EFFECTS OF HOLE GEOMETRY ON HEAT (MASS) TRANSFER AND FILM COOLING EFFECTIVENESS

1998 ◽  
Author(s):  
Hyung-Hee Cho ◽  
Byunggu Kim ◽  
Dong Ho Rhee
Keyword(s):  
Mass Transfer ◽  
Film Cooling ◽  
Heat Mass Transfer ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Hole Geometry

scholarly journals Film Cooling Effectiveness and Heat/Mass Transfer Coefficient Measurement Around a Conical-Shaped Hole With a Compound Angle Injection

1999 ◽  
Author(s):  
H. H. Cho ◽  
D. H. Rhee ◽  
B. G. Kim
Keyword(s):  
Mass Transfer ◽  
Film Cooling ◽  
Heat Mass Transfer ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
Shaped Hole ◽  
Hole Geometry ◽  
Compound Angle

The present study investigates local film cooling effectiveness values and heat/mass transfer coefficients around a conical-shaped film cooling hole with compound angle orientations. Three types of film cooling hole geometry are compared in this study; one is cylindrical hole geometry with constant cross section and the others are shaped hole geometries with conically-enlarged hole exits. The shaped holes have cylindrical passage sections at the hole inlet region to obtain a certain pressure drop through the holes. One shaped hole expands 4° in all directions from the middle of hole to the exit. The other shaped hole has the tilted center-line by 4° between the conical and metering holes and is enlarged by 8° to downstream side. The hole area ratios of the exit to the inlet are 2.55 and 2.48, respectively. The compound-angled film cooling jet is ejected through the single holes, which are inclined at 30° to the surface based on the metering hole and are rotatable in lateral direction from 0° to 90°. The blowing rates are changed from 0.5 to 2.0. The naphthalene sublimation technique is used to determine local heat/mass transfer coefficients and local adiabatic/impermeable wall film cooling effectiveness around the injection hole. The results indicate that the injected jet protects the surface effectively with low blowing rates and spreads more widely with the compound angle injections than the axial injection. For the shaped hole enlarged by 4° in all directions, the penetration of jet is reduced and higher cooling performance is obtained even at relatively high blowing rates because the increased hole exit area reduces hole exit velocity. Furthermore, the film cooling effectiveness is fairly uniform near the hole due to the wide lateral spreading of coolant with the expanded cooling hole exit.

Heat (Mass) Transfer and Film Cooling Effectiveness With Injection Through Discrete Holes: Part II—On the Exposed Surface

1995 ◽  
Vol 117 (3) ◽  
pp. 451-460 ◽  
Author(s):  
H. H. Cho ◽  
R. J. Goldstein
Keyword(s):  
Mass Transfer ◽  
Film Cooling ◽  
Heat Mass Transfer ◽  
Saturated Vapor ◽  
Back Surface ◽  
Exposed Surface ◽  
Transfer Coefficients ◽  
Lateral Direction ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness

The heat (mass) transfer coefficient and the film cooling effectiveness are obtained from separate tests using pure air and naphthalene-saturated vapor injected through circular holes into a crossflow of air. The experiments indicate that Sherwood numbers around the injection hole are up to four times those on a flat plate (without injection holes) due to the interaction of the jets and the mainstream. The mass transfer around the injection holes is dominated by formations of horseshoe, side, and kidney vortices, which are generated by the jet and crossflow interaction. For an in-line array of holes, the effectiveness is high and uniform in the streamwise direction but has a large variation in the lateral direction. The key parameters, including transfer coefficients on the back surface (Part I), inside the hole (Part I), and on the exposed surfaces, and the effectiveness on the exposed surface, are obtained so that the wall temperature distribution near the injection holes can be determined for a given heat flux condition. This detailed information will also aid the numerical modeling of flow and mass/heat transfer around film cooling holes.

Assessment of a Double Hole Film Cooling Geometry Using S-PIV and PSP

2013 ◽  
Author(s):  
Lesley M. Wright ◽  
Stephen T. McClain ◽  
Charles P. Brown ◽  
Weston V. Harmon
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Three Dimensional ◽  
Field Measurements ◽  
Secondary Flows ◽  
Cylindrical Hole ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Hole Geometry ◽  
Compound Angle

A novel, double hole film cooling configuration is investigated as an alternative to traditional cylindrical and fanshaped, laidback holes. This experimental investigation utilizes a Stereo-Particle Image Velocimetry (S-PIV) to quantitatively assess the ability of the proposed, double hole geometry to weaken or mitigate the counter-rotating vortices formed within the jet structure. The three-dimensional flow field measurements are combined with surface film cooling effectiveness measurements obtained using Pressure Sensitive Paint (PSP). The double hole geometry consists of two compound angle holes. The inclination of each hole is θ = 35°, and the compound angle of the holes is β = ± 45° (with the holes angled toward one another). The simple angle cylindrical and shaped holes both have an inclination angle of θ = 35°. The blowing ratio is varied from M = 0.5 to 1.5 for all three film cooling geometries while the density ratio is maintained at DR = 1.0. Time averaged velocity distributions are obtained for both the mainstream and coolant flows at five streamwise planes across the fluid domain (x/d = −4, 0, 1, 5, and 10). These transverse velocity distributions are combined with the detailed film cooling effectiveness distributions on the surface to evaluate the proposed double hole configuration (compared to the traditional hole designs). The fanshaped, laidback geometry effectively reduces the strength of the kidney-shaped vortices within the structure of the jet (over the entire range of blowing ratios considered). The three-dimensional velocity field measurements indicate the secondary flows formed from the double hole geometry strengthen in the plane perpendicular to the mainstream flow. At the exit of the double hole geometry, the streamwise momentum of the jets is reduced (compared to the single, cylindrical hole), and the geometry offers improved film cooling coverage. However, moving downstream in the steamwise direction, the two jets form a single jet, and the counter-rotating vortices are comparable to those formed within the jet from a single, cylindrical hole. These strong secondary flows lift the coolant off the surface, and the film cooling coverage offered by the double hole geometry is reduced.

Measured Film Cooling Effectiveness of Three Multihole Patterns

2005 ◽  
Vol 128 (2) ◽  
pp. 192-197 ◽  
Author(s):  
Yuzhen Lin ◽  
Bo Song ◽  
Bin Li ◽  
Gaoen Liu
Keyword(s):  
Experimental Data ◽  
Mass Transfer ◽  
Film Cooling ◽  
Row Spacing ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Analogy Method ◽  
Blowing Ratio ◽  
The Third ◽  
Coolant Injection

As an advanced cooling scheme to meet increasingly stringent combustor cooling requirements, multihole film cooling has received considerable attention. Experimental data of this cooling scheme are limited in the open literature in terms of different hole patterns and blowing ratios. The heat-mass transfer analogy method was employed to measure adiabatic film cooling effectiveness of three multihole patterns. Three hole patterns differed in streamwise row spacing (S), spanwise hole pitch (P), and hole inclination angle (α), with the first pattern S∕P=2 and α=30°, the second S∕P=1 and α=30°, and the third S∕P=2 and α=150°. Measurements were performed at different blow ratios (M=1-4). Streamwise coolant injection offers high cooling protection for downstream rows. Reverse coolant injection provides superior cooling protection for initial rows. The effect of blowing ratio on cooling effectiveness is small for streamwise injection but significant for reversion injection.

Film Cooling Downstream of a Row of Discrete Holes With Compound Angle

2000 ◽  
Vol 123 (2) ◽  
pp. 222-230 ◽  
Author(s):  
R. J. Goldstein ◽  
P. Jin
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Film Cooling ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Mass Transfer Coefficients ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Compound Angle

A special naphthalene sublimation technique is used to study the film cooling performance downstream of one row of holes of 35 deg inclination angle and 45 deg compound angle with 3d hole spacing and relatively small hole length to diameter ratio (6.3). Both film cooling effectiveness and mass/heat transfer coefficients are determined for blowing rates from 0.5 to 2.0 with density ratio of unity. The mass transfer coefficient is measured using pure air film injection, while the film cooling effectiveness is derived from comparison of mass transfer coefficients obtained following injection of naphthalene-vapor-saturated air with that of pure air injection. This technique enables one to obtain detailed local information on film cooling performance. General agreement is found in local film cooling effectiveness when compared with previous experiments. The laterally averaged effectiveness with compound angle injection is higher than that with inclined holes immediately downstream of injection at a blowing rate of 0.5 and is higher at all locations downstream of injection at larger blowing rates. A large variation of mass transfer coefficients in the lateral direction is observed in the present study. At low blowing rates of 0.5 and 1.0, the laterally averaged mass transfer coefficient is close to that of injection without compound angle. At the highest blowing rate used (2.0), the asymmetric vortex motion under the jets increases the mass transfer coefficient drastically ten diameters downstream of injection.

Numerical modeling of innovative film cooling hole schemes

2021 ◽  
Author(s):  
Siavash Khajehhasani
Keyword(s):  
Flat Plate ◽  
Turbine Blade ◽  
Film Cooling ◽  
Leading Edge ◽  
Lateral Spread ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Mainstream Flow ◽  
Hole Geometry

A numerical investigation of the film cooling performance on novel film hole schemes is presented using Reynolds-Averaged Navier-Stokes analysis. The investigation considers low and high blowing ratios for both flat plate film cooling and the leading edge of a turbine blade. A novel film hole geometry using a circular exit shaped hole is proposed, and the influence of an existing sister holes’ technique is investigated. The results indicate that high film cooling effectiveness is achieved at higher blowing ratios, results of which are even greater when in the presence of discrete sister holes where film cooling effectiveness results reach a plateau. Furthermore, a decrease in the strength of the counter-rotating vortex pairs is evident, which results in more attached coolant to the plate’s surface and a reduction in aerodynamic losses. Modifications are made to the spanwise and streamwise locations of the sister holes around the conventional cylindrical hole geometry. It is found that the spanwise variations have a significant influence on the film cooling effectiveness results, while only minor effects are observed for the streamwise variations. Positioning the sister holes in locations farther from the centerline increases the lateral spreading of the coolant air over the plate’s surface. This result is further verified through the flow structure analysis. Combinations of sister holes are joined with the primary injection hole to produce innovative variant sister shaped single-holes. The jet lift-off is significantly decreased for the downstream and up/downstream configurations of the proposed scheme for the flat plate film cooling. These schemes have shown notable film cooling improvements whereby more lateral distribution of coolant is obtained and less penetration of coolant into the mainstream flow is observed. The performance of the sister shaped single-holes are evaluated at the leading edge of a turbine blade. At the higher blowing ratios, a noticeable improvement in film cooling performance including the effectiveness and the lateral spread of the cooling air jet has been observed for the upstream and up/downstream schemes, in particular on the suction side. It is determined that the mixing of the coolant with the high mainstream flow at the leading edge of the blade is considerably decreased for the upstream and up/downstream configurations and more adhered coolant to the blade’s surface is achieved.

Film Cooling Effectiveness for Short Film Cooling Holes Fed by a Narrow Plenum

1999 ◽  
Vol 122 (3) ◽  
pp. 553-557 ◽  
Author(s):  
C. A. Hale ◽  
M. W. Plesniak ◽  
S. Ramadhyani
Keyword(s):  
Film Cooling ◽  
Short Film ◽  
Injection Hole ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Single Row ◽  
Hole Geometry ◽  
Thin Walled ◽  
Film Cooling Holes

The adiabatic, steady-state liquid crystal technique was used to measure surface adiabatic film cooling effectiveness values in the near-hole region X/D<10. A parametric study was conducted for a single row of short holes L/D⩽3 fed by a narrow plenum H/D=1. Film cooling effectiveness values are presented and compared for various L/D ratios (0.66 to 3.0), three different blowing ratios (0.5, 1.0, and 1.5), two different plenum feed configurations (co-flow and counterflow), and two different injection angles (35 and 90 deg). Injection hole geometry and plenum feed direction were found to affect short hole film cooling performance significantly. Under certain conditions, similar or improved coverage was achieved with 90 deg holes compared with 35 deg holes. This result has important implications for manufacturing of thin-walled film-cooled blades or vanes. [S0889-504X(00)00603-6]

Film Cooling With Large Density Differences Between the Mainstream and the Secondary Fluid Measured by the Heat-Mass Transfer Analogy

1977 ◽  
Vol 99 (4) ◽  
pp. 620-627 ◽  
Author(s):  
D. R. Pedersen ◽  
E. R. G. Eckert ◽  
R. J. Goldstein
Keyword(s):  
Mass Transfer ◽  
Film Cooling ◽  
Heat Mass Transfer ◽  
Velocity Ratio ◽  
Density Ratio ◽  
Main Stream ◽  
Constant Property ◽  
Film Cooling Effectiveness ◽  
Large Density ◽  
Porous Strip

The effect of large density differences on film cooling effectiveness was investigated through the heat-mass transfer analogy. Experiments were performed in a wind tunnel where one of the plane walls was provided with a porous strip or a row of holes with three-diameter lateral spacing and inclined 35 deg into the main stream. Helium, CO2, or refrigerant F-12, was mixed with air either in small concentrations to approach a constant property situation or in larger concentration to produce a large density difference and injected through the porous strip or the row of holes into the mainstream. The resulting local gas concentrations were measured along the wall. The density ratio of secondary to mainstream fluid was varied between 0.75 and 4.17 for both injection systems. Local film effectiveness values were obtained at a number of positions downstream of injection and at different lateral positions. From these lateral average values could also be calculated. The following results were obtained. The heat mass-transfer analogy was verified for injection through the porous strip or through holes at conditions approaching a constant property situation. Neither the Schmidt number, nor the density ratio affects the film effectiveness for injection through a porous strip. The density ratio has a strong effect on the film effectiveness for injection through holes. The film effectiveness for injection through holes has a maximum value for a velocity ratio (injection to free stream) between 0.4 and 0.6. The center-line effectiveness increases somewhat with a decreasing ratio of boundary layer thickness to injection tube diameter.

scholarly journals Film Cooling on a Gas Turbine Rotor Blade

1991 ◽  
Author(s):  
Kenichiro Takeishi ◽  
Sunao Aoki ◽  
Tomohiko Sato ◽  
Keizo Tsukagoshi
Keyword(s):  
Mass Transfer ◽  
Film Cooling ◽  
Rotor Blade ◽  
Turbine Rotor ◽  
Suction Surface ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Turbine Rotor Blade ◽  
Pressure Surface ◽  
Rotating Blade

The film cooling effectiveness on a low-speed stationary cascade and the rotating blade has been measured by using a heat-mass transfer analogy. The film cooling effectiveness on the suction surface of the rotating blade fits well with that on the stationary blade, but a low level of effectiveness appears on the pressure surface of the rotating blade. In this paper, typical film cooling data will be presented and film cooling on a rotating blade is discussed.

Film Cooling Effectiveness Distributions on a Flat Plate With a Double Hole Geometry Using PSP

2011 ◽  
Author(s):  
Lesley M. Wright ◽  
Evan L. Martin
Keyword(s):  
Flat Plate ◽  
Film Cooling ◽  
Surface Film ◽  
Density Ratio ◽  
Cooling Effectiveness ◽  
Freestream Velocity ◽  
Film Cooling Effectiveness ◽  
Single Row ◽  
Blowing Ratio ◽  
Hole Geometry

Detailed film cooling effectiveness distributions are obtained on a flat plate using the pressure sensitive paint (PSP) technique. The effects of average blowing ratio (M = 0.25–1.0) and coolant – to – mainstream density ratio (DR = 1.0–1.4) are evaluated in a low speed wind tunnel with a freestream velocity of 8.5 m/s and a freestream turbulence intensity of 6.8%. The coolant – to – mainstream density ratio is varied by using either nitrogen (DR = 1.0) or argon (DR = 1.4) as the coolant gases. The double hole geometry consists of a row of simple angle (θ = 35°), cylindrical holes coupled with one row of compound angle holes (θ = 45°, β = 50°). With the selected geometry, the compound holes effectively weaken the counter rotating vortex pair formed within the traditional simple angle hole. Therefore, the surface film cooling effectiveness is increased compared to a single row of simple angle film cooling holes. While increasing the blowing ratio decreases the film cooling effectiveness, the severity of the film cooling effectiveness reduction is less than with the single row of holes.

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