Computational Study of Parameters Affecting Turbulent Flat Plate Film Cooling

2004 ◽  
Author(s):  
Shadi Mahjoob ◽  
Mohammad Taeibi-Rahni
Keyword(s):  
Flat Plate ◽  
Film Cooling ◽  
Gas Turbines ◽  
Computational Study ◽  
Velocity Ratio ◽  
Hole Injection ◽  
Spanwise Direction ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Injection Angle

Blade film cooling is one of the best methods to improve efficiency of gas turbines. In this work, two different methods of film cooling, namely, slot injection and discrete hole injection have been numerically studied on a flat plate. Incompressible, stationary, viscous, turbulent flow has been simulated using the FLUENT CFD code with the standard k-ε model. The study of injection angle and velocity ratio show that the optimum film cooling in both methods, occurs at the jet angle of 30° but with the velocity ratio of 1.5 for slot case and 0.5 for discrete hole case. The study of jet aspect ratio in discrete hole method, shows that stretching the hole in spanwise direction increases the film cooling effectiveness. Because it not only cool a larger region in both spanwise and streamwise directions, but also can sustain the cooled flow closer to the blade’s wall. The study of jet spacing shows that increasing the jet spacing decreases the effectiveness but not as much as jet aspect ration does.

Mechanism of Film Cooling with One Inlet and Double Outlet Hole Injection at Various Turbulence Intensities

2018 ◽  
Vol 35 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Guangchao Li ◽  
Yukai Chen ◽  
Zhihai Kou ◽  
Wei Zhang ◽  
Guochen Zhang
Keyword(s):  
Turbulence Intensity ◽  
Film Cooling ◽  
Hole Injection ◽  
Spanwise Direction ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Outlet Hole ◽  
Cylindrical Holes ◽  
High Turbulence

AbstractThe trunk-branch hole was designed as a novel film cooling concept, which aims for improving film cooling performance by producing anti-vortex. The trunk-branch hole is easily manufactured in comparison with the expanded hole since it consists of two cylindrical holes. The effect of turbulence on the film cooling effectiveness with a trunk-branch hole injection was investigated at the blowing ratios of 0.5, 1.0, 1.5 and 2.0 by numerical simulation. The turbulence intensities from 0.4 % to 20 % were considered. The realizable$k - \varepsilon $turbulence model and the enhanced wall function were used. The more effective anti-vortex occurs at the low blowing ratio of 0.5 %. The high turbulence intensity causes the effectiveness evenly distributed in the spanwise direction. The increase of turbulence intensity leads to a slight decrease of the spanwise averaged effectiveness at the low blowing ratio of 0.5, but a significant increase at the high blowing ratios of 1.5 and 2.0. The optimal blowing ratio of the averaged surface effectiveness is improved from 1.0 to 1.5 when the turbulence intensity increases from 0.4 % to 20 %.

Effect of Density Ratio on Film-Cooling Effectiveness Distribution and Its Uniformity for Several Hole Geometries on a Flat Plate

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Jiaxu Yao ◽  
Jin Xu ◽  
Ke Zhang ◽  
Jiang Lei ◽  
Lesley M. Wright
Keyword(s):  
Flat Plate ◽  
Film Cooling ◽  
Density Ratio ◽  
Lateral Spread ◽  
Spanwise Direction ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cylindrical Holes ◽  
Density Ratios ◽  
Compound Angle

The film cooling effectiveness distribution and its uniformity downstream of a row of film cooling holes on a flat plate are investigated by pressure sensitive paint (PSP) under different density ratios. Several hole geometries are studied, including streamwise cylindrical holes, compound-angled cylindrical holes, streamwise fan-shape holes, compound-angled fan-shape holes, and double-jet film-cooling (DJFC) holes. All of them have an inclination angle (θ) of 35 deg. The compound angle (β) is 45 deg. The fan-shape holes have a 10 deg expansion in the spanwise direction. For a fair comparison, the pitch is kept as 4d for the cylindrical and the fan-shape holes, and 8d for the DJFC holes. The uniformity of effectiveness distribution is described by a new parameter (Lateral-Uniformity, LU) defined in this paper. The effects of density ratios (DR = 1.0, 1.5 and 2.5) on the film-cooling effectiveness and its uniformity are focused. Differences among geometries and effects of blowing ratios (M = 0.5, 1.0, 1.5, and 2.0) are also considered. The results show that at higher density ratios, the lateral spread of the discrete-hole geometries (i.e., the cylindrical and the fan-shape holes) is enhanced, while the DJFC holes is more advantageous in film-cooling effectiveness. Mostly, a higher lateral-uniformity is obtained at DR = 2.5 due to better coolant coverage and enhanced lateral spread, but the effects of the density ratio on the lateral-uniformity are not monotonic in some cases. Utilizing the compound angle configuration leads to an increased lateral-uniformity due to a stronger spanwise motion of the jet. Generally, with a higher blowing ratio, the lateral-uniformity of the discrete-hole geometries decreases due to narrower traces, while that of the DJFC holes increases due to a stronger spanwise movement.

Computational Study of the Effects of Shock Waves on Film Cooling Effectiveness

2009 ◽  
Author(s):  
Chad X.-Z. Zhang ◽  
Ibrahim G. Hassan
Keyword(s):  
Shock Waves ◽  
Flat Plate ◽  
Film Cooling ◽  
Computational Study ◽  
Strong Shock ◽  
Boundary Layer Separation ◽  
Airfoil Surface ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Transonic Airfoil

The performance of a louver cooling scheme on a transonic airfoil has been studied numerically in this paper. Film cooling holes are located near the passage throat. The Mach number at the location of the jet exit is close to unity. A comparison of film cooling effectiveness between numerical prediction and experimental data for a circular hole shows that the numerical procedures are adequate. In addition to the shock wave effects and compressibility, curvature effect was also studied by comparing cooling effectiveness on the airfoil surface with that on a flat plate. Substantially higher cooling effectiveness for the louver cooling scheme on the airfoil was predicted at blowing ratios below 1 in comparison to other cooling configurations. At higher blowing ratios than 2 the advantages of the louver cooling scheme becomes less obvious. It was also found that for the same cooling configuration the cooling effectiveness on the transonic airfoil is slightly higher than that on a flat plate at moderately low blowing ratios below 1. At high blowing ratios above 2 when the oblique shock becomes detached from the leading edge of the hole exits, dramatic reduction in cooling effectiveness occurs as a result of boundary layer separation due to the strong shock waves. A coolant-blockage and shaped-wedge analogy was proposed and found to be able to qualitatively explain this phenomenon satisfactorily.

Effect of Injection Angle on Performance of Full Coverage Film Cooling with Opposite Injection Holes

2018 ◽  
Vol 0 (0) ◽  
Author(s):  
Mukesh Prakash Mishra ◽  
A K Sahani ◽  
Sunil Chandel ◽  
R K Mishra
Keyword(s):  
Film Cooling ◽  
Velocity Ratio ◽  
Practical Importance ◽  
Density Ratio ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Injection Angle ◽  
Full Coverage ◽  
Wide Range

Abstract Characteristics of full coverage film cooling of an adiabatic flat plate are studied for opposite injection of coolant at different angles. Two in-line adjacent rows of cooling holes injecting in opposite directions are considered in this study. The cooling performance is compared with the configurations having forward and reverse injecting holes at similar injection angles. The holes are arranged in an array of 20 rows with equal spacing both span-wise and stream-wise. Computational analyses are carried out over a wide range of velocity ratios (VR) of practical importance ranging from 0.5 to 2.0 at density ratio of about 1.0. Injection angle and velocity ratio are found to have strong influence on film cooling effectiveness of opposite injection. At low velocity ratio of VR=0.5, film cooling performance of opposite injection at 45° is found better than at other angles, i. e. 30° and 60°. At higher velocity ratios, injection at 30° is found superior. Film cooling effectiveness becomes insensitive to velocity ratios at higher range for 45° and 60° injections. Evolution of effusion film layer and interaction between coolant and primary flow is also studied in this paper.

The Influence of Density Difference Between Hot and Coolant Gas on Film Cooling by a Row of Holes: Predictions and Experiments

1992 ◽  
Vol 114 (4) ◽  
pp. 747-755 ◽  
Author(s):  
W. Haas ◽  
W. Rodi ◽  
B. Scho¨nung
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Turbine Blade ◽  
Film Cooling ◽  
Density Ratio ◽  
Density Difference ◽  
Extended Model ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Injection Angle

The two-dimensional boundary-layer procedure of Scho¨nung and Rodi [1] for calculating film cooling by a row of holes was extended to account for density differences between hot gas and injected coolant gas. The extensions concern the injection model for leaping over the immediate blowing region in the boundary-layer calculation and also the dispersion model for taking into account three-dimensional effects. The extended model is tested for a density ratio of ρj/ρe ≈ 2 for both flat-plate situations and film cooling on a model turbine blade. The predicted laterally averaged film cooling effectiveness is compared with measurements for these cases. Results for the flat-plate experiments were taken from the literature, while experiments for a model turbine blade are also described in this paper. For a fixed injection angle of 32 deg, the film cooling effectiveness was measured for various spacings and velocity ratios Uj/Ue. The density ratio ρj/ρe ≈ 2 was achieved by adding Freon to the injection gas. The results are compared with those reported in [2] for negligible density difference. At the same blowing rate M = Uj/Ue, the film cooling effectiveness was found to increase with the density ratio ρj/ρe. In general, the influence of the density difference is well predicted by the model.

An Investigation of Turbine Film Cooling Effectiveness With Shaped Holes and Internal Cross-Flow With Varying Operational Parameters

2016 ◽  
Author(s):  
Ellen Wilkes ◽  
Joshua Anderson ◽  
John McClintic ◽  
David Bogard
Keyword(s):  
Film Cooling ◽  
Velocity Ratio ◽  
Cross Flow ◽  
Flow Channel ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Injection Angle ◽  
Shaped Hole ◽  
Adiabatic Effectiveness ◽  
Film Cooling Holes

This study focuses on specifics of gas turbine film cooling. Laboratory film cooling tests are important for industry because actual engine conditions are too hot, too small, and too fast to take accurate and high resolution measurements. Experiments are typically conducted using a plenum to feed coolant through round or shaped film cooling holes. Less common are experiments using cross-flow fed coolant, a method that flows coolant perpendicular to the mainstream flow and better represents engine designs. There are a few studies that have explored shaped holes in cross-flow, but none have looked at the effect cross-flow channel parameters other than Mach number. Here, the effectiveness of film cooling is quantified by measuring adiabatic effectiveness on a flat plate with a single row of shaped film cooling holes in cross-flow. A preliminary examination of the effect of cross-flow versus plenum fed coolant on the adiabatic effectiveness of the axial 7-7-7 shaped hole, a laidback fan-shaped hole with a 30 degree injection angle, is first conducted. Subsequently, the effects of two internal coolant parameters on film cooling effectiveness are presented: Reynold’s number inside the cross-flow channel, and velocity ratio (defined as the ratio of cross-flow channel average velocity to mainstream velocity). By measuring the effect of these parameters, a chain of relative importance can be generated and applied to future experimentation. Parameters that heavily influence film cooling effectiveness can be studied further and optimized for turbine film cooling design.

Computational Study of the Effects of Shock Waves on Film Cooling Effectiveness

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
C. X.-Z. Zhang ◽  
I. Hassan
Keyword(s):  
Shock Waves ◽  
Flat Plate ◽  
Film Cooling ◽  
Computational Study ◽  
Strong Shock ◽  
Boundary Layer Separation ◽  
Airfoil Surface ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Transonic Airfoil

The performance of a louver cooling scheme on a transonic airfoil has been studied numerically in this paper. Film cooling holes are located near the passage throat. The Mach number at the location of the jet exit is close to unity. A comparison of film cooling effectiveness between numerical prediction and experimental data for a circular hole shows that the numerical procedures are adequate. In addition to the shock-wave effects and compressibility, curvature effect was also studied by comparing cooling effectiveness on the airfoil surface with that on a flat plate. Substantially higher cooling effectiveness for the louver cooling scheme on the airfoil was predicted at blowing ratios below 1 in comparison to other cooling configurations. At higher blowing ratios than 2 the advantages of the louver cooling scheme become less obvious. It was also found that for the same cooling configuration the cooling effectiveness on the transonic airfoil is slightly higher than that on a flat plate at moderately low blowing ratios below 1. At high blowing ratios above 2 when the oblique shock becomes detached from the leading edge of the hole exits, dramatic reduction in cooling effectiveness occurs as a result of boundary layer separation due to the strong shock waves. A coolant-blockage and shaped-wedge similarity was proposed and found to be able to qualitatively explain this phenomenon satisfactorily.

The Influence of Density Difference Between Hot and Coolant Gas on Film Cooling by a Row of Holes: Predictions and Experiments

1991 ◽  
Author(s):  
W. Haas ◽  
W. Rodi ◽  
B. Schönung
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Turbine Blade ◽  
Film Cooling ◽  
Density Ratio ◽  
Density Difference ◽  
Extended Model ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Injection Angle

The two-dimensional boundary-layer procedure of Schönung and Rodi [1] for calculating film cooling by a row of holes was extended to account for density differences between hot gas and injected coolant gas. The extensions concern the injection model for leaping over the immediate blowing region in the boundary-layer calculation and also the dispersion model for taking into account three-dimensional effects. The extended model is tested for a density ratio of ρj/ρe ≈ 2 both for flat-plate situations and film cooling on a model turbine blade. The predicted laterally averaged film cooling effectiveness is compared with measurements for these cases. Results for the flat-plate experiments were taken from the literature, while experiments for a model turbine blade are also described in this paper. For a fixed injection angle of 32°, the film cooling effectiveness was measured for various spacings and velocity ratios Uj/Ue. The density ratio ρj/ρe ≈ 2 was achieved by adding Freon to the injection gas. The results are compared with those reported in [2] for negligible density difference. At the same blowing rate M = Uj/Ue, the film cooling effectiveness was found to increase with the density ratio ρj/ρe. In general, the influence of the density difference is well predicted by the model.

Influence of Geometrical Parameters and Reynolds Number on Flat Plate Film Cooling Effectiveness

2020 ◽  
Author(s):  
S. Rouina ◽  
H. Abdeh ◽  
A. Perdichizzi ◽  
G. Barigozzi ◽  
V. Odemondo ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Flat Plate ◽  
Film Cooling ◽  
Thermal Protection ◽  
Hole Injection ◽  
Geometrical Parameters ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cylindrical Section ◽  
Hole Geometry

Abstract In the present paper the influence of geometrical deviations, related to the manufacturing process or to a different hole positioning over the vane surface, and of coolant Reynolds number on flat plate film cooling through shaped holes are experimentally investigated. Hole geometrical parameters, such as the length of the cylindrical section, hole injection angle, lateral and forward expansion angles were varied and tested for blowing ratio M values between 1.0 and 2.0, also changing the coolant Reynolds number. The dual-luminophore Pressure Sensitive Paint (PSP) technique was used for measuring the adiabatic film cooling effectiveness distribution. Compared with the standard geometry, the V-shaped hole was shown to produce a better thermal protection, especially in the near hole region. Effectiveness is strongly affected by relatively small changes in the hole geometry, like the length of the cylindrical section and the forward expansion angle. A critical coolant Reynolds number was also identified, whose value changes depending on the hole geometry.

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