scholarly journals Numerical Prediction of Film Cooling Effectiveness and the Associated Aerodynamic Losses With a Three-Dimensional Calculation Procedure

1990 ◽  
Author(s):  
G. H. Dibelius ◽  
R. Pitt ◽  
B. Wen
Keyword(s):  
Experimental Data ◽  
Film Cooling ◽  
Reverse Flow ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Temperature Pattern ◽  
Main Stream ◽  
Cooling Efficiency ◽  
Film Cooling Effectiveness ◽  
Aerodynamic Losses

Film cooling of turbine blades by injecting air through holes or slots affects the main stream flow. A numerical model has been developed to predict the resulting three-dimensional flow and the temperature pattern under steady flow conditions. An elliptic procedure is used in the near injection area to include reverse flow situations, while in the upstream area as well as far downstream a partial-parabolic procedure is applied. As first step an adiabatic wall has been assumed as boundary condition, since for this case experimental data are readily available for comparison. At elevated momentum blowing rates, zones of reverse flow occur downstream of the injection holes resulting in a decrease of cooling efficiency. A variation of the relevant parameters momentum blowing rate m, injection angle α and ratio of hole spacing to diameter s/d revealed the combination of m ≈ 1, α ≈ 30° and s/d ≈ 2 to be the optimum with respect to the averaged cooling efficiency and to the aerodynamic losses. Cooling is more efficient with slots than with a row of holes not considering the related problems of manufacture and service life. The calculated temperature patterns compare well with the experimental data available.

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.

Full Three-Dimensional Optimization Platform of Turbine Blades Considering the Film Cooling

2013 ◽  
Author(s):  
Shaopeng Lu ◽  
Zhongran Chi ◽  
Songtao Wang ◽  
Fengbo Wen ◽  
Guotai Feng
Keyword(s):  
Film Cooling ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Optimization Process ◽  
Pareto Optimal ◽  
Cooling Efficiency ◽  
Objective Functions ◽  
Nsga Ii ◽  
Aerodynamic Efficiency ◽  
Film Cooling Efficiency

In this paper, an optimization platform was established with Isight, cfx and the self-programming program which is used to generate the mesh. Film cooling effect can be taken into account. 15 parameters are selected as optimization variables. During the optimization process, the baseline blade and cooling holes are given by parameterized method. There are two objective functions during the optimization process. The first one is aerodynamic efficiency and the second one is film cooling efficiency. As there are two objective functions, NSGA-II is chosen as the multi-objective optimization algorithm. Then the Pareto-optimal front can be got. The results show that aerodynamic efficiency and film cooling efficiency restrict each other. It’s impossible to get the best solutions in one example, so the Pareto optimal set can provide a lot of choices. Different shapes make different effects on the aerodynamic efficiency and film cooling efficiency. From the above, it can be seen that the platform is helpful especially in the case that aerodynamic efficiency and film cooling efficiency restrict each other. This paper also discusses the prospects for platform applications.

Heat Transfer in Film-Cooled Turbine Blades

1993 ◽  
Author(s):  
Vijay K. Garg ◽  
Raymond E. Gaugler
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Film Cooling ◽  
Stokes Equations ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Explicit Finite Difference ◽  
Control Volumes

In order to study the effect of film cooling on the flow and heat transfer characteristics of actual turbine blades, a three-dimensional Navier-Stokes code has been developed. An existing code (Chima and Yokota, 1990) has been modified for the purpose. The code is an explicit finite difference code with an algebraic turbulence model. The thin-layer Navier-Stokes equations are solved using a general body-fitted coordinate system. The effects of film cooling have been incorporated into the code in the form of appropriate boundary conditions at the hole locations on the blade surface. Each hole exit is represented by several control volumes, thus providing an ability to study the effect of hole shape on the film-cooling characteristics. Comparison with experimental data is fair. Further validation of the code is required, however, and in this respect, there is an urgent need for detailed experimental data on actual turbine blades.

Numerical Investigation of the Three-Dimensional Temperature Field in the Near Hole Region of a Film Cooled Turbine Vane

1990 ◽  
Author(s):  
X. Coudray
Keyword(s):  
Temperature Field ◽  
Film Cooling ◽  
Thermal Environment ◽  
Physical Phenomenon ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Internal Boundary ◽  
Surface Distribution ◽  
Film Cooling Effectiveness ◽  
Turbine Vane

The increased severity of the thermal environment of high pressure turbine blades and vanes requires accurate calculations for the successful design of these parts. In this paper, the prediction of the temperature field in the near-cooling-hole region on a film cooled turbine vane is presented. The surface distribution of the heat transfer coefficient and the film cooling effectiveness on the vane in presence of one or several film cooling injections is obtained from boundary layer calculations and via experimental correlations. Cooling jet coalescence is taken into account as well as the main parameters governing this physical phenomenon. The internal boundary conditions result from available correlations. The study was conducted on two different configurations : a flat plate including an injection through two rows of holes and a turbine vane including three injections through two rows of holes on the suction side. Thermal computations using a three-dimensional finite element code yield strong temperature distortions and high temperature gradients around the injection zones. The study also indicates that the three-dimensional temperature field just downstream of the injections becomes two-dimensional when jet coalescence takes place. The influence of one or several obstructed injection holes on the temperature field is studied; important effects are observed when the main flow temperature is high.

The Near-Field Character of a Jet Discharged Normal to a Main Stream

1976 ◽  
Vol 98 (3) ◽  
pp. 373-378 ◽  
Author(s):  
G. Bergeles ◽  
A. D. Gosman ◽  
B. E. Launder
Keyword(s):  
Film Cooling ◽  
Reverse Flow ◽  
Near Field ◽  
Flow Region ◽  
Injection Rate ◽  
Main Stream ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Visualization Experiments ◽  
External Stream

The paper reports an experimental study of the flow created by the injection of a circular jet of air at 90 deg through a plane wall past which an external stream is flowing. Particular attention has been given to obtaining details of the flow in the vicinity of the injection hole and upstream from the hole. These regions have been omitted, or received only slight attention in earlier studies of discrete-hole cooling processes. Four ratios of average injectant velocity: external velocity were chosen in the range 0.046–0.50. Even at the lowest injection rate there is still a clearly identifiable reverse flow region springing from the downstream side of the hole which extends approximately 0.3 dia downstream. The velocity distribution in the jet at discharge was found to be greatly affected by the presence of the external stream, more than 75 percent of the flow leaving from the downstream half of the discharge hole with a peak velocity in the jet approximately three times the average. Contour mappings of the surface isobars, show the upstream and lateral effects on the static pressure caused by the injection. In addition a number of flow visualization experiments help to reinforce the inferred character of the flow. Detailed film-cooling effectiveness data are reported which help delineate the near-wall flow structure.

Numerical Predictions of Three-Dimensional Unsteady Turbulent Film-Cooling for Trailing Edge of Gas-Turbine Blade Using Large Eddy Simulation

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Ahmed Khalil ◽  
Hatem Kayed ◽  
Abdallah Hanafi ◽  
Medhat Nemitallah ◽  
Mohamed Habib
Keyword(s):  
Gas Turbine ◽  
Film Cooling ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Trailing Edge ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Gas Turbine Blades ◽  
Blowing Ratio ◽  
Eddy Simulation

This work investigates the performance of film-cooling on trailing edge of gas turbine blades using unsteady three-dimensional numerical model adopting large eddy simulation (LES) turbulence scheme in a low Mach number flow regime. This study is concerned with the scaling parameters affecting effectiveness and heat transfer performance on the trailing edge, as a critical design parameter, of gas turbine blades. Simulations were performed using ANSYS-fluentworkbench 17.2. High quality mesh was adapted, whereas the size of cells adjacent to the wall was optimized carefully to sufficiently resolve the boundary layer to obtain insight predictions of the film-cooling effectiveness on a flat plate downstream the slot opening. Blowing ratio, density ratio, Reynolds number, and the turbulence intensity of the mainstream and coolant flow are optimally examined against the film-cooling effectiveness. The predicted results showed a great agreement when compared with the experiments. The results show a distinctive behavior of the cooling effectiveness with blowing ratio variation as it has a dip in vicinity of unity which is explained by the behavior of the vortex entrainment and momentum of coolant flow. The negative effect of the turbulence intensity on the cooling effectiveness is demonstrated as well.

scholarly journals Experimental Study of Showerhead Cooling on a Cylinder Comparing Several Configurations Using Cylindrical and Shaped Holes

1999 ◽  
Author(s):  
H. Reiss ◽  
A. Bölcs
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Turbine Blades ◽  
Density Ratio ◽  
Test Facility ◽  
Main Stream ◽  
Transfer Coefficients ◽  
Surface Distribution ◽  
Film Cooling Effectiveness ◽  
Shaped Hole

Film cooling and heat transfer measurements on a cylinder model have been conducted using the transient thermochromic liquid crystal technique. Three showerhead cooling configurations adapted to leading edge film cooling of gas turbine blades were directly compared: ‘classical’ cylindrical holes versus two types of shaped hole exits. The experiments were carried out in a free jet test facility at two different flow conditions, Mach numbers M = 0.14 and M = 0.26, yielding Reynolds numbers based on the cylinder diameter of 8.6e4 and 1.55e5, respectively. All experiments were done at a main stream turbulence level of Tu = 7% with an integral lengthscale of Lx = 9.1mm (M = 0.14), or Lx = 10.5mm (M = 0.26) respectively. Foreign gas injection (CO2) was used yielding an engine-near density ratio of 1.6, with blowing ratios ranging from 0.6 to 1.5. Detailed experimental results are shown, including surface distribution of film cooling effectiveness and local heat transfer coefficients. Additionally, heat transfer and heat load augmentation due to injection with respect to the uncooled cylinder are reported. For a given cooling gas consumption the laid-back shaped hole exits lead to a clear enhancement of the cooling performance compared to cylindrical exits, whereas laterally expanded holes give only slight performance enhancement.

scholarly journals Systematic Study of Film Cooling With a Three-Dimensional Calculation Procedure

1985 ◽  
Author(s):  
A. O. Demuren ◽  
W. Rodi ◽  
B. Schönung
Keyword(s):  
Systematic Study ◽  
Film Cooling ◽  
Three Dimensional ◽  
Heat Fluxes ◽  
Main Stream ◽  
Test Cases ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Injection Angle ◽  
The Individual

The present paper describes three-dimensional calculations of film cooling by injection from a single row of holes. A systematic study of the influence of different parameters on the cooling effectiveness has been carried out. 27 test cases have been calculated, varying the injection angle (α = 10° / 45° / 90°), the relative spacing (s/D = 1.5/3/5) and the blowing rate (M = 0.5/1/2) for the same main-stream conditions. The governing 3D equations are solved by a finite volume method. The turbulent stresses and heat fluxes are obtained from a k-ε model modified to account for non-isotropic eddy viscosities and diffusivities. Examples of predicted velocity and temperature distributions are presented and compared with available experimental data. For all the test cases, the laterally averaged cooling effectiveness is given. On the whole, the agreement with experiments is fairly good, even though there are discrepancies about details in some of the cases. The influence of the individual parameters on the film cooling effectiveness is predicted correctly in all cases. This influence is discussed in some detail and the parameter combination with the best overall cooling performance is identified.

scholarly journals Comparison of Two-Equation Turbulence Models for Prediction of Heat Transfer on Film-Cooled Turbine Blades

1997 ◽  
Author(s):  
Vijay K. Garg ◽  
Ali A. Ameri
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Computer Time ◽  
Suction Surface ◽  
The Heat Transfer Coefficient

A three-dimensional Navier-Stokes code has been used to compute the heat transfer coefficient on two film-cooled turbine blades, namely the VKI rotor with six rows of cooling holes including three rows on the shower head, and the C3X vane with nine rows of holes including five rows on the shower head. Predictions of heat transfer coefficient at the blade surface using three two-equation turbulence models, specifically, Coakley’s q-ω model, Chien’s k-ε model and Wilcox’s k-ω model with Menter’s modifications, have been compared with the experimental data of Camci and Arts (1990) for the VKI rotor, and of Hylton et al. (1988) for the C3X vane along with predictions using the Baldwin-Lomax (B-L) model taken from Garg and Gaugler (1995). It is found that for the cases considered here the two-equation models predict the blade heat transfer somewhat better than the B-L model except immediately downstream of the film-cooling holes on the suction surface of the VKI rotor, and over most of the suction surface of the C3X vane. However, all two-equation models require 40% more computer core than the B-L model for solution, and while the q-ω and k-ε models need 40% more computer time than the B-L model, the k-ω model requires at least 65% more time due to slower rate of convergence. It is found that the heat transfer coefficient exhibits a strong spanwise as well as streamwise variation for both blades and all turbulence models.

Assessment of a Double Hole Film Cooling Geometry Using S-PIV and PSP

2013 ◽  
Author(s):  
Lesley M. Wright ◽  
Stephen T. McClain ◽  
Charles P. Brown ◽  
Weston V. Harmon
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Three Dimensional ◽  
Field Measurements ◽  
Secondary Flows ◽  
Cylindrical Hole ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Hole Geometry ◽  
Compound Angle

A novel, double hole film cooling configuration is investigated as an alternative to traditional cylindrical and fanshaped, laidback holes. This experimental investigation utilizes a Stereo-Particle Image Velocimetry (S-PIV) to quantitatively assess the ability of the proposed, double hole geometry to weaken or mitigate the counter-rotating vortices formed within the jet structure. The three-dimensional flow field measurements are combined with surface film cooling effectiveness measurements obtained using Pressure Sensitive Paint (PSP). The double hole geometry consists of two compound angle holes. The inclination of each hole is θ = 35°, and the compound angle of the holes is β = ± 45° (with the holes angled toward one another). The simple angle cylindrical and shaped holes both have an inclination angle of θ = 35°. The blowing ratio is varied from M = 0.5 to 1.5 for all three film cooling geometries while the density ratio is maintained at DR = 1.0. Time averaged velocity distributions are obtained for both the mainstream and coolant flows at five streamwise planes across the fluid domain (x/d = −4, 0, 1, 5, and 10). These transverse velocity distributions are combined with the detailed film cooling effectiveness distributions on the surface to evaluate the proposed double hole configuration (compared to the traditional hole designs). The fanshaped, laidback geometry effectively reduces the strength of the kidney-shaped vortices within the structure of the jet (over the entire range of blowing ratios considered). The three-dimensional velocity field measurements indicate the secondary flows formed from the double hole geometry strengthen in the plane perpendicular to the mainstream flow. At the exit of the double hole geometry, the streamwise momentum of the jets is reduced (compared to the single, cylindrical hole), and the geometry offers improved film cooling coverage. However, moving downstream in the steamwise direction, the two jets form a single jet, and the counter-rotating vortices are comparable to those formed within the jet from a single, cylindrical hole. These strong secondary flows lift the coolant off the surface, and the film cooling coverage offered by the double hole geometry is reduced.

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