Enhancement in Film Cooling Effectiveness Using Delta Winglet Pair

2020 ◽  
pp. 1-37
Author(s):  
Nirmal Halder ◽  
Arun Saha ◽  
Pradipta Panigrahi
Keyword(s):  
Film Cooling ◽  
Cross Flow ◽  
Hole Diameter ◽  
Stagnation Region ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Longitudinal Vortices ◽  
Blowing Ratio ◽  
Turbulent Statistics ◽  
Delta Winglet

Abstract A simulation study is performed to inspect the influence of delta winglet pair for improving the film cooling effectiveness of gas turbine blade. Incompressible continuity, momentum, energy and two equations - SST model have been used for investigating the nature of flow field, temperature field and turbulent statistics. Reynolds number based on the jet velocity and film cooling hole diameter is 4232. The jet to cross-flow blowing ratio has been varied as 0.5, 1.0 and 1.5. The corresponding Reynolds numbers based on cross-flow velocity and film-hole diameter are equal to 6462, 4229 and 3231 respectively. It is observed that common flow down configuration augments the film cooling effectiveness which attributed to the development of secondary longitudinal vortices. Longitudinal vortices annihilate the counter rotating vortex structures present in the baseline flow. The generation of hairpin vortices and boost of shear layer vortices are modified due to the implementation of Delta winglet pair. The overall turbulence intensity and vorticity get reduced due to the presence of Delta winglet pair. A maximum of 97.46% and a minimum of 61.50% enhancement in film cooling effectiveness is observed at blowing ratio of 1.5 and 0.5 respectively.Wake region of film cooling jet is modified due to Delta winglet pair leading to formation of stagnation region and lower mixing resulting in higher film cooling effectiveness.

Effects of Double Wall Cooling Configuration and Conditions on Performance of Full-Coverage Effusion Cooling

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Nathan Rogers ◽  
Zhong Ren ◽  
Warren Buzzard ◽  
Brian Sweeney ◽  
Nathan Tinker ◽  
...  
Keyword(s):  
Film Cooling ◽  
Cross Flow ◽  
Hole Array ◽  
Adiabatic Wall ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Full Coverage ◽  
Cooling Hole ◽  
Double Wall

Experimental results are presented for a double wall cooling arrangement which simulates a portion of a combustor liner of a gas turbine engine. The results are collected using a new experimental facility designed to test full-coverage film cooling and impingement cooling effectiveness using either cross flow, impingement, or a combination of both to supply the film cooling flow. The present experiment primarily deals with cross flow supplied full-coverage film cooling for a sparse film cooling hole array that has not been previously tested. Data are provided for turbulent film cooling, contraction ratio of 1, blowing ratios ranging from 2.7 to 7.5, coolant Reynolds numbers based on film cooling hole diameter of about 5000–20,000, and mainstream temperature step during transient tests of 14 °C. The film cooling hole array consists of a film cooling hole diameter of 6.4 mm with nondimensional streamwise (X/de) and spanwise (Y/de) film cooling hole spacing of 15 and 4, respectively. The film cooling holes are streamwise inclined at an angle of 25 deg with respect to the test plate surface and have adjacent streamwise rows staggered with respect to each other. Data illustrating the effects of blowing ratio on adiabatic film cooling effectiveness and heat transfer coefficient are presented. For the arrangement and conditions considered, heat transfer coefficients generally increase with streamwise development and increase with increasing blowing ratio. The adiabatic film cooling effectiveness is determined from measurements of adiabatic wall temperature, coolant stagnation temperature, and mainstream recovery temperature. The adiabatic wall temperature and the adiabatic film cooling effectiveness generally decrease and increase, respectively, with streamwise position, and generally decrease and increase, respectively, as blowing ratio becomes larger.

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.

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.

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.

A Numerical and Experimental Investigation of the Slot Film-Cooling Jet With Various Angles

2005 ◽  
Vol 127 (3) ◽  
pp. 635-645 ◽  
Author(s):  
Rongguang Jia ◽  
Bengt Sundén ◽  
Petre Miron ◽  
Bruno Léger
Keyword(s):  
Film Cooling ◽  
Stokes Equations ◽  
Cross Flow ◽  
Turbulence Models ◽  
Temperature Fields ◽  
Cooling Effectiveness ◽  
Recirculation Bubble ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Present Solution

Numerical simulations coupled with laser Doppler velocimetry (LDV) experiments were carried out to investigate a slot jet issued into a cross flow, which is relevant in the film cooling of gas turbine combustors. The film-cooling fluid injection from slots or holes into a cross flow produces highly complicated flow fields. In this paper, the time-averaged Navier-Stokes equations were solved on a collocated body-fitted grid system with the shear stress transport k−ω, V2F k−ϵ, and stress-ω turbulence models. The fluid flow and turbulent Reynolds stress fields were compared to the LDV experiments for three jet angles, namely, 30, 60, and 90 deg, and the jet blowing ratio is ranging from 2 to 9. Good agreement was obtained. Therefore, the present solution procedure was also adopted to calculations of 15 and 40 deg jets. In addition, the temperature fields were computed with a simple eddy diffusivity model to obtain the film-cooling effectiveness, which, in turn, was used for evaluation of the various jet cross-flow arrangements. The results show that a recirculation bubble downstream of the jet exists for jet angles larger than 40 deg, but it vanishes when the angle is <30deg, which is in good accordance with the experiments. The blowing ratio has a large effect on the size of the recirculation bubble and, consequently, on the film cooling effectiveness. In addition, the influence of boundary conditions for the jet and cross flow are also addressed in the paper.

Numerical and Experimental Study of the Slot Film Cooling Jet With Various Angles

2003 ◽  
Author(s):  
Rongguang Jia ◽  
Bengt Sunde´n ◽  
Petre Miron ◽  
Bruno Le´ger
Keyword(s):  
Film Cooling ◽  
Stokes Equations ◽  
Cross Flow ◽  
Eddy Diffusivity ◽  
Temperature Fields ◽  
Cooling Effectiveness ◽  
Recirculation Bubble ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Present Solution

Numerical simulations coupled with LDV experiments were carried out to investigate a slot jet issued into a cross flow, which is relevant in the film cooling of gas turbine combustors. The film cooling fluid injection from slots or holes into a cross-flow produces highly complicated flow fields. In this paper, the time-averaged Navier-Stokes equations were solved on a collocated body-fitted grid system with the V2F turbulence model. The fluid flow and turbulent Reynolds stress fields were compared with the LDV experiments for three jet angles, namely, 30-deg, 60-deg, and 90-deg, and the jet blowing ratio is ranging from 2 to 9. Good agreement was obtained. Therefore, the present solution procedure was also adopted to calculations of 15-deg and 40-deg jets. In addition, the temperature fields, which were difficult to measure by experimental methods, were also computed with a simple eddy diffusivity model to obtain the film cooling effectiveness which was used for evaluation of the various jet-cross-flow arrangements. The results show that a recirculation bubble downstream the jet exists for jet angles larger than 40-deg, but it vanishes when the angle is less than 30-deg, which is in good accordance with the experiments. The blowing ratio has a large effect on the size of the recirculation bubble, and consequently on the film cooling effectiveness. In addition, the influence of boundary conditions for the jet and cross-flow are also addressed in the paper.

Investigation of a Novel Discrete Slot Film Cooling Scheme

2014 ◽  
Author(s):  
Karim M. Shalash ◽  
Lamyaa A. El-Gabry ◽  
Mohamed M. Abo El-Azm
Keyword(s):  
Film Cooling ◽  
Cross Flow ◽  
Sensitivity Study ◽  
Round Hole ◽  
Blade Surface ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Jet In Cross Flow ◽  
Slot Film Cooling

The future of the gas turbine industry is strongly relying on the development of new efficient cooling schemes. Film cooling is one popular and reliable cooling technique, one way to increase the film cooling effectiveness is through the use of shaped holes. In this paper two proposed shaped holes are being studied and compared thoroughly against the conventional round hole film cooling. The two proposed holes are based on the theoretically perfect continuous slot film cooling, however, these slots are not continuous, and preserves the solid surface to the total blade surface ratio. The first design to be studied is the Rectangular Divergent Slot, and the second is the Aeroslot, which is a discrete aerodynamically shaped slot; both designs showed an increase in the centerline film cooling effectiveness when compared to the conventional round holes. The Aeroslot showed a large increase in film cooling effectiveness for the same blowing ratio, and mass flow rate of coolant, when compared to the other shapes. A sensitivity study of the blowing ratio to the centerline film cooling effectiveness is carried out for several blowing ratios, covering different jet in cross flow behaviors, fully attached jet, and detached-reattached jet.

Effects of Double Wall Cooling Configuration and Conditions on Performance of Full Coverage Effusion Cooling

2016 ◽  
Author(s):  
Nathan Rogers ◽  
Zhong Ren ◽  
Warren Buzzard ◽  
Brian Sweeney ◽  
Nathan Tinker ◽  
...  
Keyword(s):  
Film Cooling ◽  
Cross Flow ◽  
Hole Array ◽  
Adiabatic Wall ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Full Coverage ◽  
Cooling Hole ◽  
Double Wall

Experimental results are presented for a double wall cooling arrangement which simulates a portion of a combustor liner of a gas turbine engine. The results are collected using a new experimental facility designed to test full coverage film cooling and impingement cooling effectiveness using either cross flow, impingement, or a combination of both to supply the film cooling flow. The present experiment primarily deals with cross flow supplied full coverage film cooling for a sparse film cooling hole array that has not been previously tested. Data are provided for turbulent film cooling, contraction ratio of 1, blowing ratios ranging from 2.7 to 7.5, coolant Reynolds numbers based on film cooling hole diameter of about 5,000–20,000, and mainstream temperature step during transient tests of 14 °C. The film cooling hole array consists of a film cooling hole diameter of 6.4 mm with non-dimensional streamwise (X/de) and spanwise (Y/de) film cooling hole spacing of 15 and 4, respectively. The film cooling holes are streamwise inclined at an angle of 25 degrees with respect to the test plate surface and have adjacent streamwise rows staggered with respect to each other. Data illustrating the effects of blowing ratio on adiabatic film cooling effectiveness and heat transfer coefficient are presented. For the arrangement and conditions considered, heat transfer coefficients generally increase with streamwise development, and increase with increasing blowing ratio. The adiabatic film cooling effectiveness is determined from measurements of adiabatic wall temperature, coolant stagnation temperature, and mainstream recovery temperature. The adiabatic wall temperature and adiabatic film cooling effectiveness generally decrease and increase, respectively, with streamwise position, and generally decrease and increase, respectively, as blowing ratio becomes larger.

Effect of Wake on Endwall Film Cooling Effectiveness for a Row of Cylindrical Holes Near the Stagnation Region of an Airfoil

2008 ◽  
Author(s):  
S. Rodri´guez ◽  
S. Kersten ◽  
V. Krishnan ◽  
J. S. Kapat
Keyword(s):  
Film Cooling ◽  
Diameter Ratio ◽  
Stagnation Region ◽  
Injection Point ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Single Row ◽  
Blowing Ratio ◽  
Cylindrical Holes ◽  
Endwall Film Cooling

Over the last decades, researchers have investigated many aspects of film cooling. The present study investigates the effect of transition wake near the stagnation region on endwall film cooling effectiveness. Experimental measurements are presented for a single row of cylindrical holes inclined at 35° with hole length to diameter ratio, L/D = 7.5, pitch to diameter ratio, PI/D = 3 with a constant density ratio of 1.26 and with nitrogen as the coolant. Nine different configurations were studied. The airfoil was positioned at x/D equal to (I) 6.4, (II) 12.7, and (III) 25.4. Configuration (IV-VI) consisted of the airfoil positioned at x/D = 6.4, 12.7 and 25.4 and a wake plate positioned at x/D = −12.7, upstream of the injection point. The presence of wake is also investigated on configuration VII through IX. Configuration (VII-IX) consisted of the airfoil positioned at x/D = 6.4, 12.7 and 25.4 and a wake plate positioned at x/D = −50.8, upstream of the injection point. Configuration 0, 0-b and 0-c are the baselines; these configurations consist of a single row of cylindrical holes with and without wake plate. In the absence of wake, the average effectiveness increases with increasing blowing ratio at a x/D further downstream of the injection point where the jet has reattached. Higher blowing ratio increases lateral spreading of the jet promoting jet to jet interaction and mainstream interaction enhancing mixing. The presence of wake promotes jet mixing with the mainstream resulting in faster decay of film cooling effectiveness. Effectiveness is higher for the cases where the plate is placed further upstream of the injection point.

scholarly journals Film Cooling Effectiveness in the Showerhead Region of a Gas Turbine Vane: Part II — Stagnation Region and Near-Suction Side

1999 ◽  
Author(s):  
Virginia C. Witteveld ◽  
Marc D. Polanka ◽  
David G. Bogard
Keyword(s):  
Gas Turbine ◽  
Film Cooling ◽  
Suction Side ◽  
Line Position ◽  
Stagnation Region ◽  
Cooling Effectiveness ◽  
Stagnation Line ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Turbine Vane

An experimental study was conducted to determine the effects of film cooling on a gas turbine vane at two mainstream turbulence intensities of Tu = 0.5% and Tu = 22%. The low speed turbine vane test facility was designed to match the Reynolds number of operating engine conditions. The nine-time scale model airfoil simulates a gas turbine first-stage stator vane. The leading edge film cooling hole showerhead array included six rows of film cooling holes configured with one stagnation row, two pressure side rows, and three suction side rows. This paper presents film cooling effectiveness measurements in the stagnation region and near-suction side. Cooled air injection was used to conduct the tests at a density ratio of DR = 1.8 and blowing conditions over a range of M = 0.5 to M = 2.9. Infrared imaging techniques were used to measure the surface temperature distribution. The results provide a detailed evaluation of the effects of blowing ratio, mainstream turbulence, and stagnation line position on the measured effectiveness in the showerhead. The effect of increasing blowing ratio generally resulted in increased spanwise averaged effectiveness levels. The effect of mainstream turbulence varies with blowing ratio within the showerhead region. At low blowing ratio, high turbulence produced greater effectiveness, whereas at high blowing ratio, low turbulence produced greater effectiveness. The effect of stagnation line position also varied with blowing ratio. Overall, the dominating effect occurred when the blowing ratio was sufficiently strong to cause a spanwise merging of adjacent cooling jets resulting in very good spanwise uniformity and high adiabatic effectiveness.

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