High Resolution Measurements of Local Effectiveness by Discrete Hole Film Cooling

1999 ◽  
Author(s):  
S. Baldauf ◽  
A. Schulz ◽  
S. Wittig
Keyword(s):  
Surface Temperature ◽  
Film Cooling ◽  
Density Ratio ◽  
Geometrical Parameters ◽  
Element Analysis ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Flow Parameters ◽  
Wide Range ◽  
Local Measurements

Local adiabatic film cooling effectiveness on a flat plate surface downstream a row of cylindrical holes was investigated. Geometrical parameters like blowing angle and hole pitch as well as the flow parameters blowing rate and density ratio were varied in a wide range emphasizing on engine relevant conditions. An IR-thermography technique was used to perform local measurements of the surface temperature field. A spatial resolution of up to 7 data points per hole diameter extending up to 80 hole diameters downstream of the ejection location was achieved. Since all technical surface materials have a finite thermoconductivity, no ideal adiabatic conditions could be established. Therefore, a procedure for correcting the measured surface temperature data based on a Finite Element analysis was developed. Heat loss over the backside of the testplate and remnant heat flux within the testplate in lateral and streamwise direction were taken into account. The local effectiveness patterns obtained are systematically analyzed to quantify the influence of the various parameters. As a result, a detailed description of the characteristics of local adiabatic film cooling effectiveness is given. Furthermore, the locally resolved experimental results can serve as a data base for the validation of CFD-codes predicting discrete hole film cooling.

High-Resolution Measurements of Local Effectiveness From Discrete Hole Film Cooling

1999 ◽  
Vol 123 (4) ◽  
pp. 758-765 ◽  
Author(s):  
S. Baldauf ◽  
A. Schulz ◽  
S. Wittig
Keyword(s):  
Surface Temperature ◽  
Film Cooling ◽  
Density Ratio ◽  
Element Analysis ◽  
Test Plate ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Flow Parameters ◽  
Wide Range ◽  
Local Measurements

Local adiabatic film cooling effectiveness on a flat plate surface downstream a row of cylindrical holes was investigated. Geometric parameters such as blowing angle and hole pitch, as well as the flow parameters blowing rate and density ratio, were varied in a wide range emphasizing engine relevant conditions. IR thermography was used to perform local measurements of the surface temperature field. A spatial resolution of up to seven data points per hole diameter extending to 80 hole diameters downstream of the ejection location was achieved. Since all technical wall materials have a finite thermoconductivity, a procedure for correcting the measured surface temperature data based on a Finite Element analysis was developed. Heat loss over the back and remnant heat flux within the test plate in lateral and streamwise directions were taken into account. The local effectiveness patterns obtained are systematically analyzed to quantify the influence of the various parameters. As a result, a detailed description of the characteristics of local adiabatic film cooling effectiveness is given. Furthermore, the locally resolved experimental results can serve as a data base for the validation of CFD codes predicting discrete hole film cooling.

Effect of Hole Geometry on the Thermal Performance of Fan-Shaped Film Cooling Holes

2005 ◽  
Vol 127 (4) ◽  
pp. 718-725 ◽  
Author(s):  
Michael Gritsch ◽  
Will Colban ◽  
Heinz Schär ◽  
Klaus Döbbeling
Keyword(s):  
Thermal Performance ◽  
Film Cooling ◽  
Density Ratio ◽  
Geometrical Parameters ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Wide Range ◽  
Cooling Hole ◽  
Hole Geometry ◽  
The Impact

This study evaluates the impact of typical cooling hole shape variations on the thermal performance of fan-shaped film holes. A comprehensive set of experimental test cases featuring 16 different film-cooling configurations with different hole shapes have been investigated. The shape variations investigated include hole inlet-to-outlet area ratio, hole coverage ratio, hole pitch ratio, hole length, and hole orientation (compound) angle. Flow conditions applied cover a wide range of film blowing ratios M=0.5 to 2.5 at an engine-representative density ratio DR=1.7. An infrared thermography data acquisition system is used for highly accurate and spatially resolved surface temperature mappings. Accurate local temperature data are achieved by an in situ calibration procedure with the help of thermocouples embedded in the test plate. Detailed film-cooling effectiveness distributions and discharge coefficients are used for evaluating the thermal performance of a row of fan-shaped film holes. An extensive variation of the main geometrical parameters describing a fan-shaped film-cooling hole is done to cover a wide range of typical film-cooling applications in current gas turbine engines. Within the range investigated, laterally averaged film-cooling effectiveness was found to show only limited sensitivity from variations of the hole geometry parameters. This offers the potential to tailor the hole geometry according to needs beyond pure cooling performance, e.g., manufacturing facilitations.

CFD Based Sensitivity Study of Flow Parameters for Engine Like Film Cooling Conditions

1996 ◽  
Author(s):  
Stefan Baldauf ◽  
Michael Scheurlen
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Sensitivity Study ◽  
Cooling Effectiveness ◽  
Turbine Engine ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Flow Parameters ◽  
Cooling Conditions ◽  
Wide Range

A standard CFD code with two-layer k-ε-model was used to calculate film cooling effectiveness of flat plate test cases. Experimental data from the literature were taken to perform extensive validation of the code for film cooling effectiveness prediction. Emphasis was put on injection of cooling gas through one row of cylindrical holes in the streamwise direction. Blowing ratio, density ratio, blowing angle, pitch, and hole length to diameter ratio were varied in a wide range. It was found that the code is well suited for the prediction of lateral averaged film cooling effectiveness for common film cooling conditions. A similarity analysis is presented for the prescribed film cooling problem to isolate the influence parameters of flow properties and geometry. A reduction of the parameters of influence was achieved using physical implications. The magnitude of the remaining parameters was compared for literature reported experimental results and gas turbine applications. It was found that experimental realized Reynolds and Eckert numbers are mostly far from turbine engine conditions. Therefore the validated CFD code was used to extrapolate the experimental configuration to engine like conditions. It was found that the examined Reynolds and Eckert numbers had no significant impact on lateral averaged film cooling effectiveness. It is hence possible to present a reduced but complete set of the governing influence parameters on the discussed film cooling problem.

High-Resolution Film Cooling Effectiveness Measurements of Axial Holes Embedded in a Transverse Trench With Various Trench Configurations

2006 ◽  
Vol 129 (2) ◽  
pp. 294-302 ◽  
Author(s):  
Scot K. Waye ◽  
David G. Bogard
Keyword(s):  
High Resolution ◽  
Film Cooling ◽  
Density Ratio ◽  
Field Measurements ◽  
Suction Side ◽  
Lateral Spreading ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Flow Parameters ◽  
Adiabatic Effectiveness

Adiabatic film cooling effectiveness of axial holes embedded within a transverse trench on the suction side of a turbine vane was investigated. High-resolution two-dimensional data obtained from infrared thermography and corrected for local conduction provided spatial adiabatic effectiveness data. Flow parameters of blowing ratio, density ratio, and turbulence intensity were independently varied. In addition to a baseline geometry, nine trench configurations were tested, all with a depth of 1∕2 hole diameter, with varying widths, and with perpendicular and inclined trench walls. A perpendicular trench wall at the very downstream edge of the coolant hole was found to be the key trench characteristic that yielded much improved adiabatic effectiveness performance. This configuration increased adiabatic effectiveness up to 100% near the hole and 40% downstream. All other trench configurations had little effect on the adiabatic effectiveness. Thermal field measurements confirmed that the improved adiabatic effectiveness that occurred for a narrow trench with perpendicular walls was due to a lateral spreading of the coolant and reduced coolant jet separation. The cooling levels exhibited by these particular geometries are comparable to shaped holes, but much easier and cheaper to manufacture.

Correlation of Film Cooling Effectiveness From Thermographic Measurements at Engine Like Conditions

2002 ◽  
Author(s):  
S. Baldauf ◽  
M. Scheurlen ◽  
A. Schulz ◽  
S. Wittig
Keyword(s):  
Film Cooling ◽  
Radiation Effects ◽  
Flow Behavior ◽  
Density Ratio ◽  
Geometrical Parameters ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Jet Interaction ◽  
New Correlation ◽  
Large Matrix

Adiabatic film cooling effectiveness on a flat plate surface downstream of a row of cylindrical holes is investigated. Highly resolved two dimensional surface data were measured by means of infrared thermography and carefully corrected for local conduction and radiation effects [1]. These locally acquired data are laterally averaged to give the streamwise distributions of the effectiveness. An independent variation of the flow parameters blowing rate, density ratio, and turbulence intensity as well as the geometrical parameters streamwise ejection angle and hole spacing is examined. The influences of these parameters on the laterally effectiveness is discussed and interpreted with the help of surface distributions of effectiveness and heat transfer coefficients presented in earlier publications [1, 2]. Besides the known jet in cross-flow behavior of coolant ejected from discrete holes, these data demonstrate the effect of adjacent jet interaction and its impact on jet lift-off and adiabatic effectiveness. In utilizing this large matrix of measurements the effect of single parameters and their interactions are correlated. The important scaling parameters of the effectiveness are shaped out during the correlation process and are discussed. The resulting new correlation is designed to yield the quantitatively correct effectiveness as a result of the interplay of the jet in crossflow behavior and the adjacent jet interaction. It is built modularly to allow for future inclusion of additional parameters. The new correlation is valid without any exception within the full region of interest, reaching from the point of the ejection to far downstream, for all combinations of flow and geometry parameters.

Correlation of Film-Cooling Effectiveness From Thermographic Measurements at Enginelike Conditions

2002 ◽  
Vol 124 (4) ◽  
pp. 686-698 ◽  
Author(s):  
S. Baldauf ◽  
M. Scheurlen ◽  
A. Schulz ◽  
S. Wittig
Keyword(s):  
Film Cooling ◽  
Radiation Effects ◽  
Flow Behavior ◽  
Density Ratio ◽  
Geometrical Parameters ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Jet Interaction ◽  
New Correlation ◽  
Large Matrix

Adiabatic film-cooling effectiveness on a flat plate surface downstream of a row of cylindrical holes is investigated. Highly resolved two-dimensional surface data were measured by means of infrared thermography and carefully corrected for local conduction and radiation effects. These locally acquired data are laterally averaged to give the streamwise distributions of the effectiveness. An independent variation of the flow parameters blowing rate, density ratio, and turbulence intensity as well as the geometrical parameters streamwise ejection angle and hole spacing is examined. The influences of these parameters on the lateral effectiveness is discussed and interpreted with the help of surface distributions of effectiveness and heat transfer coefficients presented in earlier publications. Besides the known jet in cross-flow behavior of coolant ejected from discrete holes, these data demonstrate the effect of adjacent jet interaction and its impact on jet lift-off and adiabatic effectiveness. In utilizing this large matrix of measurements the effect of single parameters and their interactions are correlated. The important scaling parameters of the effectiveness are shaped out during the correlation process and are discussed. The resulting new correlation is designed to yield the quantitatively correct effectiveness as a result of the interplay of the jet in crossflow behavior and the adjacent jet interaction. It is built modularly to allow for future inclusion of additional parameters. The new correlation is valid without any exception within the full region of interest, reaching from the point of the ejection to far downstream, for all combinations of flow and geometry parameters.

Effect of Internal Coolant Crossflow on the Effectiveness of Shaped Film-Cooling Holes

2003 ◽  
Vol 125 (3) ◽  
pp. 547-554 ◽  
Author(s):  
Michael Gritsch ◽  
Achmed Schulz ◽  
Sigmar Wittig
Keyword(s):  
Film Cooling ◽  
Gas Flow ◽  
Flow Direction ◽  
Turbine Blades ◽  
Density Ratio ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Hot Gas ◽  
Wide Range

Film-cooling was the subject of numerous studies during the past decades. However, the effect of flow conditions on the entry side of the film-cooling hole on film-cooling performance has surprisingly not received much attention. A stagnant plenum which is widely used in experimental and numerical studies to feed the holes is not necessarily a right means to re-present real engine conditions. For this reason, the present paper reports on an experimental study investigating the effect of a coolant crossflow feeding the holes that is oriented perpendicular to the hot gas flow direction to model a flow situation that is, for instance, of common use in modern turbine blades’ cooling schemes. A comprehensive set of experiments was performed to evaluate the effect of perpendicular coolant supply direction on film-cooling effectiveness over a wide range of blowing ratios (M=0.5…2.0) and coolant crossflow Mach numbers Mac=0…0.6. The coolant-to-hot gas density ratio, however, was kept constant at 1.85 which can be assumed to be representative for typical gas turbine applications. Three different hole geometries, including a cylindrical hole as well as two holes with expanded exits, were considered. Particularly, two-dimensional distributions of local film-cooling effectiveness acquired by means of an infrared camera system were used to give detailed insight into the governing flow phenomena. The results of the present investigation show that there is a profound effect of how the coolant is supplied to the hole on the film-cooling performance in the near hole region. Therefore, crossflow at the hole entry side has be taken into account when modeling film-cooling schemes of turbine bladings.

Effect of Injection Angle on Performance of Full Coverage Film Cooling with Opposite Injection Holes

2018 ◽  
Vol 0 (0) ◽  
Author(s):  
Mukesh Prakash Mishra ◽  
A K Sahani ◽  
Sunil Chandel ◽  
R K Mishra
Keyword(s):  
Film Cooling ◽  
Velocity Ratio ◽  
Practical Importance ◽  
Density Ratio ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Injection Angle ◽  
Full Coverage ◽  
Wide Range

Abstract Characteristics of full coverage film cooling of an adiabatic flat plate are studied for opposite injection of coolant at different angles. Two in-line adjacent rows of cooling holes injecting in opposite directions are considered in this study. The cooling performance is compared with the configurations having forward and reverse injecting holes at similar injection angles. The holes are arranged in an array of 20 rows with equal spacing both span-wise and stream-wise. Computational analyses are carried out over a wide range of velocity ratios (VR) of practical importance ranging from 0.5 to 2.0 at density ratio of about 1.0. Injection angle and velocity ratio are found to have strong influence on film cooling effectiveness of opposite injection. At low velocity ratio of VR=0.5, film cooling performance of opposite injection at 45° is found better than at other angles, i. e. 30° and 60°. At higher velocity ratios, injection at 30° is found superior. Film cooling effectiveness becomes insensitive to velocity ratios at higher range for 45° and 60° injections. Evolution of effusion film layer and interaction between coolant and primary flow is also studied in this paper.

Experimental and Numerical Investigation of Flow Field and Downstream Surface Temperatures of Cylindrical and Diffuser Shaped Film Cooling Holes

2011 ◽  
Author(s):  
Tilman auf dem Kampe ◽  
Stefan Vo¨lker ◽  
Torsten Sa¨mel ◽  
Christian Heneka ◽  
Helge Ladisch ◽  
...  
Keyword(s):  
Flow Field ◽  
Film Cooling ◽  
Numerical Study ◽  
Density Ratio ◽  
Quantitative Agreement ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Flow Parameters ◽  
Contour Plots ◽  
Cooling Hole

An experimental and numerical study of the flow field and the downstream film cooling performance of cylindrical and diffuser shaped cooling holes is presented. The measurements were conducted on a flat plate with a single cooling hole with coolant ejected from a plenum. The flow field was investigated by means of 3D-PIV as well as 3D-LDV measurements, the downstream film cooling effectiveness by means of infrared thermography. Cylindrical and diffuser holes without lateral inclination have been examined, varying blowing ratio and density ratio as well as freestream turbulence levels. 3D-CFD simulations have been performed and validated along with the experimental efforts. The results, presented in terms of contour plots of the three normalized velocity components as well as adiabatic film cooling effectiveness, clearly show the flow structure of the film cooling jets and the differences brought about by the variation of hole geometry and flow parameters. The quantitative agreement between experiment and CFD was reasonable, with better agreement for cylindrical holes than for diffuser holes.

scholarly journals Heat Transfer in a Coupled Impingement-Effusion Cooling System

2014 ◽  
Author(s):  
Mark Miller ◽  
Greg Natsui ◽  
Mark Ricklick ◽  
Jay Kapat ◽  
Reinhard Schilp
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Cooling System ◽  
Geometrical Parameters ◽  
Transfer Model ◽  
Unit Surface Area ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Wide Range ◽  
Reynold’S Number

Modern research on gas turbine cooling continues to focus on the optimization of different cooling designs, and better understanding of the underlying flow physics so that cooling schemes can be coupled together. The current study focuses on one particular coupled cooling design: an impingement-effusion cooling system, which combines impingement cooling on the backside of the cooled component and full coverage effusion cooling on the exposed surface. The goal of this study is to explore a wide range of geometrical parameters outside the ranges normally reported in the available literature. Particular attention is given to the total coolant spent per unit surface area cooled. Through determination of impingement heat transfer, film cooling effectiveness, and film cooling heat transfer on the target wall, a simplified heat transfer model of the cooled component is developed to show the relative impact of each parameter on the overall cooling effectiveness. The use of Temperature Sensitive Paint (TSP) for data acquisition allows for high resolution local heat transfer and effectiveness results. Impingement arrays with local extraction of coolant via effusion are able to produce higher overall heat transfer, as no significant cross flow is present to deflect the impinging jets. Low jet-to-target-plate spacing produces the highest yet most non-uniform heat transfer distribution; at high spacing the heat transfer rate is much less sensitive to impingement height. Arrays with high hole-to-hole spacing and high jet Reynold’s number are more effective (per mass of coolant used) than tightly spaced holes at low jet Reynold’s number. On the effusion side, staggered hole arrangements provide significantly higher film cooling effectiveness than their in-line counterparts as the staggered arrangement minimizes jet interactions and promotes a more even lateral distribution of coolant.

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