Numerical Investigation of Effects of Blockage, Inclination Angle, and Hole-Size on Film Cooling Effectiveness at Concave Surface

2021 ◽  
Vol 143 (2) ◽  
Author(s):  
Fu-qiang Wang ◽  
Jian Pu ◽  
Jian-hua Wang ◽  
Wei-dong Xia
Keyword(s):  
Film Cooling ◽  
Pressure Loss ◽  
Numerical Study ◽  
Density Ratio ◽  
Concave Surface ◽  
Blockage Ratio ◽  
Coverage Area ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Injection Angle

Abstract Film-hole can be often blocked by thermal-barrier coatings (TBCs) spraying, resulting in the variations of aerodynamic and thermal performances of film cooling. In this study, a numerical study of the blockage effect on the film cooling effectiveness of inclined cylindrical-holes was carried out on a concave surface to simulate the airfoil pressure side. Three typical blowing ratios (BRs) of 0.5, 1.0, and 1.5 were chosen at an engine-similar density ratio (DR) of 2.0. Two common inclination angles of 30 deg and 45 deg were designed. The blockage ratios were adjusted from 0 to 20%. The results indicated the blockage could enhance the penetration of film cooling flow to the mainstream. Thus, the averaged effectiveness and coolant coverage area were reduced. Moreover, the pressure loss inside of the hole was increased. With the increase of BR, the decrement of film cooling effectiveness caused by blockage rapidly increased. At BR = 1.5, the decrement could be acquired up to 70% for a blockage ratio of 20%. The decrement of film cooling effectiveness caused by blockage was nearly nonsensitive to the injection angle; however, the larger angle could generate the higher increment of pressure loss caused by blockage. A new design method for the couple scheme of film cooling and TBC was proposed, i.e., increasing the inlet diameter according to the blockage ratio before TBC spraying. In comparison with the original unblocked-hole, the enlarged blocked-hole not only kept the nearly same area-averaged effectiveness but also reduced slightly the pressure loss inside of the hole. Unfortunately, application of enlarged blocked-hole at large BR could lead to a more obvious reduction of effectiveness near hole-exit, in comparison with the original common-hole.

Numerical Investigation of Effects of Blockage, Inclination Angle and Hole-Size on Film Cooling Effectiveness at Concave Surface

2020 ◽  
Author(s):  
Fu-qiang Wang ◽  
Jian Pu ◽  
Jian-hua Wang ◽  
Wei-dong Xia
Keyword(s):  
Film Cooling ◽  
Pressure Loss ◽  
Numerical Study ◽  
Density Ratio ◽  
Concave Surface ◽  
Blockage Ratio ◽  
Coverage Area ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Injection Angle

Abstract Film-hole can be often blocked by the thermal-barrier coatings (TBC) spraying, resulting in the variations of film cooling performance and pressure loss. In this work, a numerical study of the effect of blockage ratio on the film cooling effectiveness of inclined cylindrical-holes was carried out on a concave surface to simulate the airfoil pressure side. Three typical blowing ratios (BRs) of 0.5, 1.0 and 1.5 were chosen at an engine-similar density ratio (DR) of 2.0. Two common inclination angles of 30° and 45° were designed. The blockage ratios were adjusted from 0 to 20%. The results indicated that the blockage near the trailing edge of hole-exit could enhance the penetration of film cooling flow to the mainstream. Thus, the averaged effectiveness and coolant coverage area were reduced. Moreover, the pressure loss inside of hole was increased. With the increase of BR, the decrement of film cooling effectiveness caused by blockage rapidly enhanced. At BR = 1.5, the decrement could be acquired up to 70% for a blockage ratio of 20%. The decrement of film cooling effectiveness caused by blockage was nearly non-sensitive to the injection angle; however, the larger injection angle could generate the higher increment of pressure loss caused by blockage. A new design method for the couple scheme of film-cooling and TBC was proposed, i.e. increasing the inlet diameter according to the blockage ratio before TBC spraying. In comparison with the original unblocked-hole, the enlarged blocked-hole not only can keep the nearly same area-averaged effectiveness, but also can reduce slightly the pressure loss inside of hole. The smaller injection angle could obtain the larger reduction of pressure loss. Unfortunately, application of enlarged blocked-hole at large BR could lead to a more obvious reduction of effectiveness near hole-exit, in comparison with the original common-hole.

Injection Angle Influence of Secondary Holes on the Enhancement of Film Cooling Effectiveness With Horn-Shaped or Cylindrical Primary Holes

2017 ◽  
Author(s):  
Rui Zhu ◽  
Gongnan Xie ◽  
Terrence W. Simon
Keyword(s):  
Film Cooling ◽  
Numerical Study ◽  
Cylindrical Hole ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Injection Angle ◽  
Inclination Angles ◽  
Cooling Hole ◽  
Cylindrical Holes

Secondary holes to a main film cooling hole are used to improve film cooling performance by creating anti-kidney vortices. The effects of injection angle of the secondary holes on both film cooling effectiveness and surrounding thermal and flow fields are investigated in this numerical study. Two kinds of primary hole shapes are adopted. One is a cylindrical hole, the other is a horn-shaped hole which is designed from a cylindrical hole by expanding the hole in the transverse direction to double the hole size at the exit. Two smaller cylindrical holes, the secondary holes, are located symmetrically about the centerline and downstream of the primary hole. Three compound injection angles (α = 30°, 45° and 60°, β = 30°) of the secondary holes are analyzed while the injection angle of the primary hole is kept at 45°. Cases with various blowing ratios are computed. It is shown from the simulation that cooling effectiveness of secondary holes with a horn-shaped primary hole is better than that with a cylindrical primary hole, especially at high blowing ratios. With a cylindrical primary hole, increasing inclination angle of the secondary holes provides better cooling effectiveness because the anti-kidney vortices created by shallow secondary holes cannot counteract the kidney vortex pairs adequately, enhancing mixing of main flow and coolant. For secondary holes with a horn-shaped primary hole, large secondary hole inclination angles provide better cooling performance at low blowing ratios; but, at high blowing ratios, secondary holes with small inclination angles are more effective, as the film coverage becomes wider in the downstream area.

Numerical Approach at Flat Plate for Predicting the Film Cooling Effectiveness Part B: Effect Injection Angle

2018 ◽  
Vol 16 ◽  
pp. 57-71 ◽  
Author(s):  
Farouk Kebir ◽  
Azzeddine Khorsi
Keyword(s):  
Film Cooling ◽  
Cfd Simulation ◽  
Numerical Study ◽  
Numerical Approach ◽  
Surface Heat ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Injection Angle ◽  
Sst Turbulence Model ◽  
The Difference

In order to improve the cooling effectiveness of the film, a numerical study was conducted to study the effects of different film-cooled angles on surface heat transfer. In this work CFD simulation has revealed the difference of injection angles ranging from 35°,45°,55°,65° and 90° with different blowing, where the low blowing ratios are represented by M = 0.5, and the high blowing ratios by M = 1.0 and 1.5. And the turbulence closure is done with the help of the k - ω shear stress transport (SST) turbulence model. It is found that the stream-wise variations in the angles of the holes do not really provide a significant change in the adiabatic film cooling effectiveness results. On the other hand, the results indicate that the hole of angles 35°and 45° improved the centerline and laterally averaged adiabatic effectiveness, and the effectiveness decrease particularly at high blowing ratios.

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.

Numerical Study on Effects of Density Ratio on Film Cooling Flow Structure and Film Cooling Effectiveness

2017 ◽  
Author(s):  
Eiji Sakai ◽  
Toshihiko Takahashi
Keyword(s):  
Shear Layer ◽  
Film Cooling ◽  
Numerical Study ◽  
Density Ratio ◽  
Hairpin Vortices ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Flow ◽  
High Density Ratio ◽  
Cooling Hole

To understand film cooling flow fields on a gas turbine blade, this paper reports a series of large-eddy simulations of an inclined round jet issuing into a crossflow. Simulations were performed at constant momentum ratio conditions, IR = 0.25, 0.5, 1.0 and Reynolds number, Re = 15,300, based on the crossflow velocity and the film cooling hole diameter. Density ratio, DR, is changed from 1.0 to 2.0, and effects of the density ratio on vortical structures around the film cooling hole exit and film cooling effectiveness are investigated. The results showed that the vortical structure of the ejected jet drastically changes with varying density ratio. When the density ratio is comparatively small, hairpin vortices are formed downstream of the hole exit. On the contrary, when the density ratio is comparatively high, the formation of the hairpin vortices is suppressed and jet shear layer vortices are formed on side edges of the cooling jet. The jet shear layer vortices conveys the coolant air to the wall surface. As a result, higher film cooling effectiveness is obtained at comparatively high density ratio conditions compared to comparatively low density ratio conditions. Additional simulations were performed to discuss a possibility of an improvement in the film cooling effectiveness by controlling the formation of the jet shear layer vortices.

Experimental and Numerical Investigation of Flow Field and Downstream Surface Temperatures of Cylindrical and Diffuser Shaped Film Cooling Holes

2011 ◽  
Author(s):  
Tilman auf dem Kampe ◽  
Stefan Vo¨lker ◽  
Torsten Sa¨mel ◽  
Christian Heneka ◽  
Helge Ladisch ◽  
...  
Keyword(s):  
Flow Field ◽  
Film Cooling ◽  
Numerical Study ◽  
Density Ratio ◽  
Quantitative Agreement ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Flow Parameters ◽  
Contour Plots ◽  
Cooling Hole

An experimental and numerical study of the flow field and the downstream film cooling performance of cylindrical and diffuser shaped cooling holes is presented. The measurements were conducted on a flat plate with a single cooling hole with coolant ejected from a plenum. The flow field was investigated by means of 3D-PIV as well as 3D-LDV measurements, the downstream film cooling effectiveness by means of infrared thermography. Cylindrical and diffuser holes without lateral inclination have been examined, varying blowing ratio and density ratio as well as freestream turbulence levels. 3D-CFD simulations have been performed and validated along with the experimental efforts. The results, presented in terms of contour plots of the three normalized velocity components as well as adiabatic film cooling effectiveness, clearly show the flow structure of the film cooling jets and the differences brought about by the variation of hole geometry and flow parameters. The quantitative agreement between experiment and CFD was reasonable, with better agreement for cylindrical holes than for diffuser holes.

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.

Numerical investigation of blowing ratio, density ratio and axial position of film holes on the vane endwall film cooling effectiveness with upstream step

2021 ◽  
pp. 095441002110165
Author(s):  
Qingzong Xu ◽  
Qiang Du ◽  
Pei Wang ◽  
Xiangtao Xiao ◽  
Jun Liu
Keyword(s):  
Secondary Flow ◽  
Film Cooling ◽  
Pressure Loss ◽  
Total Pressure ◽  
Density Ratio ◽  
Total Pressure Loss ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Endwall Film Cooling

The aerothermal performance of interrupted slot and film holes was numerically investigated. Previous study indicates that the interrupted slot performs better compared to the conventional slot. In the meanwhile, the step formed along with the interrupted slot affects the film cooling characteristics. In this article, a row of film holes is arranged downstream of the step, and the mass flow rate for the interrupted slot is constant at 1%. Blowing ratio (BR) from 0.5 to 1.5 and density ratio from 1 to 2 were studied for the film holes. Endwall film cooling effectiveness distribution indicates that film cooling is easily affected by the secondary flow inside passage and the upstream step. Coolant traces are split into two parts due to the effects of step vortex and transverse flow. For different density ratios, increasing BR shows a different trend of film cooling effectiveness due to the variation of coolant momentum. The coolant jet is easily affected by the secondary flow when its momentum is low, but tends to liftoff when its momentum is too high. As a result, it is better to position the film holes far away from the upstream step. The total pressure loss coefficient distribution at the passage exit indicates that the coolant injection increases the total pressure loss. But density ratio has smaller effect on the loss variation. Besides, two axial positions of cooling holes were studied to improve the endwall cooling performance. Without the effect of step vortex, the film effectiveness of cooling holes is improved.

Turbine Vane Endwall Film Cooling Comparison From Five Film-Hole Design Patterns and Three Upstream Leakage Injection Angles

2018 ◽  
Author(s):  
Chao-Cheng Shiau ◽  
Izzet Sahin ◽  
Nian Wang ◽  
Je-Chin Han ◽  
Hongzhou Xu ◽  
...  
Keyword(s):  
Film Cooling ◽  
Design Patterns ◽  
Density Ratio ◽  
Leakage Flow ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Injection Angle ◽  
Operation Conditions ◽  
Turbine Vane ◽  
Endwall Cooling

The effects of upstream leakage injection angle on film cooling effectiveness of a turbine vane endwall with various endwall film-hole designs were examined by applying PSP measurement technique. As the leakage flow from the slot between the combustor and the turbine vane is not considered an active source to protect the vane endwall in certain engine designs, discrete cylindrical holes are implemented near the slot to create additional controllable upstream leakage flow to cool the vane endwall. Three potential leakage injection angles were studied: 30°, 40°, and 50°. To explore the optimum endwall cooling design, five different film-hole patterns were tested: axial row, cross row, cluster, mid-chord row, and downstream row. Experiments were conducted in a four-passage linear cascade facility in a blowdown wind tunnel at the exit isentropic Mach number of 0.5 corresponding to inlet Reynolds number of 380,000 based on turbine vane axial chord length. A freestream turbulence intensity of 19% with an integral length scale of 1.7 cm was generated at the cascade inlet plane. Detailed film cooling effectiveness for each design was analyzed and compared at the design operation conditions (coolant mass flow ratio 1% and density ratio 1.5). The results are presented in terms of high-fidelity film effectiveness contours and laterally (spanwise) averaged effectiveness. This paper will provide the gas turbine designers valuable information on how to select the best endwall cooling pattern with minimum cooling air consumption over a range of upstream leakage injection angle.

Large Eddy Simulations for Film Cooling Assessment of Cylindrical and Laidback Fan-Shaped Holes With Reverse Injection

2020 ◽  
Vol 13 (3) ◽  
Author(s):  
Ashutosh Kumar Singh ◽  
Kuldeep Singh ◽  
Dushyant Singh ◽  
Niranjan Sahoo
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Large Eddy Simulations ◽  
Cylindrical Hole ◽  
Axial Velocity Component ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Injection Angle ◽  
Large Eddy ◽  
Shaped Hole

Abstract The large eddy simulations (LES) are performed to access the film cooling performance of cylindrical and reverse shaped hole for forward and reverse injection configurations. In the case of reverse/backward injection, the secondary flow is injected in such a way that its axial velocity component is in the direction opposite to mainstream flow. The study is carried out for a blowing ratio (M = 1), density ratio (DR = 2.42), and injection angle (α = 35 deg). Formation of counter-rotating vortex pair (CRVP) is one of the major issues in the film cooling. This study revealed that the CRVP found in the case of forward cylindrical hole which promotes coolant jet “liftoff” is completely mitigated in the case of the reverse shaped hole. The coolant coverage for reverse cylindrical and reverse shaped holes is uniform and higher. The reverse shaped hole shows promising results among investigated configurations. The lateral averaged film cooling effectiveness of reverse shaped hole is 1.16–1.42 times higher as compared to the forward shaped holes. The improvement in the lateral averaged film cooling effectiveness of reverse cylindrical hole (RCH) injection over forward cylindrical hole (FCH) injection is 1.33–2 times.

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