Detailed Heat Transfer Coefficient Measurements on a Scaled Realistic Turbine Blade Internal Cooling System

2019 ◽  
Vol 12 (3) ◽  
Author(s):  
Chao-Cheng Shiau ◽  
Andrew F. Chen ◽  
Je-Chin Han ◽  
Robert Krewinkel
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Cooling System ◽  
Plastic Material ◽  
Local Heat Transfer ◽  
Transfer Characteristic ◽  
Internal Cooling ◽  
Thermochromic Liquid Crystal ◽  
Transfer Coefficients ◽  
Trailing Edge

Abstract A realistic internal cooling system of a turbine blade includes both ribs and pin-fins inside the passages to enhance the heat transfer. However, the majority studies in the open literature assessing the heat transfer characteristics on a simplified cooling model by examining ribbed-roughen passages and pin-finned passage separately. This work presents the high-resolution heat transfer coefficients of a scaled realistic turbine blade internal cooling design. The cooling system, using a 3D-printed plastic material, consists of an S-shaped inlet, four serpentine passages (three U-bends) of variable aspect ratio, and the trailing edge ejection. Angled ribs are implemented inside the passages and the elongated fins and pins are used near the trailing edge. Two dust holes are realized on the blade tip, the injections are individually controlled to reflect the realistic coolant flowrate variation inside the entire internal cooling system. The tests are conducted at two Reynolds number, 45,000 and 60,000 based on the hydraulic diameter of the inlet passage. Transient heat transfer technique using thermochromic liquid crystal is applied to obtain the detailed heat transfer characteristic inside the cooling channel. The local and averaged Nusselt numbers are also compared with the correlations in the open literature. This paper provides gas turbine designers the difference of local heat transfer distributions between the realistic and simplified internal cooling designs.

Detailed Heat Transfer Coefficient Measurements on a Scaled Realistic Turbine Blade Internal Cooling System

2019 ◽  
Author(s):  
Chao-Cheng Shiau ◽  
Andrew F. Chen ◽  
Je-Chin Han ◽  
Robert Krewinkel
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Cooling System ◽  
Plastic Material ◽  
Local Heat Transfer ◽  
Rate Variation ◽  
Internal Cooling ◽  
Thermochromic Liquid Crystal ◽  
Transfer Coefficients ◽  
Trailing Edge

Abstract A realistic internal cooling system of a turbine blade includes both ribs and pin-fins inside the passages to enhance the heat transfer. However, the majority studies in the open literature assessing the heat transfer characteristics on a simplified cooling model by examining ribbed-roughen passages and pin-finned passage separately. This work presents the high-resolution heat transfer coefficients of a scaled realistic turbine blade internal cooling design. The cooling system, using a 3D-printed plastic material, consists of an S-shaped inlet, four serpentine passages (three U-bends) of variable aspect ratio, and the trailing edge ejection. Angled ribs are implemented inside the passages and the elongated fins and pins are used near the trailing edge. Two dust holes are realized on the blade tip, the injections are individually controlled to reflect the realistic coolant flow rate variation inside the entire internal cooling system. The tests are conducted at two Reynolds number, 45,000 and 60,000 based on the hydraulic diameter of the inlet passage. Transient heat transfer technique using thermochromic liquid crystal is applied to obtain the detailed heat transfer characteristic inside the cooling channel. The local and averaged Nusselt numbers are also compared with the correlations in the open literature. This paper provides gas turbine designers the difference of local heat transfer distributions between the realistic and simplified internal cooling designs.

Effect of Rib Configuration and Lateral Ejection on a High Aspect Ratio Trailing Edge Channel

2013 ◽  
Author(s):  
Rui Kan ◽  
Li Yang ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Local Heat Transfer ◽  
Large Aspect Ratio ◽  
Thermochromic Liquid Crystal ◽  
Transfer Coefficients ◽  
Trailing Edge ◽  
Average Heat ◽  
Edge Channel ◽  
Heat Transfer Coefficients

Thermal issues of gas turbine blade trailing edge are complex and challenging, due to limited space for effective cooling. The trailing edge cavities are usually large aspect ratio ducts with lateral ejection. The objective of this study is to investigate the effects of different rib configurations and lateral ejection on heat transfer characteristics inside a trailing edge channel. The investigations were conducted on a large aspect ratio wedge-shaped channel with square ribs of e/Dh = 0.05, under Reynolds number 15,000. Twelve different configurations were tested: 1)three rib types, including a symmetry V-shaped rib configuration and two non-symmetry V-shaped rib configurations, of which the rib angles are 60 degrees, 2) two rib pitches, P/e = 10 and P/e = 5, 3) two flow directions, with an open tip outlet or with lateral ejection. Spatially resolved heat transfer distributions were obtained using the transient thermochromic liquid crystal experimental method. The configurations were also investigated numerically for the detailed flow field and for the validation of CFD codes. Results show that with lateral ejection, the heat transfer coefficients decrease from inlet to outlet. The heat transfer near the ejection holes is enhanced while heat transfer coefficients near the wall opposite to the exit holes decrease. The curvature of the streamlines creates a large separation area near the end of the channel and thus results in low local heat transfer coefficients. The P/e = 10 configurations have higher average heat transfer compared with P/e = 5 configurations. Average heat transfer coefficient is the highest with the center of the V-shaped rib placed at the middle of the channel, and is the lowest when the V-shaped rib center is located near the narrow part of the channel.

Pedestal and Endwall Contribution in Heat Transfer in Thin Wedge Shaped Trailing Edge

2004 ◽  
Author(s):  
Bruno Facchini ◽  
Luca Innocenti ◽  
Lorenzo Tarchi
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Thermochromic Liquid Crystal ◽  
Transfer Coefficients ◽  
Trailing Edge ◽  
Transient Technique ◽  
Heat Transfer Coefficients ◽  
Pin Fins ◽  
Turbine Airfoils ◽  
Accelerating Flow

Short pin fins (pedestals) and long ribs (enlarged pedestals) are usually used in trailing edge cooling of turbine airfoils. To better reproduce the geometry of such cooling systems, test section of this experimental study is a wedge duct with inserts, to take into account effects of accelerating flow. A complete investigation of the system needs a separate evaluation of the heat transfer coefficients (HTC) for the pedestal surface and for the free endwall surface. In the present work an innovative technique made of different methods for these two different regions is presented, so cooling performances of each are evaluated. Thermochromic liquid crystal (TLC) transient technique is used to measure detailed heat transfer coefficients only on the endwall surface: a typical transparent (Plexiglas®) test article is used. Aluminum pedestals, employing a procedure based on a finite elements code, allow to measure the average heat transfer coefficient on the insert surface. To investigate the effects on transient technique of high conductive components, a comparison with Plexiglas inserts has been performed. Results show an underestimation of HTC with TLC transient technique only for aluminum long ribs at low Reynolds number values. Nevertheless the results seem to agree with other authors both for the endwall surface and for the entire cooling system.

Heat Transfer of a Chordwise-Oriented Internal Cooling Passage Around a Turbine Airfoil

2001 ◽  
Author(s):  
M. K. Chyu ◽  
O. B. Ojo ◽  
C. H. Yen ◽  
R. S. Nordlund
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Cooling System ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Internal Cooling ◽  
Trailing Edge ◽  
Cooling Passage

Abstract An innovative design of closed-loop cooling system for a stator airfoil consists of a number of internal cooling passages wrapping around both pressure and suction sides of the airfoil. The cooling passages feature (1) jet impingement post a sharp 90-degree turn at the passage inlet, (2) turbulators on the outermost wall, and (3) a nearly 180-degree turn in the trailing edge. In addition, the passage has an irregular cross-section and varies throughout its entire length. A series of heat transfer tests have been performed at Re = 17,000 ∼ 61,000, compared to this tests which uses a new approach, so-called the hybrid liquid crystal technique. The magnitude of local heat transfer coefficient rises sharply in three regions. The first maximum occurs in the region subjected to direct jet impingement as the flow turns into the channel. Compounded with the inlet effect, this maximum, in fact, is the highest heat transfer coefficient over the entire passage. The second and third peaks, both are comparable in magnitude, locate near the trailing edge of the airfoil where the flow experiences a 180-degree turn and near the passage exit with a 90-degree turn. The average value of heat transfer coefficient over the entire passage is about 1.9∼ 2.5 times higher than that with fully developed turbulent flow in a straight channel. This level of enhancement is comparable to that of the conventional ribturbulators with a 90-degree angle-of-attack.

Heat Transfer Implications of Acoustic Resonances in HP Turbine Blade Internal Cooling Channels

2015 ◽  
Author(s):  
C. Selcan ◽  
B. Cukurel ◽  
J. Shashank
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Cooling System ◽  
Resonance Condition ◽  
Order Approximation ◽  
Acoustic Resonance ◽  
Mode Shapes ◽  
Internal Cooling ◽  
The Impact ◽  
Standing Sound

In an attempt to investigate the acoustic resonance effect of serpentine passages on internal convection heat transfer, the present work examines a typical high pressure turbine blade internal cooling system, based on the geometry of the NASA E3 engine. In order to identify the associated dominant acoustic characteristics, a numerical FEM simulation (two-step frequency domain analysis) is conducted to solve the Helmholtz equation with and without source terms. Mode shapes of the relevant identified eigenfrequencies (in the 0–20kHz range) are studied with respect to induced standing sound wave patterns and the local node/antinode distributions. It is observed that despite the complexity of engine geometries, as a first order approximation, the predominant resonance behavior can be modeled by a same-ended straight duct. Therefore, capturing the physics observed in a generic geometry, the heat transfer ramifications are experimentally investigated in a scaled wind tunnel facility at a representative resonance condition. Focusing on the straight cooling channel’s longitudinal eigenmode in the presence of an isolated rib element, the impact of standing sound waves on convective heat transfer and aerodynamic losses are demonstrated by liquid crystal thermometry, local static pressure and sound level measurements. The findings indicate a pronounced heat transfer influence in the rib wake separation region, without a higher pressure drop penalty. This highlights the potential of modulating the aero-thermal performance of the system via acoustic resonance mode excitations.

Heat Transfer Measurements in an Internal Cooling System Using a Transient Technique With Infrared Thermography

2012 ◽  
Author(s):  
Christian Egger ◽  
Jens von Wolfersdorf ◽  
Martin Schnieder
Keyword(s):  
Heat Transfer ◽  
Data Analysis ◽  
Infrared Thermography ◽  
Outer Surface ◽  
Cooling System ◽  
Internal Cooling ◽  
Test Model ◽  
Cooling Channel ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

In this paper a transient method for measuring heat transfer coefficients in internal cooling systems using infrared thermography is applied. The experiments are performed with a two-pass internal cooling channel connected by a 180° bend. The leading edge and the trailing edge consist of trapezoidal and nearly rectangular cross sections, respectively, to achieve an engine-similar configuration. Within the channels rib arrangements are considered for heat transfer enhancement. The test model is made of metallic material. During the experiment the cooling channels are heated by the internal flow. The surface temperature response of the cooling channel walls is measured on the outer surface by infrared thermography. Additionally, fluid temperatures as well as fluid and solid properties are determined for the data analysis. The method for determining the distribution of internal heat transfer coefficients is based on a lumped capacitance approach which considers lateral conduction in the cooling system walls as well as natural convection and radiation heat transfer on the outer surface. Because of time-dependent effects a sensitivity analysis is performed to identify optimal time periods for data analysis. Results are compared with available literature data.

Evaluation of Numerical Methods to Predict Temperature Distributions of an Experimentally Investigated Convection-Cooled Gas-Turbine Blade

2017 ◽  
Author(s):  
E. Findeisen ◽  
B. Woerz ◽  
M. Wieler ◽  
P. Jeschke ◽  
M. Rabs
Keyword(s):  
Heat Transfer ◽  
Numerical Methods ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Gas Turbines ◽  
Cooling System ◽  
Fe Model ◽  
Gas Turbine Blade ◽  
Transfer Coefficients ◽  
Temperature Distributions

This paper presents two different numerical methods to predict the thermal load of a convection-cooled gas-turbine blade under realistic operating temperature conditions. The subject of the investigation is a gas-turbine rotor blade equipped with an academic convection-cooling system and investigated at a cascade test-rig. It consists of three cooling channels, which are connected outside the blade, so allowing cooling air temperature measurements. Both methods use FE models to obtain the temperature distribution of the solid blade. The difference between these methods lies in the generation of the heat transfer coefficients along the cooling channel walls which serve as a boundary condition for the FE model. One method, referred to as the FEM1D method, uses empirical one-dimensional correlations known from the available literature. The other method, the FEM2D method, uses three-dimensional CFD simulations to obtain two-dimensional heat transfer coefficient distributions. The numerical results are compared to each other as well as to experimental data, so that the benefits and limitations of each method can be shown and validated. Overall, this paper provides an evaluation of the different methods which are used to predict temperature distributions in convection-cooled gas-turbines with regard to accuracy, numerical cost and the limitations of each method. The temperature profiles obtained in all methods generally show good agreement with the experiments. However, the more detailed methods produce more accurate results by causing higher numerical costs.

scholarly journals Effect of Discrete Ribs on Heat Transfer and Friction Inside Narrow Rectangular Cross Section Cooling Passage of Gas Turbine Blade

2021 ◽  
Vol 10 (6) ◽  
pp. 192-209
Author(s):  
Karthik Krishnaswamy ◽  
◽  
Srikanth Salyan ◽  
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Turbine Blades ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Hydraulic Diameter ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Cooling Passage

The performance of a gas turbine during the service life can be enhanced by cooling the turbine blades efficiently. The objective of this study is to achieve high thermohydraulic performance (THP) inside a cooling passage of a turbine blade having aspect ratio (AR) 1:5 by using discrete W and V-shaped ribs. Hydraulic diameter (Dh) of the cooling passage is 50 mm. Ribs are positioned facing downstream with angle-of-attack (α) of 30° and 45° for discrete W-ribs and discerte V-ribs respectively. The rib profiles with rib height to hydraulic diameter ratio (e/Dh) or blockage ratio 0.06 and pitch (P) 36 mm are tested for Reynolds number (Re) range 30000-75000. Analysis reveals that, area averaged Nusselt numbers of the rib profiles are comparable, with maximum difference of 6% at Re 30000, which is within the limits of uncertainty. Variation of local heat transfer coefficients along the stream exhibited a saw tooth profile, with discrete W-ribs exhibiting higher variations. Along spanwise direction, discrete V-ribs showed larger variations. Maximum variation in local heat transfer coefficients is estimated to be 25%. For experimented Re range, friction loss for discrete W-ribs is higher than discrete-V ribs. Rib profiles exhibited superior heat transfer capabilities. The best Nu/Nuo achieved for discrete Vribs is 3.4 and discrete W-ribs is 3.6. In view of superior heat transfer capabilities, ribs can be deployed in cooling passages near the leading edge, where the temperatures are very high. The best THPo achieved is 3.2 for discrete V-ribs and 3 for discrete W-ribs at Re 30000. The ribs can also enhance the power-toweight ratio as they can produce high thermohydraulic performances for low blockage ratios.

Investigation of Endwall Heat Transfer in Staggered Pin Fin Arrays

2021 ◽  
Vol 143 (2) ◽  
Author(s):  
Marcel Otto ◽  
Gaurav Gupta ◽  
Patrick K. Tran ◽  
Shinjan Ghosh ◽  
Jayanta S. Kapat
Keyword(s):  
Heat Transfer ◽  
Maximum Velocity ◽  
Local Heat Transfer ◽  
Horseshoe Vortex ◽  
Local Heat ◽  
Channel Length ◽  
Stereoscopic Particle Image Velocimetry ◽  
Thermochromic Liquid Crystal ◽  
Transfer Coefficients ◽  
Vortical Structures

Abstract Arrays of staggered pin fins are a typical geometry found in the trailing edge region of modern airfoils. If coolant is supplied by bleeding from the mid-section of the airfoil instead of provided through the root, the channel length is insufficiently long to reach a fully developed flow which is commonly found from the fifth row downstream. This present study focuses on the developing section (four rows) of a staggered array with a height-to-diameter ratio of 2 and a spanwise and streamwise spacing of 2.5, respectively. Measurements are conducted at Reynolds numbers of 10,000 and 30,000 based on the maximum velocity and pin diameter. Stereoscopic particle image velocimetry (PIV) is used to describe the flow field and turbulence characteristics in the wake of the first and third row pin. It is found that the dominating vortical structures depend highly on the Reynolds number. A transient thermochromic liquid crystal (TLC) technique is used to obtain local heat transfer coefficients on the endwall which are then discussed in the context with the vortical structures. The structure of the horseshoe vortex and the transient wake shedding behaves differently in the first and third row. The interaction of both vortex systems affects directly the endwall heat transfer. The results are supplemented by a thorough discussion of TLC and PIV uncertainty.

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.

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