The Effect of Ribs and Tip Wall Distance on Heat Transfer for a Varying Aspect Ratio Two-Pass Ribbed Internal Cooling Channel

2008 ◽  
Author(s):  
Sean C. Jenkins ◽  
Frank Zehnder ◽  
Igor V. Shevchuk ◽  
Jens von Wolfersdorf ◽  
Bernhard Weigand ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Turbine Blades ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Thermochromic Liquid Crystal ◽  
Outlet Channel ◽  
Pressure Losses ◽  
Wall Distance ◽  
Aspect Ratios ◽  
Increased Pressure

Internal cooling channels with differing aspect ratios are typically found in gas turbine blades due to the varying thickness of the blade from the leading to trailing edge. These serpentine passages often contain several 180° bends, which are sharp edged in the region of the blade tip. The 180° bend has a pronounced effect on the heat transfer characteristics in the outlet channel and tip wall, where a strong influence is seen due to the divider wall-to-tip wall distance in the bend. The present study investigates the effect of the divider wall-to-tip wall distance for a ribbed two-pass cooling channel with a 2:1 inlet and 1:1 outlet channel. Spatially resolved heat transfer measurements were made using the transient thermochromic liquid crystal technique for a smooth and a ribbed configuration using parallel 45° ribs. Effects of the 180° bend on heat transfer and rib-induced enhancements were identified separately and bend effects were found to dominate the heat transfer increase in the outlet channel near the bend. Pressure losses due to the bend and ribs were also independently evaluated for a range of tip wall distances. Results show that the smaller tip wall distances increase heat transfer on the tip wall and outlet channel, but at the cost of an increased pressure loss. An optimum tip wall position is suggested, forming a compromise between heat transfer improvement and increased pressure losses.

The Effects of Ribs and Tip Wall Distance on Heat Transfer for a Varying Aspect Ratio Two-Pass Ribbed Internal Cooling Channel

2012 ◽  
Vol 135 (2) ◽  
Author(s):  
Sean C. Jenkins ◽  
Frank Zehnder ◽  
Igor V. Shevchuk ◽  
Jens von Wolfersdorf ◽  
Bernhard Weigand ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Turbine Blades ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Thermochromic Liquid Crystal ◽  
Outlet Channel ◽  
Pressure Losses ◽  
Wall Distance ◽  
Aspect Ratios ◽  
Increased Pressure

Internal cooling channels with differing aspect ratios are typically found in gas turbine blades due to the varying thickness of the blade from the leading to trailing edge. These serpentine passages often contain several 180 deg bends, which are sharp edged in the region of the blade tip. The 180 deg bend has a pronounced effect on the heat transfer characteristics in the outlet channel and tip wall, where a strong influence is seen due to the divider wall-to-tip wall distance in the bend. The present study investigates the effect of the divider wall-to-tip wall distance for a ribbed two-pass cooling channel with a 2:1 inlet and 1:1 outlet channel. Spatially resolved heat transfer measurements were made using the transient thermochromic liquid crystal technique for a smooth and a ribbed configuration using parallel 45 deg ribs. Effects of the 180 deg bend on heat transfer and rib-induced enhancements were identified separately and bend effects were found to dominate the heat transfer increase in the outlet channel near the bend. Pressure losses due to the bend and ribs were also independently evaluated for a range of tip wall distances. Results show that the smaller tip wall distances increase heat transfer on the tip wall and outlet channel but at the cost of an increased pressure loss. An optimum tip wall position is suggested, forming a compromise between heat transfer improvement and increased pressure losses.

Validation and Analysis of Numerical Results for a Varying Aspect Ratio Two-Pass Internal Cooling Channel

2011 ◽  
Vol 133 (5) ◽  
Author(s):  
Igor V. Shevchuk ◽  
Sean C. Jenkins ◽  
Bernhard Weigand ◽  
Jens von Wolfersdorf ◽  
Sven Olaf Neumann ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Numerical Results ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Outlet Channel ◽  
Pressure Losses ◽  
Wall Distance ◽  
Wide Range ◽  
Numerical Effort

Numerical results for an internal ribbed cooling channel including a 180 deg bend with a 2:1 inlet and a 1:1 aspect ratio outlet channel were validated against experimental results in terms of spatially resolved heat transfer distributions, pressure losses, and velocity distributions. The numerical domain consisted of one rib segment in the inlet channel and three ribs segments in the outlet channel to reduce the overall numerical effort and allow for an extensive parametric study. The results showed good agreement for both heat transfer magnitudes and spatial distributions, and the numerical results captured the predominate flow physics resulting from the 180 deg bend. The production of Dean vortices and acceleration of the flow in the bend produced strongly increased heat transfer on both the ribbed and unribbed walls in the outlet channel in addition to increases due to the ribs. Numerical simulations were performed for a wide range of divider wall-to-tip wall distances, which influenced the position of the highest heat transfer levels on the outlet walls and changed the shape of the heat transfer distribution on the tip wall. Analysis of section averages of heat transfer in the bend and outlet channel showed a strong influence of the tip wall distance, while no effect was seen upstream of the bend. A similarly large effect on pressure losses in the bend was observed with varying tip wall position. Trends in averaged heat transfer varied linearly with tip wall distance, while pressure losses followed a nonlinear trend, resulting in an optimum tip wall distance with respect to heat transfer efficiency.

Validation and Analysis of Numerical Results for a Varying Aspect Ratio Two-Pass Internal Cooling Channel

2008 ◽  
Author(s):  
Igor V. Shevchuk ◽  
Sean C. Jenkins ◽  
Bernhard Weigand ◽  
Jens von Wolfersdorf ◽  
Sven Olaf Neumann ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Linear Trend ◽  
Numerical Results ◽  
Cooling Channel ◽  
Outlet Channel ◽  
Pressure Losses ◽  
Wall Distance ◽  
Wide Range ◽  
Numerical Effort

Numerical results for an internal ribbed cooling channel including a 180° bend with a 2:1 inlet and 1:1 aspect ratio outlet channel were validated against experimental results in terms of spatially resolved heat transfer distributions, pressure losses, and velocity distributions. The numerical domain consisted of one rib segment in the inlet channel and three ribs segments in the outlet channel to reduce the overall numerical effort and allow for an extensive parametric study. The results showed good agreement for both heat transfer magnitudes and spatial distributions and the numerical results captured the predominate flow physics resulting from the 180° bend. The production of Dean vortices and acceleration of the flow in the bend produced strongly increased heat transfer on both the ribbed and unribbed walls in the outlet channel in addition to increases due to the ribs. Numerical simulations were performed for a wide range of divider wall-to-tip wall distances, which influenced the position of the highest heat transfer levels on the outlet walls and changed the shape of the heat transfer distribution on the tip wall. Analysis of section averages of heat transfer in the bend and outlet channel showed a strong influence of the tip wall distance while no effect was seen upstream of the bend. A similarly large effect on pressure losses in the bend was observed with varying tip wall position. Trends in averaged heat transfer varied linearly with tip wall distance while pressure losses followed a non-linear trend, resulting in an optimum tip wall distance with respect to heat transfer efficiency.

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.

The Effect of Turning Vanes on Pressure Loss and Heat Transfer of a Ribbed Rectangular Two-Pass Internal Cooling Channel

2010 ◽  
Vol 133 (2) ◽  
Author(s):  
Marco Schüler ◽  
Frank Zehnder ◽  
Bernhard Weigand ◽  
Jens von Wolfersdorf ◽  
Sven Olaf Neumann
Keyword(s):  
Heat Transfer ◽  
Pressure Loss ◽  
Stokes Equations ◽  
Turbine Blades ◽  
Local Heat Transfer ◽  
Width Ratio ◽  
Channel Height ◽  
Internal Cooling ◽  
Thermochromic Liquid Crystal ◽  
Sharp Turn

Gas turbine blades are usually cooled by using ribbed serpentine internal cooling passages, which are fed by extracted compressor air. The individual straight ducts are connected by sharp 180 deg bends. The integration of turning vanes in the bend region lets one expect a significant reduction in pressure loss while keeping the heat transfer levels high. Therefore, the objective of the present study was to investigate the influence of different turning vane configurations on pressure loss and local heat transfer distribution. The investigations were conducted in a rectangular two-pass channel connected by a 180 deg sharp turn with a channel height-to-width ratio of H/W=2. The channel was equipped with 45 deg skewed ribs in a parallel arrangement with e/dh=0.1 and P/e=10. The tip-to-web distance was kept constant at Wel/W=1. Spatially resolved heat transfer distributions were obtained using the transient thermochromic liquid crystal technique. Furthermore static pressure measurements were conducted in order to determine the influence of turning vane configurations on pressure loss. Additionally, the configurations were investigated numerically by solving the Reynolds-averaged Navier–Stokes equations using the finite-volume solver FLUENT. The numerical grids were generated by the hybrid grid generator CENTAUR. Three different turbulence models were considered: the realizable k-ε model with two-layer wall treatment, the k-ω-SST model, and the v2-f turbulence model. The results showed a significant influence of the turning vane configuration on pressure loss and heat transfer in the bend region and the outlet pass. While using an appropriate turning vane configuration, pressure loss was reduced by about 25%, keeping the heat transfer at nearly the same level in the bend region. An inappropriate configuration led to an increase in pressure loss while the heat transfer was reduced in the bend region and outlet pass.

Effect of Coriolis and Centrifugal Forces on Turbulence and Heat Transfer at High Rotation and Buoyancy Numbers in a Rib-Roughened Internal Cooling Channel

2004 ◽  
Author(s):  
A. K. Sleiti ◽  
J. S. Kapat
Keyword(s):  
Heat Transfer ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Centrifugal Forces ◽  
Reynolds Stresses ◽  
Rsm Model ◽  
Density Ratios ◽  
Rib Roughened

Prediction of three-dimensional flow field and heat transfer in a two pass rib-roughened square internal cooling channel of turbine blades with rounded staggered ribs rotating at high rotation and density ratios is the main focus of this study. Rotation, buoyancy, ribs, and geometry affect the flow within these channels. The full two-pass channel with bend and with rounded staggered ribs with fillets (e/Dh = 0.1 and P/e = 10) as tested by Wagner et. al [1992] is investigated. RSM is used in this study and enhanced wall treatment approach to resolve the near wall viscosity-affected region. RSM model was validated against available experimental data (which are primarily at low rotation and buoyancy numbers). The model was then used for cases with high rotational numbers (0.24, 0.475, 0.74 and 1) and high-density ratios (0.13, 0.23, and 0.3). Particular attention is given to how secondary flow, Reynolds stresses, turbulence intensity, and heat transfer are affected by coriolis and buoyancy/centrifugal forces caused by high levels of rotation and density ratios. A linear correlation for 4-side-average Nusselt number as a function of rotation number is derived.

An Experimental Investigation of Heat Transfer in an Orthogonally Rotating Channel Roughened With 45 deg Criss-Cross Ribs on Two Opposite Walls

1991 ◽  
Vol 113 (3) ◽  
pp. 346-353 ◽  
Author(s):  
M. E. Taslim ◽  
L. A. Bondi ◽  
D. M. Kercher
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Aspect Ratio ◽  
Transfer Coefficient ◽  
Rotation Number ◽  
Turbine Blades ◽  
Steady Increase ◽  
Internal Cooling ◽  
Number Range ◽  
Aspect Ratios

Turbine blade cooling is imperative in advanced aircraft engines. The extremely hot gases that operate within the turbine section require turbine blades to be cooled by a complex cooling circuit. This cooling arrangement increases engine efficiency and ensures blade materials a longer creep life. One principle aspect of the circuit involves serpentine internal cooling passes throughout the core of the blade. Roughening the inside surfaces of these cooling passages with turbulence promoters provides enhanced heat transfer rates from the surface. The purpose of this investigation was to study the effect of rotation, aspect ratio, and turbulator roughness on heat transfer in these rib-roughened passages. The investigation was performed in an orthogonally rotating setup to simulate the actual rotation of the cooling passages. Single-pass channels, roughened on two opposite walls, with turbulators positioned at 45 deg angle to the flow, in a criss-cross arrangement, were studied throughout this experiment. The ribs were arranged such that their pitch-to-height ratio remained at a constant value of 10. An aspect ratio of unity was investigated under three different rib blockage ratios (turbulator height/channel hydraulic diameter) of 0.1333, 0.25, and 0.3333. A channel with an aspect ratio of 2 was also investigated for a blockage ratio of 0.25. Air was flown radially outward over a Reynolds number range of 15,000 to 50,000. The rotation number was varied from 0 to 0.3. Stationary and rotating cases of identical geometries were compared. Results indicated that rotational effects are more pronounced in turbulated passages of high aspect and low blockage ratios for which a steady increase in heat transfer coefficient is observed on the trailing side as rotation number increases while the heat transfer coefficient on the leading side shows a steady decrease with rotation number. However, the all-smooth-wall classical pattern of heat transfer coefficient variation on the leading and trailing sides is not followed for smaller aspect ratios and high blockage ratios when the relative artificial roughness is high.

scholarly journals Experimental Study on the Influence of the Streamwise Position of Film Hole Extraction in Internal Ribbed Cooling Channels of Turbine Blades

2019 ◽  
Vol 3 ◽  
pp. 580-591 ◽  
Author(s):  
Marlene Böttger ◽  
Martin Lange ◽  
Ronald Mailach ◽  
Konrad Vogeler
Keyword(s):  
Film Cooling ◽  
Turbine Blades ◽  
Internal Flow ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Thermochromic Liquid Crystal ◽  
Cooling Channels ◽  
Concurrent Use ◽  
Streamwise Position ◽  
Film Cooling Holes

The concurrent use of film cooling and internal cooling plays an important role to maintain the life of turbine blades and increase thermal efficiency. Several studies were published on the interaction of these cooling strategies but these are mainly investigations on how internal cooling influences film cooling. The present study contributes to an improved understanding on how the cooling extraction through film cooling holes is influencing internal flow structures and therefore internal cooling. The flow field in an internal cooling channel is investigated by measuring the velocity distribution with 2D-PIV. Heat transfer measurements are performed using the thermochromic liquid crystal technique. The test stand models a rectangular cooling channel (AR=2:1), which is equipped with parallel ribs of four different geometries (90° ribs, 60° ribs, 60°-V-shaped ribs and 60°-Λ-shaped ribs). Bleed holes are placed in the rib segments and are positioned at three positions in streamwise direction. The suction ratio is varied between 0 and 6 and the cooling channel Reynolds number is 30.000.

Experimental Study on the Influence of Film Cooling Hole Extraction on Heat Transfer and Flow Field in Internal Ribbed Cooling Channels of Turbine Blades

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
Marlene Böttger ◽  
Martin Lange ◽  
Ronald Mailach ◽  
Konrad Vogeler
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Film Cooling ◽  
Turbine Blades ◽  
Internal Heat ◽  
Internal Flow ◽  
Cooling Channel ◽  
Thermochromic Liquid Crystal ◽  
Flow Measurements ◽  
Cooling Hole

Abstract Film cooling and internal passage cooling play a fundamental role in turbine blade cooling. As the cooling holes are fed by the internal crossflow, interaction of these both cooling strategies is implicated. The influence of film hole extraction on the internal flow field and heat transfer of a ribbed cooling channel is investigated in this study. Therefore, a rectangular cooling channel (AR = 2:1) is equipped with parallel ribs of four different geometries (90 deg ribs, 60 deg ribs, 60 deg V-shaped ribs, and 60 deg Λ-shaped ribs) and also with bleed holes at varying positions between the ribs. The different geometrical configurations are examined using 2D-particle image velocimetry (PIV) for flow measurements and transient thermochromic liquid crystal (TLC) technique for heat transfer measurements. Depending on the rib-induced heat transfer pattern, cooling hole positions in the rib segments are found, which can enhance passage internal heat transfer. 90 deg and 60 deg ribs show the best results for upstream hole positions regardless of the lateral positioning. V and Λ ribs reveal a benefit for lateral positioned cooling holes near the upstream rib.

The Effect of Turning Vanes on Pressure Loss and Heat Transfer of a Ribbed Rectangular Two-Pass Internal Cooling Channel

2009 ◽  
Author(s):  
Frank Zehnder ◽  
Marco Schu¨ler ◽  
Bernhard Weigand ◽  
Jens von Wolfersdorf ◽  
Sven Olaf Neumann
Keyword(s):  
Heat Transfer ◽  
Pressure Loss ◽  
Stokes Equations ◽  
Turbine Blades ◽  
Local Heat Transfer ◽  
Width Ratio ◽  
Channel Height ◽  
Internal Cooling ◽  
Thermochromic Liquid Crystal ◽  
Sharp Turn

Gas turbine blades are usually cooled by using ribbed serpentine internal cooling passages which are fed by extracted compressor air. The individual straight ducts are connected by sharp 180° bends. The integration of turning vanes in the bend region lets one expect a significant reduction in pressure loss while keeping heat transfer levels high. Therefore, the objective of the present study was to investigate the influence of different turning vane configurations on pressure loss and local heat transfer distribution. The investigations were conducted in a rectangular two-pass channel connected by a 180° sharp turn with a channel height-to-width ratio of H/W = 2. The channel was equipped with 45° skewed ribs in a parallel arrangement with e/dh = 0.1 and P/e = 10. The tip-to-web distance was kept constant at Wel/W = 1. Spatially resolved heat transfer distributions were obtained using the transient thermochromic liquid crystal technique. Furthermore static pressure measurements were conducted in order to determine the influence of turning vane configurations on pressure loss. Additionally, the configurations were investigated numerically by solving the Reynolds-Averaged Navier-Stokes equations (RANS method) using the Finite-Volume solver FLUENT. The numerical grids were generated by the hybrid grid generator CENTAUR. Three different turbulence models were considered: the realizable k-ε model with two-layer wall treatment, the k-ω-SST model, and the v2-f turbulence model. The results showed a significant influence of the turning vane configuration on pressure loss and heat transfer in the bend region and the outlet pass. While using an appropriate turning vane configuration pressure loss was reduced by about 25% keeping the heat transfer at nearly the same level in the bend region. An inappropriate configuration led to an increase in pressure loss while heat transfer was reduced in the bend region and outlet pass.

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