Flow Characteristics and Aerodynamic Losses of Film-Cooling Jets With Compound Angle Orientations

1997 ◽  
Vol 119 (2) ◽  
pp. 310-319 ◽  
Author(s):  
Sang Woo Lee ◽  
Yong Beom Kim ◽  
Joon Sik Lee
Keyword(s):  
Film Cooling ◽  
Velocity Ratio ◽  
Flow Characteristics ◽  
Orientation Angle ◽  
Surface Flow ◽  
Test Surface ◽  
Flow Measurements ◽  
Aerodynamic Loss ◽  
Flow Visualizations ◽  
Compound Angle

Oil-film flow visualizations and three-dimensional flow measurements using a five-hole probe have been conducted to investigate the flow characteristics and aerodynamic loss distributions of film-cooling jets with compound angle orientations. For a fixed inclination angle of the injection hole, measurements are performed at various orientation angles to the direction of the mainstream in the case of three velocity ratios of 0.5, 1.0, and 2.0. Flow visualizations for the velocity ratio of 2.0 show that the increase in the orientation angle furnishes better film coverage on the test surface, but gives rise to large flow disturbances in the mainstream. A near-wall flow model has been proposed based on the surface flow visualizations. It has also been found from the flow measurements that as the orientation angle increases, a pair of count-errotating vortices turn to a single strong one, and the aerodynamic loss field is closely related to the secondary flow. Even in the case of the velocity ratio of 2.0, aerodynamic loss is produced within the jet region when the orientation angle is large. Regardless of the velocity ratio, the mass-averaged aerodynamic loss increases with increasing orientation angle, the effect of which on aerodynamic loss is pronounced when the velocity ratio is large.

scholarly journals Flow Characteristics and Aerodynamic Losses of Film-Cooling Jets With Compound Angle Orientations

1995 ◽  
Author(s):  
Sang Woo Lee ◽  
Yong Beom Kim ◽  
Joon Sik Lee
Keyword(s):  
Film Cooling ◽  
Velocity Ratio ◽  
Flow Characteristics ◽  
Orientation Angle ◽  
Surface Flow ◽  
Test Surface ◽  
Flow Measurements ◽  
Aerodynamic Loss ◽  
Flow Visualizations ◽  
Compound Angle

Oil-film flow visualizations and three-dimensional flow measurements using a five-hole probe have been conducted to investigate the flow characteristics and aerodynamic loss distributions of film-cooling jets with compound angle orientations. For a fixed inclination angle of the injection hole, measurements are performed at various orientation angles to the direction of the mainstream in the case of three velocity ratios of 0.5, 1.0 and 2.0. Flow visualizations for the velocity ratio of 2.0 show that the increase in the orientation angle furnishes better film coverage on the test surface, but gives rise to large flow disturbances in the mainstream. A near-wall flow model has been proposed based on the surface flow visualizations. It has also been found from the flow measurements that as the orientation angle increases, a pair of counter-rotating vortices turn to a single strong one, and the aerodynamic loss field is closely related to the secondary flow. Even in the case of the velocity ratio of 2.0, aerodynamic loss is produced within the jet region when the orientation angle is large. Regardless of the velocity ratio, the mass-averaged aerodynamic loss increases with increasing orientation angle, the effect of which on aerodynamic loss is pronounced when the velocity ratio is large.

Investigations of improved cooling effectiveness for ramp film cooling with compound angle film cooling jets

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Krishna Anand Vasu Devan Nair Girija Kumari ◽  
Parammasivam Kanjikoil Mahali
Keyword(s):  
Film Cooling ◽  
Flat Surface ◽  
Flow Characteristics ◽  
Test Surface ◽  
Cooling Effectiveness ◽  
Content Type ◽  
Film Cooling Effectiveness ◽  
Ramp Test ◽  
Cooling Hole ◽  
Compound Angle

Purpose This paper aims to investigate the film cooling effectiveness (FCE) and mixing flow characteristics of the flat surface ramp model integrated with a compound angled film cooling jet. Design/methodology/approach Three-dimensional numerical simulation is performed on a flat surface ramp model with Reynolds Averaged Navier-Stokes approach using a finite volume solver. The tested model has a fixed ramp angle of 24° and a ramp width of two times the diameter of the film cooling hole. The coolant air is injected at 30° along the freestream direction. Three different film hole compound angles oriented to freestream direction at 0°, 90° and 180° were investigated for their performance on-ramp film cooling. The tested blowing ratios (BRs) are in the range of 0.9–2.0. Findings The film hole oriented at a compound angle of 180° has improved the area-averaged FCE on the ramp test surface by 86.74% at a mid-BR of 1.4% and 318.75% at higher BRs of 2.0. The 180° film hole compound angle has also produced higher local and spanwise averaged FCE on the ramp test surface. Originality/value According to the authors’ knowledge, this study is the first of its kind to investigate the ramp film cooling with a compound angle film cooling hole. The improved ramp model with a 180° film hole compound angle can be effectively applied for the end-wall surfaces of gas turbine film cooling.

Near Field of Film Cooling Jet Issued Into a Flat Plate Boundary Layer: LES Study

2008 ◽  
Author(s):  
Yulia V. Peet ◽  
Sanjiva K. Lele
Keyword(s):  
Boundary Layer ◽  
Film Cooling ◽  
Flat Surface ◽  
Computational Study ◽  
Near Field ◽  
Velocity Ratio ◽  
Density Ratio ◽  
Surface Flow ◽  
Test Surface ◽  
Film Cooling Effectiveness

We report results from a computational study of film cooling from cylindrical holes inclined at 35 degrees with respect to a flat surface using Large Eddy Simulations (LES). The hole length is L/d = 3.5, distance between the holes is P/d = 3, boundary layer above the flat surface is turbulent with Reθ = 938, density ratio = 0.95, velocity ratio = 0.5. All pertinent components of geometry, namely, supply plenum, film hole and crossflow region above the test surface, are simulated. The simulations are performed using a multicode approach, where a low Mach number code is employed inside the plenum and in the film hole, and a compressible code is used for the flow above the test surface. Flow inside the plenum, film hole and above the test surface is analyzed. Mean velocity and turbulence characteristics in the near field of the jet injection obtained in the simulations are compared to experimental data of Pietrzyk et al. [1]. Adiabatic film cooling effectiveness is estimated and compared with experiments of Sinha et al. [2]. Relation of the coherent vortical structures observed in the flow to film cooling performance is discussed. Advantage of LES over RANS methods for this type of flow is confirmed by showing that spanwise u′w′ shear stress and lateral growth of the jet are predicted correctly in the current LES as opposed to typical RANS computations.

scholarly journals Large Eddy Simulation of Film Cooling Involving Compound Angle Holes: Comparative Study of LES and RANS

Processes ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 198
Author(s):  
Seung Il Baek ◽  
Joon Ahn
Keyword(s):  
Large Eddy Simulation ◽  
Film Cooling ◽  
Orientation Angle ◽  
Turbulence Models ◽  
Film Cooling Effectiveness ◽  
Injection Angle ◽  
Blowing Ratio ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Compound Angle

A large eddy simulation (LES) was performed for film cooling in the gas turbine blade involving spanwise injection angles (orientation angles). For a streamwise coolant injection angle (inclination angle) of 35°, the effects of the orientation angle were compared considering a simple angle of 0° and 30°. Two ratios of the coolant to main flow mass flux (blowing ratio) of 0.5 and 1.0 were considered and the experimental conditions of Jung and Lee (2000) were adopted for the geometry and flow conditions. Moreover, a Reynolds averaged Navier–Stokes simulation (RANS) was performed to understand the characteristics of the turbulence models compared to those in the LES and experiments. In the RANS, three turbulence models were compared, namely, the realizable k-ε, k-ω shear stress transport, and Reynolds stress models. The temperature field and flow fields predicted through the RANS were similar to those obtained through the experiment and LES. Nevertheless, at a simple angle, the point at which the counter-rotating vortex pair (CRVP) collided on the wall and rose was different from that in the experiment and LES. Under the compound angle, the point at which the CRVP changed to a single vortex was different from that in the LES. The adiabatic film cooling effectiveness could not be accurately determined through the RANS but was well reflected by the LES, even under the compound angle. The reattachment of the injectant at a blowing ratio of 1.0 was better predicted by the RANS at the compound angle than at the simple angle. The temperature fluctuation was predicted to decrease slightly when the injectant was supplied at a compound angle.

Effect of Internal Crossflow Velocity on Film Cooling Effectiveness: Part II — Compound Angle Shaped Holes

2017 ◽  
Author(s):  
John W. McClintic ◽  
Joshua B. Anderson ◽  
David G. Bogard ◽  
Thomas E. Dyson ◽  
Zachary D. Webster
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Film Cooling ◽  
Velocity Ratio ◽  
Injection Rate ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Crossflow Velocity ◽  
Film Cooling Holes ◽  
Compound Angle

In gas turbine engines, film cooling holes are commonly fed with an internal crossflow, the magnitude of which has been shown to have a notable effect on film cooling effectiveness. In Part I of this study, as well as in a few previous studies, the magnitude of internal crossflow velocity was shown to have a substantial effect on film cooling effectiveness of axial shaped holes. There is, however, almost no data available in the literature that shows how internal crossflow affects compound angle shaped film cooling holes. In Part II, film cooling effectiveness, heat transfer coefficient augmentation, and discharge coefficients were measured for a single row of compound angle shaped film cooling holes fed by internal crossflow flowing both in-line and counter to the span-wise direction of coolant injection. The crossflow-to-mainstream velocity ratio was varied from 0.2–0.6 and the injection velocity ratio was varied from 0.2–1.7. It was found that increasing the magnitude of the crossflow velocity generally caused degradation of the film cooling effectiveness, especially for in-line crossflow. An analysis of jet characteristic parameters demonstrated the importance of crossflow effects relative to the effect of varying the film cooling injection rate. Heat transfer coefficient augmentation was found to be primarily dependent on injection rate, although for in-line crossflow, increasing crossflow velocity significantly increased augmentation for certain conditions.

Effects of Embedded Vortices on Injectant From Film Cooling Holes With Large Spanwise Spacing and Compound Angle Orientations in a Turbulent Boundary Layer

1994 ◽  
Vol 116 (4) ◽  
pp. 709-720 ◽  
Author(s):  
P. M. Ligrani ◽  
S. W. Mitchell
Keyword(s):  
Heat Transfer ◽  
Secondary Flow ◽  
Vortex Core ◽  
Film Cooling ◽  
Test Surface ◽  
Injection Hole ◽  
Plane Projection ◽  
Flow Vectors ◽  
Film Cooling Holes ◽  
Compound Angle

Experimental results are presented that describe the effects of embedded, longitudinal vortices on heat transfer and film injectant downstream of a single row of film cooling holes with compound angle orientations. Holes are spaced 7.8 hole diameters apart in the spanwise direction so that information is obtained on the interactions between the vortices and the injectant from a single hole. The compound angle holes are oriented so that their angles with respect to the test surface are 30 deg in a spanwise/normal plane projection, and 35 deg in a streamwise/normal plane projection. A blowing ratio of 0.5 is employed and the ratio of vortex core diameter to hole diameter is 1.6–1.67 just downstream of the injection holes (x/d=10.2). At the same location, vortex circulation magnitudes range from 0.15 m2/s to 0.18 m2/s. The most important conclusion is that local heat transfer and injectant distributions are strongly affected by the longitudinal embedded vortices, including their directions of rotation and their spanwise positions with respect to film injection holes. To obtain information on the latter, clockwise rotating vortices R0–R4 and counterclockwise rotating vortices L0–L4 are placed at different spanwise locations with respect to the central injection hole located on the spanwise centerline. With vortices R0–R4, the greatest disruption to the film is produced by the vortex whose downwash passes over the central hole (R0). With vortices L0–L4, the greatest disruption is produced by the vortices whose cores pass over the central hole (L1 and L2). To minimize such disruptions, vortex centers must pass at least 1.5 vortex core diameters away from an injection hole on the upwash sides of the vortices and 2.9 vortex core diameters away on the downwash sides of the vortices. Differences resulting from vortex rotation are due to secondary flow vectors, especially beneath vortex cores, which are in different directions with respect to the spanwise velocity components of injectant after it exits the holes. When secondary flow vectors near the wall are in the same direction as the spanwise components of the injectant velocity (vortices R0–R4), the film injectant is more readily swept beneath vortex cores and into vortex upwash regions than for the opposite situation in which near-wall secondary flow vectors are opposite to the spanwise components of the injectant velocity (vortices L0–L4). Consequently, higher Stanton numbers are generally present over larger portions of the test surface with vortices R0–R4 than with vortices L0–L4.

Parametric Cooling Study of Single-Row Cylindrical Film Holes on Pressure Side of a Rotor Blade

2017 ◽  
Author(s):  
Zhongran Chi ◽  
Haiqing Liu ◽  
Shusheng Zang
Keyword(s):  
Film Cooling ◽  
Rotor Blade ◽  
Rotor Blades ◽  
Pressure Side ◽  
Local Cooling ◽  
Cooling Effectiveness ◽  
Aerodynamic Efficiency ◽  
Film Cooling Effectiveness ◽  
Aerodynamic Loss ◽  
Compound Angle

Film cooling of 1st stage rotor blades strongly relates to the aerodynamic performance and life expectation of gas turbine. In this piece of work, a parametric study was carried out based on 3D RANS CFD methods to systematically investigate both cooling performance and aerodynamic loss of various film holes’ arrangements on the pressure side (PS) of a realistic rotor blade. In each CFD case, cylindrical film holes were arranged in one row with P/D around 4.0. More than one hundred CFD cases were carried out with various dimensionless streamwise locations (0.1, 0.2, ..., and 0.7), compound angles (−60°, −30°, ..., and 90°), and relative coolant massflows (0.2%, 0.3%, 0.45%, 0.7%, and 1.0% of mainstream massflow). Detailed distributions of adiabatic film cooling effectiveness on blade surface and aerodynamic loss with film cooling were computed for each case. It was found that coolant massflow was the decisive factor of aerodynamic efficiency φ. For near-LE film holes, −60° compound angle gave higher and more uniform η distributions at various coolant massflows. And the separation near LE could be suppressed, improving local cooling at near-hub on PS. For downstream film holes, 60° and −60° compound angles provided equivalent cooling performances, which were also better than other cases. The cooling characteristics of film holes with −30° compound angle were more susceptible to both coolant massflow and the location of ejection, which was mainly because of the blow-off and reattachment of coolant jets. For the cases with 90° compound angle, the distributions of η were generally similar, and the values increased monotonically as coolant massflows get larger.

Film-Cooling From Holes With Compound Angle Orientations: Part 1—Results Downstream of Two Staggered Rows of Holes With 3d Spanwise Spacing

1994 ◽  
Vol 116 (2) ◽  
pp. 341-352 ◽  
Author(s):  
P. M. Ligrani ◽  
J. M. Wigle ◽  
S. Ciriello ◽  
S. M. Jackson
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Test Surface ◽  
Spanwise Direction ◽  
Normal Plane ◽  
Streamwise Location ◽  
Structure Of Flow ◽  
Film Cooling Holes ◽  
Compound Angle ◽  
Angle Orientation

Experimental results are presented that describe the development and structure of flow downstream of two staggered rows of film-cooling holes with compound angle orientations. With this configuration, holes are spaced 3d apart in the spanwise direction, inclined at 35 deg with respect to the test surface when projected into the streamwise/normal plane, and inclined at 30 deg with respect to the test surface when projected into the spanwise/normal plane. Results are presented for an injectant to free-stream density ratio near 1.0, and injection blowing ratios from 0.5 to 1.50. Comparisons are made with measurements from two other configurations to determine: (1) the effects of hole angle orientation for constant spanwise hole spacing, and (2) the effects of spanwise hole spacing when the hole angle orientation is maintained constant. Results from the first comparison show that the compound angle injection configuration provides significantly improved film-cooling protection compared to a simple angle configuration for the same spanwise hole spacing, normalized streamwise location x/d, and blowing ratio m, for x/d<60. At x/d>60, spanwise-averaged adiabatic effectiveness data downstream of the two configurations generally cover about the same range. Results from the second comparison show that spanwise-averaged effectiveness values are 25 to 40 percent higher when 3d spanwise hole spacing is employed compared to 3.9d spanwise hole spacing for the same m and x/d, for x/d<40. At x/d>40, differences between the two configurations range from 12 to 30 percent. Results from all configurations studied show that spanwise-averaged iso-energetic Stanton number ratios cover approximately the same range of values and show roughly the same trends, ranging between 1.0 and 1.25. In particular, Stf/St0 values increase with m at each x/d, and show little variation with x/d for each value of m tested.

scholarly journals Film Cooling from a Single Row of Compound Angle Holes at High Blowing Ratios

1996 ◽  
Vol 2 (4) ◽  
pp. 259-267 ◽  
Author(s):  
Phillip M. Ligrani ◽  
Joon Sik Lee
Keyword(s):  
Film Cooling ◽  
Test Surface ◽  
Spanwise Direction ◽  
Mean Velocity ◽  
Single Row ◽  
Blowing Ratio ◽  
Structure Of Flow ◽  
Inclination Angles ◽  
Lift Off ◽  
Compound Angle

Experimental results are presented which describe the development and structure of flow downstream of a single row of holes with compound angle orientations producing film cooling at high blowing ratios. This film cooling configuration is important because similar arrangements are frequently employed on the first stage of rotating blades of operating gas turbine engines. With this configuration, holes are spaced 6d apart in the spanwise direction, with inclination angles of 24 degrees, and angles of orientation of 50.5 degrees. Blowing ratios range from 1.5 to 4.0 and the ratio of injectant to freestream density is near 1.0. Results show that spanwise averaged adiabatic effectiveness, spanwise-averaged iso-energetic Stanton number ratios, surveys of streamwise mean velocity, and surveys of injectant distributions change by important amounts as the blowing ratio increases. This is due to injectant lift-off from the test surface just downstream of the holes.

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