Effect of Jet Pulsing on Film Cooling—Part I: Effectiveness and Flow-Field Temperature Results

2006 ◽  
Vol 129 (2) ◽  
pp. 232-246 ◽  
Author(s):  
Sarah M. Coulthard ◽  
Ralph J. Volino ◽  
Karen A. Flack
Keyword(s):  
Film Cooling ◽  
Infrared Camera ◽  
Temperature Fields ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Cold Wire ◽  
Duty Cycles ◽  
Cooling Behavior ◽  
Film Cooling Holes

Pulsed film cooling was studied experimentally to determine its effect on film-cooling effectiveness. The film-cooling jets were pulsed using solenoid valves in the supply air line. Cases with a single row of cylindrical film-cooling holes inclined at 35 deg to the surface of a flat plate were considered at blowing ratios of 0.25, 0.5, 1.0, and 1.5 for a variety of pulsing frequencies and duty cycles. Temperature measurements were made using an infrared camera, thermocouples, and cold-wire anemometry. Hot-wire anemometry was used for velocity measurements. The local film-cooling effectiveness was calculated based on the measured temperatures, and the results were compared to baseline cases with continuous blowing. Phase-locked flow temperature fields were determined from cold-wire surveys. Pulsing at high frequencies helped to improve film-cooling effectiveness in some cases by reducing overall jet liftoff. At lower frequencies, pulsing tended to have the opposite effect. With the present geometry and a steady mainflow, pulsing did not provide an overall benefit. The highest overall effectiveness was achieved with continuous jets and a blowing ratio of 0.5. The present results may prove useful for understanding film-cooling behavior in engines, where mainflow unsteadiness causes film-cooling jet pulsation.

Effect of Jet Pulsing on Film Cooling: Part 1— Effectiveness and Flowfield Temperature Results

2006 ◽  
Author(s):  
Sarah M. Coulthard ◽  
Ralph J. Volino ◽  
Karen A. Flack
Keyword(s):  
Film Cooling ◽  
Infrared Camera ◽  
Temperature Fields ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Cold Wire ◽  
Duty Cycles ◽  
Cooling Behavior ◽  
Film Cooling Holes

Pulsed film cooling was studied experimentally to determine its effect on film cooling effectiveness. The film cooling jets were pulsed using solenoid valves in the supply air line. Cases with a single row of cylindrical film cooling holes inclined at 35 degrees to the surface of a flat plate were considered at blowing ratios of 0.25, 0.5, 1.0, and 1.5 for a variety of pulsing frequencies and duty cycles. Temperature measurements were made using an infrared camera, thermocouples, and cold wire anemometry. Hot wire anemometry was used for velocity measurements. The local film cooling effectiveness was calculated based on the measured temperatures and the results were compared to baseline cases with continuous blowing. Phase locked flow temperature fields were determined from cold wire surveys. Pulsing at high frequencies helped to improve film cooling effectiveness in some cases by reducing overall jet liftoff. At lower frequencies, pulsing tended to have the opposite effect. With the present geometry and a steady mainflow, pulsing did not provide an overall benefit. The highest overall effectiveness was achieved with continuous jets and a blowing ratio of 0.5. The present results may prove useful for understanding film cooling behavior in engines, where mainflow unsteadiness causes film cooling jet pulsation.

Effect of Jet Pulsing on Film Cooling—Part II: Heat Transfer Results

2006 ◽  
Vol 129 (2) ◽  
pp. 247-257 ◽  
Author(s):  
Sarah M. Coulthard ◽  
Ralph J. Volino ◽  
Karen A. Flack
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Film Cooling ◽  
Infrared Camera ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Duty Cycles ◽  
Horseshoe Vortices ◽  
Cooling Behavior ◽  
Film Cooling Holes

Pulsed film cooling was studied experimentally to determine its effect on film-cooling effectiveness and heat transfer. The film-cooling jets were pulsed using solenoid valves in the supply air line. Cases with a single row of cylindrical film-cooling holes inclined at 35 deg to the surface of a flat plate were considered at blowing ratios of 0.25, 0.5, 1.0, and 1.5 for a variety of pulsing frequencies and duty cycles. Temperature measurements were made using an infrared camera and thermocouples. The plate was equipped with constant flux surface heaters, and data were acquired for each flow condition with the plate both heated and unheated. The local film-cooling effectiveness, Stanton numbers, and heat flux ratios were calculated and compared to baseline cases with continuous blowing and no blowing. Stanton number signatures on the surface provided evidence of flow structures, including horseshoe vortices wrapping around the film-cooling jets and vortices within the jets. Pulsing tends to increase Stanton numbers, and the effect tends to increase with pulsing frequency and duty cycle. Some exceptions were observed, however, at the highest frequencies tested. Overall heat flux ratios also show that pulsing tends to have a detrimental effect with some exceptions at the highest frequencies. The best overall film cooling was achieved with continuous jets and a blowing ratio of 0.5. The present results may prove useful for understanding film-cooling behavior in engines, where mainflow unsteadiness causes film-cooling jet pulsation.

Effect of Jet Pulsing on Film Cooling: Part 2 — Heat Transfer Results

2006 ◽  
Author(s):  
Sarah M. Coulthard ◽  
Ralph J. Volino ◽  
Karen A. Flack
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Film Cooling ◽  
Infrared Camera ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Duty Cycles ◽  
Horseshoe Vortices ◽  
Cooling Behavior ◽  
Film Cooling Holes

Pulsed film cooling was studied experimentally to determine its effect on film cooling effectiveness and heat transfer. The film cooling jets were pulsed using solenoid valves in the supply air line. Cases with a single row of cylindrical film cooling holes inclined at 35 degrees to the surface of a flat plate were considered at blowing ratios of 0.25, 0.5, 1.0, and 1.5 for a variety of pulsing frequencies and duty cycles. Temperature measurements were made using an infrared camera and thermocouples. The plate was equipped with constant flux surface heaters, and data were acquired for each flow condition with the plate both heated and unheated. The local film cooling effectiveness, Stanton numbers, and heat flux ratios were calculated and compared to baseline cases with continuous blowing and no blowing. Stanton number signatures on the surface provided evidence of flow structures including horseshoe vortices wrapping around the film cooling jets and vortices within the jets. Pulsing tends to increase Stanton numbers, and the effect tends to increase with pulsing frequency and duty cycle. Some exceptions were observed, however, at the highest frequencies tested. Overall heat flux ratios also show that pulsing tends to have a detrimental effect with some exceptions at the highest frequencies. The best overall film cooling was achieved with continuous jets and a blowing ratio of 0.5. The present results may prove useful for understanding film cooling behavior in engines, where mainflow unsteadiness causes film cooling jet pulsation.

Influence of Coolant Density on Turbine Blade Film Cooling at Transonic Cascade Flow Conditions Using the Pressure Sensitive Paint Technique

2021 ◽  
Author(s):  
Izhar Ullah ◽  
Sulaiman M. Alsaleem ◽  
Lesley M. Wright ◽  
Chao-Cheng Shiau ◽  
Je-Chin Han
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Pressure Side ◽  
Pressure Sensitive Paint ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Pressure Sensitive ◽  
Blade Tip ◽  
Film Cooling Holes

Abstract This work is an experimental study of film cooling effectiveness on a blade tip in a stationary, linear cascade. The cascade is mounted in a blowdown facility with controlled inlet and exit Mach numbers of 0.29 and 0.75, respectively. The free stream turbulence intensity is measured to be 13.5 % upstream of the blade’s leading edge. A flat tip design is studied, having a tip gap of 1.6%. The blade tip is designed to have 15 shaped film cooling holes along the near-tip pressure side (PS) surface. Fifteen vertical film cooling holes are placed on the tip near the pressure side. The cooling holes are divided into a 2-zone plenum to locally maintain the desired blowing ratios based on the external pressure field. Two coolant injection scenarios are considered by injecting coolant through the tip holes only and both tip and PS surface holes together. The blowing ratio (M) and density ratio (DR) effects are studied by testing at blowing ratios of 0.5, 1.0, and 1.5 and three density ratios of 1.0, 1.5, and 2.0. Three different foreign gases are used to create density ratio effect. Over-tip flow leakage is also studied by measuring the static pressure distributions on the blade tip using the pressure sensitive paint (PSP) measurement technique. In addition, detailed film cooling effectiveness is acquired to quantify the parametric effect of blowing ratio and density ratio on a plane tip design. Increasing the blowing ratio and density ratio resulted in increased film cooling effectiveness at all injection scenarios. Injecting coolant on the PS and the tip surface also resulted in reduced leakage over the tip. The conclusions from this study will provide the gas turbine designer with additional insight on controlling different parameters and strategically placing the holes during the design process.

Effects of Blowing Ratio on Multiple Shallow Angle Film Cooling Holes

2012 ◽  
Vol 225 ◽  
pp. 49-54 ◽  
Author(s):  
Kamil Abdullah ◽  
Ken Ichi Funazaki
Keyword(s):  
Temperature Field ◽  
Surface Temperature ◽  
Film Cooling ◽  
Cooling Effectiveness ◽  
Ir Camera ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Hole Configuration ◽  
The Common ◽  
Film Cooling Holes

This paper presents the investigation on the effects of the blowing ratio of multiple shallow angle film cooling holes. Multiple film cooling holes having a shallow hole angle (θ = 20°), arranged to perform in-line hole configuration has been considered in the present study. The investigation focuses on the effects of high blowing ratio of the film cooling effectiveness which have been carried out at ReD= 3100 and BR = 2.0, 3.0 and 4.0. The experiments make use of the IR camera in capturing the surface temperature to determine the film cooling effectiveness. The contours of the film cooling effectiveness distribution together with plots on laterally average film cooling effectiveness along the x/D are presented. The discussions have been made with a support of the temperature field captured at x/D = 3, 13, 23, and 33. The results clearly show the benefit of the employment of shallow hole angle (θ = 20°) at high blowing ratio which is much more superior in comparison to the common hole configuration (θ = 35°).

Effect of Unheated Starting Lengths on Film Cooling Experiments

2006 ◽  
Vol 128 (3) ◽  
pp. 579-588 ◽  
Author(s):  
Sarah M. Coulthard ◽  
Ralph J. Volino ◽  
Karen A. Flack
Keyword(s):  
Film Cooling ◽  
Infrared Camera ◽  
Stanton Number ◽  
Flow Structures ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Single Row ◽  
Heat Transfer Coefficients ◽  
Film Cooling Holes

The effect of an unheated starting length upstream of a row of film cooling holes was studied experimentally to determine its effect on heat transfer coefficients downstream of the holes. Cases with a single row of cylindrical film cooling holes inclined at 35deg to the surface of a flat plate were considered at blowing ratios of 0.25, 0.5, 1.0, and 1.5. For each case, experiments were conducted to determine the film-cooling effectiveness and the Stanton number distributions in cases with the surface upstream of the holes heated and unheated. Measurements were made using an infrared camera, thermocouples, and hot and cold-wire anemometry. Ratios were computed of the Stanton number with film cooling (Stf) to corresponding Stanton numbers in cases without film cooling (Sto), but the same surface heating conditions. Contours of these ratios were qualitatively the same regardless of the upstream heating conditions, but the ratios were larger for the cases with a heating starting length. Differences were most pronounced just downstream of the holes and for the lower blowing rate cases. Even 12 diameters downstream of the holes, the Stanton number ratios were 10–15% higher with a heated starting length. At higher blowing rates the differences between the heated and unheated starting length cases were not significant. The differences in Stanton number distributions are related to jet flow structures, which vary with blowing rate.

Film-Cooling Effectiveness on a Gas Turbine Blade Tip Using Pressure-Sensitive Paint

2005 ◽  
Vol 127 (5) ◽  
pp. 521-530 ◽  
Author(s):  
Jaeyong Ahn ◽  
Shantanu Mhetras ◽  
Je-Chin Han
Keyword(s):  
Oxygen Concentration ◽  
Film Cooling ◽  
Pressure Sensitive Paint ◽  
Nitrogen Gas ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Pressure Sensitive ◽  
Blade Tip ◽  
Film Cooling Holes

Effects of the presence of squealer, the locations of the film-cooling holes, and the tip-gap clearance on the film-cooling effectiveness were studied and compared to those for a plane (flat) tip. The film-cooling effectiveness distributions were measured on the blade tip using the pressure-sensitive paint technique. Air and nitrogen gas were used as the film-cooling gases, and the oxygen concentration distribution for each case was measured. The film-cooling effectiveness information was obtained from the difference of the oxygen concentration between air and nitrogen gas cases by applying the mass transfer analogy. Plane tip and squealer tip blades were used while the film-cooling holes were located (a) along the camber line on the tip or (b) along the tip of the pressure side. The average blowing ratio of the cooling gas was 0.5, 1.0, and 2.0. Tests were conducted with a stationary, five-bladed linear cascade in a blow-down facility. The free-stream Reynolds number, based on the axial chord length and the exit velocity, was 1,138,000, and the inlet and the exit Mach numbers were 0.25 and 0.6, respectively. Turbulence intensity level at the cascade inlet was 9.7%. All measurements were made at three different tip-gap clearances of 1%, 1.5%, and 2.5% of blade span. Results show that the locations of the film-cooling holes and the presence of squealer have significant effects on surface static pressure and film-cooling effectiveness, with film-cooling effectiveness increasing with increasing blowing ratio.

Systematic Study on the Fluid Dynamical Behaviour of Streamwise and Laterally Inclined Jets in Crossflow

1997 ◽  
Author(s):  
R.-D. Baier ◽  
W. Koschel ◽  
K.-D. Broichhausen ◽  
G. Fritsch
Keyword(s):  
High Resolution ◽  
Film Cooling ◽  
Large Scale ◽  
Computational Study ◽  
Dynamical Behaviour ◽  
Temperature Fields ◽  
Navier Stokes ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Film Cooling Holes

The design of discrete film cooling holes for gas turbine airfoil applications is governed by a number of parameters influencing both their aerodynamic and thermal behaviour. This numerical and experimental study focuses on the marked differences between film cooling holes with combined streamwise and lateral inclination and film cooling holes with streamwise inclination only. The variation in the blowing angle was chosen on a newly defined and physically motivated basis. High resolution low speed experiments on a large scale turbine airfoil gave insights particularly into the intensified mixing process with lateral ejection. The extensive computational study is performed with the aid of a 3D block-structured Navier-Stokes solver incorporating a low-Reynolds-number k-ε turbulence model. Special attention is paid to mesh generation as a precondition for accurate high-resolution results. The downstream temperature fields of the jets show reduced spanwise variations with increasing lateral blowing angle; these variations are quantified for a comprehensive variety of configurations in terms of adiabatic film cooling effectiveness.

Combined Effects of Wakes and Jet Pulsing on Film Cooling

2007 ◽  
Author(s):  
Kristofer M. Womack ◽  
Ralph J. Volino ◽  
Michael P. Schultz
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Temperature Fields ◽  
Constant Current ◽  
Wake Effect ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cold Wire

Pulsed film cooling jets subject to periodic wakes were studied experimentally. The wakes were generated with a spoked wheel upstream of a flat plate. Cases with a single row of cylindrical film cooling holes inclined at 35 degrees to the surface were considered at blowing ratios, B, of 0.50, and 1.0 with jet pulsing and wake Strouhal numbers of 0.15, 0.30, and 0.60. Wake timing was varied with respect to the pulsing. Temperature measurements were made using an infrared camera, thermocouples, and constant current (cold wire) anemometry. The local film cooling effectiveness and heat transfer coefficient were determined from the measured temperatures. Phase locked flow temperature fields were determined from cold wire surveys. With B = 0.5, wakes and pulsing both lead to a reduction in film cooling effectiveness, and the reduction is larger when wakes and pulsing are combined. With B = 1.0, pulsing again causes a reduction in effectiveness, but wakes tend to counteract this effect somewhat by reducing jet liftoff. At low Strouhal numbers, wake timing had a significant effect on the instantaneous film cooling effectiveness, but wakes in general had very little effect on the time averaged effectiveness. At high Strouhal numbers, the wake effect was stronger, but the wake timing was less important. Wakes increased the heat transfer coefficient strongly and similarly in cases with and without film cooling, regardless of wake timing. Heat transfer coefficient ratios, like the time averaged film cooling effectiveness, did not depend strongly on wake timing for the cases considered.

Effect of Upstream Wake on Passage Flow and Tip Film Cooling Characteristics

2012 ◽  
Author(s):  
Jin Wang ◽  
Bengt Sundén ◽  
Min Zeng ◽  
Qiu-Wang Wang
Keyword(s):  
Film Cooling ◽  
Three Dimensional ◽  
Flow Distribution ◽  
Tip Leakage Flow ◽  
Delta Wings ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Passage Vortex ◽  
Film Cooling Holes

Three-dimensional simulations of the squealer tip on the GE-E3 blade with eight film cooling holes were carried out. To form the wake by the trailing edges of the stator vanes, cylindrical rods and delta wings were placed upstream of the blades. The rods were placed according to three positions, and the influence on the film cooling effectiveness was calculated. Because delta wings were placed upstream of the blades to generate in the vane passage, the passage flow also was investigated. However, the passage vortex generated by the delta wings had a profound effect on the passage flow distribution. For the squealer tip, the cavity contributes to the improvement of the cooling effect in the tip zone. The passage flow and the tip leakage flow influenced by cylindrical rods and delta wings were analyzed using numerical simulations with the blowing ratio of M = 0.5. In addition, calculations with and without cylindrical rods and delta wings were performed and then comparisons were enabled. It was found that the vortex created by delta wings made the passage flow more turbulent and the result indicates a slight effect on the film cooling effectiveness in the tip gap.

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