Heat Transfer in Rotating Serpentine Passages With Selected Model Orientations for Smooth or Skewed Trip Walls

1994 ◽  
Vol 116 (4) ◽  
pp. 738-744 ◽  
Author(s):  
B. V. Johnson ◽  
J. H. Wagner ◽  
G. D. Steuber ◽  
F. C. Yeh
Keyword(s):  
Heat Transfer ◽  
Turbine Blades ◽  
The Other ◽  
First Passage ◽  
Forward Flow ◽  
Coriolis Forces ◽  
The Third ◽  
Axis Of Rotation ◽  
Trailing Edges ◽  
Serpentine Passages

Experiments were conducted to determine the effects of model orientation as well as buoyancy and Coriolis forces on heat transfer in turbine blade internal coolant passages. Turbine blades have internal coolant passage surfaces at the leading and trailing edges of the airfoil with surfaces at angles that are as large as ±50 to 60 deg to the axis of rotation. Most of the previously presented, multiple-passage, rotating heat transfer experiments have focused on radial passages aligned with the axis of rotation. The present work compares results from serpentine passages with orientations 0 and 45 deg to the axis of rotation, which simulate the coolant passages for the midchord and trailing edge regions of the rotating airfoil. The experiments were conducted with rotation in both directions to simulate serpentine coolant passages with the rearward flow of coolant or with the forward flow of coolant. The experiments were conducted for passages with smooth surfaces and with 45 deg trips adjacent to airfoil surfaces for the radial portion of the serpentine passages. At a typical flow condition, the heat transfer on the leading surfaces for flow outward in the first passage with smooth walls was twice as much for the model at 45 deg compared to the model at 0 deg. However, the differences for the other passages and with trips were less. In addition, the effects of buoyancy and Coriolis forces on heat transfer in the rotating passage were decreased with the model at 45 deg, compared to the results at 0 deg. The heat transfer in the turn regions and immediately downstream of the turns in the second passage with flow inward and in the third passage with flow outward was also a function of model orientation with differences as large as 40 to 50 percent occurring between the model orientations with forward flow and rearward flow of coolant.

Heat Transfer in Rotating Serpentine Passages With Selected Model Orientations for Smooth or Skewed Trip Walls

1993 ◽  
Author(s):  
B. V. Johnson ◽  
J. H. Wagner ◽  
G. D. Steuber ◽  
F. C. Yeh
Keyword(s):  
Heat Transfer ◽  
Turbine Blades ◽  
The Other ◽  
First Passage ◽  
Forward Flow ◽  
Coriolis Forces ◽  
The Third ◽  
Axis Of Rotation ◽  
Trailing Edges ◽  
Serpentine Passages

Experiments were conducted to determine the effects of model orientation as well as buoyancy and Coriolis forces on heat transfer in turbine blade internal coolant passages. Turbine blades have internal coolant passage surfaces at the leading and trailing edges of the airfoil with surfaces at angles which are as large as +/−50 to 60 degrees to the axis of rotation. Most of the previously–presented, multiple–passage, rotating heat transfer experiments have focused on radial passages aligned with the axis of rotation. The present work compares results from serpentine passages with orientations 0 and 45 degrees to the axis of rotation which simulate the coolant passages for the midchord and trailing edge regions of the rotating airfoil. The experiments were conducted with rotation in both directions to simulate serpentine coolant passages with the rearward flow of coolant or with the forward flow of coolant. The experiments were conducted for passages with smooth surfaces and with 45 degree trips adjacent to airfoil surfaces for the radial portion of the serpentine passages. At a typical flow condition, the heat transfer on the leading surfaces for flow outward in the first passage with smooth walls was twice as much for the model at 45 degrees compared to the model at 0 degrees. However, the differences for the other passages and with trips were less. In addition, the effects of buoyancy and Coriolis forces on heat transfer in the rotating passage were decreased with the model at 45 degrees, compared to the results at 0 degrees. The heat transfer in the turn regions and immediately downstream of the turns in the second passage with flow inward and in the third passage with flow outward was also a function of model orientation with differences as large as 40 to 50 percent occurring between the model orientations with forward flow and rearward flow of coolant.

LES Simulations of Rotating Two-Pass Ribbed Duct With Coriolis and Centrifugal Buoyancy Forces at Re=100,000

2016 ◽  
Author(s):  
Cody Dowd ◽  
Danesh Tafti
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Large Eddy Simulations ◽  
The Other ◽  
Coriolis Forces ◽  
Flow And Heat Transfer ◽  
Large Eddy ◽  
Buoyancy Forces ◽  
First Pass ◽  
Duct Geometry

The focus of this research is to predict the flow and heat transfer in a rotating two-pass duct geometry with staggered ribs using Large-Eddy Simulations (LES). The geometry consists of a U-Bend with 17 ribs in each pass. The ribs are staggered with an e/Dh = 0.1 and P/e = 10. LES is performed at a Reynolds number of 100,000, a rotation number of 0.2 and buoyancy parameters (Bo) of 0.5 and 1.0. The effects of Coriolis forces and centrifugal buoyancy are isolated and studied individually. In all cases it is found that increasing Bo from 0.5 to 1.0 at Ro = 0.2 has little impact on heat transfer. It is found that in the first pass, the heat transfer is quite receptive to Coriolis forces which augment and attenuate heat transfer at the trailing and leading walls, respectively. Centrifugal buoyancy, on the other hand has a bigger effect in augmenting heat transfer at the trailing wall than in attenuating heat transfer at the leading wall. On contrary, it aids heat transfer in the second half of the first pass at the leading wall by energizing the flow near the wall. The heat transfer in the second pass is dominated by the highly turbulent flow exiting the bend. Coriolis forces have no impact on the augmentation of heat transfer on the leading wall till the second half of the passage whereas it attenuates heat transfer at the trailing wall as soon as the flow exits the bend. Contrary to phenomenological arguments, inclusion of centrifugal buoyancy augments heat transfer over Coriolis forces alone on both the leading and trailing walls of the second pass.

Large Eddy Simulation of Flow and Heat Transfer in a 90 deg Ribbed Duct With Rotation: Effect of Coriolis and Centrifugal Buoyancy Forces

2004 ◽  
Vol 126 (4) ◽  
pp. 627-636 ◽  
Author(s):  
Samer Abdel-Wahab ◽  
Danesh K. Tafti
Keyword(s):  
Heat Transfer ◽  
Secondary Flow ◽  
The Other ◽  
Additional Increase ◽  
Flow Cells ◽  
Coriolis Forces ◽  
Heat Transfer Augmentation ◽  
Eddy Simulation ◽  
Other Hand ◽  
Large Eddy

Results from large eddy simulations (LES) of fully developed flow in a 90 deg ribbed duct are presented with rib pitch-to-height ratio P/e=10 and a rib height-to-hydraulic-diameter ratio e/Dh=0.1. Three rotation numbers Ro=0.18, 0.36, and 0.68 are studied at a nominal Reynolds number based on bulk velocity of 20 000. Centrifugal buoyancy effects are included at two Richardson numbers of Ri=12, 28 (Buoyancy parameter, Bo=0.12 and 0.30) for each rotation case. Heat transfer augmentation on the trailing side of the duct due to the action of Coriolis forces alone asymptotes to a value of 3.7±5% by Ro=0.2. On the other hand, augmentation ratios on the leading surface keep decreasing with an increase in rotation number with values ranging from 1.7 at Ro=0.18 to 1.2 at Ro=0.67. Secondary flow cells augment the heat transfer coefficient on the smooth walls by 20% to 30% over a stationary duct. Centrifugal buoyancy further strengthens the secondary flow cells in the duct cross-section which leads to an additional increase of 10% to 15%. Buoyancy also accentuates the augmentation of turbulence near the trailing wall of the duct and increases the heat transfer augmentation ratio 10% to 20% over the action of Coriolis forces alone. However, it does not have any significant effect at the leading side of the duct. The overall effect of buoyancy on heat transfer augmentation for the ribbed duct is found to be less than 10% over the effect of Coriolis forces alone. Friction on the other hand is augmented 15% to 20% at the highest buoyancy number studied. Comparison with available experiments in the literature show excellent agreement.

Multi-Pass Serpentine Cooling Designs for Negating Coriolis Force Effect on Heat Transfer: 45-Degree Angled Rib Turbulated Channels

2018 ◽  
Author(s):  
Prashant Singh ◽  
Yongbin Ji ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Coriolis Force ◽  
Turbine Blades ◽  
Experimental Studies ◽  
Reynolds Numbers ◽  
Steady State Condition ◽  
Uniform Heat ◽  
Wide Range ◽  
Serpentine Passages ◽  
Rib Roughened

Traditional gas turbine blades are equipped with serpentine passages arranged along the height, wherein the coolant flows radially outward in 1st passage and radially inward in 2nd passage. Prior experimental studies have established that for traditional two-pass rib roughened ducts, under the influence of Coriolis and centrifugal forces, the heat transfer gets enhanced on trailing side for radially outward flow and gets reduced on the leading side for a radially outward flow. A reverse trend in heat transfer is observed for radially inward flow. Rotation induced forces result in non-uniform heat transfer coefficient distribution which results in non-uniform metal temperatures under steady state condition. Present study addresses the problem of non-uniform heat transfer distribution on leading and trailing sides due to rotation effect. Experimental investigation of two configurations has been carried out, where Coriolis effect was negated by aligning the coolant flow vector and rotation vector such that their cross product was effectively a null vector. Novel multi-passage serpentine ducts featuring 45-degree angled rib turbulators with four-passage and six-passage configurations have been studied. Transient liquid crystal thermography experiments were carried out under stationary and rotating conditions. Heat transfer experiments were carried out for Reynolds numbers ranging from 12000 to 80000 under stationary conditions and rotating heat transfer experiments were carried out at two Rotation numbers of 0.05 and 0.11. We found that the heat transfer characteristics of serpentine passages were not influenced by Coriolis force after the 2nd passage. The local heat transfer distribution on leading and trailing sides of serpentine passages were near-similar to each other and comparable with corresponding stationary cases. The contribution of multiple passages connected with 180-degree bends towards overall frictional losses has been evaluated in terms of pumping power and normalized friction factor. The configurations are ranked based on their thermal hydraulic performances over a wide range of Reynolds numbers. The heat transfer enhancement levels of four-passage rib roughened duct was higher than the six-passage configuration and the six-passage configuration had slightly higher thermal hydraulic performance compared to four-passage configuration.

Effect of Coriolis Forces in a Rotating Channel With Dimples and Protrusions

2008 ◽  
Author(s):  
Mohammad A. Elyyan ◽  
Danesh K. Tafti
Keyword(s):  
Heat Transfer ◽  
Turbine Blades ◽  
Recirculation Region ◽  
Channel Height ◽  
Internal Cooling ◽  
Height Ratio ◽  
Coriolis Forces ◽  
Heat Transfer Augmentation ◽  
Rotation Numbers ◽  
Flow Reynolds Number

The use of dimple-protrusions for internal cooling of rotating turbine blades has been investigated. A channel with dimple imprint diameter to channel height ratio (H/D = 1.0), dimple depth to channel height ratio (δ/H = 0.2), spanwise and streamwise pitch to channel height ratios (P/H = S/H = 1.62) was modeled. Four rotation numbers; Rob = 0.0, 0.15, 0.39, and 0.64, at nominal flow Reynolds number, ReH = 10000, were investigated to quantify the effect of Coriolis forces on the flow structure and heat transfer in the channel. Under the influence of rotation, the leading (protrusion) side of the channel showed weaker flow impingement, larger wakes and delayed flow reattachment with increasing rotation number. The trailing (dimple) side experienced a smaller recirculation region inside the dimple and stronger flow ejection from the dimple cavity with increasing rotation. Secondary flow structures in the cross-section played a major role in transporting momentum away from the trailing side at high rotation numbers and limiting heat transfer augmentation. While heat transfer augmentation on the trailing side increases by over 90% at Rob = 0.64, overall Nusselt number and friction coefficient augmentation ratios decrease from 2.5 to 2.05, and 5.74 to 4.78, respectively, as rotation increased from Rob = 0 to Rob = 0.64.

Two-Dimensional Thermal Performance Analysis of a Semi-Transparent Spectral Zirconia Thermal Barrier Coating

2004 ◽  
Author(s):  
Nalini Uppu ◽  
Patrick F. Mensah ◽  
Ravinder Diwan
Keyword(s):  
Heat Transfer ◽  
Thermal Barrier Coating ◽  
Thermal Performance ◽  
Operating Temperature ◽  
Turbine Blades ◽  
The Other ◽  
Ceramic Layer ◽  
Thermal Barrier ◽  
Barrier Coating ◽  
Super Alloy

The performance of an aero engine can be increased in two ways: one by reducing the air requirement for the cooling of the turbine blades and secondly by increasing the turbine inlet temperature (TIT) that is operating temperature of the turbine blades. Taking into account the latter approach the blade material must withstand high temperatures of above 1350°C. For this enhancing purpose, protective coatings called the thermal barrier coatings (TBC) are being employed. The thermal barrier coating mainly consists of two layers; one is the metallic coating MCrAlY, which is the premiere layer over the substrate Ni based super alloy. The other is the ceramic layer made of Yttria Stabilized Zirconia (YSZ). Apart from these two layers, an intermediate layer of Al2O3 is formed by the oxidation of the aluminum in MCrAlY called the diffusion layer which also enhances the adhesion between the two layers. M stands for Nickel or Cobalt. The present study is an investigation on the in-situ thermal performance of TBCs by considering the ceramic layer as a semi-transparent media and varying its thickness and simultaneously increasing the operating temperature on its other boundary surface. The above thermal boundary value problem is modeled in 2-dimensions and solved numerically using the discrete ordinate model for radiative heat transfer in a commercial computational fluid dynamics and heat transfer software. Two samples of Ni based super alloy substrate with dimensions 40 × 100 × 3mm are considered; one sample with a thickness of 0.25 mm ceramic layer and the other sample with 1 mm coating thickness for transient thermal analysis. Simulated transient temperature histories are presented for use in a thermo-mechanical analysis in order to predict the failure modes in the TBC. The temperature distribution in TBC coating mainly depends on the radiative effects combined with heat conduction and convection and radiation at the material boundaries.

Blade Trailing Edge Heat Transfer

1980 ◽  
Author(s):  
A. Brown ◽  
B. Mandjikas ◽  
J. M. Mudyiwa
Keyword(s):  
Heat Transfer ◽  
Turbine Blades ◽  
Internal Heat ◽  
Maximum Velocity ◽  
Reynolds Numbers ◽  
Trailing Edge ◽  
Pillar Diameter ◽  
Trailing Edges ◽  
Pillar Arrays ◽  
Internal Heat Transfer

In this article measurements of heat transfer, pressure loss, and friction factor inside simulated trailing edges of turbine blades are presented. The trailing edges considered are vented and the internal heat transfer surfaces are extended by means of staggered arrays of pillars interconnecting the blade pressure and suction surfaces. A number of pillar arrays and trailing edge configurations are considered, namely pillar pitch to diameter ratios nominally of 2, 3, and 4 and trailing edge included angles of 0, 10, 15, and 20 deg. The range of Reynolds numbers covered based on pillar diameter and maximum velocity through a row of pillars is from 104 to 2 × 105.

Numerical Simulation of the Effect of Rib Orientation on Fluid Flow and Heat Transfer in Rotating Serpentine Passages

2016 ◽  
Vol 9 (1) ◽  
Author(s):  
Berrabah Brahim
Keyword(s):  
Heat Transfer ◽  
Flow Direction ◽  
Density Ratio ◽  
Reynolds Stress Model ◽  
Secondary Flows ◽  
First Passage ◽  
Square Channel ◽  
The Third ◽  
Flow And Heat Transfer ◽  
First Case

The effect of rib orientation on flow and heat transfer in a four-pass square channel with skewed ribs in nonorthogonal-mode rotation was numerically studied by using omega-based Reynolds stress model (SMC−ω). Two cases are examined: in first case, the ribs are oriented with respect to the main flow direction at an angle of −45 deg in the first and third passage and at an angle of +45 deg in the second passage. The second case is identical to the first case with the ribs oriented at angle of +45 deg in the three passages. The calculations are carried out for a Reynolds number of 25,000, a rotation number of 0.24, and a density ratio of 0.13. The results show that the secondary flows induced by −45 deg ribs and by rotation combine partially destructively in the first and third passage of first case. In contrast, for second case, the secondary flows induced by +45 deg ribs and by rotation combine constructively in the first passage, while the flow is dominated by the vortices induced by +45 deg ribs in the third passage. In first case, a significant degradation of the heat transfer rate is observed on the coleading side of the first passage and on both cotrailing and coleading sides of the third as compared to second case. Consequently, the rib orientations at +45 deg are preferred in the radial outward flowing passage with an acceptable pressure drop. The numerical results are in agreement with the available experimental data.

Vibration and Buckling of Rotating, Pretwisted, Preconed Beams Including Coriolis Effects

1986 ◽  
Vol 108 (2) ◽  
pp. 140-149 ◽  
Author(s):  
K. B. Subrahmanyam ◽  
K. R. V. Kaza
Keyword(s):  
Equations Of Motion ◽  
Energy Functional ◽  
Solution Procedure ◽  
Thickness Ratio ◽  
The Other ◽  
Collective Effects ◽  
Coriolis Forces ◽  
Coriolis Effects ◽  
Axis Of Rotation ◽  
Setting Angle

The effects of pretwist, precone, setting angle and Coriolis forces on the vibration and buckling behavior of rotating, torsionally rigid, cantilevered beams are studied in this investigation. The beam is considered to be clamped on the axis of rotation in one case, and off the axis of rotation in the other. Two methods are employed for the solution of the vibration problem: one based upon a finite-difference approach using second-order central differences for solution of the equations of motion, and the other based upon the minimum of the total potential energy functional with a Ritz type of solution procedure making use of complex forms of shape functions for the dependent variables. Numerical results obtained by using these methods are compared to those existing in the literature for specialized simple cases. Results indicating the individual and collective effects of pretwist, precone, setting angle, thickness ratio, and Coriolis forces on the natural frequencies and the buckling boundaries are presented and discussed. Furthermore, it is shown that the inclusion of Coriolis effects is necessary for blades of moderate-to-large thickness ratios while these effects are not so important for small thickness ratio blades. Finally, the results show the possibility of buckling due to centrifugal softening terms for large values of precone and rotation.

Heat Transfer in a Rotating, Blade-Shaped Serpentine Cooling Passage With Discrete Ribbed Walls at High Reynolds Numbers

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Lesley M. Wright ◽  
Shang-Feng Yang ◽  
Hao-Wei Wu ◽  
Je-Chin Han ◽  
Ching-Pang Lee ◽  
...  
Keyword(s):  
Heat Transfer ◽  
High Reynolds Number ◽  
Reynolds Numbers ◽  
Pressure Side ◽  
Transfer Coefficients ◽  
First Passage ◽  
Heat Transfer Coefficients ◽  
The Third ◽  
High Reynolds Numbers ◽  
High Reynolds

Abstract This paper experimentally investigates the effect of rotation on heat transfer in a typical turbine blade, three-pass, serpentine coolant channel with discrete ribbed walls at high Reynolds numbers. To achieve the high Reynolds number (Re → 190,000) and low rotation number conditions, pressurized Freon R-134a vapor is utilized as the working fluid. Cooling flow in the first passage is radial outward; after the 180 deg tip turn, the flow is radial inward through the second passage; and after the 180 deg hub turn, the flow is radial outward in the third passage. The effects of rotation on the heat transfer coefficients were investigated at rotation numbers as low as 0.07 and Reynolds numbers from 85,000 to 187,000 (based on the first passage geometry and flow conditions). Heat transfer coefficients were measured using thermocouples embedded in copper plates to provide regionally averaged heat transfer coefficients. Heat transfer enhancement due to rotation is observed on the first passage, pressure-side with radially outward flow and the second passage, suction-side with radially inward flow, but a reduction in heat transfer is observed on the third passage pressure-side with radially outward flow. In addition, results from the discrete, broken ribs are compared with those from the same serpentine coolant passage with conventional, angled ribbed walls. A significant increase in the heat transfer due to the discrete ribs is observed in the first passage. These results can be useful for understanding real rotor blade coolant passage heat transfer under high Reynolds number and low rotation number conditions.

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