scholarly journals Heat Transfer Augmentation Technologies for Internal Cooling of Turbine Components of Gas Turbine Engines

2013 ◽  
Vol 2013 ◽  
pp. 1-32 ◽  
Author(s):  
Phil Ligrani
Keyword(s):  
Heat Transfer ◽  
Friction Factor ◽  
Thermal Performance ◽  
Density Ratio ◽  
Extensive Literature ◽  
Internal Cooling ◽  
Cooling Channels ◽  
Heat Transfer Augmentation ◽  
Pin Fins ◽  
Rib Turbulators

To provide an overview of the current state of the art of heat transfer augmentation schemes employed for internal cooling of turbine blades and components, results from an extensive literature review are presented with data from internal cooling channels, both with and without rotation. According to this survey, a very small number of existing investigations consider the use of combination devices for internal passage heat transfer augmentation. Examples are rib turbulators, pin fins, and dimples together, a combination of pin fins and dimples, and rib turbulators and pin fins in combination. The results of such studies are compared with data obtained prior to 2003 without rotation influences. Those data are comprised of heat transfer augmentation results for internal cooling channels, with rib turbulators, pin fins, dimpled surfaces, surfaces with protrusions, swirl chambers, or surface roughness. This comparison reveals that all of the new data, obtained since 2003, collect within the distribution of globally averaged data obtained from investigations conducted prior to 2003 (without rotation influences). The same conclusion in regard to data distributions is also reached in regard to globally averaged thermal performance parameters as they vary with friction factor ratio. These comparisons, made on the basis of such judgment criteria, lead to the conclusion that improvements in our ability to provide better spatially-averaged thermal protection have been minimal since 2003. When rotation is present, existing investigations provide little evidence of overall increases or decreases in overall thermal performance characteristics with rotation, at any value of rotation number, buoyancy parameter, density ratio, or Reynolds number. Comparisons between existing rotating channel experimental data and the results obtained prior to 2003, without rotation influences, also show that rotation has little effect on overall spatially-averaged thermal performance as a function of friction factor.

Thermal Performance of Angled, V-Shaped, and W-Shaped Rib Turbulators in Rotating Rectangular Cooling Channels (AR = 4:1)

2004 ◽  
Author(s):  
Lesley M. Wright ◽  
Wen-Lung Fu ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Thermal Performance ◽  
Density Ratio ◽  
Cooling Channels ◽  
Frictional Losses ◽  
Flow Parameters ◽  
Rib Turbulators ◽  
Overall Performance ◽  
Channel Orientation

An experimental study was performed to measure the heat transfer distributions and frictional losses in rotating ribbed channels with an aspect ratio of 4:1. Angled, discrete angled, V-shaped, and discrete V-shaped ribs were investigated, as well as the newly proposed W-shaped and discrete W-shaped ribs. In all cases, the ribs are placed on both the leading and trailing surfaces of the channel, and they are oriented 45° to the mainstream flow. The rib height-to-hydraulic diameter ratio (e/D) is 0.078, and the rib pitch-to-height ratio (P/e) is 10. The channel orientation with respect to the direction of rotation is 135°. The range of flow parameters includes Reynolds number (Re = 10000–40000), rotation number (Ro = 0.0–0.15), and inlet coolant-to-wall density ratio (Δρ/ρ = 0.12). Both heat transfer and pressure measurements were taken, so the overall performance of each rib configuration could be evaluated. It was determined that the W-shaped and discrete W-shaped ribs had the superior heat transfer performance in both non-rotating and rotating channels. However, these two configurations also incurred the greatest frictional losses while the discrete V-shaped and discrete angled ribs resulted in the lowest pressure drop. Based on the heat transfer enhancement and the pressure drop penalty, the discrete V-shaped ribs and the discrete W-shaped ribs exhibit the best overall thermal performance in both rotating and non-rotating channels. These configurations are followed closely by the W-shaped ribs. The angled rib configuration resulted in the worst performance of the six configurations of the present study.

Thermal Performance of Angled, V-Shaped, and W-Shaped Rib Turbulators in Rotating Rectangular Cooling Channels (AR=4:1)

2004 ◽  
Vol 126 (4) ◽  
pp. 604-614 ◽  
Author(s):  
Lesley M. Wright ◽  
Wen-Lung Fu ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Thermal Performance ◽  
Density Ratio ◽  
Cooling Channels ◽  
Frictional Losses ◽  
Flow Parameters ◽  
Rib Turbulators ◽  
Overall Performance ◽  
Channel Orientation

An experimental study was performed to measure the heat transfer distributions and frictional losses in rotating ribbed channels with an aspect ratio of 4:1. Angled, discrete angled, V-shaped, and discrete V-shaped ribs were investigated, as well as the newly proposed W-shaped and discrete W-shaped ribs. In all cases, the ribs are placed on both the leading and trailing surfaces of the channel, and they are oriented 45 deg to the mainstream flow. The rib height-to-hydraulic diameter ratio e/D is 0.078, and the rib pitch-to-height ratio P/e is 10. The channel orientation with respect to the direction of rotation is 135 deg. The range of flow parameters includes Reynolds number (Re=10,000–40,000), rotation number Ro=0.0-0.15, and inlet coolant-to-wall density ratio (Δρ/ρ=0.12). Both heat transfer and pressure measurements were taken, so the overall performance of each rib configuration could be evaluated. It was determined that the W-shaped and discrete W-shaped ribs had the superior heat transfer performance in both nonrotating and rotating channels. However, these two configurations also incurred the greatest frictional losses while the discrete V-shaped and discrete angled ribs resulted in the lowest pressure drop. Based on the heat transfer enhancement and the pressure drop penalty, the discrete V-shaped ribs and the discrete W-shaped ribs exhibit the best overall thermal performance in both rotating and nonrotating channels. These configurations are followed closely by the W-shaped ribs. The angled rib configuration resulted in the worst performance of the six configurations of the present study.

scholarly journals Thermal Performance of V-Shaped and X-Shaped Ribs in Trapezoidal Cooling Channels

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4826
Author(s):  
Wei-Jie Su ◽  
Yao-Hsien Liu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Thermal Performance ◽  
Secondary Flows ◽  
Internal Cooling ◽  
Transfer Enhancement ◽  
Trapezoidal Channel ◽  
Cooling Channels ◽  
Rib Turbulators ◽  
Staggered Arrangement

Convective heat transfer enhancement using rib turbulators is effective for turbine blade internal cooling. Detailed heat transfer measurement of X-shaped ribs in a trapezoidal cooling channel was experimentally conducted using infrared thermography. The novel X-shaped ribs were designed by combining two V-shaped ribs, and more secondary flows generated by the X rib delivered higher heat transfer enhancement. The Reynolds numbers in this study were 10,000, 20,000, and 30,000. These ribs were installed on two opposite walls of a trapezoidal channel in a staggered arrangement. The rib pitch-to-height ratios were 10 and 20, and the rib height-to-hydraulic diameter ratio was 0.128. Results indicated that higher heat transfer distribution was observed in the vicinity of the shorter base in the trapezoidal channel. The full X-shaped ribs and the V-shaped ribs demonstrated the highest Nusselt number ratios among all the cases. Although full X-shaped ribs contributed to higher heat transfer improvement due to intensified secondary flows, they also caused significant pressure loss. Therefore, the cutback X-shaped ribs were proposed by removing a segment in the rib at either upstream or downstream region. Consequently, the upstream cutback X-shaped rib and the V-shaped rib produced the highest thermal performance in this trapezoidal channel.

scholarly journals Heat Transfer From Low Aspect Ratio Pin Fins

2007 ◽  
Author(s):  
Michael E. Lyall ◽  
Alan A. Thrift ◽  
Atul Kohli ◽  
Karen A. Thole
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Gas Turbines ◽  
Channel Height ◽  
Internal Cooling ◽  
Number Range ◽  
Pin Fin ◽  
Heat Transfer Augmentation ◽  
Low Aspect Ratio ◽  
Pin Fins

The performance of many engineering devices from power electronics to gas turbines is limited by thermal management. Heat transfer augmentation in internal flows is commonly achieved through the use of pin fins, which increase both surface area and turbulence. The present research is focused on internal cooling of turbine airfoils using a single row of circular pin fins that is oriented perpendicular to the flow. Low aspect ratio pin fins were studied whereby the channel height to pin diameter was unity. A number of spanwise spacings were investigated for a Reynolds number range between 5000 to 30,000. Both pressure drop and spatially-resolved heat transfer measurements were taken. The heat transfer measurements were made on the endwall of the pin fin array using infrared thermography and on the pin surface using discrete thermocouples. The results show that the heat transfer augmentation relative to open channel flow is the highest for smallest spanwise spacings and lowest Reynolds numbers. The results also indicate that the pin fin heat transfer is higher than the endwall heat transfer.

Latticework (Vortex) Cooling Effectiveness: Part 2 — Rotating Channel Experiments

2004 ◽  
Author(s):  
S. Acharya ◽  
Fuguo Zhou ◽  
Jonathan Lagrone ◽  
Gazi Mahmood ◽  
Ronald S. Bunker
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Density Ratio ◽  
Transfer Coefficients ◽  
Performance Factors ◽  
Nusselt Numbers ◽  
Friction Factors ◽  
Smooth Channel ◽  
Rib Turbulators ◽  
Density Ratios

The heat transfer and pressure drop characteristics of latticework coolant blade passages have been investigated experimentally under conditions of rotation. Stationary studies with the latticework configuration have shown potential advantages including spatially-uniform streamwise distributions of the heat transfer coefficient, greater blade strength, and enhancement levels comparable to conventional rib turbulators. In the present study, a latticework coolant passage, with orthogonal-ribs, is studied in a rotating heat transfer test-rig for a range of Reynolds numbers (Res), Rotation numbers (Ros), and density ratios. Measurements indicate that for Res≥20,000, the latticework coolant passage provides very uniform streamwise distributions of the Nusselt number (Nus) with enhancement levels (relative to smooth-channel values) in the range of 2.0 to 2.5. No significant dependence of Nus on Ros and density ratio is observed except at lower Res values (≤10,000). Nusselt numbers are highest immediately downstream of a turn indicating that bend-effects play a major role in enhancing heat transfer. Friction factors are relatively insensitive to Ros, and thermal performance factors at higher Res values appear to be comparable to those obtained with conventional rib-turbulators. The present study indicates that latticework cooling geometry can provide comparable heat transfer enhancements and thermal performance factors as conventional rib-turbulators, with potential benefits of streamwise uniformity in the heat transfer coefficients and added blade strength.

Investigation of Innovative Trailing Edge Cooling Configurations With Enlarged Pedestals and Square or Semicircular Ribs: Part II—Numerical Results

2008 ◽  
Author(s):  
Emiliano Di Carmine ◽  
Bruno Facchini ◽  
Luca Mangani
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Convective Heat Transfer Coefficient ◽  
Turbulence Models ◽  
Internal Cooling ◽  
Trailing Edge ◽  
Pressure Losses ◽  
Structural Resistance ◽  
Pin Fins ◽  
Rib Turbulators

Trailing edge is a critical region for turbine airfoils since this part of the blade has to match aerodynamic, cooling and structural requirements at the same time. In fact aerodynamic losses are strictly related to trailing edge thickness which, on the contrary, tends to be increased to implement an internal cooling system, in order to face high thermal loads. At the moment the most employed devices consist of pin fins of various shapes, which contribute to both heat transfer enhancement and structural resistance improvement. Enlarged pedestals decrease pressure losses in comparison with multirow pin fins, even if the heat transfer increase is limited. This work deals with the investigation of the usage of enlarged pedestals, inserted in a wedge shaped duct, in conjunction with square or semicircular rib turbulators. The aim of the analysis is the evaluation of the convective Heat Transfer Coefficient (HTC) distribution over the endwall surface and the pressure drop of the converging duct. Numerical analysis used 3D RANS calculations. An in-house modified object-oriented CFD code and a commercial one were used. Several turbulence models and mesh types were tested. Numerical calculations were compared with experimental results obtained on the same geometries using a transient Thermochromic Liquid Crystals (TLC) based technique. Goals of this comparison are both the evaluation of the accuracy of CFD packages with standard two equation turbulence models in heat transfer problems with complex geometries and the analysis of flow details to complete and support experimental activity.

Fluid Flow and Heat Transfer in Rotating Curved Duct at High Rotation and Density Ratios

2005 ◽  
Vol 127 (4) ◽  
pp. 659-667 ◽  
Author(s):  
A. K. Sleiti ◽  
J. S. Kapat
Keyword(s):  
Heat Transfer ◽  
Turbine Blades ◽  
Density Ratio ◽  
Reynolds Stress Model ◽  
Wall Region ◽  
Internal Cooling ◽  
Cooling Channels ◽  
Rotation Numbers ◽  
Effects Of Rotation ◽  
Density Ratios

Prediction of flow field and heat transfer of high rotation numbers and density ratio flow in a square internal cooling channels of turbine blades with U-turn as tested by Wagner et al. (ASME J. Turbomach., 113, pp. 42–51, 1991) is the main focus of this study. Rotation, buoyancy, and strong curvature affect the flow within these channels. Due to the fact that RSM turbulence model can respond to the effects of rotation, streamline curvature and anisotropy without the need for explicit modeling, it is employed for this study as it showed improved prediction compared to isotropic two-equation models. The near wall region was modeled using enhanced wall treatment approach. The Reynolds Stress Model (RSM) was validated against available experimental data (which are primarily at low rotation and buoyancy numbers). The model was then used for cases with high rotation numbers (as much as 1.29) and high-density ratios (up to 0.4). Particular attention is given to how secondary flow, velocity and temperature profiles, turbulence intensity, and Nusselt number area affected by Coriolis and buoyancy/centrifugal forces caused by high levels of rotation and buoyancy in the immediate vicinity of the bend. The results showed that four-side-average Nu, similar to low Ro cases, increases linearly by increasing rotation number and, unlike low Ro cases, decreases slightly by increasing density ratio.

Characteristics of Partial Length Circular Pin Fins as Heat Transfer Augmentors for Airfoil Internal Cooling Passages

1989 ◽  
Author(s):  
S. C. Arora ◽  
W. Abdel-Messeh
Keyword(s):  
Heat Transfer ◽  
Friction Factor ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
The Other ◽  
Internal Cooling ◽  
Partial Length ◽  
Smooth Channel ◽  
Pin Fins ◽  
Turbine Airfoils

Pin fins are commonly used as heat transfer augmentors for internal cooling of turbine airfoils. These pins may extend from one wall to the other or may be segmented to meet specific requirements of removing the airfoil’s varying heat load. Three configurations of the partial pins were tested in a 25:1 aspect ratio channel and the results are compared with those for the full pins. The array average heat transfer rate decreases linearly with increasing gap and is bounded by the value for full pins at one end and that for the smooth channel at the other. However, the local distribution of the Nusselt number and the average for each of the two walls depends on the configuration of the partial pins. The friction factor was lower for partial pins than for the full pins and also decreased with increasing gap. For the configuration with all partial pins on one wall, the friction factor was found to be the lowest with no change in the corresponding heat transfer rate from a wall with pins.

Heat Transfer in Rotating Rectangular Cooling Channels AR=4 With Angled Ribs

2002 ◽  
Vol 124 (4) ◽  
pp. 617-625 ◽  
Author(s):  
Todd S. Griffith ◽  
Luai Al-Hadhrami ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Rotation Number ◽  
Strong Dependence ◽  
Rectangular Channel ◽  
Density Ratio ◽  
Transfer Enhancement ◽  
Cooling Channels ◽  
Flow Parameters ◽  
Rib Turbulators

An investigation into determining the effect of rotation on heat transfer in a rib-roughened rectangular channel with aspect ratio of 4:1 is detailed in this paper. A broad range of flow parameters have been selected including Reynolds number (Re=5000–40000), rotation number (Ro=0.04–0.3) and coolant to wall density ratio at the inlet Δρ/ρi=0.122. The rib turbulators, attached to the leading and trailing surface, are oriented at an angle α=45deg to the direction of flow. The effect of channel orientations of β=90 deg and 135 deg with respect to the plane of rotation is also investigated. Results show that the narrow rectangular passage exhibits a much higher heat transfer enhancement for the ribbed surface than the square and 2:1 duct previously investigated. Also, duct orientation significantly affects the leading and side surfaces, yet does not have much affect on the trailing surfaces for both smooth and ribbed surfaces. Furthermore, spanwise heat transfer distributions exist across the leading and trailing surfaces and are accentuated by the use of angled ribs. The smooth and ribbed case trailing surfaces and smooth case side surfaces exhibited a strong dependence on rotation number.

Rib Spacing Effect on Heat Transfer and Pressure Loss in a Rotating Two-Pass Rectangular Channel (AR=1:2) With 45-Degree Angled Ribs

2006 ◽  
Author(s):  
Yao-Hsien Liu ◽  
Lesley M. Wright ◽  
Wen-Lung Fu ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Thermal Performance ◽  
Rectangular Channel ◽  
Spacing Effect ◽  
Turbine Blades ◽  
Internal Cooling ◽  
Transfer Enhancement ◽  
Cooling Channels ◽  
Smooth Channel

Rib turbulators are commonly used to enhance the heat transfer within internal cooling passages of advanced gas turbine blades. Many factors affect the thermal performance of a cooling channel with ribs. This study experimentally investigates the effect of rib spacing on the heat transfer enhancement, pressure penalty, and thus the overall thermal performance in both rotating and non-rotating rectangular, cooling channels. In the 1:2 rectangular channels, 45° angled ribs are placed on the leading and trailing surfaces. The pitch of the ribs varies, so rib pitch-to-height (P/e) ratios of 10, 7.5, 5, and 3 are considered. Square ribs with a 1.59 mm × 1.59 mm cross-section are used for all spacings, so the height-to-hydraulic diameter (e/Dh) ratio remains constant at 0.094. With a constant rotational speed of 550 rpm and the Reynolds number ranging from 5000 to 40000, the rotation number in turn varies from 0.2 to 0.02. Because the skewed turbulators induce secondary flow along the length of the rib, the very close rib spacing of P/e = 3, has the best thermal performance in both rotating and non-rotating channels. This close spacing yields the greatest heat transfer enhancement, while the P/e = 5 spacing has the greatest pressure penalty. In addition, the effect of rotation is more pronounced in the channel with the rib spacing of 3. As more ribs are added, the channel is approaching a smooth channel, and the strength of the rotation induced vortices increases.

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