Computational Study on Pressure Side Film Cooling and Flow Structure

2013 ◽  
Author(s):  
Radheesh Dhanasegaran ◽  
Girish Venkatachalapathy ◽  
Nagarajan Gnanasekaran
Keyword(s):  
Flow Structure ◽  
Film Cooling ◽  
Computational Study ◽  
Pressure Side ◽  
Cooling Performance ◽  
Pressure Surface ◽  
Blowing Ratio ◽  
Commercial Code ◽  
Cylindrical Holes ◽  
Specific Geometry

A computational investigation is carried out to understand the film cooling performance and flow phenomenon on a pressure side of gas turbine airfoil. A specific geometry with multiple rows of cylindrical holes is considered on the pressure surface and opposite to which a flat surface is kept so as to avoid effect of imposed flow conditions. Meshing of the present model is done by using GAMBIT. Computations are carried out with K-epsilon Realizable model available in the commercial code FLUENT. The film cooling performance is discussed with flow structure followed by the effectiveness distribution on the pressure surface. The blowing ratio is varied from 0.4–2.4 and it is found that, at very low blowing ratio cases in the initial part of the pressure surface higher effectiveness values are observed but at higher blowing ratio these values become very low whereas close to the trailing edge side the effectiveness distribution is just the reverse. It was found that the optimum blowing ratio was close to unity where better flow and temperature distribution were observed.

A Parametric Investigation of Vane Showerhead Film Cooling by PSP Technique

2019 ◽  
Author(s):  
H. Abdeh ◽  
G. Barigozzi ◽  
S. Ravelli ◽  
S. Rouina
Keyword(s):  
Turbulence Intensity ◽  
Film Cooling ◽  
Cooling System ◽  
Density Ratio ◽  
Leading Edge ◽  
Intensity Level ◽  
Cooling Performance ◽  
Blowing Ratio ◽  
Cylindrical Holes ◽  
Exit Mach Number

Abstract In this study a parametric analysis of the thermal performance of a nozzle vane cascade with a showerhead cooling system made of four rows of cylindrical holes was carried out by using the Pressure Sensitive Paint (PSP) technique. Coolant-to-mainstream blowing ratio (BR), density ratio (DR), main flow isentropic exit Mach number (Ma2is) and turbulence intensity level (Tu1) were the considered parameters. The cascade was tested in an atmospheric wind tunnel at Ma2is values ranging from 0.2 to 0.6, with an inlet turbulence intensity level of 1.6% and 9%, at variable injection conditions of BR = 2.0, 3.0, 4.0. Moreover, the influence of DR on the leading edge film cooling performance was investigated: testing was carried out at DR = 1.0, using nitrogen as foreign gas, and DR = 1.5, with carbon dioxide serving as coolant. In the near-hole region, higher BR and Ma2is resulted in higher effectiveness, while higher mainstream turbulence intensity reduced the thermal coverage in between the rows of holes, whatever the BR. Further downstream along the vane pressure side, the effectiveness was negatively affected by rising BR, but positively influenced by lowering the mainstream turbulence intensity. Moreover, a decrease in DR caused a reduction in the film cooling performance, whose extent depends on the injection condition.

Experimental and Numerical Investigation on Film Cooling Performance and Flow Structure of Film Holes

2019 ◽  
Author(s):  
Nan Cao ◽  
Xue Li ◽  
Ze-yu Wu ◽  
Xiang Luo
Keyword(s):  
Flow Visualization ◽  
Numerical Investigation ◽  
Flow Structure ◽  
Film Cooling ◽  
Cylindrical Hole ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Blowing Ratio ◽  
Visualization Experiment ◽  
Shaped Hole

Abstract Discrete hole film cooling has been commonly used as an effective cooling technique to protect gas turbine blades from hot gas. There have been numerous investigations on the cylindrical hole and shaped hole, but few experimental investigations on the cooling mechanism of the novel film holes with side holes (anti-vortex hole and sister hole) are available. This paper presents an experimental and numerical investigation to study the film cooling performance and flow structure of four kinds of film holes (cylindrical hole, fan-shaped hole, anti-vortex hole and sister hole) on the flat plate. The film holes have the same main hole diameter of 4mm and the same inclination angle of 45°. The adiabatic film cooling effectiveness is obtained by the steady-state Thermochromic Liquid Crystal (TLC). The flow visualization experiment and numerical investigation are performed to investigate the flow structure and counter-rotating vortex pair (CRVP) intensity. The smoke is selected as the tracer particle in the flow visualization experiment. The mainstream Reynolds number is 2900, the blowing ratio ranges from 0.3 to 2.0, and the density ratio of coolant to mainstream is 1.065. Experimental results show that compared with the cylindrical hole, the film cooling performance of the anti-vortex hole and sister hole shows significant improvement at all blowing ratios. The sister hole can achieve the best cooling performance at blowing ratios of 0.3 to 1.5. The fan-shaped hole only performs well at high blowing ratios and it performs best at the blowing ratio of 2.0. Flow visualization experiment and numerical investigation reveal that the anti-vortex hole and sister hole can decrease the CRVP intensity of the main hole and suppress the coolant lift-off because of side holes, which increases the film coverage and cooling effectiveness. For the sister hole, the side holes are parallel to the main hole, but for the anti-vortex hole, there are lateral angles between them. The coolant interaction between the side holes and main hole of the sister hole is stronger than that of the anti-vortex hole. Therefore, the sister hole provides better film cooling performance than the anti-vortex hole.

Experimental Investigation of Film Cooling Performance on Blade Endwall with Diffusion Slot Holes and Stator-Rotor Purge Flow

2021 ◽  
pp. 1-28
Author(s):  
Zhi-Qiang Yu ◽  
Jianjun Liu ◽  
Chen Li ◽  
Baitao An ◽  
Guang-Yao Xu
Keyword(s):  
Film Cooling ◽  
Flow Direction ◽  
Cross Flow ◽  
Orientation Angle ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Pressure Surface ◽  
Blowing Ratio ◽  
Shaped Hole

Abstract This paper focuses on the influences of the discrete hole shape and layout on the blade endwall film cooling effectiveness. The diffusion slot hole was first applied to the blade endwall and compared with the fan-shaped hole. The effect of upstream purge slot injection on the film cooling performance of the discrete hole was also investigated. Experiments were performed in a linear cascade with a exit Reynolds number of 2.64×105. The film cooling effectiveness on the blade endwall were measured by the pressure sensitive paint technique. Results indicate that the diffusion slot hole significantly increases the film cooling effectiveness on the blade endwall compared to the fan-shaped hole, especially at high blowing ratio. The maximum relative increment of the cooling effectiveness is over 40%. The layout with the discrete holes arranged lining up with the tangent direction of the blade profile offset curves exhibits a comparable film cooling effectiveness with the layout with the discrete holes arranged according to the cross-flow direction. The film cooling effectiveness on the pressure surface corner is remarkably enhanced by deflecting the hole orientation angle towards the pressure surface. The combination of purge slot and diffusion slot holes supplies a full coverage film cooling for the entire blade endwall at coolant mass flow ratio of the purge slot of 1.5% and blowing ratio of 2.5. In addition, the slot injection leads to a non-negligible influence on the cooling performance of the discrete holes near the separation line.

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.

Investigations on the Influence of Rib Orientation Angle on Film Cooling Performance of Cylindrical Holes

2017 ◽  
Author(s):  
Lin Ye ◽  
Cun-liang Liu ◽  
Hui-ren Zhu ◽  
Jian-xia Luo ◽  
Ying-ni Zhai
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Discharge Coefficient ◽  
Cross Flow ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Flow Channels ◽  
Cylindrical Holes

This paper presents an experimental and numerical investigation on the film cooling with different coolant feeding channel structures. Two ribbed cross-flow channels with rib-orientation of 135° and 45° respectively and the plenum coolant channel have been studied and compared to find out the effect of rib orientation on the film cooling performances of cylindrical holes. The film cooling effectiveness and heat transfer coefficient were measured by the transient heat transfer measurement technique with narrow-band thermochromic liquid crystal. Numerical simulations with realizable k-ε turbulence model were also performed to analyze the flow mechanism. The results show that the coolant channel structure has a notable effect on the flow structure of film jet which is the most significant mechanism affecting the film cooling performance. Generally, film cooling cases fed with ribbed cross-flow channels have asymmetric counter-rotating vortex structures and related asymmetric temperature distributions, which make the film cooling effectiveness and the heat transfer coefficient distributions asymmetric to the hole centerline. The discharge coefficient of the 45° rib case is the lowest among the three cases under all the blowing ratios. And the plenum case has higher discharge coefficient than the 135° rib case under low blowing ratio. With the increase of blowing ratio, the discharge coefficient of the 135° rib case gets larger than the plenum case gradually, because the vortex in the upper half region of the coolant channel rotates in the same direction with the film hole inclination direction and makes the jet easy to flow into the film hole in the 135° rib case.

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.

Leading Edge Film Cooling and the Influence of Shaped Holes at Design and Off-Design Conditions

2007 ◽  
Author(s):  
Guillaume Wagner ◽  
Peter Ott ◽  
Gregory Vogel ◽  
Shailendra Naik
Keyword(s):  
Film Cooling ◽  
Incidence Angle ◽  
Wedge Angle ◽  
Leading Edge ◽  
Suction Side ◽  
Pressure Side ◽  
Blowing Ratio ◽  
Cylindrical Holes ◽  
Lift Off ◽  
Film Cooling Holes

Transient liquid crystal experiments have been carried out to measure the effectiveness and heat transfer characteristics of leading-edge film cooling for three different film cooling holes configurations at design and off-design incidence angle. The three configurations are based on the same representative leading edge model of a turbine blade, consisting of a symmetrical blunt body with a specific leading edge wedge angle. Film cooling is introduced from two rows of cooling holes, representative of a pressure-side row and a suction-side row. At design incidence, film cooling performances are symmetric. There is a jet lift-off situation and shaped holes significantly improve the film cooling performances because of a better lateral coverage and a reduced coolant momentum at the hole exit. At 5° off-design incidence angle, on the suction side, the situation is similar to that of a 0° incidence but with higher film cooling performances due to a reduced local blowing ratio. At 5° incidence on the pressure side, a beneficial interaction between the jets of the pressure side row appears. For middle and high blowing ratio, the film cooling performances are also better than 0° incidence. At 5° incidence on the pressure side, shaped holes also improve the film cooling performances in comparison to cylindrical holes.

Experimental Investigation of Net Heat Flux Reduction at Combustion Temperatures

2015 ◽  
Author(s):  
Nathan J. Greiner ◽  
Marc D. Polanka ◽  
James L. Rutledge ◽  
Andrew T. Shewhart
Keyword(s):  
Heat Flux ◽  
Experimental Investigation ◽  
Film Cooling ◽  
Density Ratio ◽  
Plate Surface ◽  
Cooling Performance ◽  
Single Row ◽  
Blowing Ratio ◽  
Net Heat Flux ◽  
Cylindrical Holes

The present work examines film cooling on a flat plate surface with a freestream temperature between 1430K and 1600K and a coolant to freestream density ratio of approximately two. Since the objective of film cooling is to reduce heat flux to a surface, Net Heat Flux Reduction (NHFR) is used to quantify film cooling performance. It is first demonstrated that non-dimensional matching can be used to scale NHFR between freestream temperature conditions of 1490K and 1600K. Next, the NHFR of a single row of cylindrical holes, fan-shaped holes, holes embedded in a trench, and a slot are compared at a blowing ratio of unity. Finally, the NHFR of five rows of cylindrical holes, holes embedded in trenches, and slots are compared to show the effect of a build-up of coolant near the wall.

Numerical Predictions of Flow Structures and Film Cooling Effectiveness Values of a Turbine Vane: Effects of Secondary Holes

2019 ◽  
Author(s):  
Rui Zhu ◽  
Terrence W. Simon ◽  
Gongnan Xie
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Suction Side ◽  
Pressure Side ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Single Row ◽  
Cylindrical Holes ◽  
Better Than

Abstract In modern gas turbines, film cooling is the most common and efficient way to provide thermal protection for hot components. Secondary holes to a primary film cooling hole are used to improve film cooling performance by creating anti-kidney vortices, a technique that has been well documented using flat plate models. This study aims to evaluate the effects of secondary holes on film cooling effectiveness over an airfoil. The film cooling performance and flow fields of a row of primary holes with secondary holes on the pressure side and suction side of a C3X vane are numerically investigated and compared with the results of a single row of cylindrical holes and two rows of staggered cylindrical holes. Cases with different blowing ratios are analyzed. It is shown from the simulation that film cooling effectiveness of primary holes with secondary holes is much better than with a single row of cylindrical holes, and slightly better than with two rows of staggered holes on both pressure side and suction side, with the same amount of coolant usage and blowing ratio. The enhancement is higher on the pressure side than on the suction side. The results show that adding secondary holes can enhance film cooling effectiveness by creating anti-kidney vortices, which will weaken jet lift-off from the primary holes caused by the kidney vortex pair, especially at higher blowing ratios. In addition, film coverage of primary holes with secondary holes is wider and persists further downstream than for a single row of cylindrical holes.

On Film Cooling Performance of a Turbine Vane Pressure Side: The Effect of Showerhead and Hole Alignment

2017 ◽  
Author(s):  
Hossein N. Najafabadi ◽  
Matts Karlsson ◽  
Mats Kinell
Keyword(s):  
Film Cooling ◽  
Guide Vane ◽  
Superior Performance ◽  
Pressure Side ◽  
Double Row ◽  
Cooling Performance ◽  
Single Row ◽  
Staggered Arrangement ◽  
Cooling Hole ◽  
Cylindrical Holes

This study uses transient IR-thermography to evaluate the effect of showerhead cooling and hole position on the performance of single-row cooling hole on the pressure side of a guide vane under engine representative conditions. The investigation includes both cylindrical and fan-shaped holes at two blowing conditions: 0.6 and 1.8. The influence of cooling hole alignment for these hole shapes in the performance of multiple row configurations was also studied in the presence of showerhead. For this purpose, double- and triple-row cases in staggered and non-staggered arrangements were considered for two blowing conditions, similar to the single row. The results are presented in terms of both adiabatic film effectiveness, AFE, and net heat flux reduction, NHFR. The showerhead effect was shown to be profound with regard to both AFE and NHFR for the cooling hole close to it. This holds for both hole shapes and blowing ratios. The overall film cooling performance, NHFR, of the rows further downstream of the showerhead and close to the trailing edge were affected marginally by the showerhead. The later cooling row showed superior performance compared to the other rows for fan-shaped holes in both presence and absence of shower-head at a low blowing ratio. For multiple row configurations, in general fan-shaped holes can maintain higher AFE in staggered alignment, while cylindrical holes benefit from consequent jet interaction between rows of cooling in a non-staggered arrangement. This holds for both investigated blowing ratios and double- and triple-rows. When considering NHFR, the results indicate that fan-shaped holes are less affected by the hole alignment. Cylindrical holes, however, can maintain superior performance in non-staggered alignment for all investigated cases except triple row under low blowing condition. The results also suggest that a double-row configuration in the presence of showerhead will benefit from an additional row mainly at high blowing ratios.

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