than that of the nonswirling pipe.

Effects of Jetting Orifice Geometry Parameters and Channel Reynolds Number on Bended Channel Cooling for a Novel Internal Cooling Structure

2019 ◽  
Author(s):  
Wei He ◽  
Qinghua Deng ◽  
Juan He ◽  
Tieyu Gao ◽  
Zhenping Feng
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Film Cooling ◽  
Leading Edge ◽  
Jet Impingement ◽  
Suction Side ◽  
Outer Wall ◽  
Internal Cooling ◽  
Cooling Effectiveness ◽  
Blade Leading Edge

Abstract A novel internal cooling structure has been raised recently to enhance internal cooling effectiveness and reduce coolant requirement without using film cooling. This study mainly focuses on verifying the actual cooling performance of the structure and investigating the heat transfer mechanism of the leading edge part of the structure, named bended channel cooling. The cooling performances of the first stage of GE-E3 turbine with three different blade leading edge cooling structures (impingement cooling, swirl cooling and bended channel cooling) were simulated using the conjugate heat transfer method. Furthermore, the effects of jetting orifice geometry and channel Reynolds number were studied with simplified models to illustrate the flow and heat transfer characteristics of the bended channel cooling. The results show that the novel internal cooling structure has obvious advantages on the blade leading edge and suction side under operating condition. The vortex core structure in the bended channel depends on orifice width, but not channel Reynolds number. With the ratio of orifice width to outer wall thickness smaller than a critical value of 0.5, the coolant flows along the external surface of the channel in the pattern of “inner film cooling”, which is pushed by centrifugal force and minimizes the mixing with spent cooling air. Namely, the greatly organized coolant flow generates higher cooling effectiveness and lower coolant demand. Both the Nusselt number on the channel surfaces and total pressure loss increase significantly when the orifice width falls or channel Reynolds increases, but the wall jet impingement distance appears to be less influential.

Film Cooling Jet Injection Effect in Heat Transfer Coefficient Augmentation for the Pressure Side Cooling of Turbine Vane

2014 ◽  
Author(s):  
Hossein Nadali Najafabadi ◽  
Matts Karlsson ◽  
Mats Kinell ◽  
Esa Utriainen
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Density Ratio ◽  
Leading Edge ◽  
Suction Side ◽  
Pressure Side ◽  
Time Resolved ◽  
Turbine Vane

Improving film cooling performance of turbine vanes and blades is often achieved through application of multiple arrays of cooling holes on the suction side, the showerhead region and the pressure side. This study investigates the pressure side cooling under the influence of single and multiple rows of cooling in the presence of a showerhead from a heat transfer coefficient augmentation perspective. Experiments are conducted on a prototype turbine vane working at engine representative conditions. Transient IR thermography is used to measure time-resolved surface temperature and the semi-infinite method is utilized to calculate the heat transfer coefficient on a low conductive material. Investigations are performed for cylindrical and fan-shaped holes covering blowing ratio 0.6 and 1.8 at density ratio of about unity. The freestream turbulence is approximately 5% close to the leading edge. The resulting heat transfer coefficient enhancement, the ratio of HTC with to that without film cooling, from different case scenarios have been compared to showerhead cooling only. Findings of the study highlight the importance of showerhead cooling to be used with additional row of cooling on the pressure side in order to reduce heat transfer coefficient enhancement. In addition, it is shown that extra rows of cooling will not significantly influence heat transfer augmentation, regardless of the cooling hole shape.

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