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.

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.

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.

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.

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.

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%.

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.

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/Numerical Investigation on the Effects of Trailing-Edge Cooling Hole Blockage on Heat Transfer in a Trailing-Edge Cooling Channel

2013 ◽  
Author(s):  
M. E. Taslim ◽  
X. Huang
Keyword(s):  
Heat Transfer ◽  
Mass Flow Rate ◽  
Turbulence Model ◽  
Mass Flow ◽  
Flow Rate ◽  
Transfer Coefficients ◽  
Trailing Edge ◽  
Edge Channel ◽  
Heat Transfer Coefficients ◽  
Near Wall

Hot and harsh environments, sometimes experienced by gas turbine airfoils, can create undesirable effects such as clogging of the cooling holes. Clogging of the cooling holes along the trailing edge of an airfoil on the tip side and its effects on the heat transfer coefficients in the cooling cavity around the clogged holes is the main focus of this investigation. 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 rig was made up of two adjacent channels, each with a trapezoidal cross sectional area. The first channel 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 cross-over 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 that simulated the cooling holes along the trailing edge of the airfoil. Tests were run for the baseline case with all exit holes open and for cases in which 2, 3 and 4 exit holes on the airfoil tip side were clogged. All tests were run for two cross-over jet angles. The first set of tests were run for zero angle between the jet axis and the trailing-edge channel centerline. The jets were then tilted towards the ribs by five degrees. Results of the two set of tests for a range of 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 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. The realizable k – ε turbulence model in combination with enhanced wall treatment approach for the near wall regions were 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) Clogging of the exit holes near the airfoil tip alters the distribution of the coolant mass flow rate through the crossover holes and changes the flow structure. Depending on the number of clogged exit holes (from 3 to 6, out of 12), the tip-end crossover hole experienced from 35% to 49% reductions in its mass flow rate while the root-end crossover hole, under the same conditions, experienced an increase of the same magnitude in its mass flow rate, b) up to 64% reduction in heat transfer coefficients on the tip-end surface areas around the clogged holes were observed which might have devastating effects on the airfoil life. At the same time, a gain in heat transfer coefficient of up 40% was observed around the root-end due to increased crossover flows, c) Numerical heat transfer results with the use of the realizable k – ε turbulence model in combination with enhanced wall treatment approach for the near wall regions were generally in a reasonable agreement with the test results. The overall difference between the CFD and test results was about 10%.

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

2010 ◽  
Vol 133 (3) ◽  
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 aerothermal 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 67,500 for all the experiments. Comparisons are made with the flow field visualizations presented in part I of this 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 Calcul d'Écoulements Diphasiques Réactifs pour l'Énergétique (CEDRE).

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.

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