Film Cooling System Numerical Design: Adiabatic and Conjugate Analysis

2005 ◽  
Author(s):  
Antonio Andreini ◽  
Carlo Carcasci ◽  
Stefano Gori ◽  
Marco Surace
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Conjugate Heat Transfer ◽  
Cooling System ◽  
Numerical Study ◽  
Single Row ◽  
Numerical Design ◽  
Cooling Behavior

Film cooling is certainly the most diffused system to protect metal surface against hot gases, both in turbogas blades and combustors. Although being very diffused, there are still several aspects of its behavior which need a better understanding. Mainly, the performance of multi-row holes configurations are still estimated correcting single-row correlations. Heat transfer coefficient modifications due to the presence of injected coolant are hard to evaluate, and even now few studies in literature take into account this factor. The present work is a detailed numerical study of some effects of film cooling. 3D CFD-RANS simulations have been performed to infer interesting trends of adiabatic superposition effects and conjugate heat transfer performances. In particular, several calculations have been carried out to evaluate single row and multi-row film cooling behavior in terms of heat transfer coefficient, overall and adiabatic effectiveness. Test were conducted with blowing ratios between 0.5 and 5.5, coolant Reynolds from 1000 to 16000.

Numerical Study on the Influence of Trench Width on Film Cooling Characteristics of Double-Wave Trench

2017 ◽  
Author(s):  
Bo-lun Zhang ◽  
Li Zhang ◽  
Hui-ren Zhu ◽  
Jian-sheng Wei ◽  
Zhong-yi Fu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Numerical Study ◽  
Leading Edge ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Trench Width

Film cooling performance of the double-wave trench was numerically studied to improve the film cooling characteristics. Double-wave trench was formed by changing the leading edge and trailing edge of transverse trench into cosine wave. The film cooling characteristics of transverse trench and double-wave trench were numerically studied using Reynolds Averaged Navier Stokes (RANS) simulations with realizable k-ε turbulence model and enhanced wall treatment. The film cooling effectiveness and heat transfer coefficient of double-wave trench at different trench width (W = 0.8D, 1.4D, 2.1D) conditions are investigated, and the distribution of temperature field and flow field were analyzed. The results show that double-wave trench effectively improves the film cooling effectiveness and the uniformity of jet at the downstream wall of the trench. The span-wise averaged film cooling effectiveness of the double-wave trench model increases 20–63% comparing with that of the transverse trench at high blowing ratio. The anti-counter-rotating vortices which can press the film on near-wall are formed at the downstream wall of the double-wave trench. With the double-wave trench width decreasing, the film cooling effectiveness gradually reduces at the hole center-line region of the downstream trench. With the increase of the blowing ratio, the span-wise averaged heat transfer coefficient increases. The span-wise averaged heat transfer coefficient of the double-wave trench with 0.8D and 2.1D trench width is higher than that of the double-wave trench with 1.4D trench width at the high blowing ratio conditions.

Influence of a Leaking Gap Downstream of the Injection Holes on Film Cooling Performance

1996 ◽  
Author(s):  
Y. Yu ◽  
M. K. Chyu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Cooling System ◽  
Convective Transport ◽  
Hole Injection ◽  
Thermochromic Liquid Crystal ◽  
Cooling Performance ◽  
Temperature Problem

This study investigated a practical but never exploited issue concerning the influence of flow leakage through a gap downstream on the film cooling performance with a row of discrete-hole injection. A heat transfer system as such can be categorized as either a three-temperature or a four-temperature problem, depending on the direction of leakage through the gap. To fully characterize a three-temperature based film-cooling system requires knowledge of both local film effectiveness and heat transfer coefficient. A second film effectiveness is necessary for characterizing a four-temperature problem. All these variables can be experimentally determined, based on the transient method of thermochromic liquid crystal imaging. Although the overall convective transport in the region is expected to be dependent on the blowing ratios of the coolants, the mass flow ratio of the two injectants, and the geometry, the current results indicated that the extent of flow injection or extraction through the gap has significant effects on the film effectiveness and less on the heat transfer coefficient which is primarily dominated by the geometric disturbance of gap presence.

Conjugate Heat Transfer From a Heated Disk to a Thin Liquid Film Formed by a Controlled Impinging Jet

1993 ◽  
Vol 115 (1) ◽  
pp. 116-123 ◽  
Author(s):  
A. Faghri ◽  
S. Thomas ◽  
M. M. Rahman
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Conjugate Heat Transfer ◽  
Numerical Study ◽  
Heated Surface ◽  
Thin Liquid Film ◽  
Impinging Jet ◽  
Numerical Predictions ◽  
Heated Disk

An experimental and numerical study of the heat transfer from a heated horizontal disk to a thin film of liquid is described. The liquid was delivered to the disk by a collar arrangement such that the film thickness and radial velocity were known at the outer radius of the collar. This method of delivery is termed as a controlled impinging jet. Flow visualization tests were performed and heat transfer data were collected along the radius of the disk for different volumetric flow rates and inlet temperatures in the supercritical and subcritical regions. The heat transfer coefficient was found to increase with flow rate when both supercritical and subcritical regions were present on the heated surface. A numerical simulation of this free surface problem was performed, which included the effects of conjugate heat transfer within the heated disk and the liquid. The numerical predictions agree with the experimental results and show that conjugate heat transfer has a significant effect on the local wall temperature and heat transfer coefficient.

An Investigation of the Heat Transfer for Full Coverage Film Cooling

2003 ◽  
Author(s):  
Grady B. Kelly ◽  
David G. Bogard
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Load Reduction ◽  
Injection Angle ◽  
Single Row ◽  
Full Coverage ◽  
The Heat Transfer Coefficient ◽  
Effectiveness Data

An experimental study was conducted on the heat transfer to a film-cooled flat plate with a full coverage array of normal holes. The film cooling array consisted of ten staggered coolant rows, and each coolant hole had an L/D = 1.0 and an injection angle of α = 90°. Measurements of the heat transfer coefficient with and without film cooling were taken, in order to determine the increase in the heat transfer coefficient due to coolant injection. These experiments were conducted with heated and unheated starting lengths, and with low and high mainstream turbulence levels. The heat transfer coefficient ratios were used in conjunction with adiabatic effectiveness data taken in a previous study to determine the distributions of the overall heat load reduction. Heat transfer coefficient data from a single row of coolant holes were also taken. These data were used to evaluate several concepts for predicting full coverage heat transfer coefficient distributions based on the single row data.

Heat Transfer and Effectiveness for a Turbulent Boundary Layer With Tangential Fluid Injection

1960 ◽  
Vol 82 (4) ◽  
pp. 303-312 ◽  
Author(s):  
R. A. Seban
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Free Stream ◽  
Cooling System ◽  
Leading Edge ◽  
Free Stream Velocity ◽  
Stream Velocity ◽  
The Heat Transfer Coefficient

Experimental results are presented for the effectiveness and for the heat-transfer coefficient for a film cooling system in which air was used both for the film and for the free-stream fluids. Injection occurred at a single tangential slot near the leading edge of the plate and the slot size was varied. All flows were turbulent and the injection velocities covered a range from much less to much greater than the free-stream velocity. Correlations are realized for both the effectiveness and for the heat-transfer coefficient and, as in the past experience with such systems, separate specifications are needed for injection velocities greater and less than the free-stream velocity.

Conjugate Scaling in the Presence of Bore Cooling

2015 ◽  
Author(s):  
Thomas E. Dyson ◽  
James R. Winka ◽  
David B. Helmer
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Numerical Study ◽  
Additional Parameter ◽  
Scaling Parameters ◽  
Engine Components ◽  
The Heat Transfer Coefficient ◽  
Conductivity Models

Many analyses in the literature have assessed the appropriate manner in which to scale an experimental test rig to represent film-cooled engine components. For conventional testing using low conductivity models, the key parameters are the mainstream Reynolds number, scaled coolant flow rate, and the adiabatic film effectiveness. The few studies that have sought scaling parameters for conjugate testing have identified that one must additionally match the heat transfer coefficient ratio between the internal and external surfaces and external Biot number. However, these analyses have focused on blade or nozzle regions with single or sparse film rows. The validity of this scaling approach to regions or components with substantial bore cooling contributions is unclear — for example the showerhead and/or platform of a blade or nozzle, or a component like a shroud. The present analysis outlines the drivers for potential departure from the accepted scaling. A numerical study is performed to assess potential errors due to the traditional scaling. The results of the analysis demonstrate that the additional parameter, the ratio of bore cooling to external heat transfer coefficient, is more appropriate in the near hole region especially in cases where film cooling is not significant.

Investigations on the Film Cooling of Counter-Inclined Film-Hole Row Structures for Turbine Vane Leading Edge

2018 ◽  
Vol 35 (3) ◽  
pp. 291-303 ◽  
Author(s):  
Cun-Liang Liu ◽  
Dan Zhao ◽  
Ying-Ni Zhai ◽  
Hui-Ren Zhu ◽  
Yi-Hong He ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Leading Edge ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Single Row ◽  
Blowing Ratio ◽  
Turbine Vane

AbstractNumerical simulations have been performed on the film cooling characteristics of counter-inclined structures, which have advantage in manufacturing relative to the usually used parallel-inclined film-hole row structure, on a turbine vane leading edge model. Single row structure and dual-row structure with counter-inclined film holes were applied in the simulation of leading edge film cooling of turbine vane. The effect of jet-interaction between counter-inclined film-hole rows was studied. The distributions of film cooling effectiveness and heat transfer coefficient were obtained at blowing ratios of 1.0 and 2.0. The results of single row structure show that the film cooling performances of counter-inclined film-hole row are not weakened compared to the traditional parallel-inclined film-hole row structure. The film cooling effectiveness of the counter-inclined film-hole row structure decreases with the increase of blowing ratio, while the heat transfer coefficient increases. The jet-interaction in the dual-row film cooling structure has more notable influence on the film cooling effectiveness than the heat transfer coefficient. Compared to the single row case, the interactions between the upstream counter-blowing jets and the downstream jet improve the film coverage performance and reduce the heat transfer intensity of this downstream jet under larger blowing ratio condition.

Numerical Study on Film Cooling Characteristics of C3X Vane With Wave-Trench Hole

2018 ◽  
Author(s):  
Bo-lun Zhang ◽  
Li Zhang ◽  
Hui-ren Zhu ◽  
Jian-sheng Wei ◽  
Zhong-yi Fu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Numerical Study ◽  
Navier Stokes ◽  
Cooling Effectiveness ◽  
Single Wave ◽  
Film Cooling Effectiveness ◽  
Trench Structure

To get wider laterally coverage of the cooling jet, the single-wave trench and double-wave trench were further studied on the vane. The film cooling characteristics of different film cooling structures were numerically studied using Reynolds Averaged Navier Stokes (RANS) equations. The SST turbulence model with γ-θ transition model was applied for the present simulation. The film cooling effectiveness and heat transfer coefficient of different film cooling structures were investigated, and the distribution of temperature field and flow field were analyzed. Four different blowing ratios (M) from 0.5 to 2.0 were studied. The results show that compared with the transverse trench structure, the span-wise averaged film cooling effectiveness of the double-wave trench increases 0.1–0.35. The single-wave trench and double-wave trench film cooling structures significantly improve the uniformity of the jet and increase the film cooling effectiveness. The span-wise averaged film cooling effectiveness of the double-wave trench is higher than that of the single-wave trench at high blowing ratio conditions. The anti-counter-rotating vortices which can press the cooling jet on near-wall are formed at the downstream single-wave trench and double-wave trench. Both of the double-wave trench and the single-wave trench structure can effectively improve the film cooling effectiveness of the vane in the case of a little increase in the heat transfer coefficient compared to the cylindrical hole. The guidance action of the double-wave trench is more reasonable, therefore the film cooling characteristics is better than that of the single-wave trench.

Turbine Shroud Heat Transfer and Cooling With Blade Rotation: Part I — Forward, Backward and Lateral Injection

2017 ◽  
Author(s):  
Onieluan Tamunobere ◽  
Sumanta Acharya
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Lateral Spreading ◽  
Film Cooling Effectiveness ◽  
Blade Rotation ◽  
Cooling Behavior ◽  
Injection Methods ◽  
The Heat Transfer Coefficient

This is the first in a two-part series of an experimental film cooling study on a gas turbine shroud with a blade rotation speed of 1200 RPM. In this part of the study, the effect of forward, backward and lateral injection on the shroud heat transfer and cooling behavior is investigated. The shroud with a staggered hole arrangement and a hole pitch to diameter ratio of 4.0, consists of holes angled at 45° to the surface. Four hole configurations using inline and lateral coolant injection methods are utilized in this study. The first configuration consists of streamwise and forward facing holes inclined at 45 degrees to the surface (ϕ = 0°). The second configuration consists of backward facing holes also inclined at 45 degrees to the surface (ϕ = 180°). The third and fourth configurations consist of lateral injection with a surface angle of 45 degrees in the direction of blade rotation (ϕ = 90°) and opposite the direction of blade rotation (ϕ = 270°), respectively. The heat transfer coefficient is reported for the no-coolant case and measurements of the heat transfer coefficient and film cooling effectiveness are reported for each configuration at nominal blowing ratios of 0.5, 1.0, 1.5 and 2.0 using liquid crystal thermography. The results show that in-line injection performs better than lateral injection at low blowing ratios and the reverse is true at higher blowing ratios. Backward injection does show higher laterally averaged effectiveness with increased spreading in the vicinity of the coolant holes than forward injection. With a compact coolant hole arrangement, this results in higher area averaged effectiveness for backward injection than forward injection. With increased lateral spreading of the coolant in the hole region, lateral injection results in higher peak effectiveness values than inline injection. Nevertheless, lateral injection does not have the axial penetration of inline injection and as such leaves regions of the shroud downstream of the coolant holes vulnerable.

Influence of Gap Leakage Downstream of the Injection Holes on Film Cooling Performance

1998 ◽  
Vol 120 (3) ◽  
pp. 541-548 ◽  
Author(s):  
Y. Yu ◽  
M. K. Chyu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Cooling System ◽  
Convective Transport ◽  
Hole Injection ◽  
Thermochromic Liquid Crystal ◽  
Cooling Performance ◽  
Temperature Problem

This study investigated a practical but never exploited issue concerning the influence of flow leakage through a gap downstream on the film cooling performance with discrete-hole injection. A heat transfer system as such can be categorized as either a three-temperature or a four-temperature problem, depending on the direction of leakage through the gap. To characterize a three-temperature-based film cooling system fully requires knowledge of both local film effectiveness and heat transfer coefficient. A second film effectiveness is necessary for characterizing a four-temperature problem. All these variables can be experimentally determined, based on the transient method of thermochromic liquid crystal imaging. Although the overall convective transport in the region is expected to be dependent on the blowing ratios of the coolants, the mass flow ratio of the two injectants, and the geometry, the current results indicated that the extent of flow injection or extraction through the gap has significant effects on the film effectiveness and less on the heat transfer coefficient, which is primarily dominated by the geometric disturbance of gap presence.

Sign in / Sign up

Export Citation Format

Share Document