Heat Transfer in a Rotating Cavity With a Stationary Stepped Casing

1999 ◽  
Vol 121 (2) ◽  
pp. 281-287 ◽  
Author(s):  
I. Mirzaee ◽  
P. Quinn ◽  
M. Wilson ◽  
J. M. Owen
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flow Parameter ◽  
Rotating Disk ◽  
Nusselt Numbers ◽  
Rotating Cavity ◽  
Wide Range ◽  
Heated Disc ◽  
Turbine Disks ◽  
Cooling Air

In the system considered here, corotating “turbine” disks are cooled by air supplied at the periphery of the system. The system comprises two corotating disks, connected by a rotating cylindrical hub and shrouded by a stepped, stationary cylindrical outer casing. Cooling air enters the system through holes in the periphery of one disk, and leaves through the clearances between the outer casing and the disks. The paper describes a combined computational and experimental study of the heat transfer in the above-described system. In the experiments, one rotating disk is heated, the hub and outer casing are insulated, and the other disk is quasi-adiabatic. Thermocouples and fluxmeters attached to the heated disc enable the Nusselt numbers, Nu, to be determined for a wide range of rotational speeds and coolant flow rates. Computations are carried out using an axisymmetric elliptic solver incorporating the Launder–Sharma low-Reynolds-number k–ε turbulence model. The flow structure is shown to be complex and depends strongly on the so-called turbulent flow parameter, λT, which incorporates both rotational speed and flow rate. For a given value λT, the computations show that Nu increases as Reφ, the rotational Reynolds number, increases. Despite the complexity of the flow, the agreement between the computed and measured Nusselt numbers is reasonably good.

scholarly journals Heat Transfer in a Rotating Cavity With a Stationary Stepped Casing

1998 ◽  
Author(s):  
Iraj Mirzaee ◽  
Paul Quinn ◽  
Michael Wilson ◽  
J. Michael Owen
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flow Parameter ◽  
Rotating Disc ◽  
Flow Rates ◽  
Nusselt Numbers ◽  
Rotating Cavity ◽  
Wide Range ◽  
Heated Disc ◽  
Cooling Air

In the system considered here, corotating “turbine” discs are cooled by air supplied at the periphery of the system. The system comprises two corotating discs, connected by a rotating cylindrical hub and shrouded by a stepped, stationary cylindrical outer casing. Cooling air enters the system through holes in the periphery of one disc, and leaves through the clearances between the outer casing and the discs. The paper describes a combined computational and experimental study of the heat transfer in the above system. In the experiments, one rotating disc is heated, the hub and outer casing are insulated, and the other disc is quasi-adiabatic. Thermocouples and fluxmeters attached to the heated disc enable the Nusselt numbers, Nu, to be determined for a wide range of rotational speeds and coolant flow rates. Computations are carried out using an axisymmetric elliptic solver incorporating the Launder-Sharma low-Reynolds-number k-ε turbulence model. The flow structure is shown to be complex and depends strongly on the so-called turbulent flow parameter, λT, which incorporates both rotational speed and flow rate. For a given value of λT, the computations show that Nu increases as Reϕ, the rotational Reynolds number, increases. Despite the complexity of the flow, the agreement between the computed and measured Nusselt numbers is reasonably good.

scholarly journals Heat Transfer in an Air-Cooled Rotor-Stator System

1994 ◽  
Author(s):  
Jian-Xin Chen ◽  
Xiaopeng Gan ◽  
J. Michael Owen
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbulence Model ◽  
Computational Study ◽  
Reynolds Numbers ◽  
Flow Rates ◽  
Nusselt Numbers ◽  
Heated Disc ◽  
Radial Outflow ◽  
Cooling Air

This paper describes a combined experimental and computational study of the heat transfer from an electrically-heated disc rotating close to an unheated stator. A radial outflow of cooling air was used to remove heat from the disc, and local Nusselt numbers were measured, using fluxmeters at seven radial locations, for nondimensional flow rates up to C = 9680 and rotational Reynolds numbers up to Reφ = 1.2 × 106. Computations were carried out using an elliptic solver with a low-Reynolds-number k-ε turbulence model, and the agreement between the measured and computed velocities and Nusselt numbers was mainly good.

Rotating Cavity With Axial Throughflow of Cooling Air: Heat Transfer

1992 ◽  
Vol 114 (1) ◽  
pp. 229-236 ◽  
Author(s):  
P. R. Farthing ◽  
C. A. Long ◽  
J. M. Owen ◽  
J. R. Pincombe
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Simple Correlation ◽  
Nusselt Numbers ◽  
Rotating Cavity ◽  
Wide Range ◽  
Effects Of Radiation ◽  
Increasing Temperature ◽  
Cooling Air ◽  
Made In

Heat transfer measurements were made in two rotating cavity rigs, in which cooling air passed axially through the center of the disks, for a wide range of flow rates, rotational speeds, and temperature distributions. For the case of a symmetrically heated cavity (in which both disks have the same temperature distribution), it was found that the distributions of local Nusselt numbers were similar for both disks and the effects of radiation were negligible. For an asymmetrically heated cavity (in which one disk is hotter than the other), the Nusselt numbers on the hotter disk were similar to those in the symmetrically heated cavity but greater in magnitude than those on the colder disks; for this case, radiation from the hot to the cold disk was the same magnitude as the convective heat transfer. Although the two rigs had different gap ratios (G = 0.138 and 0.267), and one rig contained a central drive shaft, there was little difference between the measured Nusselt numbers. For the case of “increasing temperature distribution” (where the temperature of the disks increases radially), the local Nusselt numbers increase radially; for a “decreasing temperature distribution,” the Nusselt numbers decrease radially and become negative at the outer radii. For the increasing temperature case, a simple correlation was obtained between the local Nusselt numbers and the local Grashof numbers and the axial Reynolds number.

Prediction of Heat Transfer in a Rotating Cavity With a Radial Outflow

1991 ◽  
Vol 113 (1) ◽  
pp. 115-122 ◽  
Author(s):  
C. L. Ong ◽  
J. M. Owen
Keyword(s):  
Boundary Layer ◽  
Turbulent Flow ◽  
Boundary Layer Equations ◽  
Nusselt Numbers ◽  
Eddy Viscosity Model ◽  
Rotating Cavity ◽  
Wide Range ◽  
Turbine Disks ◽  
Radial Outflow ◽  
Cooling Air

Solutions of the differential boundary-layer equations, using the Keller-box scheme and the Cebeci-Smith eddy-viscosity model for turbulent flow, have been used to predict the Nusselt numbers on the disks of a heated rotating cavity with a radial outflow of cooling air. Computed Nusselt numbers were in satisfactory agreement with analytical solutions of the elliptic equations for laminar flow and with solutions of the integral equations for turbulent flow. For a wide range of flow rates, rotational speeds, and disk-temperature profiles, the computed Nusselt numbers were in mainly good agreement with measurements obtained from an air-cooled rotating cavity. It is concluded that the boundary-layer equations should provide solutions accurate enough for application to air-cooled gas turbine disks.

Physical Interpretation of Flow and Heat Transfer in Preswirl Systems

2006 ◽  
Vol 129 (3) ◽  
pp. 769-777 ◽  
Author(s):  
Paul Lewis ◽  
Mike Wilson ◽  
Gary Lock ◽  
J. Michael Owen
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Turbulent Flow ◽  
Gas Turbines ◽  
Flow Parameter ◽  
Rotating Disk ◽  
Turbine Rotor ◽  
Scaled Model ◽  
Flow Rates

This paper compares heat transfer measurements from a preswirl rotor–stator experiment with three-dimensional (3D) steady-state results from a commercial computational fluid dynamics (CFD) code. The measured distribution of Nusselt number on the rotor surface was obtained from a scaled model of a gas turbine rotor–stator system, where the flow structure is representative of that found in an engine. Computations were carried out using a coupled multigrid Reynolds-averaged Navier-Stokes (RANS) solver with a high Reynolds number k-ε∕k-ω turbulence model. Previous work has identified three parameters governing heat transfer: rotational Reynolds number (Reϕ), preswirl ratio (βp), and the turbulent flow parameter (λT). For this study rotational Reynolds numbers are in the range 0.8×106<Reϕ<1.2×106. The turbulent flow parameter and preswirl ratios varied between 0.12<λT<0.38 and 0.5<βp<1.5, which are comparable to values that occur in industrial gas turbines. Two performance parameters have been calculated: the adiabatic effectiveness for the system, Θb,ad, and the discharge coefficient for the receiver holes, CD. The computations show that, although Θb,ad increases monotonically as βp increases, there is a critical value of βp at which CD is a maximum. At high coolant flow rates, computations have predicted peaks in heat transfer at the radius of the preswirl nozzles. These were discovered during earlier experiments and are associated with the impingement of the preswirl flow on the rotor disk. At lower flow rates, the heat transfer is controlled by boundary-layer effects. The Nusselt number on the rotating disk increases as either Reϕ or λT increases, and is axisymmetric except in the region of the receiver holes, where significant two-dimensional variations are observed. The computed velocity field is used to explain the heat transfer distributions observed in the experiments. The regions of peak heat transfer around the receiver holes are a consequence of the route taken by the flow. Two routes have been identified: “direct,” whereby flow forms a stream tube between the inlet and outlet; and “indirect,” whereby flow mixes with the rotating core of fluid.

Heat Transfer in a “Cover-Plate” Preswirl Rotating-Disk System

1999 ◽  
Vol 121 (2) ◽  
pp. 249-256 ◽  
Author(s):  
R. Pilbrow ◽  
H. Karabay ◽  
M. Wilson ◽  
J. M. Owen
Keyword(s):  
Heat Transfer ◽  
Rotating Disk ◽  
Reynolds Numbers ◽  
Turbine Disk ◽  
Cover Plate ◽  
Blade Cooling ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer ◽  
Cooling Air ◽  
Plate System

In most gas turbines, blade-cooling air is supplied from stationary preswirl nozzles that swirl the air in the direction of rotation of the turbine disk. In the “cover-plate” system, the preswirl nozzles are located radially inward of the blade-cooling holes in the disk, and the swirling airflows radially outward in the cavity between the disk and a cover-plate attached to it. In this combined computational and experimental paper, an axisymmetric elliptic solver, incorporating the Launder–Sharma and the Morse low-Reynolds-number k–ε turbulence models, is used to compute the flow and heat transfer. The computed Nusselt numbers for the heated “turbine disk” are compared with measured values obtained from a rotating-disk rig. Comparisons are presented, for a wide range of coolant flow rates, for rotational Reynolds numbers in the range 0.5 X 106 to 1.5 X 106, and for 0.9 < βp < 3.1, where βp is the preswirl ratio (or ratio of the tangential component of velocity of the cooling air at inlet to the system to that of the disk). Agreement between the computed and measured Nusselt numbers is reasonably good, particularly at the larger Reynolds numbers. A simplified numerical simulation is also conducted to show the effect of the swirl ratio and the other flow parameters on the flow and heat transfer in the cover-plate system.

Leading Edge Jet Impingement Under High Rotation Numbers

2012 ◽  
Author(s):  
Cassius A. Elston ◽  
Lesley M. Wright
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Rotation Number ◽  
Leading Edge ◽  
Jet Impingement ◽  
Target Surface ◽  
Test Cases ◽  
Nusselt Numbers ◽  
Supply Channel ◽  
Cooling Air

The effect of rotation on jet impingement cooling is experimentally investigated in this study. Pressurized cooling air is supplied to a smooth, square channel in the radial outward direction. To model leading edge impingement in a gas turbine, jets are formed from a single row of discrete holes. The cooling air from the first pass is expelled through the holes, with the jets impinging on a semi-circular, concave surface. The inlet Reynolds number varied from 10000–40000 in the square supply channel. The rotation number and buoyancy parameter varied from 0–1.4 and 0–6.6 near the inlet of the channel, and as coolant is extracted for jet impingement, the rotation and buoyancy numbers can exceed 10 and 500 near the end of the passage. The average jet Reynolds number varied from 6000–24000, and the jet rotation number varied from 0–0.13. For all test cases, the jet-to-jet spacing (s/djet = 4), the jet-to-target surface spacing (l/djet = 3.2), and the impingement surface diameter-to-diameter (D/djet = 6.4) were held constant. A steady state technique was implemented to determine regionally averaged Nusselt numbers on the leading and trailing surfaces inside the supply channel and three spanwise locations on the concave target surface. It was observed that in all rotating test cases, the Nusselt numbers deviated from those measured in a non-rotating channel. The degree of separation between the leading and trailing surface increased with increasing rotation number. Near the inlet of the channel, heat transfer was dominated by entrance effects, however moving downstream, the local rotation number increased and the effect of rotation was more pronounced. The effect of rotation on the target surface was most clearly seen in the absence of crossflow. With pure jet impingement, the deflection of the impinging jet combined with the rotation induced secondary flows offered increased mixing within the impingement cavity and enhanced heat transfer. In the presence of strong crossflow of the spent air, the same level of heat transfer is measured in both the stationary and rotating channels.

The Effect of Disk Geometry on Heat Transfer in a Rotating Cavity With a Radial Outflow of Fluid

1988 ◽  
Vol 110 (1) ◽  
pp. 70-77 ◽  
Author(s):  
P. R. Farthing ◽  
J. M. Owen
Keyword(s):  
Heat Transfer ◽  
Flow Visualization ◽  
Source Region ◽  
Integral Boundary ◽  
Boundary Layer Equations ◽  
Nusselt Numbers ◽  
Via Holes ◽  
Turbine Disks ◽  
Radial Outflow ◽  
Cooling Air

Flow visualization and heat transfer measurements have been made in a cavity comprising two nonplane disks of 762 mm diameter and a peripheral shroud, all of which could be rotated up to 2000 rpm. “Cobs,” made from a lightweight foam material and shaped to model the geometry of turbine disks, were attached to the center of each disk. Cooling air at flow rates up to 0.1 kg/s entered the cavity through the center of the “upstream” disk and left via holes in the shroud. The flow structure was found to be similar to that observed in earlier tests for the plane-disk case: a source region, Ekman layers, sink layer, and interior core were observed by flow visualization. Providing the source region did not fill the entire cavity, solutions of the turbulent integral boundary-layer equations provided a reasonable approximation to the Nusselt numbers measured on the heated “downstream” disk.

Disk Heat Transfer Analysis in a Heated Rotating Cavity With an Axial Throughflow

2012 ◽  
Author(s):  
Shuqing Tian ◽  
Yatao Zhu
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Rotating Disk ◽  
Outer Wall ◽  
Heat Transfer Analysis ◽  
Outlet Temperature ◽  
Rotating Cavity ◽  
Isothermal Boundary ◽  
Aero Engines ◽  
Cooling Air

In the rotating disk cavities of aero-engine compressors, buoyancy-induced flow and heat transfer can occur due to thermal gradients between cooling air and hot surfaces. The simplified rotating cavity with two plane discs, a shaft and a cylindrical rim has been investigated numerically and compared with the available measurements. Two models have been solved using a commercial CFD code, Fluent, with the RNG k-ε turbulence model. The first one is the conventional model with only fluid region solved, a temperature profile with the linear radial gradient imposed at the disk walls, and an isothermal boundary condition imposed at the shroud wall. The second one is the model with thick-walled disks and shroud, an adiabatic boundary condition imposed at the outer walls of the disks, and an isothermal boundary condition imposed at the outer wall of the shroud. The fluid and solid are coupled solved simultaneously. The disk temperatures are computed. In the present work, the numerical results are in reasonable agreement with the measurements. The computed disk temperatures in the second model have approximately linear radial gradients over the first three-quarters of the disks, and in the last quarter of the disks the temperature radial gradients are obviously non-linear. The different disk temperature profiles in these two models do not lead to obviously different disk heat transfers. The heat transfer in the rotating cavity leads to a considerable temperature increase of the cavity core fluid, therefore a corresponding increase of the outlet temperature. These two temperature increases are critical for the cooling design in aero-engines.

Leading Edge Jet Impingement Under High Rotation Numbers

2017 ◽  
Vol 9 (2) ◽  
Author(s):  
Cassius A. Elston ◽  
Lesley M. Wright
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Rotation Number ◽  
Leading Edge ◽  
Jet Impingement ◽  
Target Surface ◽  
Test Cases ◽  
Nusselt Numbers ◽  
Supply Channel ◽  
Cooling Air

The effect of rotation on jet impingement cooling is experimentally investigated in this study. Pressurized cooling air is supplied to a smooth, square channel in the radial outward direction. To model leading edge impingement in a gas turbine, jets are formed from a single row of discrete holes. The cooling air from the first pass is expelled through the holes, with the jets impinging on a semi-circular, concave surface. The inlet Reynolds number varied from 10,000 to 40,000 in the square supply channel. The rotation number and buoyancy parameter varied from 0 to 1.4 and 0 to 6.6 near the inlet of the channel, and as coolant is extracted for jet impingement, the rotation and buoyancy numbers can exceed 10 and 500 near the end of the passage. The average jet Reynolds number varied from 6000 to 24,000, and the jet rotation number varied from 0 to 0.13. For all test cases, the jet-to-jet spacing (s/djet = 4), the jet-to-target surface spacing (l/djet = 3.2), and the impingement surface diameter-to-diameter (D/djet = 6.4) were held constant. A steady-state technique was implemented to determine regionally averaged Nusselt numbers on the leading and trailing surfaces inside the supply channel and three spanwise locations on the concave target surface. It was observed that in all rotating test cases, the Nusselt numbers deviated from those measured in a nonrotating channel. The degree of separation between the leading and trailing surface increased with increasing rotation number. Near the inlet of the channel, heat transfer was dominated by entrance effects, however moving downstream, the local rotation number increased, and the effect of rotation was more pronounced. The effect of rotation on the target surface was most clearly seen in the absence of crossflow. With pure jet impingement, the deflection of the impinging jet combined with the rotation-induced secondary flows offered increased mixing within the impingement cavity and enhanced heat transfer. In the presence of strong crossflow of the spent air, the same level of heat transfer is measured in both the stationary and rotating channels.

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