Adiabatic and Overall Effectiveness Measurements of an Effusion Cooling Array for Turbine Endwall Application

2008 ◽  
Author(s):  
A. Ceccherini ◽  
B. Facchini ◽  
L. Tarchi ◽  
L. Toni
Keyword(s):  
Steady State ◽  
Plastic Material ◽  
Experimental Measurements ◽  
Post Processing ◽  
3D Fem ◽  
Injection Angle ◽  
Blowing Ratio ◽  
Processing Procedure ◽  
Adiabatic Effectiveness ◽  
Overall Effectiveness

An experimental analysis for the evaluation of adiabatic and overall effectiveness of an effusion cooling geometry is presented in this paper. Chosen configuration is a flat plate with 98 holes, with a feasible arrangement for a turbine endwall. Fifteen staggered rows with equal spanwise and streamwise pitches (Sx/D = Sy/D = 8.0), a length to diameter ratio of 42.9 and an injection angle of 30 degrees are investigated. Measurements have been done on two different test samples made both of plastic material and stainless steel. Adiabatic tests were carried out in order to obtain adiabatic effectiveness bidimensional maps. Even if a very low conductivity material (PVC) was used, adiabatic tests on a typical effusion geometry suffer, undoubtedly, from conductive phenomena: a full 3D FEM post-processing procedure for gathered experimental data was therefore developed for reckoning thermal fluxes across the surface and then correctly obtaining adiabatic effectiveness distributions. Objective of the tests performed on the conductive plate, having the same flow parameters as the adiabatic ones, was the estimation of overall efficiency of the cooled region. Experimental measurements were carried out imposing two different crossflow Mach numbers, 0.15 and 0.40, and varying blowing ratio from 0.5 to 1.7; effectiveness of the cooled surface was evaluated with a steady-state technique, using TLC (Thermochromic Liquid Crystal) wide band formulation. Finally, RANS steady-state calculations were performed employing an open source CFD code: an adiabatic case have been simulated, using both a standard and an anisotropic turbulence model. Numerical achievements have then been compared to experimental measurements. Results show that the post-processing procedure correctly succeeded in deducting undesired thermal fluxes across the plate in adiabatic effectiveness evaluation. The increasing blowing ratio effect leads to lower adiabatic effectiveness mean values, while it makes overall effectiveness to grow.

Adiabatic and Overall Effectiveness Measurements of an Effusion Cooling Array for Turbine Endwall Application

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Bruno Facchini ◽  
Lorenzo Tarchi ◽  
Lorenzo Toni ◽  
Alberto Ceccherini
Keyword(s):  
Steady State ◽  
Plastic Material ◽  
Wide Band ◽  
Experimental Measurements ◽  
Thermochromic Liquid Crystal ◽  
Mean Values ◽  
Injection Angle ◽  
Blowing Ratio ◽  
Adiabatic Effectiveness ◽  
Overall Effectiveness

An experimental analysis for the evaluation of adiabatic and overall effectiveness of an effusion cooling geometry is presented in this paper. Chosen configuration is a flat plate with 98 holes, with a feasible arrangement for a turbine endwall. Fifteen staggered rows with equal spanwise and streamwise pitches (Sx/D=Sy/D=8.0), a length to diameter ratio of 42.9 and an injection angle of 30 deg are investigated. Measurements have been done on two different test samples made both of plastic material and stainless steel. Adiabatic tests were carried out in order to obtain adiabatic effectiveness bidimensional maps. Even if a very low conductivity material polyvinyl chloride was used, adiabatic tests on a typical effusion geometry suffer, undoubtedly, from conductive phenomena: a full three-dimensional finite element method postprocessing procedure for gathered experimental data was therefore developed for reckoning thermal fluxes across the surface and then correctly obtaining adiabatic effectiveness distributions. The objective of the tests performed on the conductive plate, having the same flow parameters as the adiabatic ones, was the estimation of overall efficiency of the cooled region. Experimental measurements were carried out imposing two different crossflow Mach numbers, 0.15 and 0.40, and varying blowing ratio from 0.5 to 1.7; effectiveness of the cooled surface was evaluated with a steady-state technique, using thermochromic liquid crystal wide band formulation. Results show that the postprocessing procedure correctly succeeded in deducting undesired thermal fluxes across the plate in adiabatic effectiveness evaluation. The increasing blowing ratio effect leads to lower adiabatic effectiveness mean values, while it makes overall effectiveness to grow. Finally, Reynolds-averaged Navier–Stokes steady-state calculations were performed employing an open source computational fluid dynamics code: an adiabatic case has been simulated using both a standard and an anisotropic turbulence model. Numerical achievements have then been compared with experimental measurements.

Investigation of Circular and Shaped Effusion Cooling Arrays for Combustor Liner Application—Part 2: Numerical Analysis

2009 ◽  
Author(s):  
A. Andreini ◽  
C. Bianchini ◽  
A. Ceccherini ◽  
B. Facchini ◽  
L. Mangani ◽  
...  
Keyword(s):  
Numerical Analysis ◽  
Cross Flow ◽  
Lateral Spreading ◽  
Elliptical Cross ◽  
Injection Angle ◽  
Blowing Ratio ◽  
Combustor Liner ◽  
Effectiveness Data ◽  
Overall Effectiveness ◽  
Good Agreement

A numerical analysis of two different effusion cooled plates, with a feasible arrangement for combustor liner application, is presented in this paper. Though having the same porosity and very shallow injection angle (17°), the first configuration presents a “conventional” circular drilling, while the other has “shaped” holes with such an elliptical cross-section that leads to a circular imprint on the cooled surface. Either geometries were the object of an experimental survey in which both adiabatic and overall effectiveness were measured. In order to compensate for the lack of detailed aerodynamic measurements, 3D CFD computations were performed for the two geometries. Steady state RANS calculations were carried out using a k–ε Two Layer turbulence model, both in the standard isotropic and in an algebraically corrected non isotropic version specifically tuned to better predict the lateral spreading of jets in a cross flow. Flow characteristic reproduce typical effusion cooled combustor liner conditions with blowing ratio of 5 and coolant jet Reynolds number of 12500. Even though good agreement could not be obtained comparing thermal adiabatic effectiveness with experiments, the findings of the experiments regarding the rating of the cooling efficiency of the two configurations were confirmed. Additionally, conjugate simulations were performed for the circular hole geometry in order to quantify heat transfer effects and to directly compare them with raw experimental overall effectiveness data.

Investigation of Discrete-Hole Film Cooling Parameters Using Curved-Plate Models

1999 ◽  
Vol 121 (4) ◽  
pp. 792-803 ◽  
Author(s):  
M. K. Berthe ◽  
S. V. Patankar
Keyword(s):  
Film Cooling ◽  
Stokes Equations ◽  
Turbulent Viscosity ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Grid Turbulence ◽  
Injection Angle ◽  
Flat Surfaces ◽  
Blowing Ratio ◽  
Adiabatic Effectiveness

Computations have been conducted on curved, three-dimensional discrete-hole film cooling geometries that included the mainflow, injection hole, and supply plenum regions. Both convex and concave film cooling geometries were studied. The effects of several film cooling parameters have been investigated, including the effects of blowing ratio, injection angle, hole length, hole spacing, and hole staggering. The blowing ratio was varied from 0.5 to 1.5, the injection angle from 35 to 65 deg, the hole length from 1.75D to 6.0D, and the hole spacing from 2D to 3D. The staggered-hole arrangement considered included two rows. The computations were performed by solving the fully elliptic, three-dimensional Navier–Stokes equations over a body-fitted grid. Turbulence closure was achieved using a modified k–ε model in which algebraic relations were used for the turbulent viscosity and the turbulent Prandtl number. The results presented and discussed include plots of adiabatic effectiveness as well as plots of velocity contours and velocity vectors in cross-stream planes. The present study reveals that the blowing ratio, hole spacing, and hole staggering are among the most significant film cooling parameters. Furthermore: (1) The optimum blowing ratios for curved surfaces are higher than those for flat surfaces, (2) a reduction of hole spacing from 3D to 2D resulted in a very significant increase in adiabatic effectiveness, especially on the concave surface, (3) the increase in cooling effectiveness with decreasing hole spacing was found to be due to not only the increased coolant mass per unit area, but also the smaller jet penetration and the weaker counterrotating vortices, (4) for all practical purposes, the hole length was found to be a much less significant film cooling parameter.

scholarly journals Investigation of Discrete-Hole Film Cooling Parameters Using Curved-Plate Models

1998 ◽  
Author(s):  
Mulugeta K. Berhe ◽  
Suhas V. Patankar
Keyword(s):  
Film Cooling ◽  
Stokes Equations ◽  
Turbulent Viscosity ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Grid Turbulence ◽  
Injection Angle ◽  
Flat Surfaces ◽  
Blowing Ratio ◽  
Adiabatic Effectiveness

Computations have been conducted on curved, three-dimensional discrete-hole film cooling geometries that included the mainflow, injection hole, and supply plenum regions. Both convex and concave film cooling geometries were studied. The effects of several film cooling parameters have been investigated, including the effects of blowing ratio, injection angle, hole length, hole spacing, and hole staggering. The blowing ratio was varied from 0.5 to 1.5, the injection angle from 35° to 65°, the hole length from 1.75D to 6.0D, and the hole spacing from 2D to 3D. The staggered-hole arrangement considered included two rows. The computations were performed by solving the fully elliptic, three dimensional Navier-Stokes equations over a body fitted grid. Turbulence closure was achieved using a modified k-ε model in which algebraic relations were used for the turbulent viscosity and the turbulent Prandtl number. The results presented and discussed include plots of adiabatic effectiveness as well as plots of velocity contours and velocity vectors in cross-stream planes. The present study reveals that the blowing ratio, hole spacing, and hole staggering are among the most significant film cooling parameters. Furthermore: (1) the optimum blowing ratios for curved surfaces are higher than those for flat surfaces, (2) a reduction of hole spacing from 3D to 2D resulted in a very significant increase in adiabatic effectiveness, especially on the concave surface, (3) the increase in cooling effectiveness with decreasing hole spacing was found due to not only the increased coolant mass per unit area, but also the smaller jet penetration and the weaker counter-rotating vortices, (4) for all practical purposes, the hole length was found to be a much less significant film cooling parameter.

scholarly journals A CFD Benchmark Study: Leading Edge Film-Cooling With Compound Angle Injection

1997 ◽  
Author(s):  
C. A. Martin ◽  
K. A. Thole
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Leading Edge ◽  
Stagnation Region ◽  
Injection Angle ◽  
Blowing Ratio ◽  
Adiabatic Effectiveness ◽  
Film Cooling Holes ◽  
Compound Angle ◽  
Good Agreement

This paper presents a blind CFD benchmark of a simulated leading edge for a turbine airfoil. The geometry studied was relevant for current designs with two rows of staggered film-cooling holes located at the stagnation location (θ = 0°) and at θ = 25°. Both rows of cooling holes were blowing in the same direction which was 90° relative to the streamwise direction and had an injection angle with respect to the surface of 20°. Realistic engine conditions were simulated including a density ratio of DR = 1.8 and an average blowing ratio of M = 2 for both rows of cooling holes. This blind benchmark coincided with an experimental study that took place in a wind tunnel simulation of a quarter cylinder followed by a flat afterbody. At the stagnation region, the CFD calculation overpredicted the adiabatic effectiveness because the model failed to predict a small separation region that was measured in the experiments. Good agreement was achieved, however, between the CFD predictions and the experimentally measured values of the laterally averaged adiabatic effectiveness downstream of the stagnation location. The coolant pathlines showed that flow passed from the first row of holes over the second row of cooling holes indicating a waste of the coolant.

Overall Effectiveness for a Film Cooled Turbine Blade Leading Edge With Varying Hole Pitch

2010 ◽  
Author(s):  
Thomas E. Dyson ◽  
Dave G. Bogard ◽  
Justin D. Piggush ◽  
Atul Kohli
Keyword(s):  
Turbine Blade ◽  
Hot Spots ◽  
Leading Edge ◽  
Stagnation Line ◽  
Convective Cooling ◽  
Impingement Cooling ◽  
Blowing Ratio ◽  
Cylindrical Holes ◽  
Overall Effectiveness ◽  
Blade Leading Edge

Overall effectiveness, φ, for a simulated turbine blade leading edge was experimentally measured using a model constructed with a relatively high conductivity material selected so that the Biot number of the model matched engine conditions. The model incorporated three rows of cylindrical holes with the center row positioned on the stagnation line. Internally the model used an impingement cooling configuration. Overall effectiveness was measured for pitch variation from 7.6d to 9.6d for blowing ratios ranging from 0.5 to 3.0, and angle of attack from −7.7° to +7.7°. Performance was evaluated for operation with a constant overall mass flow rate of coolant. Consequently when increasing the pitch, the blowing ratio was increased proportionally. The increased blowing ratio resulted in increased impingement cooling internally and increased convective cooling through the holes. The increased internal and convective cooling compensated, to a degree, for the decreased coolant coverage with increased pitch. Performance was evaluated in terms of laterally averaged φ, but also in terms of the minimum φ. The minimum φ evaluation revealed localized hot spots which are arguably more critical to turbine blade durability than the laterally averaged results. For small increases in pitch there was negligible decrease in performance.

scholarly journals Large Eddy Simulation of Film Cooling Involving Compound Angle Holes: Comparative Study of LES and RANS

Processes ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 198
Author(s):  
Seung Il Baek ◽  
Joon Ahn
Keyword(s):  
Large Eddy Simulation ◽  
Film Cooling ◽  
Orientation Angle ◽  
Turbulence Models ◽  
Film Cooling Effectiveness ◽  
Injection Angle ◽  
Blowing Ratio ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Compound Angle

A large eddy simulation (LES) was performed for film cooling in the gas turbine blade involving spanwise injection angles (orientation angles). For a streamwise coolant injection angle (inclination angle) of 35°, the effects of the orientation angle were compared considering a simple angle of 0° and 30°. Two ratios of the coolant to main flow mass flux (blowing ratio) of 0.5 and 1.0 were considered and the experimental conditions of Jung and Lee (2000) were adopted for the geometry and flow conditions. Moreover, a Reynolds averaged Navier–Stokes simulation (RANS) was performed to understand the characteristics of the turbulence models compared to those in the LES and experiments. In the RANS, three turbulence models were compared, namely, the realizable k-ε, k-ω shear stress transport, and Reynolds stress models. The temperature field and flow fields predicted through the RANS were similar to those obtained through the experiment and LES. Nevertheless, at a simple angle, the point at which the counter-rotating vortex pair (CRVP) collided on the wall and rose was different from that in the experiment and LES. Under the compound angle, the point at which the CRVP changed to a single vortex was different from that in the LES. The adiabatic film cooling effectiveness could not be accurately determined through the RANS but was well reflected by the LES, even under the compound angle. The reattachment of the injectant at a blowing ratio of 1.0 was better predicted by the RANS at the compound angle than at the simple angle. The temperature fluctuation was predicted to decrease slightly when the injectant was supplied at a compound angle.

The Effect of Freestream Turbulence on Film Cooling Adiabatic Effectiveness

2002 ◽  
Author(s):  
James E. Mayhew ◽  
James W. Baughn ◽  
Aaron R. Byerley
Keyword(s):  
Flat Plate ◽  
Film Cooling ◽  
Density Ratio ◽  
Main Flow ◽  
Freestream Turbulence ◽  
Coverage Area ◽  
Liquid Crystal Thermography ◽  
Blowing Ratio ◽  
Adiabatic Effectiveness ◽  
Cooling Air

The film-cooling performance of a flat plate in the presence of low and high freestream turbulence is investigated using liquid crystal thermography. High-resolution distributions of the adiabatic effectiveness are determined over the film-cooled surface of the flat plate using the hue method and image processing. Three blowing rates are investigated for a model with three straight holes spaced three diameters apart, with density ratio near unity. High freestream turbulence is shown to increase the area-averaged effectiveness at high blowing rates, but decrease it at low blowing rates. At low blowing ratio, freestream turbulence clearly reduces the coverage area of the cooling air due to increased mixing with the main flow. However, at high blowing ratio, when much of the jet has lifted off in the low turbulence case, high freestream turbulence turns its increased mixing into an asset, entraining some of the coolant that penetrates into the main flow and mixing it with the air near the surface.

scholarly journals Redox mediation at poly(o-aminophenol) coated electrodes: Mechanistic diagnosis from steady state polarization curves

2018 ◽  
Author(s):  
Gabriel Ybarra ◽  
Carlos Moina ◽  
María Inés Florit ◽  
Dionisio Posadas
Keyword(s):  
Steady State ◽  
Polarization Curve ◽  
Experimental Measurements ◽  
Steady State Current ◽  
Thermodynamical Parameters ◽  
Reduction And Oxidation ◽  
Mediated Reduction ◽  
Coated Electrodes ◽  
Current Potential ◽  
Potential Curves

<p class="PaperAbstract"><span lang="EN-US">In this work, the mediated reduction and oxidation of Fe(CN)<sub>6</sub><sup>3-/4-</sup> and Fe<sup>3+ </sup>in poly(o-aminophenol) coated electrodes is analyzed by means of diagnosis diagram based on the features of steady state current-potential curves. This analysis allows to identify the current determining process and to reproduce the experimental characteristics of the polarization curve from the relevant kinetic and thermodynamical parameters with a minimum amount of experimental measurements. </span></p>

Experimental Study of the Effects of an Oscillating Approach Flow on Overall Cooling Performance of a Simulated Turbine Blade Leading Edge

2009 ◽  
Author(s):  
Ross Johnson ◽  
Jonathan Maikell ◽  
David Bogard ◽  
Justin Piggush ◽  
Atul Kohli ◽  
...  
Keyword(s):  
Turbine Blade ◽  
Film Cooling ◽  
Density Ratio ◽  
Leading Edge ◽  
Stagnation Line ◽  
Cooling Performance ◽  
Blowing Ratio ◽  
Oscillation Frequencies ◽  
Overall Effectiveness ◽  
Blade Leading Edge

When a turbine blade passes through wakes from upstream vanes it is subjected to an oscillation of the direction of the approach flow resulting in the oscillation of the position of the stagnation line on the leading edge of the blade. In this study an experimental facility was developed that induced a similar oscillation of the stagnation line position on a simulated turbine blade leading edge. The overall effectiveness was evaluated at various blowing ratios and stagnation line oscillation frequencies. The location of the stagnation line on the leading edge was oscillated to simulate a change in angle of attack between α = ± 5° at a range of frequencies from 2 to 20 Hz. These frequencies were chosen based on matching a range of Strouhal numbers typically seen in an engine due to oscillations caused by passing wakes. The blowing ratio was varied between M = 1, M = 2, and M = 3. These experiments were carried out at a density ratio of DR = 1.5 and mainstream turbulence levels of Tu ≈ 6%. The leading edge model was made of high conductivity epoxy in order to match the Biot number of an actual engine airfoil. Results of these tests showed that the film cooling performance with an oscillating stagnation line was degraded by as much as 25% compared to the performance of a steady flow with the stagnation line aligned with the row of holes at the leading edge.

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