Film cooling effectiveness: Comparison of adiabatic and conjugate heat transfer CFD models

Silieti, Mahmood; Kassab, Alain J.; Divo, Eduardo

doi:10.1016/j.ijthermalsci.2009.04.007

Cited by 109 publications

(35 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…For example, vane (metal) surface temperature distributions calculated by computer codes using conjugate heat transfer calculations were found to be substantially lower than the predictions using adiabatic wall, refer [14,15]. Similar comparison between the adiabatic and conjugate heat transfer for a fan shaped cooling hole was reported by Silieti et al [16] by using CFD models. Bohn and coworkers [17] conducted a conjugate heat transfer study and computed the effectiveness values using the adiabatic condition.…”

Section: Introductionsupporting

confidence: 57%

A Comparative Study of Film Cooling Effectiveness on a Flat Plate With Adiabatic and Conjugate Conditions for Different Hole Shapes

Chandran

Halder

Panda

et al. 2012

Volume 4: Heat Transfer, Parts a and B

View full text Add to dashboard Cite

A computational study is carried out for comparison of the effectiveness of film cooling through holes of different shapes: cylindrical, shaped, trenched cylindrical and trenched shaped hole. Both adiabatic and conjugate wall thermal condition with various blowing ratios (0.6 to 1.4) are considered for the investigation. The coolant-to-mainstream density ratio and temperature ratio are maintained at 1.6 and 0.625 respectively. The κ-ω SST turbulence model is used for computation. The complex flow structures within the film hole, the exit and in the interaction zone of jet with cross flow are reported. Among the configurations studied, the shaped and trenched shaped holes have shown smaller jet lift off and uniform coolant coverage in both lateral and streamwise directions. Further, the results showed a significant difference in the indicated values of centerline surface temperature and effectiveness with the adiabatic and the conjugate conditions; the conjugate values being much lower but more uniform.

show abstract

Section: Introductionsupporting

confidence: 57%

A Comparative Study of Film Cooling Effectiveness on a Flat Plate With Adiabatic and Conjugate Conditions for Different Hole Shapes

Chandran

Halder

Panda

et al. 2012

Volume 4: Heat Transfer, Parts a and B

View full text Add to dashboard Cite

show abstract

“…The conventional analysis techniques on film cooling effectiveness which neglect the conjugate heat transfer (CHT) effects were questioned by Harrison and Bogard [9,10]. In the numerical study of Silieti et al [11] on the end wall film effectiveness, a better agreement with the experimental data was achieved by using the conjugate model in comparison with the results with an adiabatic model.…”

Section: Introductionmentioning

confidence: 99%

Impact of Wall Temperature on Turbine Blade Tip Aerothermal Performance

Zhang

2014

Journal of Engineering for Gas Turbines and Power

View full text Add to dashboard Cite

Currently the aerodynamics and heat transfer over a turbine blade tip tend to be analyzed separately with the assumption that the wall thermal boundary conditions do not affect the over-tip-leakage (OTL) flow field. There are some existing correlations for correcting the wall temperature effect on heat transfer when scaled to engine realistic conditions. But they were either developed to account for the temperature dependence of fluid properties largely empirically, or based on a boundary-layer model. It would be difficult (if not impossible) to define a boundary layer in many parts of a realistic blade passage with marked three-dimensional (3D} end wall and secondary flows (including those within a blade tip and around it). The questions to be asked here are: is the OTL aerodynamics significantly affected by the wall thermal condition? And if it is, how can we count this effect consistently in turbine blade tip design and analysis using modern CFD methods? In the present study the problem has been examined for typical high-pressure turbine blade tip configurations. An extensively developed RANS code (HYDRA) is employed and validated against the experimental data from a high speed linear cascade testing rig. The numerical analysis reveals that the wall-gas temperature ratio could greatly affect the transonic OTL flow field and there is a strong two-way coupling between aerodynamics and heat transfer. The feedbacks of the thermal boundary condition to aerodynamics behave differently at different flow regimes over the tip, clearly indicating a highly localized dependence of the convective heat transfer coefficient (HTC) upon wall temperatures. This implies that to use HTC for blade metal temperature predictions without resorting a fully conjugate solution, the temperature dependence needs to be corrected locally. A nonlinear correction approach has been adopted in the present work, and the results demonstrate its effectiveness for the transonic turbine tip configurations studied.

show abstract

“…As noted from a study by Silieti et al [24], modelling the conductive transfer of heat in the plate is essential to properly capture the heating of the fl uid inside each cooling hole; this will inevitably have an effect on the heat transfer coeffi cient and temperature of the combustor wall and thus how accurately the cooling effectiveness over the combustor wall can be modelled. With this in mind, a CHT approach is adopted to account for heat transfer via plate conduction as well as fl uid convection.…”

Section: Boundary Conditionsmentioning

confidence: 99%

Numerical study of effusion cooling flow and heat transfer

Walton¹,

Yang²

2014

Int. J. CMEM

View full text Add to dashboard Cite

An isothermal and non-isothermal numerical study of effusion cooling fl ow and heat transfer is conducted using a Reynolds-averaged Navier-Stokes (RANS) approach. A Reynolds stress transport (RST) turbulence model is used to predict the fl ow fi eld of a staggered array of 12 rows of effusion holes, each hole inclined at 30° to the fl at plate. The Reynolds number based on the hole diameter and jet exit velocity is 3800. The blowing ratio in both studies is 5. A conjugate heat transfer approach is adopted in the non-isothermal simulation. For the isothermal case, the RST model is shown to be capable of predicting the injection, penetration, downstream decay and lateral mixing of the effusion jets reasonably well. In addition, the numerical model captures the existence of two counter-rotating vortices emanating from each hole, which causes the entrainment of combustor fl ow towards the surface of the plate at the leading edge and downstream, infl uences the mixing of accumulated coolant fl ow, providing a more uniform surface temperature across the plate. The presence and characteristics of these vortices are in good agreement with previously published research. In the non-isothermal case, the laterally averaged cooling effectiveness across the plate is under-predicted but the trend conforms to that exhibited during experimentation. Keywords: Conjugate heat transfer, effusion cooling, RANS, RST turbulence model. INTRODUCTIONGas turbine engines operate at extremely high temperatures; thus, components such as combustion chamber walls, turbine endwalls, turbine blades and shrouds need to be cooled. The desire to increase the effi ciency, i.e. reducing the specifi c fuel consumption and raising the thrust-to-weight ratio of gas turbines, has led to an increase in pressure and temperature in the combustion chamber and turbine. The operational life of the combustion chamber walls decreases as the temperature increases; thus, a method of cooling must be used to protect the wall. Whilst wall cooling is essential, there is also a need to minimise the proportion of air used for cooling as air taken away from the combustion process increases nitrous oxide emissions. Amongst many techniques available, effusion cooling, also known as full coverage fi lm cooling (FCFC), is considered the most practical. In this approach, cooler air, usually bled from the latter stages of the compressor, is injected from the combustor outer casing side through thousands of sub-millimetric angled perforations and enters the boundary layer on the internal wall of the combustor. The cooling fi lm that protects the liner from the hot gases results from the coalescence of the discrete micro-jets emanating from the perforations.Engineers are always trying to extract greater cooling performance from less cooling air whilst also trying to maximise the overall fi lm-cooling effectiveness so that the amount of air used for cooling can be reduced. A fundamental understanding of the mechanisms involved in effusion fl ow fi elds is therefore requir...

show abstract

Film cooling effectiveness: Comparison of adiabatic and conjugate heat transfer CFD models

Cited by 109 publications

References 35 publications

A Comparative Study of Film Cooling Effectiveness on a Flat Plate With Adiabatic and Conjugate Conditions for Different Hole Shapes

A Comparative Study of Film Cooling Effectiveness on a Flat Plate With Adiabatic and Conjugate Conditions for Different Hole Shapes

Impact of Wall Temperature on Turbine Blade Tip Aerothermal Performance

Numerical study of effusion cooling flow and heat transfer

Contact Info

Product

Resources

About