scholarly journals Evaluation of CFD Predictions Using Thermal Field Measurements on a Simulated Film Cooled Turbine Blade Leading Edge

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
Sibi Mathew ◽  
Silvia Ravelli ◽  
David G. Bogard
Keyword(s):  
Turbine Blade ◽  
Turbulence Model ◽  
Stokes Equations ◽  
Leading Edge ◽  
Experimental Measurements ◽  
Stagnation Line ◽  
Thermal Fields ◽  
Sst Model ◽  
Adiabatic Effectiveness ◽  
Blade Leading Edge

Computational fluid dynamics (CFD) predictions of film cooling performance for gas turbine airfoils are an important part of the design process for turbine cooling. Typically, industry relies on the approach based on Reynolds Averaged Navier Stokes equations, together with a two-equation turbulence model. The realizable k-ɛ (RKE) model and the shear stress transport k-ω (SST) model are recognized as the most reliable. Their accuracy is generally assessed by comparing to experimentally measured adiabatic effectiveness. In this study, the performances of the RKE and SST models were evaluated by comparing predicted and measured thermal fields in a turbine blade leading edge with three rows of cooling holes, positioned along the stagnation line and at ±25 deg. Predictions and measurements were done with high thermal conductivity models which simulated the conjugate heat transfer effects between the coolant flow and the solid. Particular attention was placed on the thermal fields along the stagnation line, and immediately downstream of the off-stagnation line row of holes. Conventional evaluations in terms of adiabatic effectiveness were also carried out. Predictions of coolant flows at the stagnation line were significantly different when using the two different turbulence models. For a blowing ratio of M = 2.0, the predictions with the SST model showed coolant jet separation at the stagnation line, while the RKE predictions showed no separation. Experimental measurements showed that there was coolant jet separation at the stagnation line, but the actual thermal fields obtained from experimental measurements were significantly different from that predicted by either turbulence model. Similar results were seen for predicted and measured thermal fields downstream of the off-stagnation row of holes.

scholarly journals Evaluation of CFD Predictions Using Thermal Field Measurements on a Simulated Film Cooled Turbine Blade Leading Edge

2011 ◽  
Author(s):  
Sibi Mathew ◽  
Silvia Ravelli ◽  
David G. Bogard
Keyword(s):  
Turbine Blade ◽  
Turbulence Model ◽  
Stokes Equations ◽  
Leading Edge ◽  
Experimental Measurements ◽  
Stagnation Line ◽  
Thermal Fields ◽  
Sst Model ◽  
Adiabatic Effectiveness ◽  
Blade Leading Edge

Computational Fluid Dynamics (CFD) predictions of film cooling performance for gas turbine airfoils are an important part of the design process for turbine cooling. Typically, industry relies on the approach based on Reynolds Averaged Navier Stokes equations, together with a two-equation turbulence model. The Realizable k-ε (RKE) model and the Shear Stress Transport k-ω (SST) model are recognized as the most reliable. Their accuracy is generally assessed by comparing to experimentally measured adiabatic effectiveness. In this study, the performances of the RKE and SST models were evaluated by comparing predicted and measured thermal fields in a turbine blade leading edge with three rows of cooling holes, positioned along the stagnation line and at ±25°. Predictions and measurements were done with high thermal conductivity models which simulated the conjugate heat transfer effects between the coolant flow and the solid. Particular attention was placed on the thermal fields along the stagnation line, and immediately downstream of the off-stagnation line row of holes. Conventional evaluations in terms of adiabatic effectiveness were also carried out. Predictions of coolant flows at the stagnation line were significantly different when using the two different turbulence models. For a blowing ratio of M = 2.0, the predictions with the SST model showed coolant jet separation at the stagnation line, while the RKE predictions showed no separation. Experimental measurements showed that there was coolant jet separation at the stagnation line, but the actual thermal fields obtained from experimental measurements were significantly different from that predicted by either turbulence model. Similar results were seen for predicted and measured thermal fields downstream of the off-stagnation row of holes.

Film Cooling Parameter Waveforms on a Turbine Blade Leading Edge Model With Oscillating Stagnation Line

2016 ◽  
Vol 138 (7) ◽  
Author(s):  
James L. Rutledge ◽  
Tylor C. Rathsack ◽  
Matthew T. Van Voorhis ◽  
Marc D. Polanka
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Turbine Blade ◽  
Film Cooling ◽  
Leading Edge ◽  
Stagnation Line ◽  
Inverse Heat Transfer ◽  
Adiabatic Effectiveness ◽  
Blade Leading Edge

It is necessary to understand how film cooling influences the external convective boundary condition involving both the adiabatic wall temperature and the heat transfer coefficient in order to predict the thermal durability of a gas turbine hot gas path component. Most studies in the past have considered only steady flow, but studies of the unsteadiness naturally present in turbine flow have become more prevalent. One source of unsteadiness is wake passage from upstream components which can cause fluctuations in the stagnation location on turbine airfoils. This in turn causes unsteadiness in the behavior of the leading edge coolant jets and thus fluctuations in both the adiabatic effectiveness and heat transfer coefficient. The dynamics of h and η are now quantifiable with modern inverse heat transfer methods and nonintrusive infrared thermography. The present study involved the application of a novel inverse heat transfer methodology to determine time-resolved adiabatic effectiveness and heat transfer coefficient waveforms on a simulated turbine blade leading edge with an oscillating stagnation position. The leading edge geometry was simulated with a circular cylinder with a coolant hole located 21.5 deg downstream from the leading edge stagnation line, angled 20 deg to the surface and 90 deg to the streamwise direction. The coolant plume is shown to shift in response to the stagnation line movement. These oscillations thus influence the film cooling coverage, and the time-averaged benefit of film cooling is influenced by the oscillation.

Numerical Simulation of a Simulated Film Cooled Turbine Blade Leading Edge Including Conjugate Heat Transfer Effects

2009 ◽  
Author(s):  
Laurene D. Dobrowolski ◽  
David G. Bogard ◽  
Justin Piggush ◽  
Atul Kohli
Keyword(s):  
Turbine Blade ◽  
Computational Study ◽  
Computational Simulation ◽  
Density Ratio ◽  
Leading Edge ◽  
Metal Temperature ◽  
Stagnation Line ◽  
Adiabatic Effectiveness ◽  
Overall Effectiveness ◽  
Blade Leading Edge

A conjugate numerical method was used to predict the normalized “metal” temperature of a simulated turbine blade leading edge. This computational study was done in conjunction with a parallel effort to experimentally determine normalized metal temperature, i.e. overall effectiveness, using a specially designed model blade leading edge. Also examined in this study were adiabatic models which provided adiabatic effectiveness results. Two different film cooling configurations were employed. The first configuration consisted of one row of holes centered on the stagnation line. The second configuration had two additional rows located at ±25 degrees from the stagnation line. These simulations were run at two different blowing ratios, M = 1 and M = 2. The coolant to mainstream density ratio was 1.5. The computational simulation was conducted using the FLUENT code using the realizable k-ε turbulence model and with grid resolution within the viscous sublayer. Adiabatic effectiveness distributions were predicted well by the computational simulations, except for localized areas near the holes. Predictions of overall effectiveness were higher than experimentally measured values in the stagnation region, but lower along downstream section of the leading edge. Reasons for the differences between computational predictions and experimental measurements were examined.

Film Cooling Parameter Waveforms on a Turbine Blade Leading Edge Model With Oscillating Stagnation Line

2015 ◽  
Author(s):  
James L. Rutledge ◽  
Tylor C. Rathsack ◽  
Matthew T. Van Voorhis ◽  
Marc D. Polanka
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Turbine Blade ◽  
Film Cooling ◽  
Leading Edge ◽  
Stagnation Line ◽  
Inverse Heat Transfer ◽  
Adiabatic Effectiveness ◽  
Blade Leading Edge

It is necessary to understand how film cooling influences the external convective boundary condition involving both the adiabatic wall temperature and the heat transfer coefficient in order to predict the thermal durability of a gas turbine hot gas path component. Most studies in the past have considered only steady flow, but studies of the unsteadiness naturally present in turbine flow have become more prevalent. One source of unsteadiness is wake passage from upstream components which can cause fluctuations in the stagnation location on turbine airfoils. This in turn causes unsteadiness in the behavior of the leading edge coolant jets and thus fluctuations in both the adiabatic effectiveness and heat transfer coefficient. The dynamics of h and η are now quantifiable with modern inverse heat transfer methods and non-intrusive infrared thermography. The present study involved the application of a novel inverse heat transfer methodology to determine time resolved adiabatic effectiveness and heat transfer coefficient waveforms on a simulated turbine blade leading edge with an oscillating stagnation position. The leading edge geometry was simulated with a circular cylinder with a coolant hole located 21.5° downstream from the leading edge stagnation line, angled 20° to the surface and 90° to the streamwise direction. The coolant plume is shown to shift in response to the stagnation line movement. These oscillations thus influence the film cooling coverage and the time-averaged benefit of film cooling is influenced by the oscillation.

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.

Influence of Turbine Blade Leading Edge Profile on Film Cooling With Shaped Holes

2017 ◽  
Author(s):  
Mingjie Zhang ◽  
Nian Wang ◽  
Andrew F. Chen ◽  
Je-Chin Han
Keyword(s):  
Turbine Blade ◽  
Film Cooling ◽  
Density Ratio ◽  
Leading Edge ◽  
Stagnation Line ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Edge Profile ◽  
Elliptical Cylinders ◽  
Blade Leading Edge

This paper presents the turbine blade leading edge model film cooling effectiveness with shaped holes, using the pressure sensitive paint (PSP) mass transfer analogy method. The effects of leading edge profile, coolant to mainstream density ratio and blowing ratio are studied. Computational simulations are performed using the realizable k-ε turbulence model. Effectiveness obtained by CFD simulations are compared with experiments. Three leading edge profiles, including one semi-cylinder and two semi-elliptical cylinders with an after body, are investigated. The ratios of major to minor axis of two semi-elliptical cylinders are 1.5 and 2.0, respectively. The leading edge has three rows of shaped holes. For the semi-cylinder model, shaped holes are located at 0 degrees (stagnation line) and ± 30 degrees. Row spacing between cooling holes and the distance between impingement plate and stagnation line are the same for three leading edge models. The coolant to mainstream density ratio varies from 1.0 to 1.5 and 2.0, and the blowing ratio varies from 0.5 to 1.0 and 1.5. Mainstream Reynolds number is about 100,900 based on the diameter of the leading edge cylinder, and the mainstream turbulence intensity is about 7%. The results provide an understanding of the effects of leading edge profile and on turbine blade leading edge region film cooling with shaped-hole designs.

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.

Film Cooling of a Cylindrical Leading Edge With Injection Through Rows of Compound-Angle Holes

2001 ◽  
Vol 123 (4) ◽  
pp. 645-654 ◽  
Author(s):  
Y.-L. Lin ◽  
T. I.-P. Shih
Keyword(s):  
Film Cooling ◽  
Three Dimensional ◽  
Leading Edge ◽  
Lateral Spreading ◽  
Blind Test ◽  
Stagnation Line ◽  
Sst Model ◽  
Sst Turbulence Model ◽  
Adiabatic Effectiveness ◽  
Compound Angle

Computations, based on the k-ω shear-stress transport (SST) turbulence model in which all conservation equations were integrated to the wall, were performed to investigate the three-dimensional flow and heat transfer about a semi-cylindrical leading edge with a flat afterbody that is cooled by film-cooling jets, injected from a plenum through three staggered rows of compound-angle holes with one row along the stagnation line and two rows along ±25 deg. Results are presented for the surface adiabatic effectiveness, normalized temperature distribution, velocity vector field, and surface pressure. These results show the interactions between the mainstream hot gas and the cooling jets, and how those interactions affect surface adiabatic effectiveness. Results also show how “hot spots” can form about the stagnation zone because of the flow induced by the cooling jets. The computed results were compared with experimental data generated under a blind test. This comparison shows the results generated to be reasonable and physically meaningful. With the SST model, the normal spreading was under predicted from 20 to 50 percent. The lateral spreading was over predicted above the surface, but under predicted on the surface. The laterally averaged surface effectiveness was well predicted.

Influence of Turbine Blade Leading Edge Profile on Film Cooling With Shaped Holes

2018 ◽  
Vol 10 (5) ◽  
Author(s):  
Mingjie Zhang ◽  
Nian Wang ◽  
Andrew F. Chen ◽  
Je-Chin Han
Keyword(s):  
Turbine Blade ◽  
Film Cooling ◽  
Density Ratio ◽  
Leading Edge ◽  
Stagnation Line ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Edge Profile ◽  
Elliptical Cylinders ◽  
Blade Leading Edge

This paper presents the turbine blade leading edge model film cooling effectiveness with shaped holes, using the pressure sensitive paint (PSP) mass transfer analogy method. The effects of leading edge profile, coolant to mainstream density ratio, and blowing ratio are studied. Computational simulations are performed using the realizable k–ɛ (RKE) turbulence model. Effectiveness obtained by computational fluid dynamics (CFD) simulations is compared with experiments. Three leading edge profiles, including one semicylinder and two semi-elliptical cylinders with an after body, are investigated. The ratios of major to minor axis of two semi-elliptical cylinders are 1.5 and 2.0, respectively. The leading edge has three rows of shaped holes. For the semicylinder model, shaped holes are located at 0 deg (stagnation line) and ±30 deg. Row spacing between cooling holes and the distance between impingement plate and stagnation line are the same for three leading edge models. The coolant to mainstream density ratio varies from 1.0 to 1.5 and 2.0, and the blowing ratio varies from 0.5 to 1.0 and 1.5. Mainstream Reynolds number is about 100,000 based on the diameter of the leading edge cylinder, and the mainstream turbulence intensity is about 7%. The results provide an understanding of the effects of leading edge profile on turbine blade leading edge region film cooling with shaped hole designs.

Novel Gas Turbine Blade Leading Edge Cooling Configuration Using Advanced Double Swirl Chambers

2015 ◽  
Author(s):  
Karsten Kusterer ◽  
Gang Lin ◽  
Takao Sugimoto ◽  
Dieter Bohn ◽  
Ryozo Tanaka ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Leading Edge ◽  
Gas Turbine Blade ◽  
Stagnation Line ◽  
Impingement Cooling ◽  
Cooling Technology ◽  
Cooling Air ◽  
Blade Leading Edge

The Double Swirl Chambers (DSC) cooling technology, which has been introduced and developed by the authors, has the potential to be a promising cooling technology for further increase of gas turbine inlet temperature and thus improvement of the thermal efficiency. The DSC cooling technology establishes a significant enhancement of the local internal heat transfer due to the generation of two anti-rotating swirls. The reattachment of the swirl flows with the maximum velocity at the center of the chamber leads to a linear impingement effect on the internal surface of the blade leading edge nearby the stagnation line of gas turbine blade. Due to the existence of two swirls both the suction side and the pressure side of the blade near the leading edge can be very well cooled. In this work, several advanced DSC cooling configurations with a row of cooling air inlet holes have been investigated. Compared with the standard DSC cooling configuration the advanced ones have more suitable cross section profiles, which enables better accordance with the real blade leading edge profile. At the same time these configurations are also easier to be manufactured in a real blade. These new cooling configurations have been numerically compared with the state of the art leading edge impingement cooling configuration. With the same configuration of cooling air supply and boundary conditions the advanced DSC cooling presents 22–26% improvement of overall heat transfer and 3–4% lower total pressure drop. Along the stagnation line the new cooling configuration can generate twice the heat flux than the standard impingement cooling channel. The influence of spent flow in the impinging position and impingement heat transfer value is in the new cooling configurations much smaller, which leads to a much more uniform heat transfer distribution along the chamber axial direction.

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