Film Cooling From Short Holes With Sister Hole Influence

2012 ◽  
Author(s):  
Marc J. Ely ◽  
B. A. Jubran
Keyword(s):  
Flow Field ◽  
Flow Structure ◽  
Film Cooling ◽  
Computational Analysis ◽  
Numerical Study ◽  
Vortical Flow ◽  
Injection Hole ◽  
Hole Configuration ◽  
Adiabatic Effectiveness ◽  
Structure Research

This paper reports a computational analysis on the effect of sister hole control on film cooling from short holes. The proposed method includes surrounding a primary injection hole by two or four smaller sister holes to actively maintain flow adhesion along the surface of the blade. A numerical study using the realizable k-ε turbulence model led to the determination that the use of sister holes significantly improves adiabatic effectiveness by countering the primary vortical flow structure. Research was carried out to determine the optimum hole configuration, arriving at the conclusion that placing sister holes slightly downstream of the primary injection hole improves the near-hole effectiveness, while placing sister holes slightly upstream of the primary hole improves downstream effectiveness. Similar results were found in evaluating both long and short hole geometries with a significantly less coherent flow field arising from the short hole. However, on the whole, the sister hole approach to film cooling was found to offer viable improvements over standard cooling regimes.

A Parametric Study on the Effect of Sister Hole Location on Active Film Cooling Flow Control

2010 ◽  
Author(s):  
Marc J. Ely ◽  
B. A. Jubran
Keyword(s):  
Flow Structure ◽  
Parametric Study ◽  
Film Cooling ◽  
Numerical Evaluation ◽  
Vortical Flow ◽  
Injection Hole ◽  
Cooling Flow ◽  
Hole Configuration ◽  
Adiabatic Effectiveness ◽  
Structure Research

This paper presents an investigation on the effect of sister holes on film cooling. The proposed technique surrounds a primary injection hole by two or four smaller sister holes to actively maintain flow adhesion along the surface of the blade. A numerical evaluation using the realizable k-ε turbulence model led to the determination that the use of sister holes significantly improves adiabatic effectiveness by countering the primary vortical flow structure. Research was performed to determine the optimal hole configuration, arriving at the conclusion that placing sister holes slightly downstream of the primary injection hole improves the near-hole effectiveness, while placing sister holes slightly upstream of the primary hole improves downstream effectiveness. On the whole, the sister hole approach to film cooling was found to offer viable improvements over standard cooling regimes.

scholarly journals A Numerical Study On Active Film Cooling Flow Control Through The Use Of Sister Holes

2021 ◽  
Author(s):  
Marc J. Ely
Keyword(s):  
Film Cooling ◽  
Numerical Evaluation ◽  
Numerical Study ◽  
Vertical Flow ◽  
Injection Hole ◽  
Cooling Flow ◽  
Novel Technique ◽  
Hole Configuration ◽  
Adiabatic Effectiveness ◽  
Structure Research

The research contained herein studied the effect of sister holes on film cooling. This novel technique surrounds a primary injection hole by two or four smaller sister holes to actively maintain flow adhesion along the surface of the blade. A numerical evaluation using the realizable κ-ε turbulence model led to the determination that the use of sister holes significantly improves adiabatic effectiveness by countering the primary vertical flow structure. Research was performed to determine the optimal hole configuration, arriving at the conclusion that placing sister holes slightly downstream of the primary injection hole improves the near-hole effectiveness, while placing sister holes slightly upstream of the primary hole improves downstream effectiveness. Similar results were found in evaluating both long and short hole geometries with a significantly less coherent flow field arising form the short hole study. However, on the whole, the sister hole approach to film cooling was found to offer viable improvements over standard cooling regimes.

scholarly journals A Numerical Study On Active Film Cooling Flow Control Through The Use Of Sister Holes

2021 ◽  
Author(s):  
Marc J. Ely
Keyword(s):  
Film Cooling ◽  
Numerical Evaluation ◽  
Numerical Study ◽  
Vertical Flow ◽  
Injection Hole ◽  
Cooling Flow ◽  
Novel Technique ◽  
Hole Configuration ◽  
Adiabatic Effectiveness ◽  
Structure Research

The research contained herein studied the effect of sister holes on film cooling. This novel technique surrounds a primary injection hole by two or four smaller sister holes to actively maintain flow adhesion along the surface of the blade. A numerical evaluation using the realizable κ-ε turbulence model led to the determination that the use of sister holes significantly improves adiabatic effectiveness by countering the primary vertical flow structure. Research was performed to determine the optimal hole configuration, arriving at the conclusion that placing sister holes slightly downstream of the primary injection hole improves the near-hole effectiveness, while placing sister holes slightly upstream of the primary hole improves downstream effectiveness. Similar results were found in evaluating both long and short hole geometries with a significantly less coherent flow field arising form the short hole study. However, on the whole, the sister hole approach to film cooling was found to offer viable improvements over standard cooling regimes.

CFD Predictions of Film Cooling Adiabatic Effectiveness for Cylindrical Holes Embedded in Narrow and Wide Transverse Trenches

2007 ◽  
Author(s):  
Katharine L. Harrison ◽  
David G. Bogard
Keyword(s):  
Film Cooling ◽  
Cylindrical Hole ◽  
Dramatic Improvement ◽  
Computational Simulations ◽  
Cooling Performance ◽  
Hole Configuration ◽  
Cylindrical Holes ◽  
Adiabatic Effectiveness

Recent studies have shown that film cooling adiabatic effectiveness can be significantly improved when holes are embedded in shallow, transverse trenches. In this study computational simulations were made using the commercial CFD code FLUENT to determine if the dramatic improvement in film cooling performance was predictable. Simulations were made of a baseline cylindrical hole configuration, and narrow and wide trench configurations. Simulations correctly predicted that the narrow trench outperformed the baseline row of cylindrical holes and the wide trench at all blowing ratios. Furthermore, the simulations showed that enhanced performance with the trench could be attributed to decreased separation of the coolant jets. The success of these predictions show that computational simulations can be used as a tool for studying and identifying promising film cooling configurations.

A numerical study of pulsating flow behind a constriction

1995 ◽  
Vol 301 ◽  
pp. 203-223 ◽  
Author(s):  
Moshe Rosenfeld
Keyword(s):  
Flow Field ◽  
Strouhal Number ◽  
Numerical Study ◽  
Pulsating Flow ◽  
Vortical Flow ◽  
Incoming Flow ◽  
Core Flow ◽  
Wide Range ◽  
Constricted Channel

The flow field behind a constricted channel is studied numerically. A pulsating incoming flow with a non-vanishing mean is imposed at the entrance and the flow field is investigated for a wide range of Reynolds and Strouhal numbers (1500 > Re > 45, 12 > St > 0.01). In most cases (except at the two ends of the Strouhal number regime or for Re < 90), propagating vortices are found downstream of the constriction with a wavy core flow between them. The size and number of coexisting vortices depend on St but less on Re. The strength and structure of the vortical regions depend on both Re and St. The formation of the vortices is discussed for the various St regimes and the characteristics of the vortical flow are described.

Effect of Self-Sustained Pulsation of Coolant Flow on Adiabatic Effectiveness and Net Heat Flux Reduction on a Flat Plate

2021 ◽  
Author(s):  
Nicola Rosafio ◽  
Simone Salvadori ◽  
Daniela Anna Misul ◽  
Mirko Baratta ◽  
Mauro Carnevale ◽  
...  
Keyword(s):  
Heat Flux ◽  
Flow Field ◽  
Working Conditions ◽  
Film Cooling ◽  
Inlet Section ◽  
Complex Flow ◽  
Cooling Systems ◽  
Length Scales ◽  
Net Heat Flux ◽  
Adiabatic Effectiveness

Abstract Advanced film-cooling systems are necessary to guarantee safe working conditions of high-pressure turbine stages. A fair prediction of the inherent unsteady interaction between the main-flow and the jet of cooling air allows for correctly describing the complex flow structures arising close to the cooled region. This proves to be crucial for the design of high-performance cooling systems. Results obtained by means of an experimental campaign performed at the University of Karlsruhe are shown along with unsteady numerical data obtained for the corresponding working conditions. The experimental rig consists of an instrumented plate where the hot flow reaches Mach = 0.6 close to the coolant jet exit section. The numerical campaign models the unsteady film cooling characteristics using a third-order accurate method. The ANSYS® FLUENT® software is used along with a mesh refinement procedure that allows for accurately modelling the flow field. Turbulence is modelled using the k-ω SST model. Time-averaged and time-resolved distributions of adiabatic effectiveness and Net Heat Flux Reduction are analysed to determine to what extent deterministic unsteadiness plays a role in cooling systems. It is found that coolant pulsates due to fluctuations generated by flow separation at the inlet section of the cooling channel. Visualizations of the fluctuating flow field demonstrate that coolant penetration depends on the phase of the pulsation, thus leading to periodically reduced shielding. Eventually, unsteadiness occurring at integral length scales does not provide enough mixing to match the experiments, thus hinting that the dominant phenomena occur at inertial length scales.

Double-Row Discrete-Hole Cooling: an Experimental and Numerical Study

1980 ◽  
Vol 102 (2) ◽  
pp. 498-503 ◽  
Author(s):  
G. Bergeles ◽  
A. D. Gosman ◽  
B. E. Launder
Keyword(s):  
Flow Field ◽  
Film Cooling ◽  
Free Stream ◽  
Numerical Study ◽  
Transport Coefficients ◽  
Three Dimensional ◽  
Double Row ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Single Row

Double-row discrete-hole cooling arrangements offer several advantages over single-row systems yet the detailed cooling mechanism is less completely understood than for the single-row. This is partly because there have been fewer studies of this geometry and partly because the flow structure is more complex. The present paper presents detailed flow-field and concentration measurements around the injection holes for double-row injection on a flat plate at 30 deg to the mainstream. The experiments span values of the blowing injection mass velocities from 0.25 to 1.0 times the free stream mass velocity and for two boundary layer thicknesses just upstream of the injection. In contrast to single-row injection the cooling effectiveness rise monotonically with M over the range studied. Computer simulation of these flows and similar experiments of [7] has been made using a three-dimensional finite-difference code that embodies a semi-elliptic treatment of the flow field in the neighborhood of the injection holes in conjunction with a two-equation turbulence model with non-isotropic effective transport coefficients. It emerged from the calculations, that, for injection velocities up to 50 percent of the free stream value, levels of film-cooling effectiveness are extremely well predicted beyond about 10 diameters behind the leading row of holes. Around the holes themselves, however, there are certain discrepancies which become more serious as the injection level is raised.

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.

Impact on Adiabatic Film Cooling Effectiveness Using Internal Cyclone Cooling

2011 ◽  
Author(s):  
Andreas Lerch ◽  
Heinz-Peter Schiffer ◽  
Daniela Klaubert
Keyword(s):  
Flow Structure ◽  
Channel Flow ◽  
Film Cooling ◽  
Full Range ◽  
Turbine Blades ◽  
Internal Heat ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
High Dependency ◽  
Adiabatic Effectiveness

The internal heat transfer of turbine blades can be augmented using cyclone cooling, but the consequential impact on the external film cooling may be significant. To determine these effects, the distribution of adiabatic film cooling effectiveness was measured on the surface of a symmetrical blade model containing a cylindrical leading-edge channel. This channel feeds one row, respectively two opposite rows, of eight cooling holes each. Inside this channel two different types and directions of swirl are generated. The resulting adiabatic effectiveness distributions, which are measured using the calibrated ammonia diazo technique, are compared to those measured with a channel flow without swirl (datum configuration). The operating points are defined by blowing ratio (0.6–1.0) and film cooling discharge coefficient (20%–50%). A high full-range resolution over the adiabatic effectiveness is achieved using a weighting average method with multiple experiments per operating point. The lateral-averaged adiabatic effectiveness is presented up to 30 diameters downstream of the cooling holes. These effectiveness values show a high dependency on the configurations and reach values of about 0.3 to 2 times the reference configuration values. This is due to the strong variation of the flow structure inside the cooling holes. PIV-measurements and basic numerical simulations of the channel flow structure and dynamic pressure measurements at the cooling hole exits are carried out to support the results of film cooling effectiveness.

Vortical Flow Structure and Loss Generation Process in a Transonic Centrifugal Compressor Impeller

2007 ◽  
Author(s):  
Seiichi Ibaraki ◽  
Masato Furukawa ◽  
Kenichiro Iwakiri ◽  
Kazuya Takahashi
Keyword(s):  
Flow Field ◽  
Flow Structure ◽  
Centrifugal Compressor ◽  
Secondary Flows ◽  
Vortical Flow ◽  
Generation Process ◽  
Tip Leakage ◽  
Transonic Centrifugal Compressor ◽  
Compressor Impeller ◽  
Flow Phenomena

Transonic centrifugal compressors are used in turbochargers and turboshaft engines because of their small dimensions, relatively high efficiency and wide operating range. The flow field of the transonic centrifugal compressor impeller is highly three dimensional, and is complicated by shock waves, tip leakage vortices, secondary flows and the interactions among them. In order to improve the performance, it is indispensable to understand these complicated flow phenomena in the impeller. Although experimental and numerical research on transonic impeller flow has been reported, thus providing important flow physics, some undetected flow phenomena remain. The authors of the present report carried out detailed Navier-Stokes computations of a transonic impeller flow measured by Laser Doppler Velocimetry (LDV) in previous work. The highly complicated vortical flow structure and the mechanism of loss generation were revealed by a visual data mining technique, namely vortex identification based on the critical point theory and limiting streamline mapping by means of line integral convolution. As a result, it was found that the tip leakage vortices have a significant impact on the flow field and vortex breakdowns that increase the blockage of the flow passage, and that these were caused by shock wave interaction.

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