Heat Transfer in a Rotating Square-Sectioned Channel Fitted With In-Line Ribs

Volume 1 ◽  
2004 ◽  
Author(s):  
A. W. Lees ◽  
J. M. J. Khamaj ◽  
W. D. Morris ◽  
S. W. Chang
Keyword(s):  
Heat Transfer ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Central Axis ◽  
Flow And Heat Transfer ◽  
Trailing Edges ◽  
Temperature Parameter ◽  
The Individual ◽  
Independent Parameters ◽  
Reduced Temperature

This investigation studies convective heat transfer in a square-sectioned duct that rotates about an axis perpendicular to the central axis of the duct. The leading and trailing sides of the duct are fitted with in-line ribs aligned at 45° to the central axis of the duct. The leading and trailing edges are heated and the two remaining sidewalls of the duct are adiabatic. Air is the coolant used and the direction of flow is in the radial outward direction. The duct simulates the flow and heat transfer that occurs in the passages of cooled turbine rotor blades. The presentation of results is in itself a non-trivial task as the heat transfer is a function of three independent parameters. It is shown how the performance of the section may be expressed in terms of a reduced temperature parameter and that this approach offers additional insight as compared to the conventional Nusselt number approach (which may be obtained by a simple transformation. The investigation has produced a range of experimental data to aid the validation of CFD codes designed to predict heat transfer in this class of rotating duct. Additionally empirical correlations for heat transfer on the leading and trailing edges are proposed that uncouple the individual effects of Coriolis forces and centripetal buoyancy.

Aero-Thermal Investigation of Tip Leakage Flow in a Film Cooled Industrial Turbine Rotor

2008 ◽  
Author(s):  
S. K. Krishnababu ◽  
H. P. Hodson ◽  
G. D. Booth ◽  
G. D. Lock ◽  
W. N. Dawes
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Mass Flow ◽  
Turbine Rotor ◽  
Total Heat ◽  
Leakage Flow ◽  
Total Heat Flux ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Flow And Heat Transfer

A numerical investigation of the flow and heat transfer characteristics of tip leakage in a typical film cooled industrial gas turbine rotor is presented in this paper. The computations were performed on a rotating domain of a single blade with a clearance gap of 1.28% chord in an engine environment. This standard blade featured two coolant and two dust holes, in a cavity-type tip with a central rib. The computations were performed using CFX 5.6, which was validated for similar flow situations by Krishnababu et al., [18]. These predictions were further verified by comparing the flow and heat transfer characteristics computed in the absence of coolant ejection with computations previously performed in the company (SIEMENS) using standard in-house codes. Turbulence was modelled using the SST k-ω turbulence model. The comparison of calculations performed with and without coolant ejection has shown that the coolant flow partially blocks the tip gap, resulting in a reduction of the amount of mainstream leakage flow. The calculations identified that the main detrimental heat transfer issues were caused by impingement of the hot leakage flow onto the tip. Hence three different modifications (referred as Cases 1 to 3) were made to the standard blade tip in an attempt to reduce the tip gap exit mass flow and the associated impingement heat transfer. The improvements and limitations of the modified geometries, in terms of tip gap exit mass flow, total area of the tip affected by the hot flow and the total heat flux to the tip, are discussed. The main feature of the Case 1 geometry is the removal of the rib and this modification was found to effectively reduce both the total area affected by the hot leakage flow and total heat flux to the tip while maintaining the same leakage mass flow as the standard blade. Case 2 featured a rearrangement of the dust holes in the tip which, in terms of aero-thermal-dynamics, proved to be marginally inferior to Case 1. Case 3, which essentially created a suction-side squealer geometry, was found to be inferior even to the standard cavity tip blade. It was also found that the hot spots which occur in the leading edge region of the standard tip and all modifications contributed significantly to the area affected by the hot tip leakage flow and the total heat flux.

scholarly journals Tip Leakage Flow in a Linear Turbine Cascade

1988 ◽  
Vol 110 (1) ◽  
pp. 18-26 ◽  
Author(s):  
J. Moore ◽  
J. S. Tilton
Keyword(s):  
Heat Transfer ◽  
Potential Flow ◽  
Pressure Rise ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Tip Clearance ◽  
Tip Leakage Flow ◽  
Vena Contracta

An experimental and analytical study of flow in the tip clearance gap of a linear turbine rotor blade cascade has been performed. Measurements of wall static pressures and flow velocities are used to verify a flow model involving a vena contracta, near the tip gap entrance, followed by flow mixing to fill the gap. A frequently referenced potential flow theory for flow into a tip gap is found to be in error and the correct theory is shown to model the unloading along the pressure surface of the blade and the endwall static pressure distribution up to the vena contracta accurately. A combined potential flow and mixing model accounts for the pressure rise in the tip gap due to mixing. Turbine tip heat transfer is also discussed and a correlation of local heat transfer rates for essentially incompressible flow over unshrouded turbine rotor blades is presented.

A DOS-Enhanced Numerical Simulation of Heat Transfer and Fluid Flow Through an Array of Offset Fins With Conjugate Heating in the Bounding Solid

2003 ◽  
Author(s):  
Ephraim M. Sparrow ◽  
John P. Abraham ◽  
Paul W. Chevalier
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Fluid Flow ◽  
Basic Problem ◽  
Accurate Representation ◽  
Flow And Heat Transfer ◽  
Flow Through ◽  
Heat And Momentum Transfer ◽  
Independent Parameters ◽  
Dimensionless Heat

The method of Design of Simulation (DOS) was used to guide and enhance a numerical simulation of fluid flow and heat transfer through offset-fin arrays which from the interior geometry of a cold plate. The basic problem involved 12 independent parameters. This prohibitive parametric burden was lessened by the creative use of nondimensionalization that was brought to fruition by a special transformation of the boundary conditions. Subsequent to the reduction of the number of parameters, the DOS method was employed to limit the number of simulation runs while maintaining an accurate representation of the parameter space. The DOS method also provided excellent correlations of both the dimensionless heat transfer and pressure drop results. The results were evaluated with respect to the Colburn Analogy for heat and momentum transfer. It was found that the offseting of the fins created a larger increase in the friction factor than that which was realized for the dimensionless heat transfer coefficient.

Measurements and Predictions of Heat Transfer on Rotor Blades in a Transonic Turbine Cascade

2004 ◽  
Vol 126 (1) ◽  
pp. 110-121 ◽  
Author(s):  
Paul W. Giel ◽  
Robert J. Boyle ◽  
Ronald S. Bunker
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Thin Foil ◽  
Reynolds Numbers ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Maximum Point ◽  
Stagnation Region ◽  
Design Point ◽  
Laminar To Turbulent Transition

Detailed heat transfer measurements and predictions are given for a power generation turbine rotor with 127 deg of nominal turning and an axial chord of 130 mm. Data were obtained for a set of four exit Reynolds numbers comprised of the facility maximum point of 2.50×106, as well as conditions which represent 50%, 25%, and 15% of this maximum condition. Three ideal exit pressure ratios were examined including the design point of 1.443, as well as conditions which represent −25% and +20% of the design value. Three inlet flow angles were examined including the design point and ±5deg off-design angles. Measurements were made in a linear cascade with highly three-dimensional blade passage flows that resulted from the high flow turning and thick inlet boundary layers. Inlet turbulence was generated with a blown square bar grid. The purpose of the work is the extension of three-dimensional predictive modeling capability for airfoil external heat transfer to engine specific conditions including blade shape, Reynolds numbers, and Mach numbers. Data were obtained by a steady-state technique using a thin-foil heater wrapped around a low thermal conductivity blade. Surface temperatures were measured using calibrated liquid crystals. The results show the effects of strong secondary vortical flows, laminar-to-turbulent transition, and also show good detail in the stagnation region.

A DOS-Enhanced Numerical Simulation of Heat Transfer and Fluid Flow Through an Array of Offset Fins With Conjugate Heating in the Bounding Solid

2005 ◽  
Vol 127 (1) ◽  
pp. 27-33 ◽  
Author(s):  
Ephraim M. Sparrow ◽  
John P. Abraham ◽  
Paul W. Chevalier
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Fluid Flow ◽  
Basic Problem ◽  
Accurate Representation ◽  
Flow And Heat Transfer ◽  
Flow Through ◽  
Heat And Momentum Transfer ◽  
Independent Parameters ◽  
Dimensionless Heat

The method of Design of Simulation (DOS) was used to guide and enhance a numerical simulation of fluid flow and heat transfer through offset-fin arrays which form the interior geometry of a cold plate. The basic problem involved 11 independent parameters. This prohibitive parametric burden was lessened by the creative use of nondimensionalization that was brought to fruition by a special transformation of the boundary conditions. Subsequent to the reduction of the number of parameters, the DOS method was employed to limit the number of simulation runs while maintaining an accurate representation of the parameter space. The DOS method also provided excellent correlations of both the dimensionless heat transfer and pressure drop results. The results were evaluated with respect to the Colburn Analogy for heat and momentum transfer. It was found that the offseting of the fins created a larger increase in the friction factor than that which was realized for the dimensionless heat transfer coefficient.

An Experimental Study of Local and Mean Heat Transfer in a Triangular-Sectioned Duct Rotating in the Orthogonal Mode

1984 ◽  
Vol 106 (3) ◽  
pp. 661-667 ◽  
Author(s):  
R. J. Clifford ◽  
W. D. Morris ◽  
S. P. Harasgama
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Turbine Rotor ◽  
Turbulent Pipe Flow ◽  
Rotor Blades ◽  
Noticeable Effect ◽  
Number Range ◽  
Selection Of

This paper presents a selection of experimental results that examines the influence of orthogonal-mode rotation on local and mean heat transfer in a triangular-sectioned duct with potential application to cooled turbine rotor blades. It is shown that Coriolis acceleration can have a beneficial influence on mean heat transfer relative to the nonrotating case at the lower range of turbulent pipe flow Reynolds numbers studied. Also, rotational buoyancy has been shown to have a noticeable effect over this same Reynolds number range in that progressively increasing buoyancy brings about an attendant reduction in heat transfer. As the Reynolds numbers are increased, say, beyond 30,000, buoyancy effects were found to have little influence on mean heat transfer over the speed range covered. Local axial variations in heat transfer along the duct were also measured, and severe reductions in local heat transfer were detected under certain operating circumstances.

scholarly journals Heat Transfer Measurements in Rectangular Channels With Orthogonal Mode Rotation

1990 ◽  
Author(s):  
W. D. Morris ◽  
G. Ghavami-Nasr
Keyword(s):  
Heat Transfer ◽  
Flow Direction ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Rotating Flow ◽  
Internal Cooling ◽  
Rectangular Channels ◽  
Flow Geometry

The influence of rotation on local heat transfer in a rectangular-sectioned duct has been experimentally studied for the case where the ductrotates about an axis orthogonal to its own central axis. The coolant used was air with the flow direction in the radially outwards direction. This rotating flow geometry is encountered in the internal cooling of gas turbine rotor blades.

Fully Scaled Transonic Turbine Rotor Heat Transfer Measurements

1989 ◽  
Vol 111 (1) ◽  
pp. 1-7 ◽  
Author(s):  
G. R. Guenette ◽  
A. H. Epstein ◽  
M. B. Giles ◽  
R. Haimes ◽  
R. J. G. Norton
Keyword(s):  
Heat Transfer ◽  
Turbine Rotor ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Time Resolved ◽  
Oxford University ◽  
Flow And Heat Transfer ◽  
Rotating Blade ◽  
Rotor Profile ◽  
Turbine Design

The heat transfer to an uncooled transonic singlestage turbine has been measured in a short-duration facility, which fully simulates all the nondimensional quantities of interest for fluid flow and heat transfer (Reynolds number, Prandtl number, Rossby number, temperature ratios, and corrected speed and weight flow). Data from heat flux gages about the midspan of the rotor profile, measured from d-c to more than 10 times blade passing frequency (60 kHz), are presented in both time-resolved and mean heat transfer form. These rotating blade data are compared to previously published heat transfer measurements taken at Oxford University on the same profile in a two-dimensional cascade with bar passing to simulate blade row interaction effects. The results are qualitatively quite similar at midspan. The data are also compared to a two-dimensional Navier–Stokes calculation of the blade mean section and the implications for turbine design are discussed.

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