Characterization of the Velocity and Heat Transfer Fields in an Internal Cooling Channel With High Blockage Ratio

2002 ◽  
Author(s):  
Luca Casarsa ◽  
Murat C¸akan ◽  
Tony Arts
Keyword(s):  
Heat Transfer ◽  
Flow Direction ◽  
Numerical Code ◽  
Internal Cooling ◽  
Blockage Ratio ◽  
Cooling Channel ◽  
Mean Flow ◽  
Turbine Blade Cooling ◽  
Image Velocimetry ◽  
Flow Features

The present experimental study is dealing with a detailed aero/thermal investigation of the turbulent flow inside a rib-roughened turbine blade cooling channel by means of Particle Image Velocimetry (PIV) and Liquid Crystal Thermometry (LCT). The main objectives of the paper are to provide detailed information about the behaviour of such a complicated flow, useful for its understanding, and to create a wide and reliable data base for numerical code validation. The measurements are carried out at engine representative Reynolds number within a scaled up model of a stationary straight cooling channel, with turbulent promoters (or ribs) installed on one wall. The ribs have an angle of attack of 90 deg with respect to the “mean” flow direction; their blockage ratio is equal to 30%. Detailed wall heat transfer distributions are presented. The main time-averaged flow features are identified and quantified; a number of rms characteristics are put in evidence and compared to the heat transfer distributions.

Experimental Investigation of the Aerothermal Performance of a High Blockage Rib-Roughened Cooling Channel

2005 ◽  
Vol 127 (3) ◽  
pp. 580-588 ◽  
Author(s):  
Luca Casarsa ◽  
Tony Arts
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Flow Field ◽  
Three Dimensional ◽  
Heat Transfer Process ◽  
Cooling Channel ◽  
Complex Flow ◽  
Turbine Blade Cooling ◽  
Flow Features ◽  
Rib Roughened

The present study deals with a detailed experimental investigation of the turbulent flow inside a rib-roughened turbine blade cooling channel. The measurements are carried out in a stationary straight channel with high blockage ribs installed on one wall. The main objective is to enhance the understanding and deepen the analysis of this complex flow field with the help of highly resolved particle image velocimetry measurements. A quasi-three-dimensional view of the flow field is achieved, allowing the identification of the main time-averaged coherent structures. The combined analysis of the present aerodynamic results with available heat transfer data emphasizes the role of the mean and fluctuating flow features in the heat transfer process. In particular, the stream wise/normal to the wall component of the Reynolds stress tensor is shown to be strictly related to the heat transfer rate on the channel surfaces. A correlation to estimate the heat transfer field from the aerodynamic data is presented for the high blockage rib roughened channel flow.

Heat Transfer Enhancement Using Angled Grooves as Turbulence Promoters

2013 ◽  
Author(s):  
Krishnendu Saha ◽  
Sumanta Acharya
Keyword(s):  
Heat Transfer ◽  
Flow Direction ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Transfer Enhancement ◽  
Number Range ◽  
Pressure Drops ◽  
Friction Factors ◽  
Mainstream Flow ◽  
Turbine Airfoils

An experimental study is conducted on a simulated internal cooling channel of a turbine airfoil using angled grooves and combination of grooves-ribs to enhance the heat transfer from the wall. The grooves are angled at 45° to the mainstream flow direction and combinations of four different geometries are studied that include: (1) angled grooves with a pitch, p/δ = 10, (2) angled groove with a larger pitch, p/δ = 15, (3) combination of angled groove and 45° angled rib, and (4) combination of angled groove with transverse rib. Transient liquid crystal experiments are conducted for a Reynolds number range of 13,000–55,000, and local and averaged heat transfer coefficient values are presented for all the geometries. Pressure drops are measured between the inlet and the exit of the grooved channel and friction factors are calculated. The combination of the angled groove and 45° angled rib provided the highest performance factor of the four cases considered, and these values were higher or comparable to among the best-performing rib geometries (45-degree broken ribs) commonly used in gas turbine airfoils.

Heat Transfer Enhancement Using Angled Grooves as Turbulence Promoters

2014 ◽  
Vol 136 (8) ◽  
Author(s):  
Krishnendu Saha ◽  
Sumanta Acharya
Keyword(s):  
Heat Transfer ◽  
Flow Direction ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Transfer Enhancement ◽  
Number Range ◽  
Pressure Drops ◽  
Friction Factors ◽  
Mainstream Flow ◽  
Turbine Airfoils

An experimental study is conducted on a simulated internal cooling channel of a turbine airfoil using angled grooves and combination of grooves-ribs to enhance the heat transfer from the wall. The grooves are angled at 45 deg to the mainstream flow direction and combinations of four different geometries are studied that include (1) angled grooves with a pitch, p/δ = 10, (2) angled groove with a larger pitch, p/δ = 15, (3) combination of angled groove and 45 deg angled rib, and (4) combination of angled groove with transverse rib. Transient liquid crystal experiments are conducted for a Reynolds number range of 13,000–55,000, and local and averaged heat transfer coefficient values are presented for all the geometries. Pressure drops are measured between the inlet and the exit of the grooved channel and friction factors are calculated. The combination of the angled groove and 45 deg angled rib provided the highest performance factor of the four cases considered, and these values were higher or comparable to among the best-performing rib geometries (45 deg broken ribs) commonly used in gas turbine airfoils.

Rotation Effects on the Heat Transfer Distribution in a Two-Pass Rotating Internal Cooling Channel Equipped With Triangular Ribs

2017 ◽  
Author(s):  
Ignacio Mayo ◽  
Tony Arts ◽  
Nicolas Van de Wyer
Keyword(s):  
Heat Transfer ◽  
Rotation Number ◽  
Channel Model ◽  
Flow Direction ◽  
Secondary Flows ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Experimental Conditions ◽  
Cfd Validation ◽  
The Impact

The present paper addresses the detailed heat transfer pattern in a two-pass rotating internal cooling channel model, with a square cross section and equipped with triangular ribs on one of its walls. The turn region consists of a smooth high curvature U-bend that generates a complex flow field and wall heat transfer. The investigation is based on Liquid Crystal Thermography (LCT) measurements in a rotating facility at Reynolds numbers varying from 20,000 to 60,000, and a maximum rotation number equal to 0.20. For these experimental conditions, the centripetal buoyancy effects are negligible. The channel is rotated around an axis perpendicular to the main flow direction in clockwise and counter-clockwise senses, in order to observe the impact of cyclonic and anti-cyclonic behavior on the heat transfer in both legs. The objective of the present study is two-fold: firstly, it aims to understand the flow physics and heat transfer phenomena at different regimes. Secondly, the detailed heat transfer measurements are intended to be a reference set for Computational Fluid Dynamics (CFD) validation. The measurements obtained in the first leg have been compared with previous experimental data in channels with square ribs and radially outward flow, showing a similar behavior in terms of heat transfer distribution and overall dependency on the rotation number. In the second leg, the heat transfer distribution is more complex. The heat transfer distribution is not symmetric, and high gradients are present in the span-wise direction. Nevertheless, the dependency of the heat transfer to increasing rotation shows a trend similar to the one observed in the first pass. The combined effects of rib-induced secondary flows stabilization/destabilization by rotation, Coriolis-induced stream-wise vortices and high streamline curvature on the heat transfer distribution are analyzed in the paper.

scholarly journals Heat Transfer in Rotating Serpentine Passages With Trips Normal to the Flow

1992 ◽  
Vol 114 (4) ◽  
pp. 847-857 ◽  
Author(s):  
J. H. Wagner ◽  
B. V. Johnson ◽  
R. A. Graziani ◽  
F. C. Yeh
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Large Scale ◽  
Flow Direction ◽  
Operating Conditions ◽  
Transfer Model ◽  
Transfer Coefficients ◽  
Flow Equations ◽  
Turbine Blade Cooling ◽  
Heat Transfer Coefficients

Experiments were conducted to determine the effects of buoyancy and Coriolis forces on heat transfer in turbine blade internal coolant passages. The experiments were conducted with a large-scale, multipass, heat transfer model with both radially inward and outward flow. Trip strips on the leading and trailing surfaces of the radial coolant passages were used to produce the rough walls. An analysis of the governing flow equations showed that four parameters influence the heat transfer in rotating passages: coolant-to-wall temperature ratio, Rossby number, Reynolds number, and radius-to-passage hydraulic diameter ratio. The first three of these four parameters were varied over ranges that are typical of advanced gas turbine engine operating conditions. Results were correlated and compared to previous results from stationary and rotating similar models with trip strips. The heat transfer coefficients on surfaces, where the heat transfer increased with rotation and buoyancy, varied by as much as a factor of four. Maximum values of the heat transfer coefficients with high rotation were only slightly above the highest levels obtained with the smooth wall model. The heat transfer coefficients on surfaces where the heat transfer decreased with rotation, varied by as much as a factor of three due to rotation and buoyancy. It was concluded that both Coriolis and buoyancy effects must be considered in turbine blade cooling designs with trip strips and that the effects of rotation were markedly different depending upon the flow direction.

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.

Effects of Pin Shape and Array Orientation on Heat Transfer and Pressure Loss in Pin Fin Arrays

1984 ◽  
Vol 106 (1) ◽  
pp. 252-257 ◽  
Author(s):  
D. E. Metzger ◽  
C. S. Fan ◽  
S. W. Haley
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Pressure Loss ◽  
Flow Direction ◽  
Circular Cross Section ◽  
Cycle Performance ◽  
Mean Flow ◽  
Pin Fin ◽  
The Mean ◽  
Cooling Air

Modern high-performance gas turbine engines operate at high turbine inlet temperatures and require internal convection cooling of many of the components exposed to the hot gas flow. Cooling air is supplied from the engine compressor at a cost to cycle performance and a design goal is to provide necessary cooling with the minimum required cooling air flow. In conjunction with this objective, two families of pin fin array geometries which have potential for improving airfoil internal cooling performance were studied experimentally. One family utilizes pins of a circular cross section with various orientations of the array with respect to the mean flow direction. The second family utilizes pins with an oblong cross section with various pin orientations with respect to the mean flow direction. Both heat transfer and pressure loss characteristics are presented. The results indicate that the use of circular pins with array orientation between staggered and inline can in some cases increase heat transfer while decreasing pressure loss. The use of elongated pins increases heat transfer, but at a high cost of increased pressure loss. In conjunction with the present measurements, previously published results were reexamined in order to estimate the magnitude of heat transfer coefficients on the pin surfaces relative to those of the endwall surfaces. The estimate indicates that the pin surface coefficients are approximately double the endwall values.

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.

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.

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