Effects of Pin-Fin Shapes on Mesh-Fed Slot Film Cooling for a Flat-Plate Model

2019 ◽  
Vol 11 (3) ◽  
Author(s):  
Xiao-Ming Tan ◽  
Jing-Zhou Zhang ◽  
Qing-Zhi Cai
Keyword(s):  
Flat Plate ◽  
Film Cooling ◽  
Coolant Flow ◽  
Plate Model ◽  
Cross Sectional ◽  
Cooling Performance ◽  
Pin Fin ◽  
Pin Fins ◽  
Cooling Hole ◽  
Slot Film Cooling

Experimental and numerical research is performed to illustrate the effects of pin-fin shapes on mesh-fed slot film cooling performance on a flat-plate model. Three types of pin-fin shapes (such as circular, elliptical, and drop-shaped) with the same cross-sectional area are taken into consideration. The results show that a pair of counter rotating vortices is still generated for the mesh-fed slot film cooling scheme due to the strong “jetting” effect of coolant flow at the slot outlet. As the coolant jet ejecting from mesh-fed slot is capable of establishing more uniform film layer over the protected surface, the kidney vortices are illustrated to have weakly detrimental role on the film cooling performance. By the shaping of pin fins, the uniformity of coolant flow exiting mesh-fed slot is improved in comparison to the baseline case of circular shape, especially for the elliptical-shape pin-fin array. Therefore, the jetting effect of coolant flow is alleviated for the elliptical and drop-shaped pin-fin meshes when compared to the circular pin-fin mesh. In general, the pin-fin shape has nearly no influence on cooling effectiveness immediately downstream the film cooling-hole outlet. However, beyond x/s = 5, the elliptical and drop-shaped pin fins are demonstrated to be advantageous over the circular pin fins.

An Experimental Investigation of an Anti-Vortex Film Cooling Geometry Under Low and High Turbulence Conditions

2012 ◽  
Author(s):  
Sebastian Schulz ◽  
Simon Maier ◽  
Jeffrey P. Bons
Keyword(s):  
Flat Plate ◽  
Secondary Flow ◽  
Infrared Thermography ◽  
Film Cooling ◽  
Streamwise Direction ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
High Turbulence

In an attempt to abate the detrimental jet vorticity and lift-off effects at high blowing ratios, the objective of the present study is to investigate the impact of an anti-vortex film cooling hole design on the film cooling effectiveness and the secondary flow field. Furthermore, the influence of low and high turbulence levels is studied with Tu ≈ .0.7% and ≈ 10%, respectively. For the experiments infrared thermography and particle image velocimetry (PIV) are employed. The experiments are conducted in a subsonic wind tunnel at a Reynolds number of 11000 based on the film cooling hole diameter. A flat plate model with an array of three cylindrical primary holes with secondary offshoots to each side represents the anti-vortex geometry. The cylindrical hole arrangement with a diameter of 17.5 mm is inclined at 30° in streamwise direction, with the anti-vortex holes branching off from the primary hole base in a 21° angle. Information from a flat plate with six cylindrical holes of 17.5 mm in diameter inclined at 30 in streamwise direction is used as baseline for comparison. The primary hole spacing was 4.75 and 3 hole diameters, respectively. Results are presented for blowing ratios of 1 and 2 with a constant density ratio of 1.1. The PIV measurements are taken in two planes perpendicular to the flow direction to record the secondary flow structures. The results of the infrared thermography show a strong decrease in film cooling effectiveness as high turbulence levels occur, especially for low blowing ratios. For higher blowing ratios low and high turbulence levels have similar effects on film cooling effectiveness. A significant improvement in film cooling performance is displayed by the anti-vortex design over the standard circular hole arrangement for every blowing ratio. The effectiveness results reveal an improved lateral spreading of the coolant with coolant jets staying attached throughout the series of experiments. By remaining inside the boundary layer, the effects of a high turbulent freestream on film cooling performance is less. The PIV results unveil information of a new vortex pair on either side of the primary hole kidney vortex. Especially at high blowing ratios the results indicate, that the anti-vortex hole design promotes the interaction between the vortical structures, explaining the increased lateral film effectiveness results. The factor which lends to the superior performance and credibility of the studied anti-vortex design is that the results are obtained for 35% less mass flow than the baseline.

Experimental and Numerical Study on Effects of Turbulence Promoters on Flat Plate Film Cooling

2011 ◽  
Author(s):  
Eiji Sakai ◽  
Toshihiko Takahashi
Keyword(s):  
Flat Plate ◽  
Secondary Flow ◽  
Film Cooling ◽  
Numerical Study ◽  
Secondary Flows ◽  
Temperature Fields ◽  
Main Stream ◽  
Cooling Performance ◽  
Cooling Hole ◽  
Stream Lines

Turbulence promoters such as ribs inside turbine blade coolant channels are used to improve convective cooling but at the same time could influence external film cooling performance. The effects of rib orientation and rib position on film cooling performance are experimentally and numerically studied with a flat plate configuration in which external (main) flow and internal (secondary) flow are oriented perpendicular to each other. In the experiment, temperature fields are measured by thermo-couples varying blowing ratio at constant Reynolds number of main and secondary flows. To obtain detailed information about flow fields, Reynolds Averaged Navier Stokes (RANS) simulation and Detached Eddy Simulation (DES) are also performed using a commercial code Fluent. Temperature measured shows that rib orientation has a strong influence on film effectiveness. With forward-oriented ribs, higher film effectiveness is observed compared to the reference case without ribs. On the contrary with inverse-oriented ribs, lower film effectiveness is observed. The difference comes from the flow structure in the film cooling hole. With the forward-oriented ribs, straight stream lines are observed in the cooling hole, while with the inverse-oriented ribs, helical stream lines are observed. Due to the helical stream lines in the hole, ejection angle of the secondary flow to the main stream becomes large, resulting in so called lift-off and lower film effectiveness.

Improvement of Flat-Plate Film Cooling Performance by Double Flow Control Devices: Part I — Investigations on Capability of a Base-Type Device

2014 ◽  
Author(s):  
Ken-ichi Funazaki ◽  
Ryota Nakata ◽  
Hirokazu Kawabata ◽  
Hisato Tagawa ◽  
Yasuhiro Horiuchi
Keyword(s):  
Flow Control ◽  
Flat Plate ◽  
Film Cooling ◽  
Laser Doppler Velocimeter ◽  
Pressure Probe ◽  
Cooling Performance ◽  
Flow Control Devices ◽  
Type Device ◽  
Cooling Hole ◽  
Control Devices

This paper deals with effects of double flow control devices (DFCDs) on flat plate film cooling performance. Aiming for further improvement of film effectiveness of discrete cooling holes, this new type of controlling method is invented and recently patented by the authors. The performance of base-type DFCDs, installed just upstream of cooling holes with conventional round or fan-shaped exits, is thoroughly investigated and reported in this study. Effects of the hole pitch are examined. Three hole-pitch cases, 3.0d, 4.5 d and 6.0 d are examined in this study to explore a possibility of reducing the cooling air by the application of DFCDs, where d is a hole diameter. In order to investigate the film effectiveness, a transient method using a high-resolution infrared camera is adopted. At the downstream of the cooling hole, the time-averaged temperature field is captured by a thermocouple rake and the time-averaged velocity field is captured by 3D Laser Doppler Velocimeter (LDV), respectively. Furthermore, the aerodynamic loss characteristics of the cooling hole with and without DFCDs are measured by a total pressure probe rake. The experiments are carried out for two blowing ratios, 0.5 and 1.0. It is found that DFCDs are quite effective in increasing the film effectiveness not only for round but also the fan-shaped holes. Starting from the base-type device, a robust optimization using Taguchi Method has been made by the present authors and will be reported as Part II.

Experimental Study of Sister Hole Film Cooling Performance in a Rotating Flat Plate Model

2015 ◽  
Author(s):  
Hong Wu ◽  
Huichuan Cheng ◽  
Yulong Li ◽  
Shuiting Ding
Keyword(s):  
Reynolds Number ◽  
Flat Plate ◽  
Rotation Number ◽  
Film Cooling ◽  
Suction Side ◽  
Pressure Side ◽  
Plate Model ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio

Film cooling performance of a sister hole was investigated in a flat plate model by applying Thermochromic Liquid Crystal (TLC) technique under the stationary and rotating conditions. The flat plate model is installed in the test section. The sister hole include one main hole and two additional side holes with the smaller diameter in the spanwise direction. The diameter of the main hole is 4 mm and the injection angle is 30°. The density ratio of coolant to mainstream is 1.05. The Reynolds number (ReD) based on the velocity of mainstream and the diameter of the main hole are 2300, 3400 and 4500. Four rotational speeds of 200, 400, 600 and 800 rpm are conducted on both pressure side (trailing wall) and suction side (leading wall) with the blowing ratio varying from 0.14 to 3.5. The effects of blowing ratio, Reynolds number (ReD) and rotation number are mainly analyzed according to film coverage and film cooling effectiveness. The results show that the film performance firstly increases then decreases with the rising of blowing ratio, the optimal blowing ratio is about M=0.5. The film cooling performance is improved with higher Reynolds number (ReD). Under the rotation condition, the film trajectory has an obvious centrifugal deflection which can be enhanced by higher rotation number on the pressure side, and the film deflection moves a little centripetally on the suction side. The film cooling effectiveness on the suction side increases with the rising of rotation number and it is higher than that on the pressure side.

Numerical Evaluation of Surface Roughness Effects on Film-Cooling Performance in a Laidback Fan-Shaped Hole

2020 ◽  
Author(s):  
Ali Zamiri ◽  
Sung Jin You ◽  
Jin Taek Chung
Keyword(s):  
Surface Roughness ◽  
Flat Plate ◽  
Film Cooling ◽  
Density Ratio ◽  
Roughness Height ◽  
Constant Density ◽  
Cooling Performance ◽  
Cooling Hole ◽  
Shaped Hole ◽  
Grain Roughness

Abstract This study numerically investigates the influences of cooling hole surface roughness in a laidback fan-shaped hole on the flow structure and film-cooling effectiveness. The three-dimensional compressible LES approach (large eddy simulation) is conducted in a baseline 7-7-7 laidback fan-shaped hole. The cooling hole is located on a flat plate surface with a 30-degree injection angle at a constant density ratio DR = 1.5 and two blowing ratios M = 1.5 and 3. The computational results were validated by the measurements in terms of velocity and thermal fields for both the smooth and rough holes. In order to numerically consider the influences of the surface roughness on cooling hole side, the equivalent sand grain roughness method was utilized. Different correlations between the equivalent sand grain roughness height and arithmetic average roughness height were numerically tested to find an accurate correlation in comparison to the measurements. The computational data revealed that the surface roughness of the hole interior walls increases the thickness of the boundary layers within the hole. This leads to a higher jet core flow at the hole exit and lower film-cooling performance at the surface of flat plate compared to those of the smooth cooling hole. The minimum area-averaged film-cooling performance was observed in the case of the highest blowing ratio and the largest surface roughness height. The present work reveals that the current LES approach by considering the proper equivalent sand grain roughness height is a powerful tool to obtain the accurate solution in the prediction of the heat transfer characteristics and the flow structures in the fan-shaped cooling holes.

Experimental and Numerical Investigations of Effects of Flow Control Devices Upon Flat-Plate Film Cooling Performance

2013 ◽  
Vol 136 (6) ◽  
Author(s):  
Hirokazu Kawabata ◽  
Ken-ichi Funazaki ◽  
Ryota Nakata ◽  
Daichi Takahashi
Keyword(s):  
Flow Field ◽  
Flow Control ◽  
Flat Plate ◽  
Vortex Structure ◽  
Film Cooling ◽  
Pressure Probe ◽  
Cooling Performance ◽  
Flow Control Devices ◽  
Cooling Hole ◽  
Control Devices

This study deals with the experimental and numerical studies of the effect of flow control devices (FCDs) on the film cooling performance of a circular cooling hole on a flat plate. Two types of FCDs with different heights are examined in this study, where each of them is mounted to the flat plate upstream of the cooling hole by changing its lateral position with respect to the hole centerline. In order to measure the film effectiveness as well as heat transfer downstream of the cooling hole with upstream FCD, a transient method using a high-resolution infrared camera is adopted. The velocity field downstream of the cooling hole is captured by 3D laser Doppler velocimeter (LDV). Furthermore, the aerodynamic loss associated with the cooling hole with/without FCD is measured by a total pressure probe rake. The experiments are carried out at blowing ratios ranging from 0.5 to 1.0. In addition, numerical simulations are also made to have a better understanding of the flow field. LES approach is employed to solve the flow field and visualize the vortex structure around the cooling hole with FCD. When a taller FCD is mounted to the plate, the film effectiveness tends to increase due to the vortex structure generated by the FCD. As FCD is laterally shifted from the centerline, the film effectiveness increases, while the lift-off of cooling air is also promoted when FCD is put on the center line.

Quantifying Blowing Ratio for Shaped Cooling Holes

2017 ◽  
Author(s):  
D. J. Cerantola ◽  
A. M. Birk
Keyword(s):  
Film Cooling ◽  
Discharge Coefficient ◽  
Area Ratio ◽  
Operating Conditions ◽  
Gas Turbine Combustor ◽  
Adiabatic Wall ◽  
Cross Sectional ◽  
Cooling Performance ◽  
Blowing Ratio ◽  
Cooling Hole

Effusion cooling was a popular technology integrated into the design of gas turbine combustor liners. A staggering amount of research was completed that quantified performance with respect to operating conditions and cooling hole geometric properties; however, most of these investigations did not address the influence of the manufacturing process on the hole shape. This study completed an adiabatic wall numerical analysis using the realizable k-ε turbulence model of a laser-drilled hole that had a nozzled profile with an area ratio of 0.24 and five additional cylindrical, nozzled, diffusing, and filleted holes that yielded the same hole mass flow rate at representative engine conditions. The traditional methods for quantifying blowing ratio yielded the same value for all holes that was not useful considering the substantial differences in film cooling performance. It was proposed to define hole mass flux based on the outlet y-cross sectional area projected onto the inclination angle plane. This gave blowing ratios that correlated to better and worse cooling performance for the diffusing and nozzled holes respectively. The diffusing hole delivered the best film cooling due to having the lowest effluent velocity and greatest amount of in-hole turbulent production, which coincided with the worst discharge coefficient.

Experimental and Numerical Investigations of Effects of Flow Control Devices Upon Flat-Plate Film Cooling Performance

2013 ◽  
Author(s):  
Hirokazu Kawabata ◽  
Ken-ichi Funazaki ◽  
Ryota Nakata ◽  
Daichi Takahashi
Keyword(s):  
Flow Field ◽  
Flow Control ◽  
Flat Plate ◽  
Vortex Structure ◽  
Film Cooling ◽  
Pressure Probe ◽  
Cooling Performance ◽  
Flow Control Devices ◽  
Cooling Hole ◽  
Control Devices

This study deals with the experimental and numerical studies of the effect of flow control devices (FCDs) on the film cooling performance of a circular cooling hole on a flat plate. Two types of FCDs with different heights are examined in this study, where each of them is mounted to the flat plate upstream of the cooling hole by changing its lateral position with respect to the hole centerline. In order to measure the film effectiveness as well as heat transfer downstream of the cooling hole with upstream FCD, a transient method using a high-resolution infrared camera is adopted. The velocity field downstream of the cooling hole is captured by 3D Laser Doppler Velocimeter (LDV). Furthermore, the aerodynamic loss associated with the cooling hole with/without FCD is measured by a total pressure probe rake. The experiments are carried out at blowing ratios ranging from 0.5 to 1.0. In addition, numerical simulations are also made to have a better understanding of the flow field. LES approach is employed to solve the flow field and visualize the vortex structure around the cooling hole with FCD. When a higher FCD is mounted to the plate, the film effectiveness tends to increase due to the vortex structure generated by the FCD. As FCD is laterally shifted from the centerline, the film effectiveness increases, while the lift-off of cooling air is also promoted when FCD is put on the center line.

Quantifying Blowing Ratio for Shaped Cooling Holes

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
D. J. Cerantola ◽  
A. M. Birk
Keyword(s):  
Film Cooling ◽  
Discharge Coefficient ◽  
Area Ratio ◽  
Operating Conditions ◽  
Gas Turbine Combustor ◽  
Adiabatic Wall ◽  
Cross Sectional ◽  
Cooling Performance ◽  
Blowing Ratio ◽  
Cooling Hole

Effusion cooling has been a popular technology integrated into the design of gas turbine combustor liners. A staggering amount of research was completed that quantified performance with respect to operating conditions and cooling hole geometric properties; however, most of these investigations did not address the influence of the manufacturing process on the hole shape. This study completed an adiabatic wall numerical analysis using the realizable k–ϵ turbulence model of a laser-drilled hole that had a nozzled profile with an area ratio of 0.24 and five additional cylindrical, nozzled, diffusing, and fileted holes that yielded the same hole mass flow rate at representative engine conditions. The traditional methods for quantifying blowing ratio yielded the same value for all holes that was not useful considering the substantial differences in film cooling performance. It was proposed to define hole mass flux based on the outlet y-cross-sectional area projected onto the inclination angle plane. This gave blowing ratios that correlated to better and worse cooling performance for the diffusing and nozzled holes, respectively. The diffusing hole delivered the best film cooling due to having the lowest effluent velocity and greatest amount of in-hole turbulent production, which coincided with the worst discharge coefficient.

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