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.

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.

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.

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.

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.

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.

Optimization of a U-Bend for Minimal Pressure Loss in Internal Cooling Channels—Part II: Experimental Validation

2013 ◽  
Vol 135 (5) ◽  
Author(s):  
Filippo Coletti ◽  
Tom Verstraete ◽  
Jérémy Bulle ◽  
Timothée Van der Wielen ◽  
Nicolas Van den Berge ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Loss ◽  
Heat Transfer Performance ◽  
Internal Cooling ◽  
Transfer Performance ◽  
Cooling Channel ◽  
Piv Measurements ◽  
Cooling Channels ◽  
Numerical Predictions ◽  
The Impact

This two-part paper addresses the design of a U-bend for serpentine internal cooling channels optimized for minimal pressure loss. The total pressure loss for the flow in a U-bend is a critical design parameter, as it augments the pressure required at the inlet of the cooling system, resulting in a lower global efficiency. In the first part of the paper, the design methodology of the cooling channel was presented. In this second part, the optimized design is validated. The results obtained with the numerical methodology described in Part I are checked against pressure measurements and particle image velocimetry (PIV) measurements. The experimental campaign is carried out on a magnified model of a two-legged cooling channel that reproduces the geometrical and aerodynamical features of its numerical counterpart. Both the original profile and the optimized profile are tested. The latter proves to outperform the original geometry by about 36%, in good agreement with the numerical predictions. Two-dimensional PIV measurements performed in planes parallel to the plane of the bend highlight merits and limits of the computational model. Despite the well-known limits of the employed eddy viscosity model, the overall trends are captured. To assess the impact of the aerodynamic optimization on the heat transfer performance, detailed heat transfer measurements are carried out by means of liquid crystals thermography. The optimized geometry presents overall Nusselt number levels only 6% lower with respect to the standard U-bend. The study demonstrates that the proposed optimization method based on an evolutionary algorithm, a Navier–Stokes solver, and a metamodel of it is a valid design tool to minimize the pressure loss across a U-bend in internal cooling channels without leading to a substantial loss in heat transfer performance.

Experimental investigations of pressure loss and heat transfer in a 180° bend of a ribbed two-pass internal cooling channel with engine-similar cross-sections

2009 ◽  
Vol 223 (6) ◽  
pp. 709-719 ◽  
Author(s):  
M Schüler ◽  
S O Neumann ◽  
B Weigand
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Cross Sections ◽  
Pressure Loss ◽  
Leading Edge ◽  
Experimental Investigations ◽  
Strong Increase ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Transfer Enhancement

In the present study, the pressure loss and heat transfer of a two-pass internal cooling channel with engine-similar cross-sections were investigated experimentally. This channel consisted of a trapezoidal leading edge pass, a sharp 180° bend, and a nearly rectangular outlet pass. The investigations focused on the influence of tip-to-web distance and rib configuration on pressure loss and heat transfer. The channel was equipped with skewed ribs (α=45°, P/ e=10, e/ dh=0.1) in an inline and a staggered configuration. The dimensionless tip-to-web distance Wel/ dS was varied from 0.6 to 1.2. The investigated Reynolds number ranged from 15 000 up to 100 000. The experimental results showed a strong increase in pressure loss with decreasing tip-to-web distance, while heat transfer was only slightly increasing. Both rib configurations showed nearly the same heat transfer enhancement in the bend region.

scholarly journals Experimental and Numerical Study of Heat Transfer Performance for an Engine Representative Two-Pass Rotating Internal Cooling Channel

2016 ◽  
Author(s):  
Zhi Wang ◽  
Roque Corral ◽  
Francois Chedevergne
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Heat Transfer Performance ◽  
Numerical Results ◽  
Test Facility ◽  
Design Parameters ◽  
Internal Cooling ◽  
Surprising Result ◽  
Transfer Performance ◽  
Cooling Channel

This paper investigates, both experimentally and computationally, the heat transfer performance on an engine representative varying aspect ratio two-pass internal cooling channel, in both stationary and rotating conditions. The test geometry and design parameters were suggested by SNECMA as a representative HPT blade two-pass internal cooling channel. The cooling channel has radially outward flow in the first passage with an aspect ratio of 1:2.25 and after a 180 degree sharp turn, a radially inward flow in the second passage with an aspect ratio of 1:1.85. One side of the two passages is equipped with 45 degree angled rib turbulators with a rib spacing P/e=7 and blockage ratio e/Dh =0.116. The other side is smooth in order to have optical access for experiment. The experiment was performed at three Reynolds numbers: 15,000, 25,000, and 35,000. Both forward and backward rotating directions were tested in order to study the heat transfer performance of the ribbed surface as trailing wall or leading wall individually. The tested Rotation numbers were Ro=±0.3 at Re=15,000 and Re=25,000, whereas the Rotation number was reduced to ±0.22 at Re=35,000, due to restrictions of the test facility. Infrared thermography technology is used to capture the temperature field for further evaluation of heat transfer performance. Numerical simulations for all experimental cases were conducted using the same geometry including the air feeding system, applying the experimental wall temperature distribution in order to properly capture inlet and buoyancy effects, with the k–ω–SST turbulence model. Numerical results show overall agreement and similar trends than the experimental data. Numerical results also show that the rotation effects alter the internal flow significantly, resulting in different surface heat transfer distributions. Particularly, it is shown that heat transfer performance of the pressure side is not enhanced by the rotation in this study, which is a surprising result. This behavior was captured both in the experiments and the numerical predictions.

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