Squealer Tip Heat Transfer With Film Cooling

2010 ◽  
Author(s):  
Sumanta Acharya ◽  
Gregory Kramer ◽  
Louis Moreaux ◽  
Chiyuki Nakamata
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Film Cooling ◽  
Leading Edge ◽  
Numerical Results ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Heat Transfer Coefficients ◽  
Pressure Distributions

Heat transfer coefficients and film cooling effectiveness values were obtained numerically on a film cooled 2-D gas turbine blade tip model featuring a cutback squealer. In addition, pressure distributions were obtained at 50% and 98% spans. The calculations were performed for a single blade with periodic boundary conditions imposed along the two mid-passage boundaries formed by the adjacent blades. The calculations were performed with the realizable k-ε turbulence model and non-equilibrium wall function using 1.1 million elements. The numerical results are obtained for 4 blowing ratios and for Reynolds number based on axial chord and inlet velocity of 75,000. Limited experimental measurements of the blade pressure distributions and the uncooled tip heat transfer coefficients were performed for validation of the numerical results. The experiments were conducted in a six-blade low-speed wind tunnel cascade at a Reynolds number of 75,000. The heat transfer experiment involved a transient infrared thermography technique. Experimental heat transfer coefficients were extracted using a transient technique. The predicted pressure distributions agree very well with the measurements while the heat transfer coefficient predictions show qualitative agreement. From the numerical results, it can be seen that as the blowing ratio is increased, larger regions of film cooling effectiveness were seen with higher effectiveness values between the camber line and suction side. Heat transfer coefficients were largest near the leading edge for all cases.

Heat Transfer and Film Cooling Effectiveness in a Linear Airfoil Cascade

1997 ◽  
Vol 119 (2) ◽  
pp. 302-309 ◽  
Author(s):  
N. Abuaf ◽  
R. Bunker ◽  
C. P. Lee
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Film Cooling ◽  
Leading Edge ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Linear Cascade ◽  
Heat Transfer Coefficients

A warm (315°C) wind tunnel test facility equipped with a linear cascade of film cooled vane airfoils was used in the simultaneous determination of the local gas side heat transfer coefficients and the adiabatic film cooling effectiveness. The test rig can be operated in either a steady-state or a transient mode. The steady-state operation provides adiabatic film cooling effectiveness values while the transient mode generates data for the determination of the local heat transfer coefficients from the temperature–time variations and of the film effectiveness from the steady wall temperatures within the same aerothermal environment. The linear cascade consists of five airfoils. The 14 percent cascade inlet free-stream turbulence intensity is generated by a perforated plate, positioned upstream of the airfoil leading edge. For the first transient tests, five cylinders having roughly the same blockage as the initial 20 percent axial chord of the airfoils were used. The cylinder stagnation point heat transfer coefficients compare well with values calculated from correlations. Static pressure distributions measured over an instrumented airfoil agree with inviscid predictions. Heat transfer coefficients and adiabatic film cooling effectiveness results were obtained with a smooth airfoil having three separate film injection locations, two along the suction side, and the third one covering the leading edge showerhead region. Near the film injection locations, the heat transfer coefficients increase with the blowing film. At the termination of the film cooled airfoil tests, the film holes were plugged and heat transfer tests were conducted with non-film cooled airfoils. These results agree with boundary layer code predictions.

Heat Transfer and Film Cooling Effectiveness in a Linear Airfoil Cascade

1995 ◽  
Author(s):  
N. Abuaf ◽  
R. Bunker ◽  
C. P. Lee
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Film Cooling ◽  
Leading Edge ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Linear Cascade ◽  
Heat Transfer Coefficients

A warm (315 C) wind tunnel test facility equipped with a linear cascade of film cooled vane airfoils was used in the simultaneous determination of the local gas side heat transfer coefficients and the adiabatic film cooling effectiveness. The test rig can be operated in either a steady-state or a transient mode. The steady-state operation provides adiabatic film cooling effectiveness values while the transient mode generates data for the determination of the local heat transfer coefficients from the temperature-time variations and of the film effectiveness from the steady wall temperatures within the same aero-thermal environment. The linear cascade consists of five airfoils. The 14% cascade inlet free stream turbulence intensity is generated by a perforated plate, positioned upstream of the airfoil leading edge. For the first transient tests, five cylinders having roughly the same blockage as the initial 20% axial chord of the airfoils were used. The cylinder stagnation point heat transfer coefficients compare well with values calculated from correlations. Static pressure distributions measured over an instrumented airfoil agree with inviscid predictions. Heat transfer coefficients and adiabatic film cooling effectiveness results were obtained with a smooth airfoil having three separate film injection locations, two along the suction side, and the third one covering the leading edge showerhead region. Near the film injection locations, the heat transfer coefficients increase with the blowing film. At the termination of the film cooled airfoil tests, the film holes were plugged and heat transfer tests were conducted with non-film cooled airfoils. These results agree with boundary layer code predictions.

Heat Transfer Coefficients and Film Cooling Effectiveness on the Squealer Tip of a Gas Turbine Blade

2003 ◽  
Vol 125 (4) ◽  
pp. 648-657 ◽  
Author(s):  
Jae Su Kwak ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Film Cooling ◽  
Rotor Blade ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Heat Transfer Coefficients ◽  
Blowing Ratio

Experimental investigations were performed to measure the detailed heat transfer coefficients and film cooling effectiveness on the squealer tip of a gas turbine blade in a five-bladed linear cascade. The blade was a two-dimensional model of a first stage gas turbine rotor blade with a profile of the GE-E3 aircraft gas turbine engine rotor blade. The test blade had a squealer (recessed) tip with a 4.22% recess. The blade model was equipped with a single row of film cooling holes on the pressure side near the tip region and the tip surface along the camber line. Hue detection based transient liquid crystals technique was used to measure heat transfer coefficients and film cooling effectiveness. All measurements were done for the three tip gap clearances of 1.0%, 1.5%, and 2.5% of blade span at the two blowing ratios of 1.0 and 2.0. The Reynolds number based on cascade exit velocity and axial chord length was 1.1×106 and the total turning angle of the blade was 97.9 deg. The overall pressure ratio was 1.2 and the inlet and exit Mach numbers were 0.25 and 0.59, respectively. The turbulence intensity level at the cascade inlet was 9.7%. Results showed that the overall heat transfer coefficients increased with increasing tip gap clearance, but decreased with increasing blowing ratio. However, the overall film cooling effectiveness increased with increasing blowing ratio. Results also showed that the overall film cooling effectiveness increased but heat transfer coefficients decreased for the squealer tip when compared to the plane tip at the same tip gap clearance and blowing ratio conditions.

Heat Transfer and Film Cooling on a Contoured Blade Endwall With Platform Gap Leakage

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Stephen P. Lynch ◽  
Karen A. Thole
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Film Cooling ◽  
Vortical Flow ◽  
Leakage Flow ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Heat Transfer Coefficients ◽  
Manufacturing Assembly

Turbine blade components in an engine are typically designed with gaps between parts due to manufacturing, assembly, and operational considerations. Coolant is provided to these gaps to limit the ingestion of hot combustion gases. The interaction of the gaps, their leakage flows, and the complex vortical flow at the endwall of a turbine blade can significantly impact endwall heat transfer coefficients and the effectiveness of the leakage flow in providing localized cooling. In particular, a platform gap through the passage, representing the mating interface between adjacent blades in a wheel, has been shown to have a significant effect. Other important turbine blade features present in the engine environment are nonaxisymmetric contouring of the endwall, and an upstream rim seal with a gaspath cavity, which can reduce and increase endwall vortical flow, respectively. To understand the platform gap leakage effect in this environment, measurements of endwall heat transfer, and film cooling effectiveness were performed in a scaled blade cascade with a nonaxisymmetric contour in the passage. A rim seal with a cavity, representing the overlap interface between a stator and rotor, was included upstream of the blades and a nominal purge flowrate of 0.75% of the mainstream was supplied to the rim seal. The results indicated that the endwall heat transfer coefficients increased as the platform gap net leakage increased from 0% to 0.6% of the mainstream flowrate, but net heat flux to the endwall was reduced due to high cooling effectiveness of the leakage flow.

Effect of Surface Roughness on Local Heat Transfer and Film Cooling Effectiveness

1995 ◽  
Author(s):  
Douglas N. Barlow ◽  
Yong W. Kim
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Smooth Surface ◽  
Rough Surfaces ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Heat Transfer Coefficients

An experimental investigation of film cooling on rough surfaces has been accomplished at a Reynolds number and dimensionless boundary layer momentum thickness found in current high performance first stage turbine vanes. A transient experimental method using thermochromic liquid crystals is employed to determine both local heat transfer coefficients and film cooling effectiveness values on planar rough surfaces. Two surface roughness configurations are investigated with a single row of cooling holes spaced three diameters apart and inclined 30° to the mainstream flow. The mainstream turbulence level at the point of film injection is 8.5% and the density ratio considered is approximately 1.0. The influence of roughness on the centerline film cooling effectiveness, laterally averaged film cooling effectiveness, laterally averaged heat transfer coefficients, as well as area averaged values are presented. It is found that the presence of roughness causes a decrease in the film cooling effectiveness over that of the smooth surface for the range of experimental parameters considered in this study. In addition, significant lateral smoothing in film cooling effectiveness distribution is observed for the rougher surfaces. Measured heat transfer coefficients on rough surfaces show a trend of monotonic increase with blowing ratio. However, such increase is not as great as that for the case of smooth surface.

Film Cooling From a Row of Holes With Both Ends Embedded in Transverse Slots

2008 ◽  
Author(s):  
D. H. Zhang ◽  
L. Sun ◽  
Q. Y. Chen ◽  
M. Lin ◽  
M. Zeng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Aerodynamic Performance ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Heat Transfer Coefficients ◽  
Discharge Coefficients ◽  
Cylindrical Holes

Embedding a row of typical cylindrical holes in a transverse slot can improve the cooling performance. Rectangular slots can increase the cooling effectiveness but is at the cost of decreasing of discharge coefficients. An experiment is conducted to examine the effects of an overlying transverse inclined trench on the film cooling performance of axial holes. Four different trench configurations are tested including the baseline inclined cylindrical holes. The influence of the geometry of the upstream lip of the exit trench and the geometry of the inlet trench on cooling performance is examined. Detailed film cooling effectiveness and heat transfer coefficients are obtained separately using the steady state IR thermography technique. The discharge coefficients are also acquired to evaluate the aerodynamic performance of different hole configurations. The results show that the film cooling holes with both ends embedded in slots can provide higher film cooling effectiveness and lower heat transfer coefficients; it also can provide higher discharge coefficients whilst retaining the mechanical strength of a row of discrete holes. The cooling performance and the aerodynamic performance of the holes with both ends embedded in inclined slots are superior to the holes with only exit trenched. To a certain extent, the configuration of the upstream lip of the exit trench affects the cooling performance of the downstream of the trench. The filleting for the film hole inlet avail the improvement of the cooling effect, but not for the film hole outlet. Comparing film cooling with embedded holes to unembedded holes, the overall heat flux ratio shows that the film holes with both ends embedded in slots and filleting for the film hole inlet can produce the highest heat flux reduction.

Film-Cooling Characteristics of Pressure-Side Discharge Slots in an Accelerating Mainstream Flow

2005 ◽  
Author(s):  
Yong W. Kim ◽  
Chad Coon ◽  
Hee-Koo Moon
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Heat Transfer Coefficients ◽  
Blowing Ratio ◽  
Mainstream Flow

Pressure-side discharge is commonly employed in turbine blades and nozzle guide vanes to keep the trailing edge metal temperatures within an allowable limit while minimizing aerodynamic penalties. Despite its widespread use, film-cooling data of the discharge slot are scarce in open literature. The objectives of the present experimental study were to measure detailed local heat transfer and film-cooling effectiveness from a 10x scale trailing-edge model of an industrial gas turbine airfoil in a low speed wind tunnel. To simulate the mainstream flow acceleration in vane and blade row passages, a linear velocity gradient was imposed using an adjustable top wall. The present work employed the composite slab quasi-steady liquid crystal method that allows measurements of local heat transfer coefficients and film-cooling effectiveness from two related tests. With this technique, the heat transfer measurement can be performed in a cold wind tunnel. The coolant-to-mainstream blowing ratio was varied between 0.25 and 1.0. The slot hydraulic diameter based Reynolds number ranged from 4,760 to 19,550. The coolant-to-mainstream density ratio was fixed at 0.95. Slot discharge coefficients were also measured with mainstream acceleration. Both local heat transfer coefficients and film-cooling effectiveness displayed a strong dependency on blowing ratio and mainstream acceleration. However, the discharge coefficients showed little dependency on the mainstream acceleration.

Prediction of Film Cooling and Heat Transfer on a Rotating Blade Platform With Stator-Rotor Purge and Discrete Film-Hole Flows in a 1-1/2 Turbine Stage

2007 ◽  
Author(s):  
H. Yang ◽  
Z. Gao ◽  
H. C. Chen ◽  
J. C. Han ◽  
M. T. Schobeiri
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Turbine Stage ◽  
Transfer Coefficients ◽  
Work Process ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Heat Transfer Coefficients ◽  
Rotating Blade ◽  
Purge Flow

Numerical simulations were performed to predict the film cooling effectiveness and heat transfer coefficient distributions on a rotating blade platform with stator-rotor purge flow and downstream discrete film-hole flows in a 1-1/2 turbine stage using a Reynolds stress turbulence model together with a non-equilibrium wall function. Simulations were carried out with sliding mesh for the rotor under three rotating speeds (2000, 2550, and 3000 rpm) to investigate the effects of rotation and stator-rotor interaction on the rotor blade platform purge flow cooling and discrete-hole film cooling and heat transfer. The adiabatic film cooling effectiveness and heat transfer coefficients were calculated using the adiabatic wall temperatures with and without coolant to examine the true coolant protection excluding the effect of turbine work process. The stator-rotor interaction strongly impacts the purge slot film cooling and heat transfer at the platform leading portion, while only slightly affects the downstream discrete-hole film cooling near the platform trailing portion. In addition, the effect of turbine work process on the film cooling effectiveness and the associated heat transfer coefficients have been reported.

Heat Transfer and Film Cooling on a Contoured Blade Endwall With Platform Gap Leakage

2015 ◽  
Author(s):  
Stephen P. Lynch ◽  
Karen A. Thole
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Film Cooling ◽  
Vortical Flow ◽  
Leakage Flow ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Heat Transfer Coefficients ◽  
Manufacturing Assembly

Turbine blade components in an engine are typically designed with gaps between parts due to manufacturing, assembly, and operational considerations. Coolant is provided to these gaps to limit the ingestion of hot combustion gases. The interaction of the gaps, their leakage flows, and the complex vortical flow at the endwall of a turbine blade can significantly impact endwall heat transfer coefficients and the effectiveness of the leakage flow in providing localized cooling. In particular, a platform gap through the passage, representing the mating interface between adjacent blades in a wheel, has been shown to have a significant effect. Other important turbine blade features present in the engine environment are non-axisymmetric contouring of the endwall, and an upstream rim seal with a gaspath cavity, which can reduce and increase endwall vortical flow, respectively. To understand the platform gap leakage effect in this environment, measurements of endwall heat transfer and film cooling effectiveness were performed in a scaled blade cascade with a non-axisymmetric contour in the passage. A rim seal with a cavity, representing the overlap interface between a stator and rotor, was included upstream of the blades and a nominal purge flowrate of 0.75% of the mainstream was supplied to the rim seal. Results indicated that endwall heat transfer coefficients increased as platform gap net leakage increased from 0% to 0.6% of the mainstream flowrate, but net heat flux to the endwall was reduced due to high cooling effectiveness of the leakage flow.

Transient Liquid Crystal Measurement of Leading Edge Film Cooling Effectiveness and Heat Transfer With High Free Stream Turbulence

2000 ◽  
Author(s):  
Shichuan Ou ◽  
Richard Rivir ◽  
Matthew Meininger ◽  
Fred Soechting ◽  
Martin Tabbita
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Film Cooling ◽  
Leading Edge ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Free Stream Turbulence ◽  
Blowing Ratio ◽  
Order Of Magnitude ◽  
High Turbulence

This paper studies the film effectiveness and heat transfer coefficients on a large scale symmetric circular leading edge with three rows of film holes. The film hole configuration focuses on a smaller injection angle of 20° and a larger hole pitch with respect to the hole diameter (P/d = 7.86). The study includes four blowing ratios (M = 1.0, 1.5, 2.0 and 2.5), two Reynolds numbers (Re = 30,000 and 60,000), and two free stream turbulence levels (approximately Tu = 1% and 20% depending on the Reynolds number). The method used to obtain the film cooling effectiveness and the heat transfer coefficient in the experiment is a transient liquid crystal technique. The distributions of film effectiveness and heat transfer coefficient are obtained with spatial resolutions of about 0.6 mm or 13% of the film cooling hole diameter. Results are presented for detailed and spanwise averaged values of film effectiveness and Frössling number. Blowing ratios investigated result in up to 2.8 times the lowest blowing ratio’s film effectiveness. Increasing the Reynolds number from 30,000 to 60,000 results in increasing the effectiveness by up to 55% at high turbulence. Turbulence intensity has up to a 60% attenuation on effectiveness between rows at Re = 30,000. The turbulence intensity has the same order of magnitude but opposite effect as Reynolds number, which also has the same order of magnitude effect as blowing ratio on the film effectiveness. A crossover from attenuation to improved film effectiveness after the second row of film holes is found for the high turbulence case as blowing ratio increases. The blowing ratio of two shows a spatial coupling of the stagnation row of film holes with the second row (21.5°) of film holes which results in the highest film effectiveness and also the highest Frössling numbers.

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