Heat Transfer in a Rotating, Blade-Shaped, Two-Pass Cooling Channel With a Variable Aspect Ratio

2021 ◽  
Author(s):  
I-Lun Chen ◽  
Izzet Sahin ◽  
Lesley M. Wright ◽  
Je-Chin Han ◽  
Robert Krewinkel
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Gas Turbine ◽  
Cross Section ◽  
Pressure Loss ◽  
Planar Geometry ◽  
Internal Cooling ◽  
Cooling Channel ◽  
First Passage ◽  
Rotating Blade

Abstract This study features a rotating, blade-shaped, two-pass cooling channel with a variable aspect ratio. Internal cooling passages of modern gas turbine blades closely follow the shape and contour of the airfoils. Therefore, the cross-section and the orientation with respect to rotation varies for each cooling channel. The effect of passage orientation on the heat transfer and pressure loss is investigated by comparing to a planar channel design with a similar geometry. Following the blade cross-section, the first pass of the serpentine channel is angled at 50° from the direction of rotation while the second pass has an orientation angle of 105°. The coolant flows radially outward in the first passage with an aspect ratio (AR) = 4:1. After a 180-degree tip turn, the coolant travels radially inward into the second passage with AR = 2:1. The copper plate method is applied to obtain the regionally-averaged heat transfer coefficients on all the interior walls of the cooling channel. In addition to the smooth surface case, 45° angled ribs with a profiled cross section are also placed on the leading and trailing surfaces in both the passages. The ribs are placed such that P/e = 10 and e/H = 0.16. The Reynolds number varies from 10,000 to 45,000 in the first passage and 16,000 to 73,000 in the second passage. The rotational speed ranges from 0 to 400 rpm, which corresponds to maximum rotation numbers of 0.38 and 0.15 in the first and second passes, respectively. The blade-shaped feature affects the heat transfer and pressure loss in the cooling channels. In the second passage, the heat transfer on the outer wall and trailing surface is higher than the inner wall and leading surface due to flow impingement and the swirling motion induced by the blade-shaped tip turn. The rotational effect on the heat transfer and pressure loss is lower in the blade-shaped design than the planar design due to the feature of angled rotation. The tip wall heat transfer is significantly enhanced by rotation in this study. The overall heat transfer and pressure loss in this study is higher than the planar geometry due to the blade-shaped feature. The heat transfer and pressure loss characteristics from this study provide important information for the gas turbine blade internal cooling designs.

HEAT TRANSFER IN A ROTATING, BLADE-SHAPED, TWO-PASS COOLING CHANNEL WITH A VARIABLE ASPECT RATIO

2021 ◽  
pp. 1-26
Author(s):  
I-Lun Chen ◽  
Izzet Sahin ◽  
Lesley Wright ◽  
Je-Chin Han ◽  
Robert Krewinkel
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Pressure Loss ◽  
Orientation Angle ◽  
Outer Wall ◽  
Planar Geometry ◽  
Internal Cooling ◽  
Cooling Channel ◽  
First Passage ◽  
Rotating Blade

Abstract This study features a rotating, blade-shaped, two-pass cooling channel with a variable aspect ratio. The effect of passage orientation on the heat transfer and pressure loss is investigated by comparing to a planar channel design with a similar geometry. The first pass of the channel is angled at 50-deg from the direction of rotation while the second pass has an orientation angle of 105-deg. The coolant flows radially outward in the first passage with an aspect ratio (AR) = 4:1 and radially inward in the second passage with AR = 2:1. In addition to the smooth surface case, 45-deg angled ribs with a profiled cross section are also placed on the leading and trailing surfaces in both the passages. The ribs are placed such that P/e = 10 and e/H= 0.16. The Reynolds number varies from 10,000 to 45,000 in the first passage and 16,000 to 73,000 in the second passage. The maximum rotation numbers are 0.38 and 0.15 in the first and second passes, respectively. In the second passage, the heat transfer on the outer wall and trailing surface is higher due to flow impingement and the swirling motion induced by the blade-shaped tip turn. The overall heat transfer and pressure loss are higher than the planar geometry due to the blade-shaped feature. The heat transfer and pressure loss characteristics from this study provide important information for the gas turbine blade internal cooling designs.

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.

Influence of the 180° Bend Geometry on the Pressure Loss and Heat Transfer in a High Aspect Ratio Rectangular Smooth Channel

2004 ◽  
Author(s):  
Detlef Pape ◽  
Herve´ Jeanmart ◽  
Jens von Wolfersdorf ◽  
Bernhard Weigand
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Aspect Ratio ◽  
Cross Section ◽  
High Aspect Ratio ◽  
Pressure Loss ◽  
Rectangular Cross Section ◽  
Flow Structures ◽  
Cooling Channel ◽  
Smooth Channel

An experimental and numerical investigation of the pressure loss and the heat transfer in the bend region of a smooth two-pass cooling channel with a 180°-turn has been performed. The channels have a rectangular cross-section with a high aspect ratio of H/W = 4. The heat transfer has been measured using the transient liquid crystal method. For the investigations the Reynolds-number as well as the distance between the tip and the divider wall (tip distance) are varied. While the Reynolds number varies from 50’000 to 200’000 and its influence on the normalized pressure loss and heat transfer is found to be small, the variations of the tip distance from 0.5 up to 3.65 W produce quite different flow structures in the bend. The pressure loss over the bend thus shows a strong dependency on these variations.

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

2020 ◽  
Vol 142 (7) ◽  
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 deg profiled rib orientations, typical parallel (usual), reversed parallel (unusual), and crisscross 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 16,000 to 114,000 for the second passage with a rotational speed range of 0–400 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-deg tip turn, and rotation number on the heat transfer and pressure drop will be addressed. According to the results, for usual, unusual and crisscross 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. The overall heat transfer enhancement of the usual and unusual rib patterns is higher than the crisscross one. In terms of the pressure losses, the crisscross 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 crisscross or unusual rib pattern might be an option to use in the internal cooling method. Therefore, the results can be useful for the turbine blade internal cooling design and heat transfer analysis.

Performance Evaluation of a Modified Cross Section Grooved Channel as Turbulence Promoter in Internal Cooling Channel of a Gas Turbine Blade

2015 ◽  
Author(s):  
Krishnendu Saha ◽  
Deoras Prabhudharwadkar
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Gas Turbine ◽  
Cross Section ◽  
Channel Wall ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Ribbed Channel ◽  
Baseline Case ◽  
Mainstream Flow

Internal cooling channel in gas turbine blades use ribs as turbulence promoter to increase local turbulence and improve heat transfer from hot wall to coolant air flowing through the internal cooling channels. The ribs protrude into the flow and result in a significant pressure drop of the coolant air. Indentations like grooves in the cooling channel wall can also be used as turbulence promoters to enhance local heat transfer and as they do not protrude into the mainstream flow, the pressure drop penalty could be much lesser than a conventional ribbed channel. A numerical study is conducted under stationary condition on a square cross section channel representing an internal cooling channel of a turbine airfoil. Some standard and modified cross sections of grooved channel are used as turbulence promoters with a goal to enhance heat transfer from the internal cooling channel wall with minimal pressure drop. The steady state solution is based on using the Reynolds Averaged Navier-Stokes (RANS) equation and k-omega-SST turbulence model. Numerical calculations are done at four Reynolds numbers (Re=15000, 30000, 68000 and 88000) based on fluid properties at the inlet of the internal cooling channel. The grooves are placed on two opposite sides of the square cross section channel and other two walls are smooth walls without any turbulence promoters. A hemispherical cross section continuous groove which is placed perpendicular to the mainstream flow direction is taken as baseline case and a teardrop shaped groove is used to compare the performance difference between the two groove cross section. A broken shaped angled groove configuration with the teardrop cross section groove is also investigated to find the relative performance improvement with the baseline case. Performance comparison with standard 90° rib geometry is done to understand the overall effectiveness of the grooved geometries with respect to common standard in gas turbine blade internal cooling. The straight teardrop cross section groove improves the heat transfer values compared to the hemispherical cross section groove by 8–12% and the broken angled teardrop groove case improves heat transfer by 11–14% compared to the hemispherical cross section groove case. The pressure drop produced by all the groove geometries is about the same. It is seen that the broken angled groove can produce the same heat transfer enhancement compared to a 90° ribbed channel but the pressure drop is more than 3 times lesser compared to the ribbed case. Considering the heat transfer and pressure drop, an increase in thermal performance factor of 37–41% is seen for the angled grooved case compared to the 90° ribbed geometry.

Heat Transfer in a Rotating Two-Pass Rectangular Channel Featuring Reduced Cross-Sectional Area After Tip Turn (AR=4:1 to 2:1) With Profiled 60 Deg Angled Ribs

2018 ◽  
Author(s):  
Andrew F. Chen ◽  
Chao-Cheng Shiau ◽  
Je-Chin Han ◽  
Robert Krewinkel
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Aspect Ratio ◽  
Cross Section ◽  
Flow Direction ◽  
Rectangular Channel ◽  
Secondary Flows ◽  
Internal Cooling ◽  
First Passage ◽  
Aspect Ratios

The internal cooling channels of an advanced gas turbine blade typically have varying aspect ratios from one pass to another due to the varying thickness of the blade profile. Most of the fundamental internal cooling studies found in the open literature used a fixed aspect ratio for multi-pass channels. Studies on a reduced cross-section and aspect ratio channel are scarce. The current study features a two-pass rectangular channel with an aspect ratio AR = 4:1 in the first pass and an AR = 2:1 in the second pass after a 180 deg tip turn. In addition to the smooth-wall case, ribs with a profiled cross-section are placed at 60 deg to the flow direction on both the leading and trailing surfaces in both passages (P/e = 10, e/Dh ≈ 0.11, parallel and inline). Regionally averaged heat transfer measurement method was used to obtain the heat transfer coefficients on all surfaces within the flow passages. The Reynolds number (Re) ranges from 10,000 to 70,000 in the first passage, and the rotational speed ranges from 0 to 400 rpm. Under pressurized condition (570 kPa), the highest rotation number achieved was Ro = 0.39 in the first passage and 0.16 in the second passage. Rotation effects on both heat transfer and pressure loss coefficient for the smooth and rib-roughened cases are presented. The results showed that the turn induced secondary flows are reduced in an accelerating flow. The effects of rotation on heat transfer are generally weakened in the ribbed case than the smooth case. Significant heat transfer reduction on the tip wall was seen in both the smooth and ribbed cases under rotating condition. A reduced overall pressure penalty was seen for the ribbed case under rotation. Reynolds number effect was found noticeable in the current study. The heat transfer and pressure drop characteristics are sensitive to the geometrical design of the channel and should be taken into account in the design process.

Study on Flow and Heat Transfer Characteristics of a New-Proposed Alternating Elliptical U-Channel

2020 ◽  
Author(s):  
Kun Xiao ◽  
Juan He ◽  
Zhenping Feng
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Cross Section ◽  
Internal Cooling ◽  
Short Axis ◽  
Cooling Channel ◽  
Heat Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
First Pass ◽  
The Cross

Abstract This paper proposed an alternating elliptical U-shaped internal cooling channel and investigated the flow and heat transfer characteristics, based on the optimal flow field structure deduced from the Field Synergy Principle. The channel consisted of the straight sections and the transition sections. In the straight sections, the cross section of the channel is ellipse, and in the transition sections, the long axis gradually shortened into the short axis, and the short axis gradually expanded to the long axis. However, the cross-section area of the channel remained unchanged. Numerical simulations were performed to solve 3D steady Reynolds-averaged Navier-Stokes equations (RANS) with the standard k-ε turbulence model. The influence of alternating of the cross section on heat transfer and pressure drop of the channel was studied by comparing with the smooth elliptical U-shaped channel, and all the cases were conducted with the Re numbers from 10,000 to 40,000. On this basis, the investigation on alternating elliptical U-shaped internal cooling channel performance was made mainly into two parts. One was the effect of aspect ratio which was set as from 1.1 to 2.0, while the other was the effect of alternating angle θ which was set as from 10° to 90°. The results showed that for the flow field, there was no vortex in the first pass of the smooth elliptical U-shaped channel. On the contrary, in the first pass of the alternating elliptical U-shaped channel, after the transition section, for different Re numbers, four or eight longitudinal vortices were generated. In the second pass, the flow separation in smooth elliptical U-shaped channel was serious because of the centrifugal force at the elbow, while the alternating elliptical channel restrained the flow separation to a certain extent and formed a double-vortex structure just like the vortex cooling. The average Nusselt number of the alternating elliptical U-shaped channel was significantly higher than that of the straight channel, but the pressure loss increased slightly. In addition, with the increase of aspect ratio, the thermal performance of the channel increased in the study range, and when the alternating angle is between 40° to 90°, the thermal performance nearly kept constant and the best.

scholarly journals Optimization Design of Lattice Structures in Internal Cooling Channel with Variable Aspect Ratio of Gas Turbine Blade

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3954
Author(s):  
Liang Xu ◽  
Qicheng Ruan ◽  
Qingyun Shen ◽  
Lei Xi ◽  
Jianmin Gao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Optimization Model ◽  
Lattice Structure ◽  
Turbine Blades ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Cooling Channels ◽  
Mechanical Performances ◽  
Type Lattice

Traditional cooling structures in gas turbines greatly improve the high temperature resistance of turbine blades; however, few cooling structures concern both heat transfer and mechanical performances. A lattice structure (LS) can solve this issue because of its advantages of being lightweight and having high porosity and strength. Although the topology of LS is complex, it can be manufactured with metal 3D printing technology in the future. In this study, an integral optimization model concerning both heat transfer and mechanical performances was presented to design the LS cooling channel with a variable aspect ratio in gas turbine blades. Firstly, some internal cooling channels with the thin walls were built up and a simple raw of five LS cores was taken as an insert or a turbulator in these cooling channels. Secondly, relations between geometric variables (height (H), diameter (D) and inclination angle(ω)) and objectives/functions of this research, including the first-order natural frequency (freq1), equivalent elastic modulus (E), relative density (ρ¯) and Nusselt number (Nu), were established for a pyramid-type lattice structure (PLS) and Kagome-type lattice structure (KLS). Finally, the ISIGHT platform was introduced to construct the frame of the integral optimization model. Two selected optimization problems (Op-I and Op-II) were solved based on the third-order response model with an accuracy of more than 0.97, and optimization results were analyzed. The results showed that the change of Nu and freq1 had the highest overall sensitivity Op-I and Op-II, respectively, and the change of D and H had the highest single sensitivity for Nu and freq1, respectively. Compared to the initial LS, the LS of Op-I increased Nu and E by 24.1% and 29.8%, respectively, and decreased ρ¯ by 71%; the LS of Op-II increased Nu and E by 30.8% and 45.2%, respectively, and slightly increased ρ¯; the LS of both Op-I and Op-II decreased freq1 by 27.9% and 19.3%, respectively. These results suggested that the heat transfer, load bearing and lightweight performances of the LS were greatly improved by the optimization model (except for the lightweight performance for the optimal LS of Op-II, which became slightly worse), while it failed to improve vibration performance of the optimal LS.

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.

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