Flow Statistics and Visualization of Multirow Film Cooling Boundary Layers Emanating From Cylindrical and Diffuser Shaped Holes

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Justin Hodges ◽  
Craig P. Fernandes ◽  
Erik Fernandez ◽  
Jayanta S. Kapat
Keyword(s):  
Boundary Layer ◽  
Film Cooling ◽  
Near Field ◽  
Trailing Edge ◽  
Film Cooling Effectiveness ◽  
Film Boundary ◽  
Piv Measurement ◽  
Hole Geometry ◽  
The Impact ◽  
Measurement Capabilities

The research presented in this paper strives to exploit the benefits of near-wall measurement capabilities using hotwire anemometry and flowfield measurement capabilities using particle image velocimetry (PIV) for analysis of the injection of a staggered array of film cooling jets into a turbulent cross-flow. It also serves to give insight into the turbulence generation, jet structure, and flow physics pertaining to film cooling for various flow conditions. Such information and analysis will be applied to both cylindrical and diffuser shaped holes, to further understand the impacts manifesting from hole geometry. Spatially resolved PIV measurements were taken at the array centerline of the holes and detailed temporally resolved hotwire velocity and turbulence measurements were taken at the trailing edge of each row of jets in the array centerline corresponding to the PIV measurement plane. Flowfields of jets emanating from eight staggered rows, of both cylindrical and diffuser shaped holes inclined at 20 deg to the main-flow, are studied over blowing ratios in the range of 0.3–1.5. To allow for deeper interpretation, companion local adiabatic film cooling effectiveness results will also be presented for the geometric test specimen from related in-house work. Results show “rising” shear layers for lower blowing ratios, inferring boundary layer growth for low blowing ratio cases. Detachment of film cooling jets is seen from a concavity shift in the u′rms line plots at the trailing edge of film cooling holes. Former rows of jets are observed to disrupt the approaching boundary layer and enhance the spreading and propagation of subsequent downstream jets. Behavior of the film boundary layer in the near-field region directly following the first row of injection, as compared to the near-field behavior after the final row of injection (recovery region), is also measured and discussed. The impact of the hole geometry on the resulting film boundary layer, as in this case of cylindrical verses diffuser shaped holes, is ascertained in the form of mean axial velocity, turbulence level (u′rms), and length scales profiles.

Flow Statistics and Visualization of Multi-Row Film Cooling Boundary Layers Emanating From Cylindrical and Diffuser Shaped Holes

2018 ◽  
Author(s):  
Craig P. Fernandes ◽  
Justin Hodges ◽  
Erik Fernandez ◽  
Jayanta S. Kapat
Keyword(s):  
Boundary Layer ◽  
Film Cooling ◽  
Near Field ◽  
Trailing Edge ◽  
Film Cooling Effectiveness ◽  
Film Boundary ◽  
Piv Measurement ◽  
Hole Geometry ◽  
The Impact ◽  
Measurement Capabilities

The research presented in this paper strives to exploit the benefits of near-wall measurement capabilities using hotwire anemometry and flowfield measurement capabilities using particle image velocimetry (PIV) for analysis of the injection of a staggered array of film cooling jets into a turbulent cross-flow. It also serves to give insight into the turbulence generation, jet structure, and flow physics pertaining to film cooling for various flow conditions. Such information and analysis will be applied to both cylindrical and diffuser shaped holes, to further understand the impacts manifesting from hole geometry. Spatially-resolved PIV measurements were taken at the array centerline of the holes and detailed temporally resolved hotwire velocity and turbulence measurements were taken at the trailing edge of each row of jets in the array centerline corresponding to the PIV measurement plane. Flowfields of jets emanating from eight staggered rows, of both cylindrical and diffuser shaped holes inclined at 20 degrees to the main-flow, are studied over blowing ratios in the range of 0.3–1.5. To allow for deeper interpretation, companion local adiabatic film cooling effectiveness results will also be presented for the geometric test specimen from related in-house work. Results show “rising” shear layers for lower blowing ratios, inferring boundary layer growth for low blowing ratio cases. Detachment of film cooling jets is seen from a concavity shift in the u’rms line plots at the trailing edge of film cooling holes. Former rows of jets are observed to disrupt the approaching boundary layer and enhance the spreading and propagation of subsequent downstream jets. Behavior of the film boundary layer in the near-field region directly following the first row of injection, as compared to the near-field behavior after the final row of injection (recovery region), is also measured and discussed. The impact of the hole geometry on the resulting film boundary layer, as in this case of cylindrical verses diffuser shaped holes, is ascertained in the form of mean axial velocity, turbulence level (u’rms), and length scales profiles.

Near Field of Film Cooling Jet Issued Into a Flat Plate Boundary Layer: LES Study

2008 ◽  
Author(s):  
Yulia V. Peet ◽  
Sanjiva K. Lele
Keyword(s):  
Boundary Layer ◽  
Film Cooling ◽  
Flat Surface ◽  
Computational Study ◽  
Near Field ◽  
Velocity Ratio ◽  
Density Ratio ◽  
Surface Flow ◽  
Test Surface ◽  
Film Cooling Effectiveness

We report results from a computational study of film cooling from cylindrical holes inclined at 35 degrees with respect to a flat surface using Large Eddy Simulations (LES). The hole length is L/d = 3.5, distance between the holes is P/d = 3, boundary layer above the flat surface is turbulent with Reθ = 938, density ratio = 0.95, velocity ratio = 0.5. All pertinent components of geometry, namely, supply plenum, film hole and crossflow region above the test surface, are simulated. The simulations are performed using a multicode approach, where a low Mach number code is employed inside the plenum and in the film hole, and a compressible code is used for the flow above the test surface. Flow inside the plenum, film hole and above the test surface is analyzed. Mean velocity and turbulence characteristics in the near field of the jet injection obtained in the simulations are compared to experimental data of Pietrzyk et al. [1]. Adiabatic film cooling effectiveness is estimated and compared with experiments of Sinha et al. [2]. Relation of the coherent vortical structures observed in the flow to film cooling performance is discussed. Advantage of LES over RANS methods for this type of flow is confirmed by showing that spanwise u′w′ shear stress and lateral growth of the jet are predicted correctly in the current LES as opposed to typical RANS computations.

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.

Exit-shape effect of film holes at pressure side on trailing edge cutback film cooling characteristics

2021 ◽  
pp. 095765092110154
Author(s):  
Jian Pu ◽  
Jian-Hua Wang ◽  
Wei Song ◽  
Wei-Long Wu
Keyword(s):  
Boundary Layer ◽  
Film Cooling ◽  
Total Pressure ◽  
Shape Effect ◽  
Pressure Side ◽  
Trailing Edge ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Pressure Losses ◽  
Boundary Layer Profile

Pressure side (PS) cutback structure has been widely employed in modern turbine blade trailing edge (TE) cooling design. However, hot gas flows around lip of TE slot to generate an impingement to cutback, resulting in a rapid decay of film cooling effectiveness and hence thermal damage of entire TE. Proper angled-ejections upstream of TE can suppress the downstream effectiveness-decay. Therefore, in present work, five types of film-holes were designed to discuss the effect of exit-shape of film-hole on TE film cooling characteristics, inlet boundary layer profile, fluid-interactions, discharge behaviors and total pressure losses. The studied models included cylindrical-hole, common and laidback fan-shaped film-holes, and converging slot-holes with two different exit-to-inlet area ratios ( ARs). The solo cutback cooling was chosen as a reference. Thermal tests were conducted in a hot wind tunnel featuring a simplified TE test section by infrared thermal technique. Engine-similar mainstream-to-coolant temperature ratio of 2.0 was controlled. Comparisons of experimental results revealed that the converging slot-holes can obtain the highest film cooling effectiveness at TE region and overall cooling effectiveness at PS film-plate, but the slightest increase of total pressure losses. Flow measurements using Particle Image Velocimetry technique indicated the converging slot-holes can modify the inlet boundary layer profile, suppress effectively the impingement of mainstream and change the flow separation features at cutback. In addition, applying shaped-holes can effectively suppress the flow ingestion under low coolant amounts. However, relative to the exit-shape effect, the coolant amount plays a more important role on the aerodynamic and thermal characteristics of TE cooling.

Impact of Different Film-Cooling Modes at Trailing Edge on the Aerodynamic Performance of Heavy Duty Gas Turbine Cascade

2011 ◽  
Vol 84-85 ◽  
pp. 259-263
Author(s):  
Xun Liu ◽  
Song Tao Wang ◽  
Xun Zhou ◽  
Guo Tai Feng
Keyword(s):  
Gas Turbine ◽  
Film Cooling ◽  
Large Mass ◽  
Turbine Cascade ◽  
Heavy Duty ◽  
Trailing Edge ◽  
Central Difference ◽  
Adiabatic Effectiveness ◽  
Heavy Duty Gas Turbine ◽  
The Impact

In this paper, the trailing edge film cooling flow field of a heavy duty gas turbine cascade has been studied by central difference scheme and multi-block grid technique. The research is based on the three-dimensional N-S equation solver. By way of analysis of the temperature field, the distribution of profile pressure, and the distribution of film-cooling adiabatic effectiveness in the region of trailing edge with different cool air injection mass and different angles, it is found that the impact on the film-cooling adiabatic effectiveness is slightly by changing the injection mass. The distribution of profile pressure dropped intensely at the pressure side near the injection holes line with the large mass cooling air. The cooling effect is good in the region of trailing edge while the injection air is along the direction of stream.

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.

Account of Film Turbulence for Predicting Film Cooling Effectiveness in Gas Turbine Combustors

1979 ◽  
Author(s):  
G. J. Sturgess
Keyword(s):  
Gas Turbine ◽  
Film Cooling ◽  
Cooling Effectiveness ◽  
Turbine Engine ◽  
Film Cooling Effectiveness ◽  
Wide Range ◽  
Engine Combustion ◽  
Turbulence Effects ◽  
The Impact ◽  
Combustor Liner

The paper deals with a small but important part of the overall gas turbine engine combustion system and continues earlier published work on turbulence effects in film cooling to cover the case of film turbulence. Film cooling of the gas turbine combustor liner imposes certain geometric limitations on the coolant injection device. The impact of practical film injection geometry on the cooling is one of increased rates of film decay when compared to the performance from idealized injection geometries at similar injection conditions. It is important to combustor durability and life estimation to be able to predict accurately the performance obtainable from a given practical slot. The coolant film is modeled as three distinct regions, and the effects of injection slot geometry on the development of each region are described in terms of film turbulence intensity and initial circumferential non-uniformity of the injected coolant. The concept of the well-designed slot is introduced and film effectiveness is shown to be dependent on it. Only slots which can be described as well-designed are of interest in practical equipment design. A prediction procedure is provided for well-designed slots which describes growth of the film downstream of the first of the three film regions. Comparisons of predictions with measured data are made for several very different well-designed slots over a relatively wide range of injection conditions, and good agreement is shown.

Optimization of Trenched Film Cooling Using RSM Coupled CFD

2018 ◽  
Vol 0 (0) ◽  
Author(s):  
V.G. Krishna Anand ◽  
K.M. Parammasivam
Keyword(s):  
Film Cooling ◽  
Three Dimensional ◽  
Response Surfaces ◽  
Test Surface ◽  
Response Factor ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Flow Parameters ◽  
Considerable Impact ◽  
The Impact

AbstractThe trench film cooling employs film holes embedded in a slot created on the surface that requires protection from the impact of hot mainstream flow. The present investigation employs Response Surface Methodology (RSM) approach coupled with CFD analysis to develop a regression predictive model and to optimize the trench geometric and flow parameters viz., trench width (w), trench depth (d), film hole compound angle (β) and blowing ratio (M). The Area-averaged film cooling effectiveness (ȠAA) were chosen as a response factor for RSM and with trench design and flow parameters used as input factors for regression analysis. Analysis of variance (ANOVA) analysis was carried out on the regression model to identify the influence of individual parameters. Three dimensional response surfaces that relate the effect of input parameters on the response factor were analyzed. Experimental results of a case identified from the RSM matrix was found to correlate well with computational investigations. Results from the study indicate that the parameters d, β and M have considerable impact on film cooling performance of test surface with trenches.

Rib Turbulator Effects on Crossflow-Fed Shaped Film Cooling Holes

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
Dale W. Fox ◽  
Fraser B. Jones ◽  
John W. McClintic ◽  
David G. Bogard ◽  
Thomas E. Dyson ◽  
...  
Keyword(s):  
Film Cooling ◽  
Velocity Ratio ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Smooth Channel ◽  
Cooling Hole ◽  
Film Cooling Holes ◽  
Inlet Position ◽  
The Impact

Most studies of turbine airfoil film cooling in laboratory test facilities have used relatively large plenums to feed flow into the coolant holes. However, a more realistic inlet condition for the film cooling holes is a relatively small channel. Previous studies have shown that the film cooling performance is significantly degraded when fed by perpendicular internal crossflow in a smooth channel. In this study, angled rib turbulators were installed in two geometric configurations inside the internal crossflow channel, at 45 deg and 135 deg, to assess the impact on film cooling effectiveness. Film cooling hole inlets were positioned in both prerib and postrib locations to test the effect of hole inlet position on film cooling performance. A test was performed independently varying channel velocity ratio and jet to mainstream velocity ratio. These results were compared to the film cooling performance of previously measured shaped holes fed by a smooth internal channel. The film cooling hole discharge coefficients and channel friction factors were also measured for both rib configurations with varying channel and inlet velocity ratios. Spatially averaged film cooling effectiveness is largely similar to the holes fed by the smooth internal crossflow channel, but hole-to-hole variation due to inlet position was observed.

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