Heat Transfer and Friction Studies in a Tilted and Rib-Roughened Trailing-Edge Cooling Cavity With and Without the Trailing-Edge Cooling Holes

2014 ◽  
Author(s):  
Mohammad Taslim ◽  
Joseph S. Halabi
Keyword(s):  
Heat Transfer ◽  
Boundary Conditions ◽  
Flow Direction ◽  
Transfer Coefficients ◽  
Trailing Edge ◽  
Cross Sectional ◽  
Heat Transfer Coefficients ◽  
Cfd Models ◽  
Cooling Cavity ◽  
Rib Roughened

Local and average heat transfer coefficients and friction factors were measured in a test section simulating the trailing edge cooling cavity of a turbine airfoil. The test rig with a trapezoidal cross sectional area was rib-roughened on two opposite sides of the trapezoid (airfoil pressure and suction sides) with tapered ribs to conform to the cooling cavity shape and had a 22-degree tilt in the flow direction upstream of the ribs that affected the heat transfer coefficients on the two rib-roughened surfaces. The radial cooling flow traveled from the airfoil root to the tip while exiting through 22 cooling holes along the airfoil trailing edge. Two rib geometries, with and without the presence of the trailing-edge cooling holes, were examined. The numerical model contained the entire trailing-edge channel, ribs and trailing-edge cooling holes to simulate exactly the tested geometry. A pressure-correction based, multi-block, multi-grid, unstructured/adaptive commercial software was used in this investigation. Realizable k–ε turbulence model in conjunction with enhanced wall treatment approach for the near wall regions, was used for turbulence closure. The applied thermal boundary conditions to the CFD models matched the test boundary conditions. Comparisons are made between the experimental and numerical results.

scholarly journals Heat Transfer and Friction Studies in a Tilted and Rib-Roughened Trailing-Edge Cooling Cavity with and without the Trailing-Edge Cooling Holes

2014 ◽  
Vol 2014 ◽  
pp. 1-14 ◽  
Author(s):  
M. E. Taslim ◽  
J. S. Halabi
Keyword(s):  
Heat Transfer ◽  
Boundary Conditions ◽  
Flow Direction ◽  
Transfer Coefficients ◽  
Trailing Edge ◽  
Cross Sectional ◽  
Heat Transfer Coefficients ◽  
Cfd Models ◽  
Cooling Cavity ◽  
Rib Roughened

Local and average heat transfer coefficients and friction factors were measured in a test section simulating the trailing-edge cooling cavity of a turbine airfoil. The test rig with a trapezoidal cross-sectional area was rib-roughened on two opposite sides of the trapezoid (airfoil pressure and suction sides) with tapered ribs to conform to the cooling cavity shape and had a 22-degree tilt in the flow direction upstream of the ribs that affected the heat transfer coefficients on the two rib-roughened surfaces. The radial cooling flow traveled from the airfoil root to the tip while exiting through 22 cooling holes along the airfoil trailing-edge. Two rib geometries, with and without the presence of the trailing-edge cooling holes, were examined. The numerical model contained the entire trailing-edge channel, ribs, and trailing-edge cooling holes to simulate exactly the tested geometry. A pressure-correction based, multiblock, multigrid, unstructured/adaptive commercial software was used in this investigation. Realizablek-εturbulence model in conjunction with enhanced wall treatment approach for the near wall regions was used for turbulence closure. The applied thermal boundary conditions to the CFD models matched the test boundary conditions. Comparisons are made between the experimental and numerical results.

Measurements of Heat Transfer Coefficients in Rib-Roughened Trailing-Edge Cavities With Crossover Jets

1998 ◽  
Author(s):  
M. E. Taslim ◽  
T. Li ◽  
S. D. Spring
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Test Section ◽  
Transfer Coefficients ◽  
Trailing Edge ◽  
Cross Sectional ◽  
Heat Transfer Coefficients ◽  
Symmetric Pattern ◽  
Cooling Cavity ◽  
Rib Roughened

Liquid crystals were used in this experimental investigation to measure the local and average heat transfer coefficients on the walls of six test sections simulating the trailing edge cooling cavity of a modern turbine blade. All test sections had trapezoidal cross sectional areas with two rows of racetrack-shaped slots on two opposite bases. Crossover jets, issued from the slots on one base, impinged on the test section rib-roughened walls and exited from the slots on the opposite wall. The first test section had all smooth walls and served as a baseline. The remaining five test sections were rib-roughened on either one wall or two opposite walls simulating the pressure and suction sides of the blade trailing-edge cooling cavity. In the first four tests, the jets issued into the test section along the test section plane of symmetry. Therefore, the two opposite walls, simulating pressure and suction sides of the blade, saw the same jet effects. This symmetric pattern was altered in test sections 5 and 6 in which the jets were tilted towards one or the other wall at an angle of 6°. The ribs in the roughened test sections, covering only 62% of the wall span, were mounted to the surface with an angle of attack to the jet axis, α, of 30°. The objective of this study was to investigate the effects that crossover jets have on the heat transfer coefficient and pressure recovery in a cooling cavity of a modern gas turbine blade. Major conclusions of this study were that combining the crossover jets with rib-roughened surfaces can be an effective method of cooling the trailing edge cavities and by proper arrangement of the jets and ribs, heat transfer coefficients on the two opposite walls can be tailored.

Experimental and Numerical Crossover Jet Impingement in a Rib-Roughened Airfoil Trailing-Edge Cooling Channel

2013 ◽  
Vol 135 (5) ◽  
Author(s):  
M. E. Taslim ◽  
M. K. H. Fong
Keyword(s):  
Heat Transfer ◽  
Turbulence Model ◽  
Transfer Coefficients ◽  
Trailing Edge ◽  
Edge Channel ◽  
Heat Transfer Coefficients ◽  
Numerical Predictions ◽  
Cooling Cavity ◽  
Near Wall ◽  
Rib Roughened

Local and average heat transfer coefficients were measured in a test section simulating a rib-roughened trailing edge cooling cavity of a turbine airfoil. The test rig was made up of two adjacent channels, each with a trapezoidal cross sectional area. The first channel, simulating the cooling cavity adjacent to the trailing-edge cavity, supplied the cooling air to the trailing-edge channel through a row of racetrack-shaped slots on the partition wall between the two channels. Eleven crossover jets, issued from these slots entered the trailing-edge channel, impinged on eleven radial ribs and exited from a second row of race-track shaped slots on the opposite wall in staggered or inline arrangement. Two jet angles of 0 deg and 5 deg and a range of jet Reynolds number from 10,000 to 35,000 were tested and compared. The numerical models contained the entire trailing-edge and supply channels with all slots and ribs to simulate exactly the tested geometries. They were meshed with all-hexa structured mesh of high near-wall concentration. A pressure-correction based, multiblock, multigrid, unstructured/adaptive commercial software was used in this investigation. The realizable k-ε turbulence model was employed in combination with an enhanced wall treatment approach for the near wall regions. Boundary conditions identical to those of the experiments were applied and several turbulence model results were compared. The numerical analyses also provided the share of each crossover and each exit hole from the total flow for different geometries. The major conclusions of this study were: (a) except for the first and last cross-flow jets, which had different flow structures, other jets produced the same heat transfer results on their target surfaces; (b) tilted crossover jets produced higher heat transfer coefficients on the target surface towards which they were tilted and lower values on the opposite surface, and (c) the numerical predictions of impingement heat transfer coefficients were in good agreement with the measured values for most cases thus CFD could be considered a viable tool in airfoil cooling circuit designs.

Experimental and Numerical Crossover Jet Impingement in a Rib-Roughened Airfoil Trailing-Edge Cooling Channel

2011 ◽  
Author(s):  
M. E. Taslim ◽  
M. K. H. Fong
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbulence Model ◽  
Transfer Coefficients ◽  
Trailing Edge ◽  
Edge Channel ◽  
Heat Transfer Coefficients ◽  
Numerical Predictions ◽  
Cooling Cavity ◽  
Rib Roughened

Local and average heat transfer coefficients were measured in a test section simulating a rib-roughened trailing edge cooling cavity of a turbine airfoil. The test rig was made up of two adjacent channels, each with a trapezoidal cross sectional area. The first channel, simulating the cooling cavity adjacent to the trailing-edge cavity, supplied the cooling air to the trailing-edge channel through a row of racetrack-shaped slots on the partition wall between the two channels. Eleven crossover jets, issued from these slots entered the trailing-edge channel, impinged on eleven radial ribs and exited from a second row of race-track shaped slots on the opposite wall in staggered or inline arrangement. Two jet angles of 0 and 5° and a range of jet Reynolds number from 10,000 to 35,000 were tested and compared. The numerical models contained the entire trailing-edge and supply channels with all slots and ribs to simulate exactly the tested geometries. They were meshed with all-hexa structured mesh of high near-wall concentration. A pressure-correction based, multi-block, multi-grid, unstructured/adaptive commercial software was used in this investigation. Standard high Reynolds number k–ε turbulence model in conjunction with the generalized wall function for most parts was used for turbulence closure. Boundary conditions identical to those of the experiments were applied and several turbulence model results were compared. The numerical analyses also provided the share of each crossover and each exit hole from the total flow for different geometries. The major conclusions of this study were: a) except for the first and last cross-flow jets which had different flow structures, other jets produced the same heat transfer results on their target surfaces, b) tilted crossover jets produced higher heat transfer coefficients on the target surface towards which they were tilted and lower values on the opposite surface and c) the numerical predictions of impingement heat transfer coefficients were in good agreement with the measured values for most cases thus CFD could be considered a viable tool in airfoil cooling circuit designs.

Crossover Jet Impingement in a Rib-Roughened Trailing-Edge Cooling Channel

2017 ◽  
Vol 139 (7) ◽  
Author(s):  
Mohammad E. Taslim ◽  
Fei Xue
Keyword(s):  
Heat Transfer ◽  
Numerical Results ◽  
Test Results ◽  
Transfer Coefficients ◽  
Trailing Edge ◽  
Numerical Work ◽  
Edge Channel ◽  
Heat Transfer Coefficients ◽  
The Cross ◽  
Rib Roughened

Airfoil trailing-edge cooling is the main focus of this study. The test section was made up of two adjacent trapezoidal channels, simulating the trailing-edge cooling cavity of a gas turbine airfoil and its neighboring cavity. Eleven racetrack-shaped holes were drilled on the partition wall between the two channels to produce 11 cross-over jets that impinged on the rib-roughened wall of the trailing-edge channel. The jets, after impinging on their respective target surface, turned toward the trailing-edge channel exit. Smooth target wall, as a baseline case, as well as four rib angles with the flow of 0 deg, 45 deg, 90 deg, and 135 deg are investigated. Cross-over holes axes were on the trailing-edge channel center plane, i.e., no tilting of the cross-over jets. Steady-state liquid crystal thermography technique was used in this study for a range of jet Reynolds number of 10,000–35,000. The test results are compared with the numerical results obtained from the Reynolds-averaged Navier–Stokes and energy equation. Closure was attained by k–ω with shear stress transport (SST) turbulence model. The entire test rig (supply and trailing-edge channels) was meshed with variable density hexagonal meshes. The numerical work was performed for boundary conditions identical to those of the tests. In addition to the impingement heat transfer coefficients, the numerical results provided the mass flow rates through individual cross-over holes. This study concluded that: (a) the local Nusselt numbers correlate well with the local jet Reynolds numbers, (b) 90 deg rib arrangement, that is, when the cross-over jet axis was parallel to the rib longitudinal axis, produced higher heat transfer coefficients, compared to other rib angles, and (c) numerical heat transfer results were generally in good agreement with the test results. The overall difference between the computational fluid dynamics (CFD) and test results was about 10%.

Aero-Thermal Investigation of a Rib-Roughened Trailing Edge Channel With Crossing-Jets: Part II—Heat Transfer Analysis

2008 ◽  
Author(s):  
Filippo Coletti ◽  
Alessandro Armellini ◽  
Tony Arts ◽  
Christophe Scholtes
Keyword(s):  
Heat Transfer ◽  
Computational Study ◽  
Heat Transfer Analysis ◽  
Navier Stokes ◽  
Transfer Coefficients ◽  
Trailing Edge ◽  
Present Contribution ◽  
Heat Transfer Coefficients ◽  
Numerical Predictions ◽  
Rib Roughened

The present contribution addresses the aero-thermal experimental and computational study of a trapezoidal cross-section model simulating a trailing edge cooling cavity with one rib-roughened wall and slots along two opposite walls. Highly resolved heat transfer distributions for the geometry with and without ribs are achieved using a steady state liquid crystals method in part II of this paper. The reference Reynolds number, defined at the entrance of the test section, is set at 67500 for all the experiments. Comparisons are made with the flow field visualizations presented in part I of the paper. The results show the dramatic impact of the flow structures on the local and global heat transfer coefficients along the cavity walls. Of particular importance is the jet deflected by the rib-roughened wall and impinging on the opposite smooth wall. The experimental results are compared with the numerical predictions obtained using the finite volume, Reynolds-Averaged Navier-Stokes solver CEDRE.

Experimental and Numerical Cross-Over Jet Impingement in an Airfoil Trailing-Edge Cooling Channel

2010 ◽  
Author(s):  
M. E. Taslim ◽  
A. Nongsaeng
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbulence Model ◽  
Numerical Models ◽  
Transfer Coefficients ◽  
Trailing Edge ◽  
Edge Channel ◽  
Heat Transfer Coefficients ◽  
Numerical Predictions ◽  
Cooling Cavity

Trailing edge cooling cavities in modern gas turbine airfoils play an important role in maintaining the trailing edge temperature at levels consistent with airfoil design life. In this study, local and average heat transfer coefficients were measured in a test section simulating the trailing edge cooling cavity of a turbine airfoil using the steady-state liquid crystal technique. The test rig was made up of two adjacent channels, each with a trapezoidal cross sectional area. The first channel, simulating the cooling cavity adjacent to the trailing-edge cavity, supplied the cooling air to the trailing-edge channel through a row of racetrack-shaped slots on the partition wall between the two channels. Eleven crossover jets, issued from these slots entered the trailing-edge channel and exited from a second row of race-track shaped slots on the opposite wall in staggered or inline arrangement. Two jet angles were examined. The baseline tests were for zero angle between the jet axis and the trailing-edge channel centerline. The jets were then tilted towards one wall (pressure or suction side) of the trailing-edge channel by five degrees. Results of the two set of tests for a range of local jet Reynolds number from 10,000 to 35,000 were compared. The numerical models contained the entire trailing-edge and supply channels with all slots to simulate exactly the tested geometries. They were meshed with all-hexa structured mesh of high near-wall concentration. A pressure-correction based, multi-block, multi-grid, unstructured/adaptive commercial software was used in this investigation. Standard high Reynolds number k–ε turbulence model in conjunction with the generalized wall function for most parts was used for turbulence closure. Boundary conditions identical to those of the experiments were applied and several turbulence model results were compared. The numerical analyses also provided the share of each cross-over and each exit hole from the total flow for different geometries. The major conclusions of this study were: a) except for the first and last cross-flow jets which had different flow structures, other jets produced the same heat transfer results on their target surfaces, b) jets tilted at an angle of 5 degrees produced higher heat transfer coefficients on the target surface. The tilted jets also produced the same level of heat transfer coefficients on the wall opposite the target wall and c) the numerical predictions of impingement heat transfer coefficients were in good agreement with the measured values for most cases thus CFD could be considered a viable tool in airfoil cooling circuit designs.

Heat Transfer in Rotating, Trailing Edge, Converging Channels With Full and Partial Height Strip-Fins

2021 ◽  
Author(s):  
Izzet Sahin ◽  
I-Lun Chen ◽  
Lesley M. Wright ◽  
Je-Chin Han ◽  
Hongzhou Xu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flow Direction ◽  
Internal Cooling ◽  
Transfer Coefficients ◽  
Trailing Edge ◽  
Cooling Channels ◽  
Heat Transfer Coefficients ◽  
Pin Fins ◽  
Full Height

Abstract A wide variety of pin-fins have been used to enhance heat transfer in internal cooling channels. However, due to their large blockage in the flow direction, they result in an undesirable high pressure drop. This experimental study aims to reduce pressure drop while increasing the heat transfer surface area by utilizing strip-fins in converging internal cooling channels. The channel is designed with a trapezoidal cross-section, converges in both transverse and longitudinal directions, and is also skewed β = 120° with respect to the direction of rotation in order to model a trailing edge cooling channel. Only the leading and trailing surfaces of the channel are instrumented, and each surface is divided into eighteen isolated copper plates to measure the regionally averaged heat transfer coefficient. Utilizing pressure taps at the inlet and outlet of the channel, the pressure drop is obtained. Three staggered arrays of strip-fins are investigated: one full height configuration and two partial fin height arrangements (Sz = 2mm and 1mm). In all cases, the strip fins are 2mm wide (W) and 10mm long (Lf) in the flow direction. The fins are spaced such that Sy/Lf = 1 in the streamwise direction. However, due to the convergence the spanwise spacing Sx/W, was varied from 8 to 6.2 along the channel. The rotation number of the channel varied up to 0.21 by ranging the inlet Reynolds number from 10,000 to 40,000 and rotation speed from 0 to 300rpm. It is found that the full height strip-fin channel results in a more non-uniform spanwise heat transfer distribution than the partial height strip-fin channel. Both trailing and leading surface heat transfer coefficients are enhanced under rotation conditions. The 2mm height partial strip-fin channel provided the best thermal performance, and it is comparable to the performance of the converging channels with partial length circular pins. The strip-fin channel can be a design option when the pressure drop penalty is a major concern.

Experimental and Numerical Cross-Over Jet Impingement in an Airfoil Trailing-Edge Cooling Channel

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
M. E. Taslim ◽  
A. Nongsaeng
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbulence Model ◽  
Numerical Models ◽  
Transfer Coefficients ◽  
Trailing Edge ◽  
Edge Channel ◽  
Heat Transfer Coefficients ◽  
Numerical Predictions ◽  
Cooling Cavity

Trailing edge cooling cavities in modern gas turbine airfoils play an important role in maintaining the trailing-edge temperature at levels consistent with airfoil design life. In this study, local and average heat transfer coefficients were measured in a test section, simulating the trailing-edge cooling cavity of a turbine airfoil using the steady-state liquid crystal technique. The test rig was made up of two adjacent channels, each with a trapezoidal cross-sectional area. The first channel, simulating the cooling cavity adjacent to the trailing-edge cavity, supplied the cooling air to the trailing-edge channel through a row of racetrack-shaped slots on the partition wall between the two channels. Eleven crossover jets issued from these slots entered the trailing-edge channel and exited from a second row of race-track shaped slots on the opposite wall in staggered or inline arrangement. Two jet angles were examined. The baseline tests were for zero angle between the jet axis and the trailing-edge channel centerline. The jets were then tilted toward one wall (pressure or suction side) of the trailing-edge channel by 5 deg. Results of the two set of tests for a range of local jet Reynolds number from 10,000 to 35,000 were compared. The numerical models contained the entire trailing-edge and supply channels with all slots to simulate exactly the tested geometries. They were meshed with all-hexa structured mesh of high near-wall concentration. A pressure-correction based, multiblock, multigrid, unstructured/adaptive commercial software was used in this investigation. Standard high Reynolds number k−ε turbulence model in conjunction with the generalized wall function for most parts was used for turbulence closure. Boundary conditions identical to those of the experiments were applied and several turbulence model results were compared. The numerical analyses also provided the share of each cross-over and each exit hole from the total flow for different geometries. The major conclusions of this study were (a) except for the first and last cross-flow jets which had different flow structures, other jets produced the same heat transfer results on their target surfaces, (b) jets tilted at an angle of 5 deg produced higher heat transfer coefficients on the target surface. The tilted jets also produced the same level of heat transfer coefficients on the wall opposite the target wall, and (c) the numerical predictions of impingement heat transfer coefficients were in good agreement with the measured values for most cases; thus, computational fluid dynamics could be considered a viable tool in airfoil cooling circuit designs.

Heat Transfer and Pressure Drop Measurements on Rotating Matrix Cooling Geometries for Airfoil Trailing Edges

2015 ◽  
Author(s):  
Carlo Carcasci ◽  
Bruno Facchini ◽  
Marco Pievaroli ◽  
Lorenzo Tarchi ◽  
Alberto Ceccherini ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Gas Turbine ◽  
Rotation Number ◽  
Flow Direction ◽  
Open Area ◽  
Transfer Coefficients ◽  
Trailing Edge ◽  
Heat Transfer Coefficients ◽  
The Matrix

In the present paper the combined effects of rotation and channel orientation on heat transfer and pressure drop along two scaled up matrix geometries suitable for trailing edge cooling of gas turbine airfoils are investigated. Experimental tests were carried out under static and rotating conditions. Rotating tests were performed for two different orientations of the matrix channel with respect to the rotating plane: 0deg and 30deg. This latter configuration is representative of the exit angle of a real gas turbine blade. Test models are designed in order to replicate an internal geometry suitable for blade trailing edge cooling, with a 90deg turning flow before entering the matrix array which has an axial development. Both the investigated geometries have a cross angle of 45deg between ribs and different values of sub-channels and rib thickness: one has four sub-channels and lower rib thickness (open area 84.5%), one has six sub-channels and higher rib thickness (open area 53.5%). Both geometries have a converging angle of 11.4deg. Matrix models have been axially divided in 5 aluminum elements per side in order to evaluate the heat transfer coefficient in 5 different locations in the main flow direction. Metal temperature was measured with embedded thermocouples and thin-foil heaters were used to provide a constant heat flux during each test. Heat transfer coefficients were measured applying a steady state technique based on a regional average method and varying the sub-channel Reynolds number Res from 2000 to 10000 and the sub-channel Rotation number Ros from 0 to 0.250 in order to have both Reynolds and Rotation number similitude with the real conditions. A post-processing procedure, which takes into account the temperature gradients within the model, was developed to correctly compute average heat transfer coefficients starting from discrete temperature measurements.

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