Recent Advances in the Study of High Efficiency Novel Film Cooling Holes

2013 ◽  
Vol 740 ◽  
pp. 830-835
Author(s):  
Ping Dai ◽  
Nai Yun Yu
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
High Performance ◽  
High Efficiency ◽  
Turbine Blades ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
New Generation ◽  
Film Cooling Holes ◽  
Air Film

The development of a new generation of high performance aircraft turbine jet engine desires gas turbines to be operated at very high rotor inlet gas temperatures. This brings a problem on the effective cooling of turbine blades. Up to now, modified film cooling is still an effective cooling technique. The influence of air-film hole structures on the air-film cooling efficiency cant be ignored. A survey of the research results concerning novel air-film cooling hole about home and abroad were given and high efficiency crescent air-film hole geometry was put forward. Through a comparative study of film cooling characteristic with cylindrical air-film hole and forward diffused air-film hole and crescent air-film hole found effectiveness of the crescent air-film hole was superior to other air-film holes in various blowing ratios. The crescent air-film hole could greatly reduce the kidney vortex intensity, and then enhanced the air-film cooling effectiveness.

scholarly journals Entrance Effects on Diffused Film-Cooling Holes

1998 ◽  
Author(s):  
A. Kohli ◽  
K. A. Thole
Keyword(s):  
Reynolds Number ◽  
Film Cooling ◽  
Gas Turbines ◽  
High Performance ◽  
Computational Study ◽  
Density Ratio ◽  
Reynolds Numbers ◽  
Supply Channel ◽  
Cooling Hole ◽  
Film Cooling Holes

Film-cooling is a widely used method of prolonging blade life in high performance gas turbines and is implemented by injecting cold air through discrete holes on the blade surface. Most experimental research on film-cooling has been performed using round holes supplied by a stagnant plenum. This can be quite different from the actual turbine blade conditions in that a crossflow may be present whereby the internal channel Reynolds number could be as high as 90,000. This computational study uses a film-cooling hole that is inclined at 35° with respect to the mainstream and is diffused at the hole exit by 15°. An engine representative jet-to-mainstream density ratio of two was simulated. The test matrix consisted of fourteen different cases that were simulated for the two different blowing ratios in which the following effects were investigated: a) the effect of the orientation of the coolant supply channel relative to the cooling hole, b) the effect of the channel Reynolds number, and c) the effect of the metering length of the cooling hole. Results showed that the orientation of the coolant supply had a large effect whereby the worst orientation, in terms of a reduced adiabatic effectiveness, was predicted when the channel supplying the cooling hole was perpendicular to the mainstream. For this particular orientation, higher laterally averaged effectiveness occurred at lower channel Reynolds numbers and with the hole having a short metering length.

The Effect of a Meter-Diffuser Offset on Shaped Film Cooling Hole Adiabatic Effectiveness

2017 ◽  
Vol 139 (9) ◽  
Author(s):  
Shane Haydt ◽  
Stephen Lynch ◽  
Scott Lewis
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Electrical Discharge Machining ◽  
Density Ratio ◽  
Navier Stokes ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
Adiabatic Effectiveness ◽  
Improved Performance ◽  
Film Cooling Holes

Shaped film cooling holes are used extensively in gas turbines to reduce component temperatures. These holes generally consist of a metering section through the material and a diffuser to spread coolant over the surface. These two hole features are created separately using electrical discharge machining (EDM), and occasionally, an offset can occur between the meter and diffuser due to misalignment. The current study examines the potential impact of this manufacturing defect to the film cooling effectiveness for a well-characterized shaped hole known as the 7-7-7 hole. Five meter-diffuser offset directions and two offset sizes were examined, both computationally and experimentally. Adiabatic effectiveness measurements were obtained at a density ratio of 1.2 and blowing ratios ranging from 0.5 to 3. The detriment in cooling relative to the baseline 7-7-7 hole was worst when the diffuser was shifted upstream (aft meter-diffuser offset), and least when the diffuser was shifted downstream (fore meter-diffuser offset). At some blowing ratios and offset sizes, the fore meter-diffuser offset resulted in slightly higher adiabatic effectiveness than the baseline hole, due to a reduction in the high-momentum region of the coolant jet caused by a separation region created inside the hole by the fore meter-diffuser offset. Steady Reynolds-averaging Navier–Stokes (RANS) predictions did not accurately capture the levels of adiabatic effectiveness or the trend in the offsets, but it did predict the fore offset's improved performance.

Enhancement of Film Cooling Effectiveness Using Upstream Ramp

2012 ◽  
Author(s):  
Paresh Halder ◽  
Abdus Samad
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Surface Heat Flux ◽  
High Performance ◽  
Flat Surface ◽  
Surface Heat ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Cooling Hole

Film cooling is widely used in high-performance gas turbines to reduce surface heat flux and placing a ramp at the upstream of film cooling hole improves film cooling effectiveness. In this work, RANS based numerical simulations were carried out for a flat surface having two rows of injection holes and an upstream ramp. The parameters which were considered in this computation were different blowing ratios (M = 0.6, 1.0 and 1.6) and upstream ramp angles (α = 14° to 24°). Surface effectiveness was increased with increase in angle of upstream ramp and blowing ratio but further increasing these parameters decreased the effectiveness. The downstream of the second row hole effectiveness was more than that of the upstream hole for high blowing ratios in case of without ramp.

The Effect of a Meter-Diffuser Offset on Shaped Film Cooling Hole Adiabatic Effectiveness

2016 ◽  
Author(s):  
Shane Haydt ◽  
Stephen Lynch ◽  
Scott Lewis
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Electrical Discharge Machining ◽  
Density Ratio ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
Adiabatic Effectiveness ◽  
Improved Performance ◽  
Film Cooling Holes

Shaped film cooling holes are used extensively in gas turbines to reduce component temperatures. These holes generally consist of a metering section through the material and a diffuser to spread coolant over the surface. These two hole features are created separately using electrical discharge machining, and occasionally an offset can occur between the meter and diffuser due to misalignment. The current study examines the potential impact of this manufacturing defect to the film cooling effectiveness for a well-characterized shaped hole known as the 7-7-7 hole. Five meter-diffuser offset directions and two offset sizes were examined, both computationally and experimentally. Adiabatic effectiveness measurements were obtained at a density ratio of 1.2 and blowing ratios ranging from 0.5 to 3. The detriment in cooling relative to the baseline 7-7-7 hole was worst when the diffuser was shifted upstream (aft meter-diffuser offset), and least when the diffuser was shifted downstream (fore meter-diffuser offset). At some blowing ratios and offset sizes, the fore meter-diffuser offset resulted in slightly higher adiabatic effectiveness than the baseline hole, due to a reduction in the high-momentum region of the coolant jet caused by a separation region created inside the hole by the fore meter-diffuser offset. Steady RANS predictions did not accurately capture the levels of adiabatic effectiveness or the trend in the offsets, but it did predict the fore offset’s improved performance.

Recent Advances in the Study of Film Cooling on the Gas Turbine Blade

2014 ◽  
Vol 971-973 ◽  
pp. 143-147 ◽  
Author(s):  
Ping Dai ◽  
Shuang Xiu Li
Keyword(s):  
Gas Turbine ◽  
Turbine Blade ◽  
Film Cooling ◽  
Gas Turbines ◽  
High Performance ◽  
Leading Edge ◽  
Development Trend ◽  
Research Progress ◽  
Gas Turbine Blade ◽  
New Generation

The development of a new generation of high performance gas turbine engines requires gas turbines to be operated at very high inlet temperatures, which are much higher than the allowable metal temperatures. Consequently, this necessitates the need for advanced cooling techniques. Among the numerous cooling technologies, the film cooling technology has superior advantages and relatively favorable application prospect. The recent research progress of film cooling techniques for gas turbine blade is reviewed and basic principle of film cooling is also illustrated. Progress on rotor blade and stationary blade of film cooling are introduced. Film cooling development of leading-edge was also generalized. Effect of various factor on cooling effectiveness and effect of the shape of the injection holes on plate film cooling are discussed. In addition, with respect to progress of discharge coefficient is presented. In the last, the future development trend and future investigation direction of film cooling are prospected.

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.

Implementation of Hole-Pair in Ramp to Improve Film Cooling Effectiveness on a Plain Surface

2020 ◽  
Author(s):  
Sadam Hussain ◽  
Xin Yan
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Density Ratio ◽  
Hole Pair ◽  
Cooling Effect ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Cooling Hole ◽  
Plain Surface

Abstract Film cooling is one of the most critical technologies in modern gas turbine engine to protect the high temperature components from erosion. It allows gas turbines to operate above the thermal limits of blade materials by providing the protective cooling film layer on outer surfaces of blade against hot gases. To get a higher film cooling effect on plain surface, current study proposes a novel strategy with the implementation of hole-pair into ramp. To gain the film cooling effectiveness on the plain surface, RANS equations combined with k-ω turbulence model were solved with the commercial CFD solver ANSYS CFX11.0. In the numerical simulations, the density ratio (DR) is fixed at 1.6, and the film cooling effect on plain surface with different configurations (i.e. with only cooling hole, with only ramp, and with hole-pair in ramp) were numerically investigated at three blowing ratios M = 0.25, 0.5, and 0.75. The results show that the configuration with Hole-Pair in Ramp (HPR) upstream the cooling hole has a positive effect on film cooling enhancement on plain surface, especially along the spanwise direction. Compared with the baseline configuration, i.e. plain surface with cylindrical hole, the laterally-averaged film cooling effectiveness on plain surface with HPR is increased by 18%, while the laterally-averaged film cooling effectiveness on plain surface with only ramp is increased by 8% at M = 0.5. As the blowing ratio M increases from 0.25 to 0.75, the laterally-averaged film cooling effectiveness on plain surface with HPR is kept on increasing. At higher blowing ratio M = 0.75, film cooling effectiveness on plain surface with HPR is about 19% higher than the configuration with only ramp.

Effect of Hole Pitch Ratio and Compound Angle on the Thermal Flow Fields of Double-Jet Film Cooling Hole

2014 ◽  
Author(s):  
Moon-Young Cho ◽  
Hyeon-Seok Seo ◽  
Youn-Jea Kim
Keyword(s):  
Film Cooling ◽  
Numerical Study ◽  
Turbine Blades ◽  
Flow Characteristics ◽  
Thermal Flow ◽  
Film Cooling Effectiveness ◽  
Gas Turbine Blades ◽  
Ansys Cfx ◽  
Cooling Hole ◽  
Pitch Distance

In this study, the effect of a row of double-jet film-cooling hole configurations on the thermal-flow characteristics of gas turbine blades was examined. To investigate the effect of the interference of anti-kidney vortices, the ratios of the pitch distance and hole diameter (P/d=5, 6.25, 8.333) were considered with two different compound angles (λ=0°, 4°). The film cooling performance and the generated losses were studied. Then, the relevant mechanisms were identified and explained. A numerical study was performed using ANSYS CFX 14.5 with the shear stress transport (SST) turbulent model. The blowing ratio was kept at a constant value of M=1.5. The film cooling effectiveness and temperature distribution are graphically depicted with various geometrical configurations.

Effect of Film-Cooling Hole Location on Turbulator Heat Transfer Enhancement in Turbine Blade Internal Air-Cooling Circuits

1999 ◽  
Author(s):  
J. M. McDonough ◽  
V. E. Garzón ◽  
D. E. Schulte
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
High Performance ◽  
Turbulence Modeling ◽  
Pressure Coefficient ◽  
Turbine Blades ◽  
Air Cooling ◽  
Eddy Simulation ◽  
Cooling Hole ◽  
Cooling Air

Numerical results demonstrating the effect of film-cooling hole placement on turbulator heat transfer effectiveness in internal convective cooling air circuits of turbine blades in high-performance gas turbine engines is presented for a two-dimensional model problem. Of particular interest will be the performance of a new turbulence modeling formalism similar to large-eddy simulation (LES) but employing subgrid-scale models constructed from nonlinear discrete dynamical systems, and not requiring filtering of the resolved-scale governing equations. Computed results for temperature distribution, flow streamlines, pressure coefficient and heat transfer Stanton number are compared for three different cooling hole/turbulator configurations, and turbulence kinetic energy is compared with results from a standard k-ε model.

Film Cooling Measurements for a Laidback Fan-Shaped Hole: Effect of Coolant Crossflow on Cooling Effectiveness and Heat Transfer

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Marc Fraas ◽  
Tobias Glasenapp ◽  
Achmed Schulz ◽  
Hans-Jörg Bauer
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Film Cooling ◽  
Gas Flow ◽  
Density Ratio ◽  
Coolant Flow ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
Film Cooling Holes

Internal coolant passages of gas turbine vanes and blades have various orientations relative to the external hot gas flow. As a consequence, the inflow of film cooling holes varies as well. To further identify the influencing parameters of film cooling under varying inflow conditions, the present paper provides detailed experimental data. The generic study is performed in a novel test rig, which enables compliance with all relevant similarity parameters including density ratio. Film cooling effectiveness as well as heat transfer of a 10–10–10 deg laidback fan-shaped cooling hole is discussed. Data are processed and presented over 50 hole diameters downstream of the cooling hole exit. First, the parallel coolant flow setup is discussed. Subsequently, it is compared to a perpendicular coolant flow setup at a moderate coolant channel Reynolds number. For the perpendicular coolant flow, asymmetric flow separation in the diffuser occurs and leads to a reduction of film cooling effectiveness. For a higher coolant channel Reynolds number and perpendicular coolant flow, asymmetry increases and cooling effectiveness is further decreased. An increase in blowing ratio does not lead to a significant increase in cooling effectiveness. For all cases investigated, heat transfer augmentation due to film cooling is observed. Heat transfer is highest in the near-hole region and decreases further downstream. Results prove that coolant flow orientation has a severe impact on both parameters.

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