An Experimental Investigation of Film Cooling Heat Transfer Coefficients Using the Mass/Heat Analogy

1995 ◽  
Vol 117 (4) ◽  
pp. 851-858 ◽  
Author(s):  
Y. Sun ◽  
I. S. Gartshore ◽  
M. E. Salcudean
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Mass Transfer ◽  
Experimental Investigation ◽  
Mass Flow ◽  
Film Cooling ◽  
Wall Function ◽  
Transfer Coefficients ◽  
Correction Formula ◽  
Heat Transfer Coefficients

An experimental investigation has been carried out to determine the heat/mass transfer coefficient downstream of a two-dimensional, normal, film cooling injection slot. The plate downstream of the slot is porous, and air contaminated with propane is bled through it. By measuring the propane concentration very close to the wall using a flame ionization detector, mass transfer measurements are conducted for film cooling mass flow ratios ranging from 0 to 0.5. The mass transfer coefficients are calculated using a wall function correction formula, which corrects the measurements for displacement from the surface, and are then related directly to corresponding heat transfer coefficients using the mass/heat analogy. The validity of the method and the wall function correction formula are checked by examining the case with zero film coolant injection, a situation analogous to the well-known turbulent boundary layer mass/heat transfer with impermeable/unheated starting length. Good agreement with predicted data is obtained for this experiment. For film cooling with low mass flow ratios, heat transfer coefficients close to those of a conventional turbulent boundary layer are obtained. At high values of mass flow ratios quite different trends are observed, reflecting the important effect of the separation bubble, which is present just downstream of the injection slot.

Buoyancy Driven Flow in Saturated Porous Media

2006 ◽  
Vol 129 (6) ◽  
pp. 727-734 ◽  
Author(s):  
H. Sakamoto ◽  
F. A. Kulacki
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Boundary Layer ◽  
Mass Transfer ◽  
Porous Medium ◽  
Saturated Porous Medium ◽  
Saturated Porous Media ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Bulk Medium

Measurements are reported of heat transfer coefficients in steady natural convection on a vertical constant flux plate embedded in a saturated porous medium. Results show that heat transfer coefficients can be adequately determined via a Darcy-based model, and our results confirm a correlation proposed by Bejan [Int. J. Heat Mass Transfer. 26(9), 1339–1346 (1983)]. It is speculated that the reason that the Darcy model works well in the present case is that the porous medium has a lower effective Prandtl number near the wall than in the bulk medium. The factors that contribute to this effect include the thinning of the boundary layer near the wall and an increase of effective thermal conductivity.

The Influence of the Boundary Layer State and Reynolds Number on Film Cooling and Heat Transfer on a Cooled Nozzle Guide Vane

2000 ◽  
Author(s):  
Hans Reiss ◽  
Albin Bölcs
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Film Cooling ◽  
Guide Vane ◽  
Suction Side ◽  
Flow Conditions ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Nozzle Guide Vane ◽  
Nozzle Guide

Film cooling and heat transfer measurements were carried out on a cooled nozzle guide vane in a linear cascade, using a transient liquid crystal technique. Three flow conditions were realized: the nominal operating condition of the vane with an exit Reynolds number of 1.47e6, as well as two lower flow conditions: Re2L = 1.0e6 and 7.5e5. The vane model was equipped with a single row of inclined round film cooling holes with compound angle orientation on the suction side. Blowing ratios ranging form 0.3 to 1.5 were covered, all using foreign gas injection (CO2) yielding an engine-representative density ratio of 1.6. Two distinct states of the incoming boundary layer onto the injection station were compared, an undisturbed laminar boundary layer as it forms naturally on the suction side, and a fully turbulent boundary layer which was triggered with a trip wire upstream of injection. The aerodynamic flow field is characterized in terms of profile Mach number distribution, and the associated heat transfer coefficients around the uncooled airfoil are presented. Both detailed and spanwise averaged results of film cooling effectiveness and heat transfer coefficients are shown on the suction side, which indicate considerable influence of the state of the incoming boundary layer on the performance of a film cooling row. The influence of the mainstream flow condition on the film cooling behavior at constant blowing ratio is discussed for three chosen injection regimes.

Heat Transfer from a Flat Plate in Two-Component Mist Flow

1980 ◽  
Vol 102 (3) ◽  
pp. 513-518 ◽  
Author(s):  
K. Hishida ◽  
M. Maeda ◽  
S. Ikai
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Flat Plate ◽  
Mass Flow ◽  
Wall Temperature ◽  
Single Phase ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Mist Flow ◽  
Two Component

An experimental study concerning the characteristics of heat transfer from a dry isothermal flat plate in two-component (water-air) mist flow has been performed for lower water-air mass flow ratios up to 2.3 percent. Heat transfer coefficients in mist flow increase several times corresponding to single phase coefficients with increasing mass flow ratio and free stream velocity, and with decreasing wall temperature. The measurements of droplet velocity employing laser Doppler anemometry indicate the similarity of velocity distributions in boundary layer of mist flow, which approximately fit the laminar single phase one. It is confirmed that an augmentation of heat transfer is attributable to a latent heat due to evaporation of water droplets within the boundary layer, and that, at a constant Reynolds number and wall temperature, the enhanced rates of heat transfer coefficients are linearly correlated to water mass flow rates for unit cross-sectional area.

An Experimental Investigation of Boundary Layer and Heat Transfer in the Region of Separated Flow Downstream of Normal Injection Slots

1975 ◽  
Vol 97 (2) ◽  
pp. 260-266 ◽  
Author(s):  
R. C. Foster ◽  
A. Haji-Sheikh
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Flow Separation ◽  
Film Cooling ◽  
Flow Characteristics ◽  
Separated Flow ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Heat Transfer Coefficients

An experimental investigation was conducted to determine the flow characteristics, heat transfer coefficients, and film cooling effectiveness in the region immediately downstream of flush, normal injection slots. Air was injected through these slots into a turbulent primary flow produced by a small wind tunnel. Velocity measurements and tuft studies indicated that there was a significant region of separated flow immediately downstream of the slot. The heat transfer coefficients were appreciably increased as a result of this flow separation, and the film cooling effectiveness was decreased in comparison to previous studies involving no flow separation.

Turbine Airfoil Net Heat Flux Reduction With Cylindrical Holes Embedded in a Transverse Trench

2007 ◽  
Author(s):  
Katharine L. Harrison ◽  
John R. Dorrington ◽  
Jason E. Dees ◽  
David G. Bogard ◽  
Ronald S. Bunker
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Flux ◽  
Film Cooling ◽  
Suction Side ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Heat Transfer Augmentation ◽  
Net Heat Flux ◽  
Cylindrical Holes

Film cooling adiabatic effectiveness and heat transfer coefficients for cylindrical holes embedded in a 1d transverse trench on the suction side of a simulated turbine vane were investigated to determine the net heat flux reduction. For reference, measurements were also conducted with standard inclined, cylindrical holes. Heat transfer coefficients were determined with and without upstream heating to isolate the hydrodynamic effects of the trench and to investigate the effects of the thermal approach boundary layer. Also the effects of a tripped versus an un-tripped boundary layer were explored. For both the cylindrical holes and the trench, heat transfer augmentation was much greater with no tripping of the approach flow. A further increase in heat transfer augmentation was caused by use of upstream heating, with as much as a 150% augmentation with the trench. With a tripped approach flow the heat transfer augmentation was much less. The net heat flux reduction for the trench was found to be significantly higher than for the row of cylindrical holes.

Turbine Airfoil Net Heat Flux Reduction With Cylindrical Holes Embedded in a Transverse Trench

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Katharine L. Harrison ◽  
John R. Dorrington ◽  
Jason E. Dees ◽  
David G. Bogard ◽  
Ronald S. Bunker
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Flux ◽  
Film Cooling ◽  
Suction Side ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Heat Transfer Augmentation ◽  
Net Heat Flux ◽  
Cylindrical Holes

Film cooling adiabatic effectiveness and heat transfer coefficients for cylindrical holes embedded in a 1d transverse trench on the suction side of a simulated turbine vane were investigated to determine the net heat flux reduction. For reference, measurements were also conducted with standard inclined, cylindrical holes. Heat transfer coefficients were determined with and without upstream heating to isolate the hydrodynamic effects of the trench and to investigate the effects of the thermal approach boundary layer. Also, the effects of a tripped versus an untripped boundary layer were explored. For both the cylindrical holes and the trench, heat transfer augmentation was much greater for the untripped approach flow. A further increase in heat transfer augmentation was caused by use of upstream heating, with as much as a 180% augmentation for the trench. The tripped approach flow led to much lower heat transfer augmentation than the untipped case. The net heat flux reduction for the trench was found to be significantly higher than for the row of cylindrical holes.

scholarly journals Prediction of Heat Transfer Characteristics for Discrete Hole Film Cooling for Turbine Blade Applications

1989 ◽  
Author(s):  
Daneshmund K. Tafti ◽  
Savash Yavuzkurt
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Film Cooling ◽  
Three Dimensional ◽  
Hole Injection ◽  
Transfer Coefficients ◽  
Film Cooling Effectiveness ◽  
Heat Transfer Coefficients ◽  
Injection Process ◽  
Prediction Scheme

A two-dimensional (2-D) injection model is used with a 2-D low Reynold’s number k-ε model boundary layer code. The three-dimensional effects of the discrete hole injection process is introduced in the 2-D prediction scheme through an “entrainment fraction” (T). An established correlation between T and the injection parameters obtained in a previous paper is used to predict the film cooling effectiveness (η̄) and heat transfer coefficients for multirow injection, injection into a laminar boundary layer and finally injection on convex curved surfaces. Predictions of η̄ are in good agreement with experimental data for most of the cases tested. Predictions of Stanton numbers defined by St(0) and St(1) are good for low injection ratios (M) but as M increases the values are underpredicted. In spite of some shortcomings, in the authors’ opinion the present 2-D prediction scheme is one of the most comprehensive developed so far. It is seen that the entrainment fraction T is quite universal in its application to 2-D predictions of the discrete hole film cooling process.

Heat Transfer Coefficients and Film Cooling Effectiveness on the Squealer Tip of a Gas Turbine Blade

2003 ◽  
Vol 125 (4) ◽  
pp. 648-657 ◽  
Author(s):  
Jae Su Kwak ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Film Cooling ◽  
Rotor Blade ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Heat Transfer Coefficients ◽  
Blowing Ratio

Experimental investigations were performed to measure the detailed heat transfer coefficients and film cooling effectiveness on the squealer tip of a gas turbine blade in a five-bladed linear cascade. The blade was a two-dimensional model of a first stage gas turbine rotor blade with a profile of the GE-E3 aircraft gas turbine engine rotor blade. The test blade had a squealer (recessed) tip with a 4.22% recess. The blade model was equipped with a single row of film cooling holes on the pressure side near the tip region and the tip surface along the camber line. Hue detection based transient liquid crystals technique was used to measure heat transfer coefficients and film cooling effectiveness. All measurements were done for the three tip gap clearances of 1.0%, 1.5%, and 2.5% of blade span at the two blowing ratios of 1.0 and 2.0. The Reynolds number based on cascade exit velocity and axial chord length was 1.1×106 and the total turning angle of the blade was 97.9 deg. The overall pressure ratio was 1.2 and the inlet and exit Mach numbers were 0.25 and 0.59, respectively. The turbulence intensity level at the cascade inlet was 9.7%. Results showed that the overall heat transfer coefficients increased with increasing tip gap clearance, but decreased with increasing blowing ratio. However, the overall film cooling effectiveness increased with increasing blowing ratio. Results also showed that the overall film cooling effectiveness increased but heat transfer coefficients decreased for the squealer tip when compared to the plane tip at the same tip gap clearance and blowing ratio conditions.

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.

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