Effect of Density Ratio on Film-Cooling Effectiveness Distribution and Its Uniformity for Several Hole Geometries on a Flat Plate

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Jiaxu Yao ◽  
Jin Xu ◽  
Ke Zhang ◽  
Jiang Lei ◽  
Lesley M. Wright
Keyword(s):  
Flat Plate ◽  
Film Cooling ◽  
Density Ratio ◽  
Lateral Spread ◽  
Spanwise Direction ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cylindrical Holes ◽  
Density Ratios ◽  
Compound Angle

The film cooling effectiveness distribution and its uniformity downstream of a row of film cooling holes on a flat plate are investigated by pressure sensitive paint (PSP) under different density ratios. Several hole geometries are studied, including streamwise cylindrical holes, compound-angled cylindrical holes, streamwise fan-shape holes, compound-angled fan-shape holes, and double-jet film-cooling (DJFC) holes. All of them have an inclination angle (θ) of 35 deg. The compound angle (β) is 45 deg. The fan-shape holes have a 10 deg expansion in the spanwise direction. For a fair comparison, the pitch is kept as 4d for the cylindrical and the fan-shape holes, and 8d for the DJFC holes. The uniformity of effectiveness distribution is described by a new parameter (Lateral-Uniformity, LU) defined in this paper. The effects of density ratios (DR = 1.0, 1.5 and 2.5) on the film-cooling effectiveness and its uniformity are focused. Differences among geometries and effects of blowing ratios (M = 0.5, 1.0, 1.5, and 2.0) are also considered. The results show that at higher density ratios, the lateral spread of the discrete-hole geometries (i.e., the cylindrical and the fan-shape holes) is enhanced, while the DJFC holes is more advantageous in film-cooling effectiveness. Mostly, a higher lateral-uniformity is obtained at DR = 2.5 due to better coolant coverage and enhanced lateral spread, but the effects of the density ratio on the lateral-uniformity are not monotonic in some cases. Utilizing the compound angle configuration leads to an increased lateral-uniformity due to a stronger spanwise motion of the jet. Generally, with a higher blowing ratio, the lateral-uniformity of the discrete-hole geometries decreases due to narrower traces, while that of the DJFC holes increases due to a stronger spanwise movement.

Film Cooling Effectiveness From Two-Row of Compound Angled Cylindrical Holes Using PSP Technique

2018 ◽  
Author(s):  
Nian Wang ◽  
Mingjie Zhang ◽  
Chao-Cheng Shiau ◽  
Je-Chin Han
Keyword(s):  
Flat Plate ◽  
Film Cooling ◽  
Density Ratio ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Free Stream Turbulence ◽  
Cooling Hole ◽  
Cylindrical Holes ◽  
Inclined Angle ◽  
Density Ratios

This study investigates the combined effects of blowing ratio and density ratio on flat plate film cooling effectiveness from two-row of compound angled cylindrical holes. Two arrangements of two-row compound angled cylindrical holes are tested: the first row and second row are oriented in staggered but same compound angled direction (β = +45° for the first row, +45° for the second row); the first row and second row are oriented in inline but opposite direction (β = +45° for the first row, −45° for the second row). Each cooling hole is 4 mm in diameter with an inclined angle 30°. The streamwise distance between the two rows is fixed at 4d and the spanwise pitch between the two holes (p) is 4d, 6d, and 8d, respectively. The experiments are performed at four blowing ratios (M = 0.5, 1.0, 1.5, 2.0) and three density ratios (DR = 1.0, 1.5, 2.0). The free stream turbulence intensity is kept at 6%. Detailed film cooling effectiveness distributions are obtained using the steady state pressure-sensitive paint (PSP) technique. The detailed film cooling effectiveness contours are presented and the spanwise averaged film effectiveness results are compared over the range of flow parameters. Film cooling effectiveness correlations are developed for both inline and staggered compound angled cylindrical holes. The results provide baseline information for the flat plate film cooling analysis with two-row of compound angled cylindrical holes.

Effect of Density Ratio on Film-Cooling Effectiveness Distribution and its Uniformity for Several Hole Geometries on a Flat Plate

2017 ◽  
Author(s):  
Jiaxu Yao ◽  
Jin Xu ◽  
Ke Zhang ◽  
Jiang Lei ◽  
Lesley M. Wright
Keyword(s):  
Flat Plate ◽  
Film Cooling ◽  
Cylindrical Hole ◽  
Lateral Spread ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Density Ratios ◽  
Film Cooling Holes ◽  
Compound Angle ◽  
Effects Of Density

Film cooling effectiveness distribution and its uniformity downstream of a row of film cooling holes on a flat plate are investigated by Pressure Sensitive Paint (PSP) under different density ratios. Several hole geometries are studied, including a streamwise cylindrical hole, a compound-angled cylindrical hole, a streamwise fan-shape hole, a compound-angled fan-shape hole, and double-jet film-cooling (DJFC) holes. All of them have an inclination angle (θ) of 35°.The compound angle (β) is 45°. The fan-shape hole has a 10° expansion in the spanwise direction. In order to have a fair comparison, the pitches are kept as 4d for the cylindrical and the fan-shape holes, and 8d for the double-jet film-cooling holes. The investigated uniformity of effectiveness distribution is described by a new parameter (Lateral-Uniformity, LU) defined in this paper. Effects of density ratios (DR = 1.0, 1.5 and 2.5) on film-cooling effectiveness and its uniformity are focused. Differences among geometries and effects of blowing ratios (M = 0.5, 1.0, 1.5, and 2.0) are also considered. Results show that at higher density ratios, the lateral spread for discrete-hole geometries (i.e., the cylindrical and the fan-shape holes) is enhanced, and the DJFC holes is more advantageous, and the high effectiveness region near the downstream hole exit is larger. Mostly, increased lateral-uniformity is obtained at DR = 2.5 due to better coolant coverage and enhanced lateral spread, but the effects of density ratios on lateral-uniformity are not monotonic in some cases. Utilizing compound angle configuration leads to increased lateral-uniformity due to stronger spanwise motion of the jet. Generally, with higher blowing ratio, the lateral-uniformity for the discrete-hole geometries decreases due to narrower traces, while it for the DJFC holes increases due to stronger spanwise movement.

Influence of Coolant Density on Turbine Platform Film-Cooling With Stator–Rotor Purge Flow and Compound-Angle Holes

2014 ◽  
Vol 6 (4) ◽  
Author(s):  
Kevin Liu ◽  
Shang-Feng Yang ◽  
Je-Chin Han
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Fundamental Parameters ◽  
Blowing Ratio ◽  
Purge Flow ◽  
Cylindrical Holes ◽  
Exit Mach Number ◽  
Compound Angle

A detailed parametric study of film-cooling effectiveness was carried out on a turbine blade platform. The platform was cooled by purge flow from a simulated stator–rotor seal combined with discrete hole film-cooling. The cylindrical holes and laidback fan-shaped holes were accessed in terms of film-cooling effectiveness. This paper focuses on the effect of coolant-to-mainstream density ratio on platform film-cooling (DR = 1 to 2). Other fundamental parameters were also examined in this study—a fixed purge flow of 0.5%, three discrete-hole film-cooling blowing ratios between 1.0 and 2.0, and two freestream turbulence intensities of 4.2% and 10.5%. Experiments were done in a five-blade linear cascade with inlet and exit Mach number of 0.27 and 0.44, respectively. Reynolds number of the mainstream flow was 750,000 and was based on the exit velocity and chord length of the blade. The measurement technique adopted was the conduction-free pressure sensitive paint (PSP) technique. Results indicated that with the same density ratio, shaped holes present higher film-cooling effectiveness and wider film coverage than the cylindrical holes, particularly at higher blowing ratios. The optimum blowing ratio of 1.5 exists for the cylindrical holes, whereas the effectiveness for the shaped holes increases with an increase of blowing ratio. Results also indicate that the platform film-cooling effectiveness increases with density ratio but decreases with turbulence intensity.

High Resolution Film Cooling Effectiveness Comparison of Axial and Compound Angle Holes on the Suction Side of a Turbine Vane

2006 ◽  
Author(s):  
Scot K. Waye ◽  
David G. Bogard
Keyword(s):  
High Resolution ◽  
Flat Plate ◽  
Film Cooling ◽  
Density Ratio ◽  
Suction Side ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Turbine Vane ◽  
Adiabatic Effectiveness ◽  
Compound Angle

Film cooling adiabatic effectiveness for axial and compound angle holes on the suction side of a simulated turbine vane was investigated to determine the relative performance of these configurations. The effect of the surface curvature was also evaluated by comparing to previous curvature studies and flat plate film cooling results. Experiments were conducted for varying coolant density ratio, mainstream turbulence levels, and hole spacing. Results from these measurements showed that for mild curvature, 2r/d ≈ 160, flat plate results are sufficient to predict the cooling effectiveness. Furthermore, the compound angle injection improves adiabatic effectiveness for higher blowing ratios, similar to previous studies using flat plate facilities.

Film Cooling Effectiveness From Two Rows of Compound Angled Cylindrical Holes Using Pressure-Sensitive Paint Technique

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Nian Wang ◽  
Mingjie Zhang ◽  
Chao-Cheng Shiau ◽  
Je-Chin Han
Keyword(s):  
Flat Plate ◽  
Film Cooling ◽  
Density Ratio ◽  
Pressure Sensitive Paint ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Pressure Sensitive ◽  
Staggered Arrangement ◽  
Cylindrical Holes

This study investigates the effects of blowing ratio, density ratio, and spanwise pitch on the flat plate film cooling from two rows of compound angled cylindrical holes. Two arrangements of two-row compound angled cylindrical holes are tested: (a) the first row and the second row are oriented in staggered and same compound angled direction (β = +45 deg for the first row and +45 deg for the second row); (b) the first row and the second row are oriented in inline and opposite direction (β = +45 deg for the first row and −45 deg for the second row). The cooling hole is 4 mm in diameter with an inclined angle of 30 deg. The streamwise row-to-row spacing is fixed at 3d, and the spanwise hole-to-hole (p) is varying from 4d, 6d to 8d for both designs. The film cooling effectiveness measurements were performed in a low-speed wind tunnel in which the turbulence intensity is kept at 6%. There are 36 cases for each design including four blowing ratios (M = 0.5, 1.0, 1.5, and 2.0), three density ratios (DR = 1.0, 1.5, and 2.0), and three hole-to-hole spacing (p/d = 4, 6, and 8). The detailed film cooling effectiveness distributions were obtained by using the steady-state pressure-sensitive paint (PSP) technique. The spanwise-averaged cooling effectiveness are compared over the range of flow parameters. Some interesting observations are discovered including blowing ratio effect strongly depending on geometric design; staggered arrangement of the hole with same orientation does not yield better effectiveness at higher blowing ratio. Currently, film cooling effectiveness correlation of two-row compound angled cylindrical holes is not available, so this study developed the correlations for the inline arrangement of holes with opposing angles and the staggered arrangement of holes with same angles. The results and correlations are expected to provide useful information for the two-row flat plate film cooling analysis.

Interaction of Flow and Film-Cooling Effectiveness Between Double-Jet Film-Cooling Holes With Various Spanwise Distances

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Jiaxu Yao ◽  
Jin Xu ◽  
Ke Zhang ◽  
Jiang Lei ◽  
Lesley M. Wright
Keyword(s):  
Flat Plate ◽  
Film Cooling ◽  
Density Ratio ◽  
Vortex Pair ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Film Cooling Holes ◽  
Two Jets ◽  
Compound Angle

The interaction of flow and film-cooling effectiveness between jets of double-jet film-cooling (DJFC) holes on a flat plate is studied experimentally. The time-averaged flow field in several axial positions (X/d = −2.0, 1.0, and 5.0) is obtained through a seven-hole probe. The downstream film-cooling effectiveness on the flat plate is measured by pressure sensitive paint (PSP). The inclination angle (θ) of all the holes is 35 deg, and the compound angle (β) is ±45 deg. Effects of the spanwise distance (p = 0, 0.5d, 1.0d, 1.5d, and 2.0d) between the two interacting jets of DJFC holes are studied, while the streamwise distance (s) is kept as 3d. The blowing ratio (M) varies as 0.5, 1.0, 1.5, and 2.0. The density ratio (DR) is maintained at 1.0. Results show that the interaction between the two jets of DJFC holes has different effects at different spanwise distances. For a small spanwise distance (p/d = 0), the interaction between the jets presents a pressing effect. The downstream jet is pressed down and kept attached to the surface by the upstream one. The effectiveness is not sensitive to blowing ratios. For mid-spanwise distances (p/d = 0.5 and 1.0), the antikidney vortex pair dominates the interaction and pushes both of the jets down, thus leading to better coolant coverage and higher effectiveness. As the spanwise distance becomes larger (p/d ≥ 1.5), the pressing effect almost disappears, and the antikidney vortex pair effect is weaker. The jets separate from each other and the coolant coverage decreases. At a higher blowing ratio, the interaction between the jets of DJFC holes happens later.

Film-Cooling Performance of Anti-Vortex Hole on a Flat Plate

2011 ◽  
Author(s):  
Diganta P. Narzary ◽  
Christopher LeBlanc ◽  
Srinath Ekkad
Keyword(s):  
Flat Plate ◽  
Film Cooling ◽  
Density Ratio ◽  
Poor Performance ◽  
Diameter Ratio ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Density Ratios

Film cooling performance of two hole geometries is evaluated on a flat plate surface with steady-state IR (infrared thermography) technique. The base geometry is a simple cylindrical hole design inclined at 30° from the surface with pitch-to-diameter ratio of 3.0. The second geometry is an anti-vortex design where the two side holes, also of the same diameter, branch out from the root at 15° angle. The pitch-to-diameter ratio is 6.0 between the main holes. The mainstream Reynolds number is 3110 based on the coolant hole diameter. Two secondary fluids — air and carbon-dioxide — were used to study the effects of coolant-to-mainstream density ratio (DR = 0.95 and 1.45) on film cooling effectiveness. Several blowing ratios in the range 0.5 –4.0 were investigated independently at the two density ratios. Results indicate significant improvement in effectiveness with anti-vortex holes compared to cylindrical holes at all the blowing ratios studied. At any given blowing ratio, the anti-vortex hole design uses 50% less coolant and provides at least 30–40% higher cooling effectiveness. The use of relatively dense secondary fluid improves effectiveness immediately downstream of the anti-vortex holes but leads to poor performance downstream.

High-Resolution Film Cooling Effectiveness Comparison of Axial and Compound Angle Holes on the Suction Side of a Turbine Vane

2006 ◽  
Vol 129 (2) ◽  
pp. 202-211 ◽  
Author(s):  
Scot K. Waye ◽  
David G. Bogard
Keyword(s):  
High Resolution ◽  
Flat Plate ◽  
Film Cooling ◽  
Density Ratio ◽  
Suction Side ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Turbine Vane ◽  
Adiabatic Effectiveness ◽  
Compound Angle

Film cooling adiabatic effectiveness for axial and compound angle holes on the suction side of a simulated turbine vane was investigated to determine the relative performance of these configurations. The effect of the surface curvature was also evaluated by comparing to previous curvature studies and flat plate film cooling results. Experiments were conducted for varying coolant density ratio, mainstream turbulence levels, and hole spacing. Results from these measurements showed that for mild curvature, 2r∕d≈160, flat plate results are sufficient to predict the cooling effectiveness. Furthermore, the compound angle injection improves adiabatic effectiveness for higher blowing ratios, similar to previous studies using flat plate facilities.

Effect of Density Ratio on Flat Plate Film Cooling With Shaped Holes Using PSP

2010 ◽  
Author(s):  
Lesley M. Wright ◽  
Stephen T. McClain ◽  
Michael D. Clemenson
Keyword(s):  
Flat Plate ◽  
Turbulence Intensity ◽  
Film Cooling ◽  
Density Ratio ◽  
Freestream Turbulence ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Cylindrical Holes ◽  
Film Cooling Holes

Detailed film cooling effectiveness distributions are obtained on a flat plate using the pressure sensitive paint (PSP) technique. The applicability of the PSP technique is expanded to include a coolant-to-mainstream density ratio of 1.4. The effect of density ratio on the film cooling effectiveness is coupled with varying blowing ratio (M = 0.25–2.0), freestream turbulence intensity (Tu = 1%–12.5%), and film hole geometry. The effectiveness distributions are obtained on three separate flat plates containing either simple angle, cylindrical holes, simple angle, fanshaped holes (α = 10°), or simple angle, laidback, fanshaped holes (α = 10°, γ = 10°). In all three cases, the film cooling holes are angled at θ = 35° from the mainstream flow. Using the PSP technique, the combined effects of blowing ratio, turbulence intensity, and density ratio are captured for each film cooling geometry. The detailed film cooling effectiveness distributions, for cylindrical holes, clearly show the effectiveness at the lowest blowing ratio is enhanced at the lower density ratio (DR = 1). However, as the blowing ratio increases, a transition occurs, leading to increased effectiveness with the elevated density ratio (DR = 1.4). In addition, the PSP technique captures an upstream shift of the coolant jet reattachment point as the density ratio increases or the turbulence intensity increases (at moderate blowing ratios for cylindrical holes). With the decreased momentum of the shaped film cooling holes, the greatest film cooling effectiveness is obtained at the lower density ratio (DR = 1.0) over the entire range of blowing ratios considered. In all cases, as the freestream turbulence intensity increases, the film effectiveness decreases; this effect is reduced as the blowing ratio increases for all three film hole configurations.

Effect of Breakout Angle on Tripod Injection Hole Geometries on Flat Plate Film Cooling

2012 ◽  
Author(s):  
Christopher LeBlanc ◽  
Sridharan Ramesh ◽  
Srinath Ekkad ◽  
Mary Anne Alvin
Keyword(s):  
Flat Plate ◽  
Film Cooling ◽  
Density Ratio ◽  
Diameter Ratio ◽  
Cylindrical Hole ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Shaped Hole ◽  
Jet Interactions ◽  
Density Ratios

In this study, effect of breakout angle of side holes from the main hole in a tripod hole design on film cooling performance is evaluated on a flat plate surface with steady-state IR (infrared thermography) technique. The designs are compared a cylindrical hole design inclined at 30° from the surface with pitch-to-diameter ratio of 3.0 and a shaped hole design, which is identical to the cylindrical hole design with the addition of adding a 10° flare and laydown to the exit on the mainstream surface. The two tripod hole designs are one where the two side holes, also of the same diameter, branch from the root at a 15° angle while maintaining the same 30° inclination as the cylindrical and shaped designs witha pitch-to-diameter ratio between the main holes for this design is 6.0. The other tripod hole design is a modified tripod hole design that increases the branch angle to 30°, which has the added effect of increasing the pitch-to-diameter ratio between the main holes to 7.5. Two secondary fluids — air and carbon-dioxide — were used to study the effects of coolant-to-mainstream density ratio (DR = 0.95 and 1.45) on film cooling effectiveness. Several blowing ratios in the range 0.5–4.0 were investigated independently at the two density ratios. Results show that the tripod hole design provides similar film cooling effectiveness as the shaped hole case with overall reduced coolant usage. Increasing the breakout angle from 15° to 30° reduces overall cooling effectiveness but increases jet-to-jet interactions.

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