A Comparative Investigation of Round and Fan-Shaped Cooling Hole Near Flow Fields

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
James S. Porter ◽  
Jane E. Sargison ◽  
Gregory J. Walker ◽  
Alan D. Henderson
Keyword(s):  
High Speed ◽  
Near Field ◽  
Steady State Solution ◽  
Comparative Investigation ◽  
Round Hole ◽  
High Shear ◽  
Cooling Hole ◽  
Turbulence Data ◽  
Shaped Hole ◽  
Layer Flow

This study presents velocity and turbulence data measured experimentally in the near field of a round and a laterally expanded fan-shaped cooling hole. Both holes are fed by a plenum inlet, and interact with a turbulent mainstream boundary layer. Flow is Reynolds number matched to engine conditions to preserve flow structure, and two coolant to mainstream blowing momentum ratios are investigated experimentally. Results clearly identify regions of high shear for the round hole as the jet penetrates into the mainstream. In contrast, the distinct lack of high shear regions for the fan-shaped hole points to reasons for improvements in cooling performance noted by previous studies. Two different computational fluid dynamics codes are used to predict the flow within and downstream of the fan-shaped hole, with validation from the experimental measurements. One code is the commercially available ANSYS CFX 10.0, and the other is the density-based solver with low Mach number preconditioning, HYDRA, developed in-house by Rolls-Royce plc for high speed turbomachinery flows. Good agreement between numerical and experimental data for the center-line traverses was obtained for a steady state solution, and a region of reversed flow within the expansion region of the fan-shaped hole was identified.

A Comparative Investigation of Round and Fan-Shaped Cooling Hole Near Flow Fields

2007 ◽  
Author(s):  
James S. Porter ◽  
Jane E. Sargison ◽  
Gregory J. Walker ◽  
Alan D. Henderson
Keyword(s):  
High Speed ◽  
Near Field ◽  
Steady State Solution ◽  
Comparative Investigation ◽  
Round Hole ◽  
High Shear ◽  
Cooling Hole ◽  
Turbulence Data ◽  
Shaped Hole ◽  
Layer Flow

This study presents velocity and turbulence data measured experimentally in the near field of a round and a laterally expanded fan-shaped cooling hole. Both holes are fed by a plenum inlet, and interact with a turbulent mainstream boundary layer. Flow is Reynolds number matched to engine conditions to preserve flow structure, and two coolant to mainstream blowing momentum ratios are investigated experimentally. Results clearly identify regions of high shear for the round hole as the jet penetrates into the mainstream. In contrast, the distinct lack of high shear regions for the fan shaped hole point to reasons for improvements in cooling performance noted by previous studies. Two different CFD codes are used to predict the flow within and downstream of the fan shaped hole, with validation from the experimental measurements. One code is the commercially available ANSYS CFX 10.0, and the other is the density-based solver with low Mach number preconditioning, HYDRA, developed in-house by Rolls-Royce plc for high speed turbomachinery flows. Good agreement between numerical and experimental data for the center-line traverses was obtained for a steady state solution, and a region of reversed flow within the expansion region of the fan-shaped hole was identified.

Application of S-PIV for Investigation of Round and Shaped Film Cooling Holes at High Density Ratios

2016 ◽  
Author(s):  
Travis B. Watson ◽  
Sara Nahang-Toudeshki ◽  
Lesley M. Wright ◽  
Daniel C. Crites ◽  
Mark C. Morris ◽  
...  
Keyword(s):  
Film Cooling ◽  
High Speed ◽  
Density Ratio ◽  
High Density ◽  
Round Hole ◽  
Turbine Engine ◽  
Flow Vorticity ◽  
Cooling Hole ◽  
Shaped Hole ◽  
Density Ratios

Hot section turbine engine components are often cooled through the use of a cool film of air on the component wall. The source of the air used for film cooling comes from the compressor of the gas turbine engine and may be 800°C, or more, cooler than the hot gas path air. The temperature differential between the hot mainstream gas and the film coolant results in a large difference in density between the two gases. In order to investigate the effect of high density ratios on film cooling performance, a traditional, round hole (θ = 30°) and a laidback, fan shaped hole (θ = 30°, α = γ = 10°) were observed using Stereo-Particle Image Velocimetry (S-PIV). Flowfield measurements were performed on various planes downstream of the film cooling hole (x/d = 0, 1, 3 and 10 for the round hole and x/d = 0, 3, and 10 for the shaped hole). At each location the coolant-to-mainstream interaction was captured at multiple density ratios (DR = 1, 2, 3, 4) and blowing ratios (M = 0.5, 1.0, 1.5). Using S-PIV, the three-dimensional flow field was measured. Distributions of the flow vorticity were derived from the high speed velocity measurements taken during S-PIV testing. For the simple angle, round holes, the results show at the elevated density ratios, the coolant spreads laterally near the hole; while at DR = 1, the coolant trace is limited to the width of the film cooling hole. Furthermore, as the cooling jet exits from the round hole, the vorticity within the jet is very strong, leading to increased mixing with the mainstream. However, as the density ratio increases (at a given blowing ratio), this mixing was reduced. For a given flow condition, the rotation was reduced with the jet exiting the shaped hole (compared to the round hole), and this led to enhanced protection on the surface. While investigating both round and shaped holes, it was shown the S-PIV method is a valuable tool to observe and quantify the jet–to–mainstream interactions near the film cooled surface.

Film Cooling Effectiveness Improvements Using a Nondiffusing Oval Hole

2015 ◽  
Vol 138 (4) ◽  
Author(s):  
Emin Issakhanian ◽  
Christopher J. Elkins ◽  
John K. Eaton
Keyword(s):  
Film Cooling ◽  
Measurement Techniques ◽  
Round Hole ◽  
Blade Surface ◽  
Mean Velocity ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
Shaped Hole ◽  
Film Cooling Holes

The need for improvements in film cooling effectiveness over traditional cylindrical film cooling holes has led to varied shaped hole and sister hole designs of increasing complexity. This paper presents a simpler shaped hole design which shows improved film cooling effectiveness over both cylindrical holes and diffusing fan-shaped holes without the geometric complexity of the latter. Magnetic resonance imaging measurement techniques are used to reveal the coupled 3D velocity and coolant mixing from film cooling holes which are of a constant oval cross section as opposed to round. The oval-shaped hole yielded an area-averaged adiabatic effectiveness twice that of the diffusing fan-shaped hole tested. Three component mean velocity measurements within the channel and cooling hole showed the flow features and vorticity fields which explain the improved performance of the oval-shaped hole. As compared to the round hole, the oval hole leads to a more complex vorticity field, which reduces the strength of the main counter-rotating vortex pair (CVP). The CVP acts to lift the coolant away from the turbine blade surface, and thus strongly reduces the film cooling effectiveness. The weaker vortices allow the coolant to stay closer to the blade surface and to remain relatively unmixed with the main flow over a longer distance. Thus, the oval-shaped film cooling hole provides a simpler solution for improving film cooling effectiveness beyond circular hole and diffusing hole designs.

Effect of Row Spacing on the Accuracy of Film Cooling Superposition Method

2018 ◽  
Author(s):  
Lang Wang ◽  
Xueying Li ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Film Cooling ◽  
Row Spacing ◽  
Superposition Method ◽  
Round Hole ◽  
Cooling Effectiveness ◽  
Blowing Ratio ◽  
Cooling Hole ◽  
Shaped Hole ◽  
The Difference ◽  
Density Ratios

Film cooling technique is widely used in a modern gas turbine. Many applications in hot sections require multiple film cooling rows to get better cooled. In most situation, the additive effect is computed using Sellers superposition method, but it is not accurate when the hole rows are close to each other. In this paper, row spacing between two rows of cooling hole was investigated by numerical method, which was validated by PSP results. The validation experiments are performed on flat test bench and the freestream is maintained at 25m/s. The inlet boundary conditions of numerical simulations were same with the experiment. Both round hole and shaped hole were investigated at blowing ratio M = 0.5, density ratios DR = 1.5 and row spacing S/D = 6, 10, 15, 20. It is found that the round hole results by Sellers method are similar to experiment results only at large row spacing, and the results of Sellers are always higher than experimental results. The boundary layer has a big effect on cooling effectiveness for round hole, but very little effect on shaped hole. When the row spacing increase, the difference between experiment and prediction become smaller. The vortex is the major factor to effect the accuracy of superposition method.

Film Cooling Effectiveness Improvements Using a Non-Diffusing Oval Hole

2015 ◽  
Author(s):  
Emin Issakhanian ◽  
Christopher J. Elkins ◽  
John K. Eaton
Keyword(s):  
Film Cooling ◽  
Vortex Pair ◽  
Round Hole ◽  
Blade Surface ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
Counter Rotating Vortex Pair ◽  
Shaped Hole ◽  
Film Cooling Holes

The need for improvements in film cooling effectiveness over traditional cylindrical film cooling holes has led to varied shaped hole and sister hole designs of increasing complexity. This paper presents a simpler shaped-hole design which shows improved film cooling effectiveness over both cylindrical holes and diffusing fan-shaped holes without the geometric complexity of the latter. Magnetic resonance imaging measurement techniques are used to reveal the coupled 3D velocity and coolant mixing from film cooling holes which are of a constant oval cross-section as opposed to round. The oval shaped hole yielded an area-averaged adiabatic effectiveness twice that of the diffusing fan-shaped hole tested. Three component mean velocity measurements within the channel and cooling hole showed the flow features and vorticity fields which explain the improved performance of the oval shaped hole. As compared to the round hole, the oval hole leads to a more complex vorticity field which reduces the strength of the main counter-rotating vortex pair. The counter-rotating vortex pair acts to lift the coolant away from the turbine blade surface and thus strongly reduces the film cooling effectiveness. The weaker vortices allow coolant to stay closer to the blade surface and to remain relatively unmixed with the main flow over a longer distance. Thus, the oval-shaped film cooling hole provides a simpler solution for improving film cooling effectiveness beyond circular hole and diffusing hole designs.

scholarly journals Effects of Hole Shape on Film Cooling With Large Angle Injection

1999 ◽  
Author(s):  
Atui Kohil ◽  
David G. Bogard
Keyword(s):  
Velocity Field ◽  
Film Cooling ◽  
Field Measurements ◽  
Round Hole ◽  
Cooling Performance ◽  
Injection Angle ◽  
Hole Shape ◽  
Shaped Hole ◽  
Adiabatic Effectiveness ◽  
Better Than

In this study the film cooling performance of a single row of discrete holes inclined at an injection angle of 55° is investigated at a density ratio of DR = 1.6. Three different hole geometries were used in this study, a round hole and two shaped holes. One shaped hole had forward and lateral expansions of 15°, and the other a 15° lateral with a 25° forward expansion. For reference, a round hole with an injection angle of 35° was also tested. The film cooling performance of each hole shape was evaluated using adiabatic effectiveness, thermal field, and velocity field measurements. The shaped holes showed higher spatially averaged adiabatic effectiveness than the round hole over the whole range of momentum flux ratios (I) investigated. The effectiveness values for the shaped holes were only marginally better than the round hole at the low I, but at the high I, the shaped holes performed much better than the round hole. The temperature and velocity field measurements near the hole exit suggest that there is a slight detachment of the jet from the wall for the round hole, while the jets remain attached for the two shaped holes. The shaped hole with the larger forward expansion had a warmer jet with a higher trajectory at the hole exit suggesting ingestion of mainstream fluid and flow separation within the hole.

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