Computational and Experimental Investigation of Heat Transfer in Stationary and Rotating Internal Cooling Ducts with High Rotation Numbers

2017 ◽  
Author(s):  
Ryoichi S. Amano ◽  
Saman Beyhaghi ◽  
Ping Dong ◽  
Mandana S. Saravani ◽  
Madison Morrison
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Internal Cooling ◽  
Rotation Numbers ◽  
Cooling Ducts

Numerical Optimization, Characterization, and Experimental Investigation of Additively Manufactured Communicating Microchannels

2018 ◽  
Vol 140 (11) ◽  
Author(s):  
Kathryn L. Kirsch ◽  
Karen A. Thole
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Pressure Loss ◽  
Reynolds Numbers ◽  
Transport Systems ◽  
Optimized Design ◽  
Internal Cooling ◽  
Natural Systems ◽  
Flow And Heat Transfer ◽  
Successful Replication

The degree of complexity in internal cooling designs is tied to the capabilities of the manufacturing process. Additive manufacturing (AM) grants designers increased freedom while offering adequate reproducibility of microsized, unconventional features that can be used to cool the skin of gas turbine components. One such desirable feature can be sourced from nature; a common characteristic of natural transport systems is a network of communicating channels. In an effort to create an engineered design that utilizes the benefits of those natural systems, the current study presents wavy microchannels that were connected using branches. Two different wavelength baseline configurations were designed; then each was numerically optimized using a commercial adjoint-based method. Three objective functions were posed to (1) minimize pressure loss, (2) maximize heat transfer, and (3) maximize the ratio of heat transfer to pressure loss. All baseline and optimized microchannels were manufactured using laser powder bed fusion (L-PBF) for experimental investigation; pressure loss and heat transfer data were collected over a range of Reynolds numbers. The AM process reproduced the desired optimized geometries faithfully. Surface roughness, however, strongly influenced the experimental results; successful replication of the intended flow and heat transfer performance was tied to the optimized design intent. Even still, certain test coupons yielded performances that correlated well with the simulation results.

scholarly journals An Experimental Investigation on the Flow Characteristics Over Dimple Arrays Pertinent to Internal Cooling of Turbine Blades

2014 ◽  
Author(s):  
Wenwu Zhou ◽  
Hui Hu ◽  
Yu Rao
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Heat Transfer Enhancement ◽  
Channel Flow ◽  
Flat Surface ◽  
Reynolds Shear Stress ◽  
Turbine Blades ◽  
Flow Characteristics ◽  
Internal Cooling ◽  
Transfer Enhancement

Due to the dimple’s unique characteristics of comparatively low pressure loss penalty and good heat transfer enhancement performance, dimple provides a very desirable alternative internal cooling technique for gas turbine blades. In the present study, an experimental investigation was conducted to quantify the flow characteristics over staggered dimple arrays and to examine the vortex structures inside the dimples. In addition to the surface pressure measurements, a high-resolution digital Particle Image Velocimetry (PIV) system was also utilized to achieve detailed flow field measurements to quantify the characteristics of the turbulent channel flow over the dimple arrays in terms of the ensemble-averaged velocity, Reynolds shear stress and turbulence kinetic energy (TKE) distributions. The experimental measurement results show that the friction factor of the dimpled surface is much higher than that of a flat surface. The measured pressure distribution within a dimple reveals clearly that flow separation and attachment would occur inside each dimple. In comparison with those of a conventional channel flow with flat surface, the channel flow over the dimpled arrays was found to have much stronger Reynolds stress and higher TKE level. Such unique flow characteristics are believed to be the reasons why a dimpled surface would have a better heat transfer enhancement performance for internal cooling of turbine blades as reported in those previous studies.

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.

Numerical Optimization, Characterization, and Experimental Investigation of Additively Manufactured Communicating Microchannels

2018 ◽  
Author(s):  
Kathryn L. Kirsch ◽  
Karen A. Thole
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Additive Manufacturing ◽  
Manufacturing Process ◽  
Pressure Loss ◽  
Transport Systems ◽  
Optimized Design ◽  
Internal Cooling ◽  
Natural Systems ◽  
Successful Replication

The degree of complexity in internal cooling designs is tied to the capabilities of the manufacturing process. Additive manufacturing grants designers increased freedom while offering adequate reproducibility of micro-sized, unconventional features that can be used to cool the skin of gas turbine components. One such desirable feature can be sourced from nature; a common characteristic of natural transport systems is a network of communicating channels. In an effort to create an engineered design that utilizes the benefits of those natural systems, the current study presents wavy microchannels that were connected using branches. Two different wavelength baseline configurations were designed, then each were numerically optimized using a commercial adjoint-based method. Three objective functions were posed to (1) minimize pressure loss, (2) maximize heat transfer, and (3) maximize the ratio of heat transfer to pressure loss. All baseline and optimized microchannels were manufactured using Laser Powder Bed Fusion for experimental investigation; pressure loss and heat transfer data were collected over a range of Reynolds numbers. The additive manufacturing process reproduced the desired optimized geometries faithfully. Surface roughness, however, strongly influenced the experimental results; successful replication of the intended flow and heat transfer performance was tied to the optimized design intent. Even still, certain test coupons yielded performances that correlated well with the simulation results.

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.

Heat Transfer and Flow Field Measurements in a Rib-Roughened Branch of a Rotating Two-Pass Duct

2003 ◽  
Author(s):  
Yves Servouze ◽  
J. Chris Sturgis
Keyword(s):  
Heat Transfer ◽  
Flow Direction ◽  
Turbine Blades ◽  
Field Measurements ◽  
Reynolds Numbers ◽  
Experimental Program ◽  
Internal Cooling ◽  
Nusselt Numbers ◽  
Critical Technology ◽  
Rotation Numbers

Internal cooling of gas engine turbine blades is a critical technology. This paper addresses the subject by presenting the results of an experimental program that uses a rotating, square-cross-section, U-shaped channel to model the blade coolant passage. The channel is heated, instrumented and furnished with angled ribs (60° to flow direction) on two walls of one branch. Air is the coolant. Internal Nusselt numbers are calculated on the four walls at various locations along the flow in both the centrifugal and centripetal branches for two Reynolds numbers (5000, 25000) and several Rotation numbers (0.033, 0.066, 0.1, 0.33). Data indicate greater heat transfer on the trailing wall than leading wall in the centrifugal branch; likewise, for the upper wall compared to the lower wall. Centripetal branch heat transfer is affected by bend effects. Particle Image Velocimetry measurements in both the stationary and rotating channels reveal the presence of vortices. The large number of measurements is useful for comparison with numerical calculations.

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

2004 ◽  
Author(s):  
A. K. Sleiti ◽  
J. S. Kapat
Keyword(s):  
Heat Transfer ◽  
Turbine Blades ◽  
Density Ratio ◽  
Wall Region ◽  
Internal Cooling ◽  
Cooling Channels ◽  
Streamline Curvature ◽  
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 (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. 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 4-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.

Internal Cooling in 4:1 AR Passages at High Rotation Numbers

2004 ◽  
Author(s):  
Fuguo Zhou ◽  
Jonathan Lagrone ◽  
Sumanta Acharya
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Density Ratio ◽  
Rotational Axis ◽  
Internal Cooling ◽  
Transfer Enhancement ◽  
Rotation Numbers ◽  
Slip Rings ◽  
Rotating Frames ◽  
Density Ratios

Heat transfer and pressure drop measurements are reported for a rotating 4:1 aspect ratio (AR, (the ratio of the width of leading/trailing wall to the height of sidewalls) smooth coolant passage for Reynolds number in the range of 10,000–150,000, rotation number in the range of 0–0.6, and density ratios between 0.1–0.2. The measurements are performed for both 90° and 45° orientations of the coolant passage relative to the rotational axis. These measurements are done in a rotating heat transfer rig utilizing segmented foil heated elements and thermocouples, with slip rings providing the interface between the stationary and rotating frames. Results indicate that beyond specific Ro values (different values for the inlet and outlet passages) the expected trends of heat transfer enhancement on the destabilized surface and degradation on the stabilized surface are reversed. The inlet leading surface shows enhancement with Ro only at low Re, and shows degradation at high Re. Increasing density ratio enhances the heat transfer on all walls. Orientation of the coolant passage relative to the rotational axis has an important effect, with the 45° orientation reducing the heat transfer on the destabilized surface and enhancing it on the stabilized surface.

Heat Transfer Enhancement in Turbine Blade Internal Cooling Ducts

2014 ◽  
Vol 1016 ◽  
pp. 743-747
Author(s):  
Mehmet Karaman ◽  
Ibrahim Özkol ◽  
Güven Kömürgöz
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Turbine Blades ◽  
Fuel Mixture ◽  
Internal Cooling ◽  
Flow Conditions ◽  
Atmospheric Flow ◽  
Rotary Engine ◽  
Duct Geometry ◽  
Cooling Ducts

Gas turbine is a type of rotary engine that consists of compressor, combustion chamber, and turbine sections. This type of engine works in the Brayton Cycle principle that is compression of atmospheric flow, combustion of air-fuel mixture and expanding high temperature combustion flow to generate power output from turbine. The aim of this study is to determine the duct geometry and flow conditions of the gas turbine blades having the internal cooling ducts that acquire highest heat transfer on turbine blades. For different design of internal duct geometries and flow conditions, Fluent solver is used and solutions are validated with Han’s experimental results.

Internal Cooling in 4:1 AR Passages at High Rotation Numbers

2007 ◽  
Vol 129 (12) ◽  
pp. 1666-1675 ◽  
Author(s):  
Fuguo Zhou ◽  
Jonathan Lagrone ◽  
Sumanta Acharya
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Large Scale ◽  
Density Ratio ◽  
Rotational Axis ◽  
Internal Cooling ◽  
Transfer Enhancement ◽  
Rotation Numbers ◽  
Density Ratios

Heat transfer and pressure drop measurements are reported for a rotating 4:1 aspect ratio (AR) smooth two-pass coolant passage for Reynolds number in the range of 10,000–150,000, rotation number in the range of 0–0.6, and density ratios in the range of 0.1–0.2. The measurements are performed for both 90deg and 45deg orientations of the coolant passage relative to the rotational axis. A large-scale rotating heat transfer rig is utilized, with the test section consisting of segmented foil-heated elements and thermocouples. Results for the 4:1 AR indicate that beyond specific Ro values (different values for the inlet and outlet passages), the expected trends of heat transfer enhancement on the destabilized surface and degradation on the stabilized surface are arrested or reversed. Unlike the 1:1 AR, the inlet-leading surface for the 4:1 AR shows enhancement with Ro at low Re (less than 20,000) and shows the expected degradation only at high Re. Increasing the density ratio enhances the heat transfer on all walls. Orientation of the coolant passage relative to the rotational axis has an important effect, with the 45deg orientation reducing the heat transfer on the destabilized surface and enhancing it on the stabilized surface.

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