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.

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.

Numerical investigation of fluid flow structure and heat transfer in a passage with continuous and truncated V-shaped ribs

2015 ◽  
Vol 25 (1) ◽  
pp. 171-189 ◽  
Author(s):  
Shian Li ◽  
Gongnan Xie ◽  
Bengt Sunden
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Fluid Flow ◽  
Pressure Drop ◽  
Heat Transfer Enhancement ◽  
Thermal Performance ◽  
Internal Cooling ◽  
Transfer Enhancement ◽  
Content Type ◽  
Flow And Heat Transfer

Purpose – The employment of continuous ribs in a passage involves a noticeable pressure drop penalty, while other studies have shown that truncated ribs may provide a potential to reduce the pressure drop while keeping a significant heat transfer enhancement. The purpose of this paper is to perform computer-aided simulations of turbulent flow and heat transfer of a rectangular cooling passage with continuous or truncated 45-deg V-shaped ribs on opposite walls. Design/methodology/approach – Computational fluid dynamics technique is used to study the fluid flow and heat transfer characteristics in a three-dimensional rectangular passage with continuous and truncated V-shaped ribs. Findings – The inlet Reynolds number, based on the hydraulic diameter, is ranged from 12,000 to 60,000 and a low-Re k-e model is selected for the turbulent computations. The local flow structure and heat transfer in the internal cooling passages are presented and the thermal performances of the ribbed passages are compared. It is found that the passage with truncated V-shaped ribs on opposite walls provides nearly equivalent heat transfer enhancement with a lower (about 17 percent at high Reynolds number of 60,000) pressure loss compared to a passage with continuous V-shaped ribs or continuous transversal ribs. Research limitations/implications – The fluid is incompressible with constant thermophysical properties and the flow is steady. The passage is stationary. Practical implications – New and additional data will be helpful in the design of ribbed passages to achieve a good thermal performance. Originality/value – The results imply that truncated V-shaped ribs are very effective in improving the thermal performance and thus are suggested to be applied in gas turbine blade internal cooling, especially at high velocity or Reynolds number.

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.

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.

Heat Transfer Enhancement in a Rectangular (AR = 3:1) Channel With V-Shaped Dimples

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
C. Neil Jordan ◽  
Lesley M. Wright
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Liquid Crystal ◽  
Pressure Drop ◽  
Heat Transfer Enhancement ◽  
Thermal Performance ◽  
Secondary Flows ◽  
Transfer Enhancement ◽  
Reduced Pressure

An alternative to ribs for internal heat transfer enhancement of gas turbine airfoils is dimpled depressions. Relative to ribs, dimples incur a reduced pressure drop, which can increase the overall thermal performance of the channel. This experimental investigation measures detailed Nusselt number ratio distributions obtained from an array of V-shaped dimples (δ/D = 0.30). Although the V-shaped dimple array is derived from a traditional hemispherical dimple array, the V-shaped dimples are arranged in an in-line pattern. The resulting spacing of the V-shaped dimples is 3.2D in both the streamwise and spanwise directions. A single wide wall of a rectangular channel (AR = 3:1) is lined with V-shaped dimples. The channel Reynolds number ranges from 10,000–40,000. Detailed Nusselt number ratios are obtained using both a transient liquid crystal technique and a newly developed transient temperature sensitive paint (TSP) technique. Therefore, the TSP technique is not only validated against a baseline geometry (smooth channel), but it is also validated against a more established technique. Measurements indicate that the proposed V-shaped dimple design is a promising alternative to traditional ribs or hemispherical dimples. At lower Reynolds numbers, the V-shaped dimples display heat transfer and friction behavior similar to traditional dimples. However, as the Reynolds number increases to 30,000 and 40,000, secondary flows developed in the V-shaped concavities further enhance the heat transfer from the dimpled surface (similar to angled and V-shaped rib induced secondary flows). This additional enhancement is obtained with only a marginal increase in the pressure drop. Therefore, as the Reynolds number within the channel increases, the thermal performance also increases. While this trend has been confirmed with both the transient TSP and liquid crystal techniques, TSP is shown to have limited capabilities when acquiring highly resolved detailed heat transfer coefficient distributions.

Experimental Study on Flow Behavior and Heat Transfer Enhancement with Distinct Dimpled Gas Turbine Blade Internal Cooling Channel

2021 ◽  
pp. 1-28
Author(s):  
Farah Nazifa Nourin ◽  
Ryoichi S. Amano
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Transfer Enhancement ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Thermal Performance ◽  
Diameter Ratio ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Transfer Enhancement

Abstract The study presents the investigation on heat transfer distribution along a gas turbine blade internal cooling channel. Six different cases were considered in this study, using the smooth surface channel as a baseline. Three different dimples depth-to-diameter ratios with 0.1, 0.25, and 0.50 were considered. Different combinations of partial spherical and leaf dimples were also studied with the Reynolds numbers of 6,000, 20,000, 30,000, 40,000, and 50,000. In addition to the experimental investigation, the numerical study was conducted using Large Eddy Simulation (LES) to validate the data. It was found that the highest depth-to-diameter ratio showed the highest heat transfer rate. However, there is a penalty for increased pressure drop. The highest pressure drop affects the overall thermal performance of the cooling channel. The results showed that the leaf dimpled surface is the best cooling channel based on the highest Reynolds number's heat transfer enhancement and friction factor. However, at the lowest Reynolds number, partial spherical dimples with a 0.25 depth to diameter ratio showed the highest thermal performance.

Full Surface Heat Transfer Measurement of a Turbine Internal Cooling System Using a Large Scaled Model

2018 ◽  
Author(s):  
Nojin Park ◽  
Changmin Son ◽  
Jangsik Yang ◽  
Changyong Lee ◽  
Kidon Lee
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Enhancement ◽  
Pressure Loss ◽  
Cooling System ◽  
Surface Heat ◽  
Internal Cooling ◽  
Transfer Enhancement ◽  
Scaled Model ◽  
Surface Heat Transfer

A series of experiments were conducted to investigate the detailed heat transfer characteristics of a large scaled model of a turbine blade internal cooling system. The cooling system has one passage in the leading edge and a triple passage for the remained region with two U-bends. A large scaled model (2 times) is designed to acquire high resolution measurement. The similarity of the test model was conducted with Reynolds number at the inlet of the internal cooling system. The model is designed to simulate the flow at engine condition including film extractions to match the changes in flowrates through the internal cooling system. Also, 45 deg ribs were installed for heat transfer enhancement. The experiments were performed varying Reynolds number in the range of 20,000 to 100,000 with and without ribs under stationary condition. This study employs transient heat transfer technique using thermochromic liquid crystal (TLC) to obtain full surface heat transfer distributions. The results show the detailed heat transfer distributions and pressure loss. The characteristics of pressure loss is largely dependent on the changes in cross-sectional area along the passages, the presence of U-bends and the extraction of coolant flow through film holes. The local and area averaged Nusselt number were compared to available correlations. Finally, the thermal performance counting the heat transfer enhancement as well as pressure penalty is presented.

Effect of 45-Deg Rib Orientations on Heat Transfer in a Rotating Two-Pass Channel With Aspect Ratio From 4:1 to 2:1

2019 ◽  
Author(s):  
Izzet Sahin ◽  
Andrew F. Chen ◽  
Chao-Cheng Shiau ◽  
Je-Chin Han ◽  
Robert Krewinkel
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Aspect Ratio ◽  
Heat Transfer Enhancement ◽  
Rotation Number ◽  
Pressure Loss ◽  
Heat Transfer Analysis ◽  
Internal Cooling ◽  
Transfer Enhancement ◽  
First Passage

Abstract The internal cooling passages of gas turbine blades mostly have varying aspect ratios from one passage to another. However, there are limited data available in the open literature that used a reduced cross-section and aspect ratio, AR, after the tip turn. Therefore, the current study presents heat transfer and pressure drop of three different α = 45° profiled rib orientations, typical parallel (usual), reversed parallel (unusual), and criss-cross patterns in a rotating two-pass rectangular channel with AR = 4:1 and 2:1 in the first radially outward flow and second radially inward flow passages respectively. For each rib orientation, regional averaged heat transfer results are obtained for both the flow passages with the Reynolds number ranging from 10,000 to 70,000 for the first passage and 16000 to 114000 for the second passage with a rotational speed range of 0 rpm to 400 rpm. This results in the highest rotation number of 0.39 and 0.16 for the first and second passage respectively. The effects of rib orientation, aspect ratio variation, 180° tip turn, and rotation number on the heat transfer and pressure drop will be addressed. According to the results, for usual, unusual and criss-cross rib patterns, increasing rotation number causes the heat transfer to decrease on the leading surface and increase on the trailing surface for the first passage and vice versa for the second passage. Overall heat transfer enhancement of the usual and unusual rib patterns is higher than criss-cross one. In terms of the pressure losses, the criss-cross rib pattern has the lowest and the usual rib pattern has the highest-pressure loss coefficients. When pressure loss and heat transfer enhancement are both taken into account together, the criss-cross or unusual rib pattern might be an option to use in the internal cooling method. Therefore, the results can be useful for turbine blade internal cooling design and heat transfer analysis.

Lateral-Flow Effect on Endwall Heat Transfer and Pressure Drop in a Pin-Fin Trapezoidal Duct of Various Pin Shapes

2000 ◽  
Vol 123 (1) ◽  
pp. 133-139 ◽  
Author(s):  
Jenn-Jiang Hwang ◽  
Chau-Ching Lu
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Flow Rate ◽  
Lateral Flow ◽  
Transfer Enhancement ◽  
Pin Fin ◽  
Flow Reynolds Number ◽  
Outlet Flow ◽  
Flow Through

The effects of lateral-flow ejection 0<ε<1.0, pin shapes (square, diamond, and circular), and flow Reynolds number (6000<Re<40,000) on the endwall heat transfer and pressure drop for turbulent flow through a pin-fin trapezoidal duct are studied experimentally. A staggered pin array of five rows and five columns is inserted in the trapezoidal duct, with the same spacings between the pins in the streamwise and spanwise directions: Sx/d=Sy/d=2.5. Three different-shaped pins of length from 2.5<l/d<4.6 span the distance between two endwalls of the trapezoidal duct. Results reveal that the pin-fin trapezoidal duct with lateral-flow rate of ε=0.3-0.4 has a local minimum endwall-averaged Nusselt number and Euler number for all pin shapes investigated. The trapezoidal duct of lateral outlet flow only (ε=1.0) has the highest endwall heat transfer and pressure drop. Moreover, the square pin results in a better heat transfer enhancement than the diamond pin, and subsequently than the circular pin. Finally, taking account of the lateral-flow rate and the flow Reynolds number, the work develops correlations of the endwall-averaged heat transfer with three different pin shapes.

Heat Transfer in Rotating Multi-Pass Rectangular Smooth Channel With and Without a Turning Vane in Hub Region

2013 ◽  
Author(s):  
Jiang Lei ◽  
Shiou-Jiuan Li ◽  
Je-Chin Han ◽  
Luzeng Zhang ◽  
Hee-Koo Moon
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Reynolds Number ◽  
Density Ratio ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
The Third ◽  
Rotation Numbers ◽  
Smooth Channel ◽  
Turn Region

This paper experimentally investigates the effect of a turning vane on hub region heat transfer in a multi-pass rectangular smooth channel at high rotation numbers. The experimental data were taken in the second and the third passages (Aspect Ratio = 2:1) connected by an 180° U-bend. The flow was radial inward in the second passage and was radial outward after the 180° U-bend in the third passage. The Reynolds number ranged 10,000 to 40,000 while the rotation number ranged 0 to 0.42. The density ratio was a constant of 0.12. Results showed that rotation increases heat transfer on leading surface but decreases it on the trailing surface in the second passage. In the third passage, the effect of rotation is reversed. Without a turning vane, rotation reduces heat transfer substantially on all surfaces in the hub 180° turn region. After adding a half-circle-shaped turning vane, heat transfer coefficients do not change in the second passage (before turn) while they are quite different in the turn region and the third passage (after turn). Regional heat transfer coefficients are correlated with rotation numbers for multi-pass rectangular smooth channel with and without a turning vane.

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