Effects of Rotation on Blade Surface Heat Transfer: An Experimental Investigation

1998 ◽  
Vol 120 (3) ◽  
pp. 530-540 ◽  
Author(s):  
R. W. Moss ◽  
R. W. Ainsworth ◽  
T. Garside
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Free Stream ◽  
Time History ◽  
Surface Heat ◽  
Blade Surface ◽  
Surface Heat Transfer ◽  
Free Stream Turbulence ◽  
Effects Of Rotation ◽  
Wake Passing

Measurements of turbine blade surface heat transfer in a transient rotor facility are compared with predictions and equivalent cascade data. The rotating measurements involved both forward and reverse rotation (wake-free) experiments. The use of thin-film gages in the Oxford Rotor Facility provides both time-mean heat transfer levels and the unsteady time history. The time-mean level is not significantly affected by turbulence in the wake; this contrasts with the cascade response to free-stream turbulence and simulated wake passing. Heat transfer predictions show the extent to which such phenomena are successfully modeled by a time-steady code. The accurate prediction of transition is seen to be crucial if useful predictions are to be obtained.

Effects of Rotation on Blade Surface Heat Transfer: An Experimental Investigation

1997 ◽  
Author(s):  
Roger W. Moss ◽  
Roger W. Ainsworth ◽  
Tom Garside
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Experimental Investigation ◽  
Turbine Blade ◽  
Time History ◽  
Surface Heat ◽  
Blade Surface ◽  
Surface Heat Transfer ◽  
Effects Of Rotation ◽  
Wake Passing

Measurements of turbine blade surface heat transfer in a transient rotor facility are compared with predictions and equivalent cascade data. The rotating measurements involved both forwards and reverse rotation (wake free) experiments. The use of thin-film gauges in the Oxford Rotor Facility provides both time-mean heat transfer levels and the unsteady time history. The time-mean level is not significantly affected by turbulence in the wake; this contrasts with the cascade response to freestream turbulence and simulated wake passing. Heat transfer predictions show the extent to which such phenomena are successfully modelled by a time-steady code. The accurate prediction of transition is seen to be crucial if useful predictions are to be obtained.

Enhanced Heat Transfer and Shear Stress Due to High Free-Stream Turbulence

1995 ◽  
Vol 117 (3) ◽  
pp. 418-424 ◽  
Author(s):  
K. A. Thole ◽  
D. G. Bogard
Keyword(s):  
Heat Transfer ◽  
Shear Stress ◽  
Skin Friction ◽  
Free Stream ◽  
Surface Heat ◽  
Wall Region ◽  
Transfer Enhancement ◽  
Enhanced Heat Transfer ◽  
Free Stream Turbulence ◽  
Wall Interaction

Surface heat transfer and skin friction enhancements, as a result of free-stream turbulence levels between 10 percent < Tu > 20 percent, have been measured and compared in terms of correlations given throughout the literature. The results indicate that for this range of turbulence levels, the skin friction and heat transfer enhancements scale best using parameters that are a function of turbulence level and dissipation length scale. However, as turbulence levels approach Tu = 20 percent, the St′ parameter becomes more applicable and simpler to apply. As indicated by the measured rms velocity profiles, the maximum streamwise rms value in the near-wall region, which is needed for St′, is the same as that measured in the free stream at Tu = 20 percent. Analogous to St′, a new parameter, Cf′, was found to scale the skin friction data. Independent of all the correlations evaluated, the available data show that the heat transfer enhancement is greater than the enhancement of skin friction with increasing turbulence levels. At turbulence levels above Tu = 10 percent, the free-stream turbulence starts to penetrate the boundary layer and inactive motions begin replacing shear-stress producing motions that are associated with the fluid/wall interaction. Although inactive motions do not contribute to the shear stress, these motions are still active in removing heat.

scholarly journals Direct Numerical Simulations of a High Pressure Turbine Vane

2015 ◽  
Author(s):  
Andrew P. S. Wheeler ◽  
Richard D. Sandberg ◽  
Neil D. Sandham ◽  
Richard Pichler ◽  
Vittorio Michelassi ◽  
...  
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Surface Flow ◽  
Surface Heat ◽  
High Pressure Turbine ◽  
Suction Surface ◽  
Data Set ◽  
Surface Heat Transfer ◽  
Free Stream Turbulence ◽  
Turbine Vane

In this paper we establish a benchmark data set of a generic high-pressure turbine vane generated by direct numerical simulation (DNS) to resolve fully the flow. The test conditions for this case are a Reynolds number of 0.57 million and an exit Mach number of 0.9, which is representative of a modern transonic high-pressure turbine vane. In this study we first compare the simulation results with previously published experimental data. We then investigate how turbulence affects the surface flow physics and heat transfer. An analysis of the development of loss through the vane passage is also performed. The results indicate that free-stream turbulence tends to induce streaks within the near wall flow, which augment the surface heat transfer. Turbulent breakdown is observed over the late suction surface, and this occurs via the growth of two-dimensional Kelvin-Helmholtz spanwise roll-ups, which then develop into lambda vortices creating large local peaks in the surface heat transfer. Turbulent dissipation is found to significantly increase losses within the trailing-edge region of the vane.

Effect of Unsteady Wake With Trailing Edge Coolant Ejection on Film Cooling Performance for a Gas Turbine Blade

1998 ◽  
Author(s):  
Hui Du ◽  
Srinath V. Ekkad ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Film Cooling ◽  
Surface Heat ◽  
Blade Surface ◽  
Transfer Coefficients ◽  
Trailing Edge ◽  
Surface Heat Transfer ◽  
Heat Transfer Coefficients ◽  
Unsteady Wake

The effect of unsteady wakes with trailing edge coolant ejection on surface heat transfer coefficients and film cooling effectiveness is presented for a downstream film-cooled turbine blade. The detailed heat transfer coefficient and film effectiveness distributions on the blade surface are obtained using a transient liquid crystal technique. Unsteady wakes are produced by a spoked wheel-type wake generator upstream of the five-blade linear cascade. The coolant jet ejection is simulated by ejecting coolant through holes on the hollow spokes of the wake generator. For a blade without film holes, unsteady wake increases both pressure side and suction side heat transfer levels due to early boundary layer transition. Adding trailing edge ejection to the unsteady wake further enhances the blade surface heat transfer coefficients particularly near the leading edge region. For a film-cooled blade, unsteady wake effects slightly enhance surface heat transfer coefficients but significantly reduces film effectiveness. Addition of trailing edge ejection to the unsteady wake has a small effect on surface heat transfer coefficients compared to other significant parameters such as film injection, unsteady wakes, and grid generated turbulence, in that order. Trailing edge ejection effect on film effectiveness distribution is stronger than on the heat transfer coefficients.

Effect of Unsteady Wake With Trailing Edge Coolant Ejection on Detailed Heat Transfer Coefficient Distributions for a Gas Turbine Blade

1997 ◽  
Vol 119 (2) ◽  
pp. 242-248 ◽  
Author(s):  
H. Du ◽  
S. Ekkad ◽  
J.-C. Han
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Free Stream ◽  
Surface Heat ◽  
Trailing Edge ◽  
Surface Heat Transfer ◽  
Linear Cascade ◽  
Pressure Surface ◽  
Unsteady Wake

Detailed heat transfer coefficient distributions on a turbine blade under the combined effects of trailing edge jets and unsteady wakes at various free-stream conditions are presented using a transient liquid crystal image method. The exit Reynolds number based on the blade axial chord is varied from 5.3 × 105 to 7.6 × 105 for a five blade linear cascade in a low speed wind tunnel. Unsteady wakes are produced using a spoked wheel-type wake generator upstream of the linear cascade. Upstream trailing edge jets are simulated by air ejection from holes located on the hollow spokes of the wake generator. The mass flux ratio of the jets to free-stream is varied from 0.0 to 1.0. Results show that the surface heat transfer coefficient increases with an increase in Reynolds number and also increases with the addition of unsteady wakes. Adding grid generated turbulence to the unsteady wake further enhances the blade surface heat transfer coefficients. The trailing edge jets compensate the defect in the velocity profile caused by the unsteady passing wakes and give an increase in free-stream velocity and produce a more uniformly disturbed turbulence intensity profile. The net effect is to increase both the front parts of blade suction and pressure surface heat transfer. However, the jet effect diminishes in and after the transition regions on suction surface, or far away from the leading edge on pressure surface.

New Heat Transfer Gages for Use on Multilayered Substrates

1986 ◽  
Vol 108 (1) ◽  
pp. 153-160 ◽  
Author(s):  
J. E. Doorly ◽  
M. L. G. Oldfield
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Wind Tunnel ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Surface Heat ◽  
Basic Flow ◽  
Surface Heat Transfer ◽  
Vitreous Enamel ◽  
Coated Metal

The paper describes a technique which enables measurements of the surface heat transfer rate to be made using thin-film gages deposited on a vitreous enamel-coated metal model. It is intended that this will have particular application in rotating turbine test rigs, where it offers considerable advantages over present techniques. These include ease of manufacture, instrumentation, durability, and lack of interference with the basic flow. The procedures for gage calibration and measurement processing are outlined, and the results of wind tunnel tests which confirm that the method is both practical and accurate are described.

scholarly journals Entropy Generation Measurement in a Laminar Turbine Blade Boundary-Layer

1997 ◽  
Author(s):  
John D. Wallace ◽  
Mark R. D. Davies
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Transfer Rate ◽  
Turbine Blade ◽  
Entropy Generation ◽  
Transfer Rate ◽  
Surface Heat ◽  
Entropy Generation Rate ◽  
Blade Surface ◽  
Surface Heat Transfer

This paper demonstrates a method of calculating the entropy generation rate in an incompressible laminar turbine blade boundary-layer from measurements of surface heat transfer rate. It is shown that the entropy generated by fluid friction in an incompressible blade boundary-layer is significantly less than that generated by heat transfer at engine representative temperature ratios. The centre blade in a low-speed linear cascade is electrically heated and isolated from the airflow with a bypass valve. Upon opening the valve the blade is transiently cooled and thin film heat transfer gauges, painted on machinable glass ceramic inserts mounted into the surface of the blade, are used to record blade surface temperature and surface heat transfer rate signals; local Nusselt numbers are then calculated. Non-dimensional temperature distributions are derived across the boundary-layer using the blade surface heat transfer rate and a similarity condition. The equation describing the local entropy generation per unit volume is then integrated through the boundary-layer at each chordwise measurement point on the blade surface.

Effects of Free-Stream Turbulence Intensity and Frequency on Heat Transfer to Turbine Blading

1981 ◽  
Vol 103 (1) ◽  
pp. 60-64 ◽  
Author(s):  
F. J. Bayley ◽  
W. J. Priddy
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Free Stream ◽  
Turbine Blades ◽  
Theoretical Work ◽  
Experimental Program ◽  
Blade Surface ◽  
Free Stream Turbulence ◽  
Mainstream Flow ◽  
Turbine Blading

This paper describes a continuing experimental program in which the frequency and amplitude of turbulence in the mainstream flow over a cascade of turbine blades are separately and controllably varied. The effects of these two characteristics of the flow are demonstrated showing the significant effect of each upon the rates of convection to most of the blade surface. A correlation following the predictions of the theoretical work of reference [2] is shown to have some promise, although some modification is required to allow for changes in mainstream Reynolds number not accounted for by the usual normalizing procedure.

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