Effect of Hole Diameter on Nozzle Endwall Film Cooling and Associated Phantom Cooling

2015 ◽  
Author(s):  
Luzeng Zhang ◽  
Juan Yin ◽  
Kevin Liu ◽  
Moon Hee-Koo
Keyword(s):  
Film Cooling ◽  
High Speed ◽  
Leading Edge ◽  
Suction Side ◽  
Hole Diameter ◽  
Two Dimensional ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Injection Angle ◽  
Blowing Ratio

Flow fields near the turbine nozzle endwall are highly complex due to the passage vortices and endwall cross flows. Consequently, it is challenging to provide proper cooling to the endwall surfaces. An effective way to cool the endwall is to have film cooling holes forward of the leading edge, often called “inlet-film cooling”. This paper presents the results of an experimental investigation on how the film hole diameter affects the film effectiveness on nozzle endwall and associated phantom cooling effectiveness on airfoil suction side. The measurements were conducted in a high speed linear cascade, which consists of three nozzle vanes and four flow passages. Double staggered rows of film injections, which were located upstream from the nozzle leading edge, provided cooling to the contoured endwall surfaces. Film cooling effectiveness on the endwall surface and corresponding phantom cooling effectiveness on the airfoil suction side were measured separately with a Pressure Sensitive Paint (PSP) technique through the mass transfer analogy. Four different film hole diameters with the same injection angle and the same pitch to diameter ratio were studied for up to six different MFR’s (mass flow ratios). Two dimensional film effectiveness distributions on the endwall surface and two dimensional phantom cooling distributions on the airfoil suction side are presented. Film/phantom cooling effectiveness distributions are pitchwise/spanwise averaged along the axial direction and also presented. The results indicate that both the endwall film effectiveness and the suction side phantom cooling effectiveness increases with the hole diameter (as decreases in blowing ratio for a given MFR) up to a specific diameter, then starts decreasing. An optimal value of the film hole diameter (blowing ratio) for the given injection angle is also suggested based on current study.

Film Cooling Effectiveness Distribution on First-Stage Vane Endwall With and Without Leading-Edge Fillets: Part I—Effect of Leading Edge Geometry

2011 ◽  
Author(s):  
Yang Zhang ◽  
Xin Yuan
Keyword(s):  
Film Cooling ◽  
Flow Direction ◽  
Leading Edge ◽  
Suction Side ◽  
Axial Direction ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Edge Geometry ◽  
Blade Cascade

The paper is focused on the effect of leading edge airfoil geometry on endwall film cooling. Fillets placed at the junctions of the leading edge and the endwall are used in investigation. Three types of fillet profiles are tested, and the results are compared with baseline geometry without fillet. The design of the fillet is based on the suggestion by previous literature data indicating that sharp is effective in controlling the secondary flow. Three types of sharp slope fillet with the length to height ratio of 2.8, 1.2 and 0.5 are made using stereo lithography (SLA) and assessed in the experiment. Distributed with the approximately inviscid flow direction, four rows of compound angle laidback fan-shaped holes are arranged on the endwall to form full covered coolant film. The four rows of fanshaped holes are inclined 30 deg to the endwall surface and held an angle of 0, 30, 45 and 60 deg to axial direction respectively. The fanshaped holes have a lateral diffusion angle of 10 deg from the hole-centerline and a forward expansion angle of 10 deg to the endwall surface. The Reynolds number based on the axial chord and inlet velocity of the free-stream flow is 3.5*105, and the testing is done in a four-blade cascade with low Mach number condition (0.1 at the inlet) while the blowing ratio of the coolant through the discrete holes varies from 0.4 to 1.2. The film-cooling effectiveness distributions are obtained using the PSP (pressure sensitive paint) technique, by which the effect of different fillet geometry on passage induced flow and coolant is shown. The present paper compares the film cooling effectiveness distributions in a baseline blade cascade with three similar blades with different leading edge by adding fillets. The results show that with blowing ratio increasing, the film cooling effectiveness increases on the endwall. For specific blowing ratio, the effects of leading edge geometries could be illustrated as follows. The baseline geometry provides the best film cooling performance near leading edge pressure side. As for the leading edge suction side, the best leading edge geometry depends on the blowing ratio. The longfillet is the more effective in controlling horseshoe vortex at low blowing ratio, but for the high blowing ratio shortfillet and mediumfillet are better.

Numerical Investigation on Film Cooling Effectiveness of Stator Blade with Different Density Ratio

2014 ◽  
Vol 521 ◽  
pp. 104-107
Author(s):  
Ling Zhang ◽  
Quan Heng Jin ◽  
Da Fei Guo
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Leading Edge ◽  
Suction Side ◽  
Pressure Side ◽  
Middle Section ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Stator Blade

The Realizable k-ε turbulence model was performed to investigate the film cooling effectiveness with different blowing ratio 1,1.5,2 and different density ratio 1,1.5,2.The results show that, cooling effectiveness increases with the augment of blowing ratio. On the pressure side, cooling effectiveness increases with the augment of density ratio. On the suction side, with higher density ratio the leading edge cooling increases, the middle section reduces, and the trailing edge cooling effectiveness increases first decreases.

The Experimental and Numerical Research for Linear Cascade Film Cooling With Different Hole Shapes

2010 ◽  
Author(s):  
Yi Lu ◽  
Yinyi Hong ◽  
Zhirong Lin ◽  
Xin Yuan
Keyword(s):  
Film Cooling ◽  
Large Scale ◽  
Leading Edge ◽  
Suction Side ◽  
Pressure Side ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Linear Cascade ◽  
Blowing Ratio ◽  
Cylindrical Holes

Detailed film cooling effectiveness distributions were experimentally obtained on a turbine vane platform within a linear cascade. Testing was done in a large scale five-vane cascade with low freestream Renolds number condition 634,000 based on the axial chord length and the exit velocity. The detailed film-cooling effectiveness distributions on the platform were obtained using pressure sensitive paint technique. Two film-cooling hole configurations, cylindrical and fan-shaped, were used to cool the vane surface with two rows on pressure side, two rows on suction side and three rows on leading edge. For cylindrical holes, the blowing ratio of the coolant through the discrete cooling holes on pressure side and suction side ranged from 0.3 to 1.5 (based on the inlet mainstream velocity) while the blowing ratio ranging from 0.15 to 1.5 on leading edge; for fan-shaped holes, the four blowing ratios were 0.5, 1.0, 1.5 and 2.0. Results showed that average film-cooling effectiveness decreased with increasing blowing rate for the cylindrical holes, while the fan-shaped passage showed increased film-cooling effectiveness with increasing blowing ratio, indicating the fan-shaped cooling holes helped to improve film-cooling effectiveness by reducing overall jet liftoff. Fan-shaped holes improved average film-cooling effectiveness by 93.2%, 287.6% and 489.6% on pressure side, −4.1%, 27.9% and 78.2% on suction side over cylindrical holes at the blowing ratio of 0.5, 1.0 and 1.5 respectively. Numerical results were used to analyze the details of the flow and heat transfer on the cooling area with two turbulence models. Results demonstrated that tendency of the film cooling effectiveness distribution of numerical calculation and experimental measurement was generally consistent at different blowing ratio.

Turbine Blade Tip Cooling With Blade Rotation: Part II — Shroud Coolant Injection

2015 ◽  
Author(s):  
Onieluan Tamunobere ◽  
Sumanta Acharya
Keyword(s):  
Film Cooling ◽  
Leading Edge ◽  
Suction Side ◽  
Tip Clearance ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Complementary Method ◽  
Blowing Ratio ◽  
Coolant Injection ◽  
Blade Tip

In this paper, blade-tip cooling is investigated with coolant injection from the shroud alone and a combination of shroud coolant injection and tip cooling. The blade rotates at a nominal speed of 1200 RPM, and consists of a cut back squealer tip with a tip clearance of 1.7% of the blade span. The blade consists of tip holes and pressure side shaped holes, while the shroud has an array of angled holes and a circumferential slot upstream of the rotor section. Different combinations of the three cooling configurations are utilized to study the effectiveness of shroud cooling as a complementary method of cooling the blade tip. The measurements are done using liquid crystal thermography. Blowing ratios of 0.5, 1.0, 2.0, 3.0 and 4.0 are studied for shroud slot cooling and blowing ratios of 1.0, 2.0, 3.0, 4.0 and 5.0 are studied for shroud hole cooling. For cases with coolant injection from the tip, the blowing ratios used are 1.0, 2.0, 3.0 and 4.0. The results show an increase in film cooling effectiveness with increasing blowing ratio for shroud hole cooling. The increased effectiveness from shroud hole cooling is concentrated mainly in the tip-region below the shroud holes and towards the blade suction side and the suction side squealer rim. Slot cooling injection results in increased effectiveness on the blade tip near the blade leading edge up to a maximum blowing ratio, after which the cooling effectiveness decreases with increasing blowing ratio. The combination of the different cooling methods results in better overall cooling coverage of the blade tip with the shroud hole and blade tip cooling combination being the most effective. The level of coolant protection is strongly dependent on the blowing ratio and combination of blowing ratios.

Rotating Film Cooling Performance of the Hole Near the Leading Edge on the Suction Side of the Turbine Blade

2018 ◽  
Author(s):  
Zhi-yu Zhou ◽  
Hai-wang Li ◽  
Hai-chao Wang ◽  
Guo-qin Zhao ◽  
Feng Han ◽  
...  
Keyword(s):  
Film Cooling ◽  
Leading Edge ◽  
Suction Side ◽  
Axial Direction ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Rotating Speed ◽  
Blowing Ratio ◽  
Numerical Studies

This paper reports the experimental and numerical studies on the effects of rotating speed and blowing ratio on the film cooling performance of the hole near the leading edge on the suction side of the turbine blade. The chord and height of the blade are 60mm and 80mm respectively. The film hole with diameter of 0.8mm is located in the mid span on the suction side at axial location of 8%. The injection angle of the hole is 45° to the suction surface of the blade and is nearly perpendicular to the axial direction. Both experimental and numerical studies were carried out with rotating speeds of 300rpm, 450rpm and 600rpm, and with blowing ratios of 0.5, 1.0, 1.5 and 2.0. CO2 was used as the coolant. Experimental data was measured by applying the Thermochromic Liquid Crystal (TLC) technique and the Stroboscopic Imaging Technique. Mainstream and coolant were heated to 308K and 318K respectively. Numerical studies were performed to assist the analysis of the experimental results. The SST turbulence model was applied in the simulations. Results show that the film cooling performance of the hole near the leading edge is different from that of the hole further downstream on the suction side. This is because the direction of the jet is nearly perpendicular to the axial direction, which increases the effect of the Coriolis force. Besides, the mainstream from leading edge also has effects on film cooling performance. With the increase of the blowing ratio, the film coverage area and spatially averaged film cooling effectiveness increase first and then decrease. The maximum film coverage and averaged film cooling effectiveness appear at blowing ratio of 1.0 and rotating speed of 300rpm. Moreover, the upward deflection angle of the film trajectory increases slightly with the increase of the blowing ratio. Higher rotating speed intensifies the deflection of the film trajectory. Therefore, the film coverage and the averaged film cooling effectiveness decrease rapidly.

Film Cooling Performance on Turbine Blade Suction Side With Various Film Cooling Hole Arrangements

2020 ◽  
Author(s):  
Zhiyu Zhou ◽  
Haiwang Li ◽  
Gang Xie ◽  
Ruquan You
Keyword(s):  
Turbine Blade ◽  
Film Cooling ◽  
Stokes Equations ◽  
Suction Side ◽  
Suction Surface ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Injection Angle ◽  
Blowing Ratio

Abstract Numerical simulations were carried out to study the film cooling effectiveness distributions of different hole arrangements on the suction side of a high pressure turbine blade under rotating condition. The chord length and the height of the blade are 60mm and 80mm, respectively. Totally 12 models with different hole arrangements and different injection angles were studied. Each blade model has three rows of round holes with diameter of 0.9mm on the suction surface. The first row and the third row are fixed at streamwise location of 12.4% and 34% respectively. Three injection angles, 30°, 45°, and 60°, were investigated. Simulations were conducted under three rotational speeds, 600rpm, 800rpm, 1000rpm, with blowing ratio varying from 0.5 to 2.0. The Mainstream Reynolds numbers corresponding to the rotational speeds are 40560, 54080, and 67600 respectively. The temperature of the mainstream and the coolant is set at 463K and 303K so as to control the density ratio at 1.47. Simulations were performed by using SST turbulence model and were solved by using the three-dimensional Reynolds-averaged Navier–Stokes equations. Results showed that on the rotating turbine blade suction surface, film trajectories are drawn toward the midspan. The film trajectory arrangement may be different from the hole arrangement. Inline film trajectory arrangement can achieve higher film cooling effectiveness with slightly larger injection angle. Staggered film trajectory arrangement is better for uniform film cooling effectiveness distribution in spanwise and can achieve higher film cooling effectiveness with smaller injection angle. A smaller distance between the first row and the second row can achieve better film cooling performance at the downstream. With the increase of rotational speed, the mainstream Reynolds number increases, which improves the film cooling performance with smaller blowing ratio.

Prediction of Film Cooling Effectiveness on a Gas Turbine Blade Leading Edge Using ANN and CFD

2018 ◽  
Vol 35 (2) ◽  
pp. 101-111 ◽  
Author(s):  
J. O. Dávalos ◽  
J. C. García ◽  
G. Urquiza ◽  
A. Huicochea ◽  
O. De Santiago
Keyword(s):  
Gas Turbine ◽  
Turbine Blade ◽  
Film Cooling ◽  
Leading Edge ◽  
Hole Diameter ◽  
Relative Importance ◽  
Gas Turbine Blade ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio

Abstract In this work, the area-averaged film cooling effectiveness (AAFCE) on a gas turbine blade leading edge was predicted by employing an artificial neural network (ANN) using as input variables: hole diameter, injection angle, blowing ratio, hole and columns pitch. The database used to train the network was built using computational fluid dynamics (CFD) based on a two level full factorial design of experiments. The CFD numerical model was validated with an experimental rig, where a first stage blade of a gas turbine was represented by a cylindrical specimen. The ANN architecture was composed of three layers with four neurons in hidden layer and Levenberg-Marquardt was selected as ANN optimization algorithm. The AAFCE was successfully predicted by the ANN with a regression coefficient R2<0.99 and a root mean square error RMSE=0.0038. The ANN weight coefficients were used to estimate the relative importance of the input parameters. Blowing ratio was the most influential parameter with relative importance of 40.36 % followed by hole diameter. Additionally, by using the ANN model, the relationship between input parameters was analyzed.

scholarly journals Enhancing film cooling effectiveness in a gas turbine end-wall with a passive semi cylindrical trench

2019 ◽  
Vol 23 (3 Part B) ◽  
pp. 2013-2023
Author(s):  
Duraisamy Ravi ◽  
Kanjikovil Parammasivam
Keyword(s):  
Film Cooling ◽  
Leading Edge ◽  
Hole Diameter ◽  
Ansys Fluent ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Cooling Hole ◽  
Film Cooling Holes ◽  
End Wall

Computational studies were carried out in the end-wall of a linear cascade, of chosen blade profile, which is provided with one row of cylindrical film cooling holes inclined at 30o to the end wall. The CO gas was used as the coolant supplied through the film holes, 2 maintaining a blowing ratio of 0.6. The film cooling hole row was positioned at the leading edge of the cascade. The mainstream fluid was air and based on its properties at the cascade inlet, the flow was found turbulent. A semi cylindrical trench was placed at two positions upstream of the cascade leading edge and three positions downstream of it. ANSYS FLUENT 15.0 was used to compute the film cooling effectiveness of the cascade endwall. Trench positioned at a distance of twice that of film hole diameter, was found to show a highest increase of area averaged effectiveness value by 30.4% over the baseline. Further to this, the influence of the trench diameter was carried out where the trench with diameter twice that of film hole diameter was found to show a 31.3% increase of cooling effectiveness over the baseline. Studies on the influence of blowing ratio showed a highest increment of cooling effectiveness value by 43.5% over the baseline a blowing ratio of 1.2.

Turbine Blade Tip Cooling With Blade Rotation—Part II: Shroud Coolant Injection

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
Onieluan Tamunobere ◽  
Sumanta Acharya
Keyword(s):  
Film Cooling ◽  
Leading Edge ◽  
Suction Side ◽  
Tip Clearance ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Complementary Method ◽  
Blowing Ratio ◽  
Coolant Injection ◽  
Blade Tip

In this paper, blade tip cooling is investigated with coolant injection from the shroud alone and a combination of shroud coolant injection and tip cooling. With a nominal rotation speed of 1200 rpm, each blade consists of a cut back squealer tip with a tip clearance of 1.7% of the blade span. The blades also consist of tip holes and pressure side (PS) shaped holes, while the shroud has an array of angled holes and a circumferential slot upstream of the rotor section. Different combinations of the three cooling configurations (tip and PS holes, shroud angled holes, and shroud circumferential slot) are utilized to study the effectiveness of coolant injected from the shroud as a complementary method of cooling the blade tip. The measurements are done using liquid crystal thermography. Blowing ratios of 0.5, 1.0, 2.0, 3.0, and 4.0 are studied for shroud slot cooling, and blowing ratios of 1.0, 2.0, 3.0, 4.0, and 5.0 are studied for shroud hole cooling. For cases with coolant injection from the blade tip, the blowing ratios used are 1.0, 2.0, 3.0, and 4.0. The results show an increase in film cooling effectiveness with increasing blowing ratio for shroud hole coolant injection. The increased effectiveness from shroud hole coolant is concentrated mainly in the tip region below the shroud holes and toward the blade suction side and the suction side squealer rim. Slot coolant injection results in increased effectiveness on the blade tip near the blade leading edge up to a maximum blowing ratio, after which the cooling effectiveness decreases with increasing blowing ratio. The combination of the different cooling methods results in better overall cooling coverage of the blade tip with the shroud hole and blade tip coolant combination being the most effective. The level of coolant protection is strongly dependent on the blowing ratio and combination of blowing ratios.

Numerical Study on the Influence of Trench Width on Film Cooling Characteristics of Double-Wave Trench

2017 ◽  
Author(s):  
Bo-lun Zhang ◽  
Li Zhang ◽  
Hui-ren Zhu ◽  
Jian-sheng Wei ◽  
Zhong-yi Fu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Numerical Study ◽  
Leading Edge ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Trench Width

Film cooling performance of the double-wave trench was numerically studied to improve the film cooling characteristics. Double-wave trench was formed by changing the leading edge and trailing edge of transverse trench into cosine wave. The film cooling characteristics of transverse trench and double-wave trench were numerically studied using Reynolds Averaged Navier Stokes (RANS) simulations with realizable k-ε turbulence model and enhanced wall treatment. The film cooling effectiveness and heat transfer coefficient of double-wave trench at different trench width (W = 0.8D, 1.4D, 2.1D) conditions are investigated, and the distribution of temperature field and flow field were analyzed. The results show that double-wave trench effectively improves the film cooling effectiveness and the uniformity of jet at the downstream wall of the trench. The span-wise averaged film cooling effectiveness of the double-wave trench model increases 20–63% comparing with that of the transverse trench at high blowing ratio. The anti-counter-rotating vortices which can press the film on near-wall are formed at the downstream wall of the double-wave trench. With the double-wave trench width decreasing, the film cooling effectiveness gradually reduces at the hole center-line region of the downstream trench. With the increase of the blowing ratio, the span-wise averaged heat transfer coefficient increases. The span-wise averaged heat transfer coefficient of the double-wave trench with 0.8D and 2.1D trench width is higher than that of the double-wave trench with 1.4D trench width at the high blowing ratio conditions.

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