Heat Transfer and Thermal Mechanical Stress Distributions in Gas Turbine Blades

2009 ◽  
Author(s):  
Fernando Z. Sierra ◽  
Diganta Narzary ◽  
Candelario Bolaina ◽  
Je Chin Han ◽  
Janusz Kubiak ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mechanical Stress ◽  
Finite Volume ◽  
Turbine Blades ◽  
Numerical Approach ◽  
Conjugate Problem ◽  
Operating Conditions ◽  
Temperature Sensitive ◽  
Blade Surface ◽  
Cooling Effectiveness

In this paper the distributions of heat transfer and thermal mechanical stress in the metal blade surface are investigated. The stream that surrounds the blade was considered at the time that the cooling airflow runs through the blade interior. Cooling channel flow and gases were simulated using a finite volume program, Fluent. The conjugate problem was addressed using coupled domains solid-fluid. Beside the numerical approach, measurements of metal blade surface temperature distributions based on the temperature sensitive paint technique, TSP, were conducted. The cooling effectiveness was compared showing good agreement between computational/experimental results. Additionally to laboratory conditions, finite volume results were obtained for real engine operating conditions. These results were used to establish temperature boundary conditions into a second computational model programmed in ANSYS, based on finite elements. This second model allowed calculating the distribution of thermo-mechanical stress in the blade material. The results show the temperature distribution in the blade surface. Based on this, the heat transfer rate was calculated finding it as a strong function of position. The cooling effectiveness was also calculated, which in turn performs with less variation over the sections of the blade under investigation. Following, the thermal effects in the metal blade surface lead to calculate the stress distribution. Differences in stresses magnitude were also found, suggesting a strong correlation between heat transfer and stress in the metal blade surface.

Determination of Heat Transfer Coefficients Around a Blade Surface From Temperature Measurements

1979 ◽  
Author(s):  
D. K. Mukherjee
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Turbine Blades ◽  
Operating Conditions ◽  
Main Stream ◽  
Blade Surface ◽  
Transfer Coefficients ◽  
Gas Turbine Blades ◽  
Heat Transfer Coefficients

To design cooled gas turbine blades, heat transfer coefficients around its surface are required. The calculated heat transfer data under operating conditions in the turbine are often inaccurate and require experimental verification. A method is presented here to determine the heat transfer coefficients around the blade surface and in the coolant channels. This requires measurements of the main stream and coolant temperatures together with the outer surface temperature distribution at varying mass flows. In order to conduct these tests in a gas turbine, test blades have to be specially prepared allowing the variation and measurement of coolant mass flow.

Conjugate Heat Transfer Characteristics of Double Wall Cooling With Gradient Diameter of Film and Impingement Holes

2021 ◽  
Author(s):  
Juan He ◽  
Qinghua Deng ◽  
Zhenping Feng
Keyword(s):  
Heat Transfer ◽  
Pressure Loss ◽  
Total Pressure ◽  
Flow Direction ◽  
Turbine Blades ◽  
Total Pressure Loss ◽  
Advanced Technique ◽  
Cooling Effectiveness ◽  
Uniform Pattern ◽  
Double Wall

Abstract Double wall cooling, consisting of internal impingement cooling and external film cooling, is believed to be the most advanced technique in modern turbine blades cooling. In this paper, to improve the uniformity of temperature distribution, a flat plate double wall cooling model with gradient diameter of film and impingement holes was proposed, and the heat transfer and flow characteristics were investigated by solving steady three-dimensional Reynolds-Averaged Navier-Stokes (RANS) equations with SST k-ω turbulence model. The influence of gradient diameter on overall cooling effectiveness and total pressure loss was studied by comparing with the uniform pattern at the blowing ratios ranging from 0.5 to 2. For gradient diameter of film hole patterns, results show that −10% film pattern always has the lowest film flow non-uniformity coefficient. The laterally averaged overall cooling effectiveness of uniform pattern lies between that of +10% and −10% film patterns, but the intersection of three patterns moves upstream from the middle of flow direction with the increase of blowing ratio. Therefore, the −10% film pattern exerts the highest area averaged cooling effectiveness, which is improved by up to 1.6% and 1% at BR = 0.5 and 1 respectively compared with a uniform pattern. However, at higher blowing ratios, the +10% film pattern maintains higher cooling effectiveness and lower total pressure loss. For gradient diameter of impingement hole patterns, the intersection of laterally averaged overall cooling effectiveness in three patterns is located near the middle of flow direction under all blowing ratios. The uniform pattern has the highest area averaged cooling effectiveness and the smallest non-uniform coefficient, but the −10% jet pattern has advantages of reducing pressure loss, especially in the laminated loss.

Cooling of Turbine Blades With Expanded Exit Holes: Computational Analyses of Leading Edge and Pressure-Side of a Turbine Blade

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Fariborz Forghan ◽  
Omid Askari ◽  
Uichiro Narusawa ◽  
Hameed Metghalchi
Keyword(s):  
High Speed ◽  
Turbine Blades ◽  
Leading Edge ◽  
Weak Shock ◽  
Suction Side ◽  
Pressure Side ◽  
Blade Surface ◽  
Cooling Effectiveness ◽  
Hot Gas ◽  
Computational Analyses

Turbine blades are cooled by a jet flow from expanded exit holes (EEH) forming a low-temperature film over the blade surface. Subsequent to our report on the suction-side (low-pressure, high-speed region), computational analyses are performed to examine the cooling effectiveness of the flow from EEH located at the leading edge as well as at the pressure-side (high-pressure, low-speed region). Unlike the case of the suction-side, the flow through EEH on the pressure-side is either subsonic or transonic with a weak shock front. The cooling effectiveness, η (defined as the temperature difference between the hot gas and the blade surface as a fraction of that between the hot gas and the cooling jet), is higher than the suction-side along the surface near the exit of EEH. However, its magnitude declines sharply with an increase in the distance from EEH. Significant effects on the magnitude of η are observed and discussed in detail of (1) the coolant mass flow rate (0.001, 0.002, and 0.004 (kg/s)), (2) EEH configurations at the leading edge (vertical EEH at the stagnation point, 50 deg into the leading-edge suction-side, and 50 deg into the leading-edge pressure-side), (3) EEH configurations in the midregion of the pressure-side (90 deg (perpendicular to the mainstream flow), 30 deg EEH tilt toward upstream, and 30 deg tilt toward downstream), and (4) the inclination angle of EEH.

Heat Transfer and Electrokinetic Flow Analysis in Poly(Dimethylsiloxane) Microfluidic Systems

2003 ◽  
Author(s):  
David Erickson ◽  
David Sinton ◽  
Vesna Nikolic ◽  
Dongqing Li
Keyword(s):  
Heat Transfer ◽  
Joule Heating ◽  
Volume Flow Rate ◽  
Flow Analysis ◽  
Numerical Approach ◽  
Temperature Sensitive ◽  
Microfluidic Systems ◽  
Buffer Solution ◽  
Channel Network ◽  
Electrokinetic Flow

Electrokinetic pumping is commonly used as a mechanism for species transport in microfluidic systems. Joule heating, caused by current flow through the buffer solution during electroosmotic flow, can lead to significant increases in the system temperature which can be detrimental to electrophoretic separations and temperature sensitive chemical reactions. In this paper, a combined experimental and numerical approach was used to examine Joule heating and heat transfer at a T intersection for PDMS/PDMS and PDMS/Glass hybrid microfluidic systems. In general it was found the PDMS/Glass chips maintained a more uniform and lower buffer temperature than the PDMS/PDMS systems, since the internally generated heat could be transferred more efficiently (due to the higher thermal conductivity of the glass component) from the channel network to the room temperature reservoir. This increase in temperature was shown to significantly increase the current load and the volume flow rate through the PDMS/PDMS system.

scholarly journals Prediction of Film Cooling Effectiveness of Steam

1982 ◽  
Author(s):  
Je-Chin Han ◽  
P. E. Jenkins
Keyword(s):  
Film Cooling ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Air Cooling ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Gas Turbine Blades ◽  
Fluid Properties ◽  
Three Dimensional Models

The intent of this work is to show, analytically, that superheated steam can provide better film cooling than conventional air for gas turbine blades and vanes. Goldstein’s two-dimensional and Eckert’s three-dimensional models have been reexamined and modified in order to include the effects of thermal-fluid properties of foreign gas injection on the film cooling effectiveness. Based on the modified models, the computed results for steam film cooling effectiveness, showing an increase of 80 to 100 percent when compared with air cooling at the same operating conditions, are presented.

scholarly journals Recent Studies in Turbine Blade Cooling

2004 ◽  
Vol 10 (6) ◽  
pp. 443-457 ◽  
Author(s):  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Gas Turbines ◽  
Critical Role ◽  
Turbine Blades ◽  
Moment Closure ◽  
Image Method ◽  
Blade Surface ◽  
Film Cooling Effectiveness ◽  
Free Stream Turbulence

Gas turbines are used extensively for aircraft propulsion, land-based power generation, and industrial applications. Developments in turbine cooling technology play a critical role in increasing the thermal efficiency and power output of advanced gas turbines. Gas turbine blades are cooled internally by passing the coolant through several rib-enhanced serpentine passages to remove heat conducted from the outside surface. External cooling of turbine blades by film cooling is achieved by injecting relatively cooler air from the internal coolant passages out of the blade surface in order to form a protective layer between the blade surface and hot gas-path flow. For internal cooling, this presentation focuses on the effect of rotation on rotor blade coolant passage heat transfer with rib turbulators and impinging jets. The computational flow and heat transfer results are also presented and compared to experimental data using the RANS method with various turbulence models such as k-ε, and second-moment closure models. This presentation includes unsteady high free-stream turbulence effects on film cooling performance with a discussion of detailed heat transfer coef- ficient and film-cooling effectiveness distributions for standard and shaped film-hole geometry using the newly developed transient liquid crystal image method.

Trailing Edge Film Cooling of Gas Turbine Airfoils: External Cooling Performance of Various Internal Pin Fin Configurations

2010 ◽  
Author(s):  
T. Horbach ◽  
A. Schulz ◽  
H.-J. Bauer
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Turbine Blades ◽  
Back Surface ◽  
Trailing Edge ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Major Interest ◽  
Pin Fins ◽  
Discharge Behavior

The present paper describes an experimental study on trailing edge film cooling of modern high-pressure turbine blades using coolant ejection through planar slots on a pressure side cutback. The experimental test section consists of a generic scaled-up trailing edge model in an atmospheric open loop wind tunnel, which has been used in earlier studies by Martini et al. (e.g. [1]). An infrared thermographic measurement technique is employed, which allows for the application of engine-realistic density ratios around 1.6 by increasing the main flow temperature. The effects of different geometric configurations on the structure and performance of the cooling film are investigated in terms of film cooling effectiveness, heat transfer, and discharge behavior. Among other issues, the interaction between internal turbulators, namely an array of pin fins, with the ejection slot lip is of major interest. Therefore, different designs of the coolant ejection lip are studied. Four different ratios of lip thickness to ejection slot height (t/H = 0.2, 0.5, 1.0, 1.5) are investigated as well as three different lip profiles representing typical manufacturing imperfections and wear. Other geometric variations comprise elliptic pin fins with spanwise and streamwise orientation and the application of land extensions from the internal coolant cavity onto the cut-back surface. The blowing ratio is varied between 0.2 < M < 1.25. In terms of film cooling effectiveness the results show a strong dependency on ejection lip thickness and minor improvements are obtained with a rounded ejection lip profile. Significant improvements are achieved using land extensions. The elliptic pin fins have a strong effect on discharge behavior as well as on film cooling effectiveness and heat transfer. Except for the elliptic pin fins, the geometric variations have only a minor influence on heat transfer.

Boundary Layer Calculation Including the Prediction of Transition and Curvature Effects

1989 ◽  
Author(s):  
B. Guyon ◽  
T. Arts
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Boundary Layers ◽  
Convex Surface ◽  
Turbine Blades ◽  
Operating Conditions ◽  
Detailed Knowledge ◽  
Flat Plates ◽  
Transfer Rates ◽  
Curvature Effects

The calculation of surface temperature on gas turbine blades in severe operating conditions requires a detailed knowledge of boundary layers behaviour. The prediction of laminar to turbulent transition as to existence and location, as well as the evaluation of heat transfer rates are major concerns. The program developed by SNECMA for this purpose is presented, in which models are introduced to take into account the main effects occuring on blades without film-cooling. The algorithm and discretisation scheme for boundary layer equations is Patankar and Spalding’s, with profiles initialization by Pohlhausen’s method. The turbulence and transition model, after Mc Donald and Fish, was improved in search for more stability and to have a better detection of the beginning of the transition. Adams and Johnston’s model for curvature, including propagation effects, was adapted to a transitional boundary layer. The validation tests of this program are described, which are based on numerous experimental data taken from a bibliography of tests over flat plates and blades. Other tests use heat transfer rate measurements conducted by SNECMA, together with VKI, on vanes and blades in non-rotating grids. The calculation results are further compared to the STAN5 program results; they show a superiority in predicting the transfer rates on a convex surface and for transitional boundary layers.

Developing Buoyancy-Modified Turbulent Flow in Ducts Rotating in Orthogonal Mode

1995 ◽  
Vol 117 (3) ◽  
pp. 474-484 ◽  
Author(s):  
T. Bo ◽  
H. Iacovides ◽  
B. E. Launder
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Rotation Number ◽  
Numerical Study ◽  
Turbine Blades ◽  
Turbulence Models ◽  
Operating Conditions ◽  
Wall Region ◽  
Flow Development

A numerical study of developing flow through a heated duct of square cross section rotating in orthogonal mode is reported. The two main aims are to explore the effects of rotational buoyancy on the flow development and to assess the ability of available turbulence models to predict such flows. Two test cases have been computed corresponding to values of the rotation number, Ro, of 0.12 and 0.24, which are typical of operating conditions in internal cooling passages of gas turbine blades. Computations from three turbulence models are presented: a k–ε eddy viscosity (EVM) model matched to a low-Reynolds-number one-equation EVM in the near-wall region; a low-Re k–ε EVM and a low-Re algebraic stress model (ASM). Additional computations in which the fluid density is assumed to remain constant allow the distinct contributions from buoyancy and Coriolis forces to be separated. It is thus shown that rotational buoyancy can have a substantial influence on the flow development and that, in the case of outward flow, it leads to a considerable increase of the side-averaged heat transfer coefficient. The Coriolis-induced secondary motion leads to an augmentation of the mean heat transfer coefficient on the pressure surface and a reduction on the suction side. The k–ε/one-equation EVM produces a mostly reasonable set of heat transfer predictions, but some deficiencies do emerge at the higher rotation number. In contrast, predictions with the low-Re k–ε EVM return a spectacularly unrealistic behavior while the low-Re ASM thermal predictions are in encouragingly close agreement with available measurements.

Parametric Study of Showerhead Film Cooling Performance on a Gas Turbine Blade

2014 ◽  
Author(s):  
G. Urquiza ◽  
J. O. Davalos ◽  
J. C. Garcia ◽  
L. Castro ◽  
J. A. Rodríguez ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Turbine Blade ◽  
Film Cooling ◽  
Operating Conditions ◽  
Geometrical Parameters ◽  
Blade Surface ◽  
Gas Turbine Blade ◽  
Gas Temperature ◽  
Cooling Effectiveness ◽  
Blade Geometry

Gas turbine power and efficiency have direct relation with inlet gas temperature. However, high gas temperature could cause thermal damage to gas turbine blade material. Gas turbine blade could be cooled using the so-called film cooling technique which is necessary to ensure blade material integrity. In film cooling, air from compressor is injected through internal blade ducts. The air leaves the internal ducts through holes placed on blade surface, creating a cooling film on the blade surface. Operating conditions and hole geometrical factors can influence the cooling effectiveness. Several investigations have been conducted related to film cooling in order to study its behavior under different conditions. Due to its complexity, many studies replace blade geometry for flat plates. A better approximation to realistic results could be obtained by modeling the blade geometry with cooling holes. In this work, influence of geometrical parameters on cooling effectiveness under different operating conditions, like blowing ratio and angular velocity, is studied by means of numerical analysis using a commercial CFD code. The object of study is a typical showerhead configuration at mid-span of the tested blade, with three rows of cooling holes. In order to reduce computational cost, an algorithm was implemented to generate blade geometries and grids, performing numerical analyses and computing results in an automatic way, based on selected parameters. The algorithm could be used in optimization process to reduce the effort used in the construction geometries. The results show the effects of change geometrical parameters on cooling effectiveness. Additionally, changes on cooling flow direction are observed at high angular velocities.

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