scholarly journals A Detailed Analysis of Film Cooling Physics: Part II — Compound–Angle Injection With Cylindrical Holes

1997 ◽  
Author(s):  
Kevin T. McGovern ◽  
James H. Leylek
Keyword(s):  
Experimental Data ◽  
Vortex Structure ◽  
Film Cooling ◽  
Density Ratio ◽  
Lateral Spreading ◽  
Diameter Ratio ◽  
Operating Conditions ◽  
Wall Region ◽  
Cooling Performance ◽  
Compound Angle

Detailed analyses of computational simulations with comparisons to experimental data were performed to identify and explain the dominant flow mechanisms responsible for film cooling performance with compound angle injection, Φ, of 45°, 60°, and 90°. A novel vorticity and momentum based approach was implemented to document how the symmetric, counter–rotating vortex structure typically found in the crossflow region in streamwise injection cases, becomes asymmetric with increasing Φ. This asymmetry eventually leads to a large, single vortex system at Φ = 90° and fundamentally alters the interaction of the coolant jet and hot crossflow. The vortex structure dominates the film cooling performance in compound angle injection cases by enhancing the mixing of the coolant and crossflow in the near wall region, and also by enhancing the lateral spreading of the coolant. The simulations consist of fully–elliptic and fully–coupled solutions for field results in the supply plenum, film–hole, and crossflow regions and includes surface results for adiabatic effectiveness η and heat transfer coefficient h. Realistic geometries with length–to–diameter ratio of 4.0 and pitch–to–diameter ratio of 3.0 allowed for accurate capturing of the strong three–way coupling of flow in this multi–region flowfield. The cooling configurations implemented in this study exactly matched experimental work used for validation purposes and were represented by high quality computational grid meshes using a multi–block, unstructured grid topology. Blowing ratios of 1.25 and 1.88, and density ratio of 1.6 were used to simulate realistic operating conditions and to match the experiments used for validation. Predicted results for η and h show good agreement with experimental data.

A Detailed Analysis of Film Cooling Physics: Part II—Compound-Angle Injection With Cylindrical Holes

1997 ◽  
Vol 122 (1) ◽  
pp. 113-121 ◽  
Author(s):  
K. T. McGovern ◽  
J. H. Leylek
Keyword(s):  
Experimental Data ◽  
Vortex Structure ◽  
Film Cooling ◽  
Density Ratio ◽  
Lateral Spreading ◽  
Diameter Ratio ◽  
Operating Conditions ◽  
Wall Region ◽  
Cooling Performance ◽  
Compound Angle

Detailed analyses of computational simulations with comparisons to experimental data were performed to identify and explain the dominant flow mechanisms responsible for film cooling performance with compound angle injection, Φ, of 45, 60, and 90 deg. A novel vorticity and momentum based approach was implemented to document how the symmetric, counterrotating vortex structure typically found in the crossflow region in streamwise injection cases, becomes asymmetric with increasing Φ. This asymmetry eventually leads to a large, single vortex system at Φ=90 deg and fundamentally alters the interaction of the coolant jet and hot crossflow. The vortex structure dominates the film cooling performance in compound angle injection cases by enhancing the mixing of the coolant and crossflow in the near wall region, and also by enhancing the lateral spreading of the coolant. The simulations consist of fully elliptic and fully coupled solutions for field results in the supply plenum, film hole, and crossflow regions and includes surface results for adiabatic effectiveness η and heat transfer coefficient h. Realistic geometries with length-to-diameter ratio of 4.0 and pitch-to-diameter ratio of 3.0 allowed for accurate capturing of the strong three-way coupling of flow in this multiregion flowfield. The cooling configurations implemented in this study exactly matched experimental work used for validation purposes and were represented by high-quality computational grid meshes using a multiblock, unstructured grid topology. Blowing ratios of 1.25 and 1.88, and density ratio of 1.6 were used to simulate realistic operating conditions and to match the experiments used for validation. Predicted results for η and h show good agreement with experimental data. [S0889-504X(00)01301-5]

Numerical Analysis of Film-Cooling Performance and Optimization for a Novel Shaped Film-Cooling Hole

2012 ◽  
Author(s):  
Ki-Don Lee ◽  
Sun-Min Kim ◽  
Kwang-Yong Kim
Keyword(s):  
Film Cooling ◽  
Numerical Study ◽  
Density Ratio ◽  
Lateral Spreading ◽  
Diameter Ratio ◽  
The Novel ◽  
Cooling Performance ◽  
Cooling Hole ◽  
Shaped Hole ◽  
Film Cooling Holes

In the present work, a numerical study on a novel shaped film-cooling hole has been performed. The novel shaped hole is designed to enhance lateral spreading of coolant on the cooling surface. The film-cooling performance of the novel shaped hole is compared with the fan, laidback fan, and dumbbell shaped film-cooling holes at density ratio of 1.75 in the range of blowing ratio from 0.5 to 2.5. The optimization of the novel shaped hole has been carried out to increase film-cooling effectiveness with four design variables, i.e., lateral expansion of the diffuser, forward expansion angle of the hole, length to diameter ratio of the hole, and pitch to diameter ratio of the hole. To optimize the hole shape, the radial basis neural network model is constructed and sequential quadratic programming is used to find optimal point from the surrogate model. The novel shaped hole shows remarkably improved film-cooling performance in comparison with the other film-cooling holes. The novel shaped hole modified by the optimization gives enhanced performance in comparison with the reference geometry.

The Effect of Internal Cross-Flow on the Adiabatic Effectiveness of Compound Angle Film Cooling Holes

2014 ◽  
Author(s):  
John W. McClintic ◽  
Sean R. Klavetter ◽  
Joshua B. Anderson ◽  
James R. Winka ◽  
David G. Bogard ◽  
...  
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Experimental Studies ◽  
Cross Flow ◽  
Operating Conditions ◽  
Turbine Engines ◽  
Turbine Engine ◽  
Adiabatic Effectiveness ◽  
Film Cooling Holes ◽  
Compound Angle

In gas turbine engines, film cooling holes are often fed by an internal cross-flow, with flow normal to the direction of the external flow around the airfoil. Many experimental studies have used a quiescent plenum to feed model film cooling holes and thus do not account for the effects of internal cross-flow. In this study, an experimental flat plate facility was constructed to study the effects of internal cross-flow on a row of cylindrical compound angle film cooling holes. Operating conditions were scaled, based on coolant hole Reynolds number and turbulence level, to match realistic turbine engine conditions. A cross-flow channel allowed for coolant to flow alternately in either direction perpendicular to the mainstream flow. Film cooling holes were operated at blowing ratios ranging from 0.5 to 2.0 at a density ratio of 1.5. There are relatively few studies available in literature that focus on the effects of cross-flow on film cooling performance, with no studies examining the effects of internal cross-flow on film cooling with round, compound angled holes. This study showed that significantly greater adiabatic effectiveness was achieved for cross-flow in the opposite direction of the span-wise direction of the coolant holes and provides possible explanations for this result.

Effects of Coolant Density Ratio on Film Cooling Performance on a Vane

2003 ◽  
Author(s):  
J. Michael Cutbirth ◽  
David G. Bogard
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Operating Conditions ◽  
Cooling Performance ◽  
Large Density ◽  
Performance Trends ◽  
Large Density Ratio ◽  
Small Density ◽  
Adiabatic Effectiveness ◽  
Density Ratios

Film cooling performance was studied on a simulated turbine vane model with an objective of determining how much the coolant density ratio affects this performance. Experiments were conducted using coolant density ratios of 1.8 and 1.2. The purpose of the study was to determine if tests done at small density ratios (which is often more viable in a laboratory) can give reasonable predictions of performance at more realistic large density ratios. Furthermore, appropriate scaling parameters were determined. The mainstream flow was operated with low and high turbulence levels. Adiabatic effectiveness was measured in the showerhead region of the vane, and following the first row of coolant holes on the pressure side. Adiabatic effectiveness performance using small density ratio coolant gave performance trends similar to the large density ratio coolant, but quantitative values differed by varying amount depending on operating conditions.

Film Cooling of Compound Angle Upstream Sister Holes

2019 ◽  
Author(s):  
Sana Abd Alsalam ◽  
Bassam Jubran
Keyword(s):  
Film Cooling ◽  
Turbulence Modeling ◽  
Stokes Equations ◽  
Density Ratio ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Simple Strategy ◽  
Compound Angle

Abstract This study introduces a novel and simple strategy; compound angle upstream sister holes (CAUSH) to increase film cooling performance of the cylindrical hole by combining two techniques: Sister holes; (two small round holes placed upstream the primary hole) and compound angle hole. Whereas the upstream sister holes were injected at several compound angles β = 0°, 45°, 75°, and 90°, while the main hole was injected to the streamwise direction at 35° on a flat plate. FLUENT-ANSYS code was used to perform the simulation by solving the 3D Reynolds Averaged Navier-Stokes Equations. The capability of three types of k-ε turbulence modeling combined with the enhanced wall treatment is investigated to predict the film cooling performance of sister holes. A detailed computational analysis of the cooling performance of the (CAUSH) and the flow field was done at a density ratio equal to two (D.R = 2) and four blowing ratios M = 0.25, 0.5, 1.0 and 1.5 to predict the centerline and laterally averaged film cooling performance. The centerline effectiveness results showed that the highest cooling performance from the examined (CAUSH) was obtained at β = 0°, 45°, and 90° for low and high blowing ratio, the highest laterally averaged film cooling performance was captured at β = 0° and 90° for all tested blowing ratios. Also, the results indicated that the upstream sister hole with 90° compound angle holes has the best overall film cooling effectiveness while the worst performance is attained at β = 75°.

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.

Film Cooling Performance of the Embedded Holes in Trenches With Compound Angles

2010 ◽  
Author(s):  
Jia Li ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Film Cooling ◽  
Free Stream ◽  
Lateral Spreading ◽  
Stream Velocity ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Axial Ejection ◽  
Cooling Air ◽  
Compound Angle

Film cooling performance for a row of cylindrical holes can be enhanced by embedding the row in a suitable transverse slot. The compound angle of the holes can even more affects the cooling performance at downstream of the injections. In this study the cooling performance of the embedded holes in transverse trenches with different compound angles are explored both by pressure sensitive paint (PSP) experiment technology and RANS algorithm. A film cooling test rig was built up in Tsinghua University, which contains an accelerating free stream section to model the surface of a turbine airfoil. The PSP technology is applied in the tests to obtain the film cooling effectiveness. The experiments are performed for a single mainstream Reynolds number based on free-stream velocity and film hole diameter of 4000. Considering three compound angles, 0°, 45° and 90°, and with or without transverse trenches. All six cases are tested at three different coolant-to-mainstream blowing ratios of 0.5, 1.0, and 1.5. Meanwhile, the test cases are numerically simulated based on RANS with k-ε turbulence model to show the detail of the flow patterns. Both the experimental and numerical results show that the adiabatic film effectiveness is relative insensitive to the blowing ratio in the case of holes with trenches. Moreover, it could be improved with a more uniform spanwise distribution. It is mainly due to the blockage of the ejected coolant at the downstream edge of the trench, which forces a portion of the cooling air to spread laterally within the trench prior to issuing onto the upper surface. Both 45° and 90° compound angles can further enhance the film cooling effectiveness over the axial ejection, this is mainly due to the lateral momentum component of the ejection. A lateral passage vortex is formed inside the trench which strengthens the lateral spreading of the jets. The 45° compound angle gives a higher film cooling effectiveness overall.

Performance Evaluation of a Novel Film-Cooling Hole

2012 ◽  
Vol 134 (10) ◽  
Author(s):  
Ki-Don Lee ◽  
Kwang-Yong Kim
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Three Dimensional ◽  
Lateral Spreading ◽  
The Novel ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Cooling Hole ◽  
Shaped Hole

This paper presents a numerical investigation of the film-cooling performance of a novel film-cooling hole in comparison with a fan-shaped hole. The novel shaped hole is designed to increase the lateral spreading of coolant on the cooling surface. The film-cooling performance of the novel shaped hole is evaluated at a density ratio of 1.75 and the range of the blowing ratio of 0.5–2.5. The simulations were performed using three-dimensional Reynolds-averaged Navier–Stokes analysis with the SST k-ω model. The numerical results for the fan-shaped hole show very good agreement with the experimental data. For the blowing ratio of 0.5, the novel shaped film-cooling hole shows a similar cooling performance as the fan-shaped hole. However, as the blowing ratio increases, the novel shaped hole shows greatly improved lateral spreading of the coolant and the cooling performance in terms of the film-cooling effectiveness in comparison with the fan-shaped hole.

Numerical Evaluation of Novel Shaped Holes for Enhancing Film Cooling Performance

2015 ◽  
Vol 137 (7) ◽  
Author(s):  
Xing Yang ◽  
Zhao Liu ◽  
Zhenping Feng
Keyword(s):  
Experimental Data ◽  
Turbulence Model ◽  
Film Cooling ◽  
Density Ratio ◽  
Cylindrical Hole ◽  
Transfer Coefficients ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Wide Range

The overall film cooling performance of three novel film cooling holes has been numerically investigated in this paper, including adiabatic film cooling effectiveness, heat transfer coefficients as well as discharge coefficients. The novel holes were proposed to help cooling injection spread laterally on a cooled endwall surface. Three-dimensional Reynolds-averaged Navier–Stokes (RANS) equations with shear stress transport (SST) k-ω turbulence model were solved to perform the simulation based on turbulence model validation by using the relevant experimental data. Additionally, the grid independent test was also carried out. With a mainstream Mach number of 0.3, flow conditions applied in the simulation vary in a wide range of blowing ratio from 0.5 to 2.5. The coolant-to-mainstream density ratio (DR) is fixed at 1.75, which can be more approximate to real typical gas turbine applications. The numerical results for the cylindrical hole are in good agreement with the experimental data. It is found that the flow structures and temperature distributions downstream of the cooling injection are significantly changed by shaping the cooling hole exit. For a low blowing ratio of 0.5, the three novel shaped cooling holes present similar film cooling performances with the traditional cylindrical hole, while with the blowing ratio increasing, all the three novel cooling holes perform better, of which the bean-shaped hole is considered to be the best one in terms of the overall film cooling performance.

A Three-Regime Based Method for Correlating Film Cooling Effectiveness for Cylindrical and Shaped Holes

2015 ◽  
Author(s):  
Lieke Wang ◽  
Mats Kinell ◽  
Hossein N. Najafabadi ◽  
Matts Karlsson
Keyword(s):  
Experimental Data ◽  
Film Cooling ◽  
Gas Turbines ◽  
Density Ratio ◽  
Transition Regime ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Lift Off

To cope with high temperature of the gas from combustor, cooling is often used in the hot gas components in gas turbines. Film cooling is one of the effective methods used in this application. Both cylindrical and fan-shaped holes are used in film cooling. There have been a number of correlations published for both cylindrical and fan-shaped holes regarding film cooling effectiveness. Unfortunately there are no definitive correlations for either cylindrical or fan-shaped holes. This is due to the nature of the complexity of film cooling where many factors influence its performance, e.g., blowing ratio, density ratio, surface angle, downstream distance, expansion angle, hole length, turbulence level, etc. A test rig using infrared camera was built to test the film cooling performance for a scaled geometry from a real nozzle guide vane. Both cylindrical and fan-shaped holes were tested. To correlate the experimental data, a three-regime based method was developed for predicting the film cooling effectiveness. Based on the blowing ratio, the proposed method divides the film cooling performance in three regimes: fully attached (or no jet lift-off), fully jet lift-off, and the transition regime in between. Two separate correlations are developed for fully attached and full jet lift-off regimes, respectively. The method of interpolation from these two regimes is used to predict the film cooling effectiveness for the transition regime, based on the blowing ratio. It has been found this method can give a good correlation to match the experimental data, for both cylindrical and fan-shaped holes. A comparison with literature was also carried out, and it showed a good agreement.

Sign in / Sign up

Export Citation Format

Share Document