Investigation of Detailed Film Cooling Effectiveness and Heat Transfer Distributions on a Gas Turbine Airfoil

1999 ◽  
Vol 121 (2) ◽  
pp. 233-242 ◽  
Author(s):  
U. Drost ◽  
A. Bo¨lcs
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Density Ratio ◽  
Suction Side ◽  
Lateral Spreading ◽  
Double Row ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Flow Acceleration ◽  
Single Compound

In the present study film cooling effectiveness and heat transfer were systematically investigated on a turbine NGV airfoil employing the transient liquid crystal technique and a multiple regression procedure. Tests were conducted in a linear cascade at exit Reynolds numbers of 0.52e6, 1.02e6 and 1.45e6 and exit Mach numbers of 0.33, 0.62 and 0.8, at two mainstream turbulence intensities of 5.5 and 10 percent. The film cooling geometry consisted of a single compound angle row on the pressure side (PS), and a single or a double row on the suction side (SS). Foreign gas injection was used to obtain a density ratio of approximately 1.65, while air injection yielded a density ratio of unity. Tests were conducted for blowing ratios of 0.25 to 2.3 on the SS, and 0.55 to 7.3 on the PS. In general film cooling injection into a laminar BL showed considerably higher effectiveness in the near-hole region, as compared to a turbulent BL. While mainstream turbulence had only a weak influence on SS cooling, higher effectiveness was noted on the PS at high turbulence due to increased lateral spreading of the coolant. Effects of mainstream Mach and Reynolds number were attributed to changes of the BL thickness and flow acceleration. Higher density coolant yielded higher effectiveness on both SS and PS, whereas heat transfer ratios were increased on the SS and decreased on the PS. Comparison of the single and double row cooling configurations on the SS revealed a better film cooling performance of the double row due to an improved film coverage and delayed jet separation.

Investigation of Detailed Film Cooling Effectiveness and Heat Transfer Distributions on a Gas Turbine Airfoil

1998 ◽  
Author(s):  
U. Drost ◽  
A. Bölcs
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Density Ratio ◽  
Suction Side ◽  
Lateral Spreading ◽  
Double Row ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Flow Acceleration ◽  
Single Compound

In the present study film cooling effectiveness and heat transfer were systematically investigated on a turbine NGV airfoil employing the transient liquid crystal technique and a multiple regression procedure. Tests were conducted in a linear cascade at exit Reynolds numbers of 0.52e6, 1.02e6 and 1.45e6 and exit Mach numbers of 0.33, 0.62 and 0.8, at two mainstream turbulence intensities of 5.5% and 10%. The film cooling geometry consisted of a single compound angle row on the pressure side (PS), and a single or a double row on the suction side (SS). Foreign gas injection was used to obtain a density ratio of approximately 1.65, while air injection yielded a density ratio of unity. Tests were conducted for blowing ratios of 0.25 to 2.3 on the SS, and 0.55 to 7.3 on the PS. In general film cooling injection into a laminar BL showed considerably higher effectiveness in the near hole region, as compared to a turbulent BL. While mainstream turbulence had only a weak influence on SS cooling, higher effectiveness was noted on the PS at high turbulence due to increased lateral spreading of the coolant. Effects of mainstream Mach and Reynolds number were attributed to changes of the BL thickness and flow acceleration. Higher density coolant yielded higher effectiveness on both SS and PS, whereas heat transfer ratios were increased on the SS and decreased on the PS. Comparison of the single and double row cooling configurations on the SS revealed a better film cooling performance of the double row due to an improved film coverage and delayed jet separation.

Measurement of Local Heat Transfer Coefficient and Film Cooling Effectiveness Through Discrete Holes

2000 ◽  
Author(s):  
R. F. Martinez-Botas ◽  
C. H. N. Yuen
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Liquid Crystal ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Density Ratio ◽  
Local Heat Transfer ◽  
Double Row ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness

An efficient steady-state wide band liquid crystal technique is used to study the film cooling performance of a variety of geometries in a flat plate: a single row of holes, a double row of holes (both in-line and staggered), and a single cooling hole. This method allows temperature information to be captured in one image, without the difficulty involved in a transient experiment. The streamwise inclinations tested are 30°, 60°, and 90°. The freestream is maintained at 13m/s, and at ambient temperature. The range of blowing ratios varied from 0.33 to 2.0. Both heat transfer coefficient and adiabatic cooling effectiveness are measured for all the cases. Air is used to produce a density ratio near unity. From the range of blowing ratios tested, the most effective film cooling is achieved at a value close to 0.5, for near unity density ratio. It has been revealed that film cooling effectiveness is improved when the jet remains attached to the surface, however, this is generally coupled with an augmentation in heat transfer owing to the disturbance the attached jet causes to the boundary layer. The 30° inclined holes show to be the most effective. Results demonstrate the full coverage capability of liquid crystal thermography.

High-Resolution Film Cooling Effectiveness Measurements of Axial Holes Embedded in a Transverse Trench With Various Trench Configurations

2006 ◽  
Vol 129 (2) ◽  
pp. 294-302 ◽  
Author(s):  
Scot K. Waye ◽  
David G. Bogard
Keyword(s):  
High Resolution ◽  
Film Cooling ◽  
Density Ratio ◽  
Field Measurements ◽  
Suction Side ◽  
Lateral Spreading ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Flow Parameters ◽  
Adiabatic Effectiveness

Adiabatic film cooling effectiveness of axial holes embedded within a transverse trench on the suction side of a turbine vane was investigated. High-resolution two-dimensional data obtained from infrared thermography and corrected for local conduction provided spatial adiabatic effectiveness data. Flow parameters of blowing ratio, density ratio, and turbulence intensity were independently varied. In addition to a baseline geometry, nine trench configurations were tested, all with a depth of 1∕2 hole diameter, with varying widths, and with perpendicular and inclined trench walls. A perpendicular trench wall at the very downstream edge of the coolant hole was found to be the key trench characteristic that yielded much improved adiabatic effectiveness performance. This configuration increased adiabatic effectiveness up to 100% near the hole and 40% downstream. All other trench configurations had little effect on the adiabatic effectiveness. Thermal field measurements confirmed that the improved adiabatic effectiveness that occurred for a narrow trench with perpendicular walls was due to a lateral spreading of the coolant and reduced coolant jet separation. The cooling levels exhibited by these particular geometries are comparable to shaped holes, but much easier and cheaper to manufacture.

High Resolution Film Cooling Effectiveness Measurements of Axial Holes Embedded in a Transverse Trench With Various Trench Configurations

2006 ◽  
Author(s):  
Scot K. Waye ◽  
David G. Bogard
Keyword(s):  
High Resolution ◽  
Film Cooling ◽  
Density Ratio ◽  
Field Measurements ◽  
Suction Side ◽  
Lateral Spreading ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Flow Parameters ◽  
Adiabatic Effectiveness

Adiabatic film cooling effectiveness of axial holes embedded within a transverse trench on the suction side of a turbine vane was investigated. High resolution two dimensional data obtained from IR thermography and corrected for local conduction provided spatial adiabatic effectiveness data. Flow parameters of blowing ratio, density ratio, and turbulence intensity were independently varied. In addition to a baseline geometry, nine trench configurations were tested, all with a depth of 1/2 hole diameter, with varying widths, and with perpendicular and inclined trench walls. A perpendicular trench wall at the very downstream edge of the coolant hole was found to be the key trench characteristic that yielded much improved adiabatic effectiveness performance. This configuration increased adiabatic effectiveness up to 100% near the hole and 40% downstream. All other trench configurations had little effect on the adiabatic effectiveness. Thermal field measurements confirmed that the improved adiabatic effectiveness that occurred for a narrow trench with perpendicular walls was due a lateral spreading of the coolant and reduced coolant jet separation. The cooling levels exhibited by these particular geometries are comparable to shaped holes, but much easier and cheaper to manufacture.

Conjugate Heat Transfer and Film Cooling of a Multi-Stage Cooling Scheme

2008 ◽  
Author(s):  
M. Ghorab ◽  
S. I. Kim ◽  
I. Hassan
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Gas Turbines ◽  
Conjugate Heat Transfer ◽  
Density Ratio ◽  
Design Parameters ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Multi Stage ◽  
Internal Gap

Cooling techniques play a key role in improving efficiency and power output of modern gas turbines. The conjugate technique of film and impingement cooling schemes is considered in this study. The Multi-Stage Cooling Scheme (MSCS) involves coolant passing from inside to outside turbine blade through two stages. The first stage; the coolant passes through first hole to internal gap where the impinging jet cools the external layer of the blade. Finally, the coolant passes through the internal gap to the second hole which has specific designed geometry for external film cooling. The effect of design parameters, such as, offset distance between two-stage holes, gap height, and inclination angle of the first hole, on upstream conjugate heat transfer rate and downstream film cooling effectiveness performance are investigated computationally. An Inconel 617 alloy with variable properties is selected for the solid material. The conjugate heat transfer and film cooling characteristics of MSCS are analyzed across blowing ratios of Br = 1 and 2 for density ratio, 2. This study presents upstream wall temperature distributions due to conjugate heat transfer for different gap design parameters. The maximum film cooling effectiveness with upstream conjugate heat transfer is less than adiabatic film cooling effectiveness by 24–34%. However, the full coverage of cooling effectiveness in spanwise direction can be obtained using internal cooling with conjugate heat transfer, whereas adiabatic film cooling effectiveness has narrow distribution.

Film Cooling Effectiveness of Transonic Turbine Vane Suction Side With Compound-Angle Shaped Hole Configuration

2015 ◽  
Author(s):  
Shang-Feng Yang ◽  
Je-Chin Han ◽  
Alexander MirzaMoghadam ◽  
Ardeshir Riahi
Keyword(s):  
Transonic Flow ◽  
Film Cooling ◽  
Surface Film ◽  
Density Ratio ◽  
Suction Side ◽  
Flow Loop ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Turbine Vane ◽  
Compound Angle

This paper studies the effect of transonic flow velocity on local film cooling effectiveness distribution of turbine vane suction side, experimentally. A conduction-free Pressure Sensitive Paint (PSP) method is used to determine the local film cooling effectiveness. Tests were performed in a five-vane annular cascade at Texas A&M Turbomachinery laboratory blow-down flow loop facility. The exit Mach numbers are controlled to be 0.7, 0.9, and 1.1, from subsonic to transonic flow conditions. Three foreign gases N2, CO2 and Argon/SF6 mixture are selected to study the effects of three coolant-to-mainstream density ratios, 1.0, 1.5, and 2.0 on film cooling. Four averaged coolant blowing ratios in the range, 0.7, 1.0, 1.3 and 1.6 are investigated. The test vane features 3 rows of radial-angle cylindrical holes around the leading edge, and 2 rows of compound-angle shaped holes on the suction side. Results suggest that the PSP technique is capable of producing clear and detailed film cooling effectiveness contours at transonic condition. The effects of coolant to mainstream blowing ratio, density ratio, and exit Mach number on the vane suction-surface film cooling distribution are obtained, and the consequence results are presented and explained in this investigation.

Effects of Inlet Swirl on Pressure Side Film Cooling of Neighboring Vane Surface

2019 ◽  
Vol 11 (6) ◽  
Author(s):  
Yang Zhang ◽  
Yifei Li ◽  
Xiutao Bian ◽  
Xin Yuan
Keyword(s):  
Film Cooling ◽  
Swirling Flow ◽  
Density Ratio ◽  
Suction Side ◽  
Scale Model ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Lean Combustion ◽  
Inlet Swirl ◽  
Nozzle Guide

The lean combustion chamber of low NOx emission engines has a short distance between combustion outlet and nozzle guide vanes (NGVs), with strong swirlers located upstream of the turbine inlet to from steady circulation in the combustion region. Although the lean combustion design benefits emission control, it complicates the turbine’s aerodynamics and heat transfer. The strong swirling flow will influence the near-wall flow field where film cooling acts. This research investigates the influence of inlet swirl on the film cooling of cascades. The test cascades are a 1.95 scale model based on the GE-E3 profile, with an inlet Mach number of 0.1 and Reynolds number of 1.48 × 105. Film cooling effectiveness is measured with pressure-sensitive paint (PSP) technology, with nitrogen simulating coolant at a density ratio of near to 1.0. Two neighboring passages are investigated simultaneously, so that pressure and suction side the film cooling effectiveness can be compared. The inlet swirl is produced by a swirler placed upstream, near the inlet, with five positions along the pitchwise direction. These are as follows: blade 1 aligned, passage 1–2 aligned, blade 2 aligned, passage 2–3 aligned and blade 3 aligned. According to the experimental results, the near-hub region is strongly influenced by inlet swirl, where the averaged film cooling effectiveness can differ by up to 12% between the neighboring blades. At the spanwise location Z/Span = 0.7, when the inlet swirl is moved from blade 1 aligned (position 5) to blade 2 aligned (position 3), the film cooling effectiveness in a small area near the endwall can change by up to 100%.

Film Cooling Measurements for a Laidback Fan-Shaped Hole: Effect of Coolant Crossflow on Cooling Effectiveness and Heat Transfer

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Marc Fraas ◽  
Tobias Glasenapp ◽  
Achmed Schulz ◽  
Hans-Jörg Bauer
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Film Cooling ◽  
Gas Flow ◽  
Density Ratio ◽  
Coolant Flow ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
Film Cooling Holes

Internal coolant passages of gas turbine vanes and blades have various orientations relative to the external hot gas flow. As a consequence, the inflow of film cooling holes varies as well. To further identify the influencing parameters of film cooling under varying inflow conditions, the present paper provides detailed experimental data. The generic study is performed in a novel test rig, which enables compliance with all relevant similarity parameters including density ratio. Film cooling effectiveness as well as heat transfer of a 10–10–10 deg laidback fan-shaped cooling hole is discussed. Data are processed and presented over 50 hole diameters downstream of the cooling hole exit. First, the parallel coolant flow setup is discussed. Subsequently, it is compared to a perpendicular coolant flow setup at a moderate coolant channel Reynolds number. For the perpendicular coolant flow, asymmetric flow separation in the diffuser occurs and leads to a reduction of film cooling effectiveness. For a higher coolant channel Reynolds number and perpendicular coolant flow, asymmetry increases and cooling effectiveness is further decreased. An increase in blowing ratio does not lead to a significant increase in cooling effectiveness. For all cases investigated, heat transfer augmentation due to film cooling is observed. Heat transfer is highest in the near-hole region and decreases further downstream. Results prove that coolant flow orientation has a severe impact on both parameters.

Unsteady Wake and Coolant Density Effects on Turbine Blade Film Cooling Using PSP Technique

2010 ◽  
Author(s):  
Akhilesh P. Rallabandi ◽  
Shiou-Jiuan Li ◽  
Je-Chin Han
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Leading Edge ◽  
Suction Side ◽  
Suction Surface ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Unsteady Wake ◽  
Lift Off ◽  
Film Cooling Holes

The effect of an unsteady stator wake (simulated by wake rods mounted on a spoke wheel wake generator) on the modeled rotor blade is studied using the Pressure Sensitive Paint (PSP) mass transfer analogy method. Emphasis of the current study is on the mid-span region of the blade. The flow is in the low Mach number (incompressible) regime. The suction (convex) side has simple angled cylindrical film-cooling holes; the pressure (concave) side has compound angled cylindrical film cooling holes. The blade also has radial shower-head leading edge film cooling holes. Strouhal numbers studied range from 0 to 0.36; the exit Reynolds Number based on the axial chord is 530,000. Blowing ratios range from 0.5 to 2.0 on the suction side; 0.5 to 4.0 on the pressure side. Density ratios studied range from 1.0 to 2.5, to simulate actual engine conditions. The convex suction surface experiences film-cooling jet lift-off at higher blowing ratios, resulting in low effectiveness values. The film coolant is found to reattach downstream on the concave pressure surface, increasing effectiveness at higher blowing ratios. Results show deterioration in film cooling effectiveness due to increased local turbulence caused by the unsteady wake, especially on the suction side. Results also show a monotonic increase in film-cooling effectiveness on increasing the coolant to mainstream density ratio.

Unsteady Wake and Coolant Density Effects on Turbine Blade Film Cooling Using Pressure Sensitive Paint Technique

2012 ◽  
Vol 134 (8) ◽  
Author(s):  
Akhilesh P. Rallabandi ◽  
Shiou-Jiuan Li ◽  
Je-Chin Han
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Suction Side ◽  
Pressure Sensitive Paint ◽  
Suction Surface ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Pressure Sensitive ◽  
Unsteady Wake ◽  
Film Cooling Holes

The effect of an unsteady stator wake (simulated by wake rods mounted on a spoke-wheel wake generator) on the modeled rotor blade is studied using the pressure sensitive paint (PSP) mass-transfer analogy method. Emphasis of the current study is on the midspan region of the blade. The flow is in the low Mach number (incompressible) regime. The suction (convex) side has simple angled cylindrical film-cooling holes; the pressure (concave) side has compound angled cylindrical film-cooling holes. The blade also has radial shower-head leading edge film-cooling holes. Strouhal numbers studied range from 0 to 0.36; the exit Reynolds number based on the axial chord is 530,000. Blowing ratios range from 0.5 to 2.0 on the suction side and 0.5 to 4.0 on the pressure side. Density ratios studied range from 1.0 to 2.5, to simulate actual engine conditions. The convex suction surface experiences film-cooling jet lift-off at higher blowing ratios, resulting in low effectiveness values. The film coolant is found to reattach downstream on the concave pressure surface, increasing effectiveness at higher blowing ratios. Results show deterioration in film-cooling effectiveness due to increased local turbulence caused by the unsteady wake, especially on the suction side. Results also show a monotonic increase in film-cooling effectiveness on increasing the coolant to mainstream density ratio.

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