AN EXPERIMENTALLY VALIDATED LOW ORDER MODEL OF THE THERMAL RESPONSE OF DOUBLE-WALL EFFUSION COOLING SYSTEMS FOR HP TURBINE BLADES

2021 ◽  
pp. 1-13
Author(s):  
Alexander V Murray ◽  
Peter Ireland ◽  
Eduardo Romero
Keyword(s):  
Heat Transfer ◽  
Thermal Model ◽  
Transpiration Cooling ◽  
Transfer Coefficients ◽  
Order Model ◽  
Cooling Performance ◽  
Convective Cooling ◽  
Heat Transfer Coefficients ◽  
Double Wall ◽  
Low Order

Abstract Transpiration cooling represents the pinnacle of turbine cooling and is characterised by an intrinsic porosity achieving high internal convective cooling, and full coverage film cooling. The quasi-transpiration, double-wall effusion system attempts to replicate the cooling effect of transpiration cooling. The system is characterised by a large wetted area providing high internal convective cooling performance, with a highly porous external wall allowing the formation of a protective cooling film. This paper presents a low-order thermal model of a double-wall system designed to rapidly ascertain cooling performance based solely on the geometry, thermal conductivity, and approximate surface heat transfer coefficients. Initially validation uses experimental data with heat transfer coefficients for the low order model obtained from fully conjugate CFD simulations. A more controlled CFD study is then undertaken with both fully conjugate and fluid only simulations performed on several double-wall geometries to ascertain both overall and film effectiveness data. Data from these simulations are used as inputs to the low order thermal model and the results compared. The low order model successfully captures both the trends and absolute cooling effectiveness achieved by the various double-wall geometries. The model therefore provides a powerful tool whereby the cooling performance of double-wall geometries can be near instantaneously predicted during the initial design stage, potentially allowing geometry optimisation to rapidly occur prior to more in-depth, costly and time-consuming analyses. This benefit is demonstrated via the implementation of the model with input boundary conditions obtained using empirical correlations.

An Experimentally Validated Low Order Model of the Thermal Response of Double-Wall Effusion Cooling Systems for HP Turbine Blades

2020 ◽  
Author(s):  
Alexander V. Murray ◽  
Peter T. Ireland ◽  
Eduardo Romero
Keyword(s):  
Heat Transfer ◽  
Thermal Model ◽  
External Surface ◽  
Transfer Coefficients ◽  
Order Model ◽  
Cooling Performance ◽  
Heat Transfer Coefficients ◽  
Double Wall ◽  
Wall System ◽  
Low Order

Abstract Transpiration cooling represents the pinnacle of turbine cooling and is characterised by an intrinsic material porosity which achieves high internal convective cooling, and full coverage cooling films on the external surface subjected to the hot gases. Quasi-transpiration systems, such as the double-wall effusion system discussed here, attempt to replicate the cooling effect of transpiration systems. The double-wall system is characterised by a large internal wetted area providing high internal convective cooling performance, with a highly porous external wall allowing the formation of a protective film over the external surface. This paper presents a low-order thermal model of a double-wall system designed to rapidly ascertain cooling performance based solely on the geometry, solid thermal conductivity, and approximate surface heat transfer coefficients. The performance of the model is initially validated using experimental data with heat transfer coefficients for the low order model obtained from fully conjugate CFD simulations. Following this, a more controlled CFD study is undertaken with both fully conjugate and fluid only simulations performed on several double-wall geometries to ascertain both overall effectiveness and film effectiveness data. Data from these simulations are used as inputs to the low order thermal model developed and the results compared. The low order model successfully captures both the trends and absolute cooling effectiveness achieved by the various double-wall geometries. The model therefore provides an extremely powerful tool in which the cooling performance of double-wall geometries can be near instantaneously predicted during the initial design stage, potentially allowing geometry optimisation to rapidly occur prior to more in-depth, costly and time-consuming analyses of the systems being performed. This potential benefit is demonstrated via the implementation of the model with input boundary conditions obtained using empirical correlations.

Experimental and Numerical Study on the Effects of the Relative Position of Film Hole and Orientation Ribs on the Film Cooling With Ribbed Cross-Flow Coolant Channel

2020 ◽  
Author(s):  
Bingran Li ◽  
Cunliang Liu ◽  
Lin Ye ◽  
Huiren Zhu ◽  
Fan Zhang
Keyword(s):  
Heat Transfer ◽  
Relative Position ◽  
Film Cooling ◽  
Numerical Study ◽  
Cross Flow ◽  
Internal Cooling ◽  
Transfer Coefficients ◽  
Cooling Performance ◽  
Heat Transfer Coefficients ◽  
Numerical Studies

Abstract To investigate the application of ribbed cross-flow coolant channels with film hole effusion and the effects of the internal cooling configuration on film cooling, experimental and numerical studies are conducted on the effect of the relative position of the film holes and different orientation ribs on the film cooling performance. Three cases of the relative position of the film holes and different orientation ribs (post-rib, centered, and pre-rib) in two ribbed cross-flow channels (135° and 45° orientation ribs) are investigated. The film cooling performances are measured under three blowing ratios by the transient liquid crystal measurement technique. A RANS simulation with the realizable k-ε turbulence model and enhanced wall treatment is performed. The results show that the cooling effectiveness and the downstream heat transfer coefficient for the 135° rib are basically the same in the three position cases, and the differences between the local effectiveness average values for the three are no more than 0.04. The differences between the heat transfer coefficients are no more than 0.1. The “pre-rib” and “centered” cases are studied for the 45° rib, and the position of the structures has little effect on the film cooling performance. In the different position cases, the outlet velocity distribution of the film holes, the jet pattern and the discharge coefficient are consistent with the variation in the cross flow. The related research previously published by the authors showed that the inclination of the ribs with respect to the holes affects the film cooling performance. This study reveals that the relative positions of the ribs and holes have little effect on the film cooling performance. This paper expands and improves the study of the effect of the internal cooling configuration on film cooling and makes a significant contribution to the design and industrial application of the internal cooling channel of a turbine blade.

Heat Transfer Coefficient Measurements of Film-Cooling Holes With Expanded Exits

1998 ◽  
Author(s):  
M. Gritsch ◽  
A. Schulz ◽  
S. Wittig
Keyword(s):  
Heat Transfer ◽  
Mach Number ◽  
Film Cooling ◽  
Cylindrical Hole ◽  
Superposition Method ◽  
Transfer Coefficients ◽  
Cooling Performance ◽  
Heat Transfer Coefficients ◽  
Film Cooling Holes ◽  
Injection Location

Detailed measurements of heat transfer coefficients in the nearfield of three different film-cooling holes are presented. The hole geometries investigated include a cylindrical hole and two holes with a diffuser shaped exit portion (i.e. a fan-shaped and a laidback fanshaped hole). They were tested over a range of blowing ratios M = 0.25…1.75 at an external crossflow Mach number of 0.6 and a coolant-to-mainflow density ratio of 1.85. Additionally, the effect of the internal coolant supply Mach number is addressed. Temperatures of the diabatic surface downstream of the injection location are measured by means of an infrared camera system. They are used as boundary conditions for a finite element analysis to determine surface heat fluxes and heat transfer coefficients. The superposition method is applied to evaluate the overall film-cooling performance of the hole geometries investigated. As compared to the cylindrical hole, both expanded holes show significantly lower heat transfer coefficients downstream of the injection location, particularly at high blowing ratios. The laidback fanshaped hole provides a better lateral spreading of the injected coolant than the fanshaped hole which leads to lower laterally averaged heat transfer coefficients. Coolant passage crossflow Mach number affects the flowfield of the jet being ejected from the hole and, therefore, has an important impact on film-cooling performance.

Hole Staggering Effect on the Cooling Performance of Narrow Impingement Channels Using the Transient Liquid Crystal Technique

2014 ◽  
Vol 136 (7) ◽  
Author(s):  
Alexandros Terzis ◽  
Guillaume Wagner ◽  
Jens von Wolfersdorf ◽  
Peter Ott ◽  
Bernhard Weigand
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Jet Impingement ◽  
Transfer Coefficients ◽  
Noticeable Effect ◽  
Cooling Performance ◽  
Heat Transfer Coefficients ◽  
Cooling Hole ◽  
Turbine Airfoils ◽  
Transient Liquid Crystal Technique

This study examines experimentally the cooling performance of narrow impingement channels as could be cast-in in modern turbine airfoils. Full surface heat transfer coefficients are evaluated for the target plate and the sidewalls of the channels using the transient liquid crystal technique. Several narrow impingement channel geometries, consisting of a single row of five cooling holes, have been investigated composing a test matrix of nine different models. The experimental data are analyzed by means of various post-processing procedures aiming to clarify and quantify the effect of cooling hole offset position from the channel centerline on the local and average heat transfer coefficients and over a range of Reynolds numbers (11,100–86,000). The results indicated a noticeable effect of the jet pattern on the distribution of convection coefficients as well as similarities with conventional multi-jet impingement cooling systems.

Film Cooling From a Row of Holes With Both Ends Embedded in Transverse Slots

2008 ◽  
Author(s):  
D. H. Zhang ◽  
L. Sun ◽  
Q. Y. Chen ◽  
M. Lin ◽  
M. Zeng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Aerodynamic Performance ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Heat Transfer Coefficients ◽  
Discharge Coefficients ◽  
Cylindrical Holes

Embedding a row of typical cylindrical holes in a transverse slot can improve the cooling performance. Rectangular slots can increase the cooling effectiveness but is at the cost of decreasing of discharge coefficients. An experiment is conducted to examine the effects of an overlying transverse inclined trench on the film cooling performance of axial holes. Four different trench configurations are tested including the baseline inclined cylindrical holes. The influence of the geometry of the upstream lip of the exit trench and the geometry of the inlet trench on cooling performance is examined. Detailed film cooling effectiveness and heat transfer coefficients are obtained separately using the steady state IR thermography technique. The discharge coefficients are also acquired to evaluate the aerodynamic performance of different hole configurations. The results show that the film cooling holes with both ends embedded in slots can provide higher film cooling effectiveness and lower heat transfer coefficients; it also can provide higher discharge coefficients whilst retaining the mechanical strength of a row of discrete holes. The cooling performance and the aerodynamic performance of the holes with both ends embedded in inclined slots are superior to the holes with only exit trenched. To a certain extent, the configuration of the upstream lip of the exit trench affects the cooling performance of the downstream of the trench. The filleting for the film hole inlet avail the improvement of the cooling effect, but not for the film hole outlet. Comparing film cooling with embedded holes to unembedded holes, the overall heat flux ratio shows that the film holes with both ends embedded in slots and filleting for the film hole inlet can produce the highest heat flux reduction.

scholarly journals Bayesian Parameter Estimation of Convective Heat Transfer Coefficients of a Roof-Mounted Radiant Barrier System

2005 ◽  
Vol 128 (2) ◽  
pp. 213-225 ◽  
Author(s):  
Philippe Lauret ◽  
Frédéric Miranville ◽  
Harry Boyer ◽  
François Garde ◽  
Laetitia Adelard
Keyword(s):  
Heat Transfer ◽  
Parameter Estimation ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Bayesian Methods ◽  
Thermal Model ◽  
Estimation Method ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Convective Heat Transfer Coefficients

This paper deals with the application of Bayesian methods to the estimation of two convective heat-transfer coefficients of a roof-mounted radiant barrier system. As part of an empirical validation of the thermal model of the roofing complex, a parametric sensitivity analysis highlighted the importance of convective coefficients in the thermal behavior of a roofing complex. A parameter estimation method is then used in order to find the values of the coefficients that lead to an improvement of the thermal model. However, instead of using a classical parameter estimation method, we used a Bayesian inference approach to parameter estimation. The aim of the paper is to introduce the basic concepts of this powerful method in this simple two-parameter case. We show that Bayesian methods introduce an explicit treatment of uncertainty in modeling and a corresponding measure of reliability for the conclusions reached.

Heat Transfer Coefficient Distributions for the Convective Cooling of Non-Cylindrical Geometries in Crossflow Using Extended Surfaces

1997 ◽  
Author(s):  
Andrew J. Neely ◽  
Peter T. Ireland ◽  
Les R. Harper
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Gas Turbines ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Convective Cooling ◽  
Heat Transfer Coefficients ◽  
Cylindrical Geometries

An experimental investigation of the performance of extended fin surfaces for the forced convective cooling of a range of engine component geometries in crossflow is reported. The experiments were undertaken to measure the surface heat transfer coefficient distributions of external finning around non-cylindrical geometries for use in aviation gas turbines in which the cooling performance/mass ratio must be maximised. The geometries examined were a box (square with rounded corners), a flute (rectangle with circular ends) and a 30° wedge. These models were sized to have equivalent cross sectional area to allow a direct comparison of performance. Perspex models coated with thermochromic liquid crystal were tested at a range of Reynolds numbers in a heat transfer wind tunnel in which a step change in flow temperature was used to measure the transient thermal behaviour of the fins. This technique enables the full surface mapping of local heat transfer coefficients on the surface of the fins. These measurements are compared with those for the equivalent smooth geometries and also with empirical calculations from the literature where available. A comparison with previous cylindrical measurements is also made. Knowledge of the distributions of local heat transfer coefficients enables the optimisation of the geometry through strategies such as baffling of the fins. Some examples of these strategies have been implemented and the results are reported. The finned geometries are seen to outperform the unfinned geometries (by factors greater than 3) though by factors less than simply the increase in area. The enhancement in h results because the increased surface area of the fins more than outweighs the decrease in local h on the fin surface as compared to the smooth geometries.

Comparison of the Cooling Performance of Staggered and In-Line Arrays of Electronic Packages

1996 ◽  
Vol 118 (1) ◽  
pp. 27-30 ◽  
Author(s):  
R. A. Wirtz ◽  
D. M. Colban
Keyword(s):  
Heat Transfer ◽  
Applied Pressure ◽  
Electronic Packages ◽  
Pumping Power ◽  
Transfer Coefficients ◽  
Cooling Performance ◽  
Heat Transfer Coefficients ◽  
Friction Factors ◽  
Significant Difference ◽  
Flow Pressure

The cooling performance of in-line and staggered regular arrays of simulated electronic packages is compared for both sparse and dense packaging configurations. At equal flow rates, staggered arrays exhibit higher element heat transfer coefficients and friction factors than in-line arrays. Furthermore, an increase in the packaging density of the elements results in a moderate reduction in the friction factor with negligible change in the heat transfer coefficient. However, when performance is expressed in terms of heat transfer rate per unit packaging system volume, dense arrays are found to out perform sparse arrays at equal flow rate, applied pressure gradient or pumping power. Furthermore, no significant difference in performance is observed between staggered and in-line configurations when they are compared on the basis of either equal coolant flow pressure drop or pumping power.

Degradation of Film Cooling Performance on a Turbine Vane Suction Side due to Surface Roughness

2005 ◽  
Vol 128 (3) ◽  
pp. 547-554 ◽  
Author(s):  
James L. Rutledge ◽  
David Robertson ◽  
David G. Bogard
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Film Cooling ◽  
Extended Period ◽  
Suction Side ◽  
Transfer Coefficients ◽  
Cooling Performance ◽  
Heat Transfer Coefficients ◽  
Turbine Vane ◽  
Adiabatic Effectiveness

After an extended period of operation, the surfaces of turbine airfoils become extremely rough due to deposition, spallation, and erosion. The rough airfoil surfaces will cause film cooling performance degradation due to effects on adiabatic effectiveness and heat transfer coefficients. In this study, the individual and combined effects of roughness upstream and downstream of a row of film cooling holes on the suction side of a turbine vane have been determined. Adiabatic effectiveness and heat transfer coefficients were measured for a range of mainstream turbulence levels and with and without showerhead blowing. Using these parameters, the ultimate film cooling performance was quantified in terms of net heat flux reduction. The dominant effect of roughness was a doubling of the heat transfer coefficients. Maximum adiabatic effectiveness levels were also decreased significantly. Relative to a film cooled smooth surface, a film cooled rough surface was found to increase the heat flux to the surface by 30%–70%.

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