CFD Predictions of the Frequency Dependence of Pulsed Film Cooling Heat Flux on a Turbine Blade Leading Edge

2009 ◽  
Author(s):  
James Rutledge ◽  
Paul King ◽  
Richard Rivir
Keyword(s):  
Heat Flux ◽  
Frequency Dependence ◽  
Turbine Blade ◽  
Film Cooling ◽  
Leading Edge ◽  
Blade Leading Edge

Net Heat Flux Reduction and Overall Effectiveness for a Turbine Blade Leading Edge

2005 ◽  
Author(s):  
Brian D. Mouzon ◽  
Elon J. Terrell ◽  
Jason E. Albert ◽  
David G. Bogard
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Turbine Blade ◽  
Film Cooling ◽  
Leading Edge ◽  
Cooling Performance ◽  
Net Heat Flux ◽  
Laboratory Models ◽  
Overall Effectiveness ◽  
Blade Leading Edge

The external cooling performance of a film cooled turbine airfoil can be quantified as a net reduction in heat transfer relative to the turbine airfoil without film cooling. This quantification is generally accomplished by using measurements of the adiabatic effectiveness and the change in heat transfer coefficients (hf/h0) for the film cooled surface to determine the net heat flux reduction (Δqr). Although measurement of Δqr for laboratory models give an indication of the ultimate film cooling performance, this does not show how much the surface temperature of the airfoil is reduced by film cooling. Measurement of scaled surface temperatures can be accomplished by using laboratory models constructed so that the Biot number is matched with that of the actual airfoil. These measurements provide a scaled temperature distribution on the airfoil that is referred to as the overall effectiveness, φ. For the current study, measurements of Δqr and φ have been made for a simulated turbine blade leading edge. The simulated leading edge incorporated shaped coolant holes, and had three rows of coolant holes. Improvements due to the shaped holes were determined by comparisons with previously measured round hole configurations. Spatially distributed hf/h0 show increases of 5% to 15% for M = 1.0 and 10% to 30% for M = 2.0. Results show that local variation in Δqr much greater than variation in φ, but laterally averaged Δqr distributions are reasonable predictors of the laterally averaged φ distributions.

CFD Predictions of Pulsed Film Cooling Heat Flux on a Turbine Blade Leading Edge

2008 ◽  
Author(s):  
James L. Rutledge ◽  
Paul I. King ◽  
Richard Rivir
Keyword(s):  
Heat Flux ◽  
Turbine Blade ◽  
Film Cooling ◽  
Computational Study ◽  
Leading Edge ◽  
Time Resolved ◽  
Average Mass ◽  
Blowing Ratio ◽  
Net Heat Flux ◽  
Blade Leading Edge

Unsteadiness in film cooling jets may arise due to inherent unsteadiness of the blade-vane interaction or may be induced as a means of flow control. A computational study was conducted to determine how leading edge film cooling performance is affected by pulsing the coolant flow. A cylindrical leading edge with a flat afterbody is used to simulate the turbine blade leading edge region. A single coolant hole was located 21.5° from the leading edge, angled 20° to the surface and 90° from the streamwise direction. The leading edge diameter to hole diameter ratio is D/d = 18.7. Time resolved adiabatic effectiveness and heat transfer coefficient are used to calculate the temporally averaged, spatially resolved net heat flux reduction for several pulsing scenarios. The net heat flux reduction with pulsed film cooling is compared to the steady jet with matched average mass flow rate. Steady blowing ratios of M = 0.25 and 0.50 are each compared with two pulsed jet cases with matching averaging blowing ratio, M, at a nondimensional frequency, F = 0.151 and duty cycle, DC = 50%. Simulations were performed at ReD = 60000. Net heat flux is generally increased by pulsing the film coolant, with greater degradation for higher pulsation amplitudes relative to the average blowing ratio.

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.

scholarly journals Numerical investigation about backflow of film cooling in static turbine blade leading edge

2019 ◽  
Vol 11 (11) ◽  
pp. 168781401988581
Author(s):  
Chao Gao ◽  
Haiwang Li ◽  
Huimin Zhou ◽  
Yiwen Ma ◽  
Ruquan You
Keyword(s):  
Turbine Blade ◽  
Film Cooling ◽  
Pressure Ratio ◽  
Leading Edge ◽  
Hole Diameter ◽  
Computational Method ◽  
Coverage Area ◽  
Slowing Down ◽  
Film Cooling Holes ◽  
Blade Leading Edge

In this article, film cooling characteristics, especially the phenomenon of backflow for the straight turbine blade leading edge, are investigated. Shear stress transport k-ω turbulence model and structured grids are employed to assure the accuracy of the simulation, and the computational method is verified by the available experimental data. The influences of blow ratio, hole diameter, and the spacing between holes in each row are analyzed. The formation mechanism of backflow is discussed to prevent it from happening or relieve the degree of backflow, thereby to improve the cooling efficiency. The results showed that backflow can be avoided by adjusting the structure and the layout of film cooling holes. With increase in blow ratio, the cooling film becomes more obvious at first and then fades gradually for departing from the blade surface. The jet flow is influenced by the total pressure ratio between coolant cavity and surface of blade leading edge. Smaller film hole diameter and larger hole spacing makes it easier to eject coolant and form continuous film by slowing down the pressure in the cavity. Increasing ratio of hole spacing to hole diameter ( p/ d) can effectively prevent backflow, whereas larger p/ d also makes the film coverage area smaller.

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.

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