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

Hale, Charles A.; Ramadhyani, S.; Plesniak, Michael W.

doi:10.1115/99-gt-162

Cited by 8 publications

(7 citation statements)

References 24 publications

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“…Numerical simulations (Hale, 1998) provide confirmation of the existence of this vortex pair. Using FLUENT v.4 on an IBM RS 6000 with 512 MB of RAM, the plenum flow (H/D = 0.66), flow within the injection hole (a = 90°, UD = 0.66), and the crossflow were modeled.…”

Section: Flow Visualization and Numerical Simulationmentioning

confidence: 72%

“…Studies have also been reported by Leylek (1996, 1997) and Ferguson et at (1998), who emphasize the importance of properly modeling the flow physics by including the plenum and injection hole within the computational domain. Hale et at (1999), in a companion computational study, evaluated various turbulence models for their ability to predict adiabatic effectiveness for the same configurations reported here.…”

Section: Literature Reviewmentioning

confidence: 99%

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Influence of Coolant Feed Direction and Hole Length on Film Cooling Jet Velocity Profiles

Brundage

Plesniak

Ramadhyani

1999

Volume 3: Heat Transfer; Electric Power; Industrial and Cogeneration

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Measurements were taken of the exit velocity and turbulence intensity distributions for film cooling holes fed from a narrow plenum above the middle jet in a row of five jets using hot-wire anemometry. Parameters varied in the experiments included the length-to-diameter ratio of the holes, the coolant-to-mainstream blowing ratio, the angle of inclination of the holes, and the plenum flow direction, which was either in the same direction as, or opposite to, the mainstream. Flow visualization within the film cooling holes and in the plenum revealed large secondary flow structures that affected the jet exit velocity distributions. The exit velocity profiles for short holes had “peaky” signatures associated with jetting in the upstream portion of the 35° holes and in the downstream portion of the 90° holes. For the longer holes, the exit velocity profiles were more uniform. Crossflow boundary layer fluid was found to enter into the film cooling holes in some short hole configurations. The coolant feed direction affects the details of the flow separation at the hole entrance and within the hole, and consequently influences the jet exit velocity profile. These effects are most pronounced for higher blowing ratios.

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Section: Flow Visualization and Numerical Simulationmentioning

confidence: 72%

Section: Literature Reviewmentioning

confidence: 99%

Influence of Coolant Feed Direction and Hole Length on Film Cooling Jet Velocity Profiles

Brundage

Plesniak

Ramadhyani

1999

Volume 3: Heat Transfer; Electric Power; Industrial and Cogeneration

Self Cite

View full text Add to dashboard Cite

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“…The criteria for convergence of the conservation equations were a reduction in the residuals by more than four orders of magnitude for each equation, and an imbalance in the mass flow rate at the film hole exit plane inferior to 10 2 5 . Film cooling scheme for gas turbines Hale et al (1999) evaluated several different turbulence models and wall function treatments available in the commercial CFD code FLUENT, assessing the ability of these combined models to predict the film cooling effectiveness for streamwise blowing from short injection holes (with L/D h ¼ 2.91, b ¼ 08 and a ¼ 358 in the present notation) fed by a narrow plenum. The results of their study indicated that the use of usual wall functions to predict film cooling effectiveness in the near-hole region is problematic due to apparent boundary layer separation in that region.…”

Section: Mathematical Modeling and Boundary Conditionsmentioning

confidence: 99%

An advanced impingement/film cooling scheme for gas turbines – numerical study

Immarigeon

Hassan

2006

International Journal of Numerical Methods for Heat &Amp; Fluid Flow

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Purpose -The present study aims to conduct a numerical investigation of a novel film cooling scheme combining in-hole impingement cooling and flow turbulators with traditional downstream film cooling, and was originally proposed by Pratt & Whitney Canada for high temperature gas turbine applications. Design/methodology/approach -Steady-state simulations were performed and the flow was considered incompressible and turbulent. The CFD package FLUENT 6.1 was used to solve the Navier-Stokes equations numerically, and the preprocessor, Gambit, was used to generate the required grid.Findings -It was determined that the proposed scheme geometry can prevent coolant lift-off much better than standard round holes, since the cooling jet remains attached to the surface at much higher blowing rates, indicating a superior performance for the proposed scheme.Research limitations/implications -The present study was concerned only with the downstream effectiveness aspect of performance. The performance related to the heat transfer coefficient is a prospective topic for future studies. Practical implications -Advanced and innovative cooling techniques are essential in order to improve the efficiency and power output of gas turbines. This scheme combines in-hole impingement cooling and flow turbulators with traditional downstream film cooling for improved cooling capabilities. Originality/value -This new advanced cooling scheme both combines the advantages of traditional film cooling with those of impingement cooling, and provides greater airfoil protection than traditional film cooling. This study is of value for those interested in gas turbine cooling.

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“…The small separation region downstream of the blowing holes that Hale et al 21 identify in their streamwise blowing case will be signi cantly altered for the present compound angle blowing. Because it is known that the structure within square jets is likely to be more complex than that in round jets and that the separation will be very different for the compound blowing orientation, it was thoughtthat simple engineeringmodels of turbulencemight perform better in predictions of compound injection with round holes than with square.…”

Section: Numerical Methods and Comparisons With Measured Resultsmentioning

confidence: 93%

“…Nevertheless, their numerical predictionsshow that the ow near the jet exit is grossly oscillatory, with effective Strouhal numbers of about 0.4, based on jet velocity and size. Modest agreement is obtained in comparisons with the detailed measurements of mean quantities reported by Ajersch et al 15 Hale et al 21 evaluated several different turbulence models and wall function treatments available in the commercial computational uid dynamics code FLUENT, assessing the ability of these combined models to predictthe lm coolingeffectivenessfor streamwise blowing from short injectionholes (with L=d D 2:91,¯D 0 deg, and ® D 35 deg in the present notation) fed by a narrow plenum. The results of their study indicated that the use of usual wall functions to predict lm cooling effectivenessin the near-holeregionis problematic due to apparent boundary-layer separation in that region.…”

Section: Numerical Methods and Comparisons With Measured Resultsmentioning

confidence: 97%

Film Cooling Injection Hole Geometry: Hole Shape Comparison for Compound Cooling Orientation

2001

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Film cooling, for gas turbine blades or other applications,is done by injecting cool air through a row of holes in a solid wall, past which hot gas is owing. To investigate the effect of hole shape directly, the present experimental and computational study compares the lm cooling effectiveness of two sets of compound-oriented holes, one square and the other round, both placed (alternatively) in a plane wall. Both have the same cross-sectional area, and both are tested in the same facility at the same three blowing ratios R: 0.5, 1.0, and 1.5. Numerical simulations are made using the standard k-" turbulence model. Film cooling effectiveness is measured using a ame ionization detector. Results show that the holes perform quite differently, the square holes being slightly superior only very close to the injection point and only at low R. For all higher blowing ratios and larger downstream distances investigated, the round holes are better due to the lower integrated momentum ux away from the wall plane at the hole exit. The marked differences between the effectiveness of round and square holes con rms that hole exit geometry is an extremely important factor in lm cooling design, even at compound orientation angles. NomenclatureA = area C = coolant concentration in the freestream D = round hole diameter d = effective cross-sectional hole diameter, equal to jet width in the case of square hole k = turbulence kinetic energy L = length of coolant hole tubes Q = average normal volume ux A W ¢ dA R = jet-to-cross ow velocity (blowing) ratio, V j =V 1 Re = Reynolds number V ; W = mean velocity components in the y and z directions, respectively V j = bulk jet velocity W M = average value of W taken over the jet exit area X; Y; Z = axes of tunnel coordinate system ® = injection angle (Fig. 1a) = hole axis orientation angle with respect to the freestream direction (Fig. 1b) z = momentum correction factor de ned by Eq. (2) "= turbulence dissipation raté = adiabatic lm cooling effectiveness Ń = spanwise-averaged lm cooling effectiveness º = kinematic viscosity ½ = density Subscripts j = jet 1 = cross ow

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

Cited by 8 publications

References 24 publications

Influence of Coolant Feed Direction and Hole Length on Film Cooling Jet Velocity Profiles

Influence of Coolant Feed Direction and Hole Length on Film Cooling Jet Velocity Profiles

An advanced impingement/film cooling scheme for gas turbines – numerical study

Film Cooling Injection Hole Geometry: Hole Shape Comparison for Compound Cooling Orientation

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