Preswirl Blade-Cooling Effectiveness in an Adiabatic Rotor–Stator System

1989 ◽  
Vol 111 (4) ◽  
pp. 522-529 ◽  
Author(s):  
Z. B. El-Oun ◽  
J. M. Owen
Keyword(s):  
Frictional Heating ◽  
Rotating Disk ◽  
Reynolds Numbers ◽  
Reynolds Analogy ◽  
Cooling Effectiveness ◽  
Cooling Flows ◽  
Blade Cooling ◽  
Experimental Errors ◽  
Radial Outflow ◽  
Cooling Air

Blade-cooling air for a high-pressure turbine is often supplied from preswirl nozzles attached to a stationary casing. By swirling the cooling air in the direction of rotation of the turbine disk, the temperature of the air relative to the blades can be reduced. The question addressed in this paper is: Knowing the temperatures of the preswirl and disk-cooling flows, what is the temperature of the blade-cooling air? A simple theoretical model, based on the Reynolds analogy applied to an adiabatic rotor–stator system, is used to calculate the preswirl effectiveness (that is, the reduction in the temperature of the blade-cooling air as a result of preswirling the flow). A mixing model is used to account for the “contamination” of the blade coolant with disk-cooling air, and an approximate solution is used to estimate the effect of frictional heating on the disk-cooling air. Experiments were conducted in a rotor–stator rig that had preswirl nozzles in the stator and blade-cooling passages in the rotating disk. A radial outflow or inflow of disk-cooling air was also supplied, and measurements of the temperature difference between the preswirl and blade-cooling air were made for a range of flow rates and for rotational Reynolds numbers up to Reθ = 1.8 × 106. Considering the experimental errors in measuring the small temperature differences, good agreement between theory and experiment was achieved.

Pre-Swirl Blade-Cooling Effectiveness in an Adiabatic Rotor-Stator System

1988 ◽  
Author(s):  
Z. B. El-Oun ◽  
J. M. Owen
Keyword(s):  
Frictional Heating ◽  
Reynolds Numbers ◽  
Rotating Disc ◽  
Reynolds Analogy ◽  
Cooling Effectiveness ◽  
Cooling Flows ◽  
Blade Cooling ◽  
Experimental Errors ◽  
Radial Outflow ◽  
Cooling Air

Blade-cooling air for a high-pressure turbine is often supplied from pre-swirl nozzles attached to a stationary casing. By swirling the cooling air in the direction of rotation of the turbine disc, the temperature of the air relative to the blades can be reduced. The question addressed in this paper is: knowing the temperatures of the pre-swirl and disc-cooling flows, what is the temperature of the blade-cooling air? A simple theoretical model, based on the Reynolds analogy applied to an adiabatic rotor-stator system, is used to calculate the pre-swirl effectiveness (that is, the reduction in the temperature of the blade-cooling air as a result of pre-swirling the flow). A mixing model is used to account for the ‘contamination’ of the blade-coolant with disc-cooling air, and an approximate solution is used to estimate the effect of frictional heating on the disc-cooling air. Experiments were conducted in a rotor-stator rig which had pre-swirl nozzles in the stator and blade-cooling passages in the rotating disc. A radial outflow or inflow of disc-cooling air was also supplied, and measurements of the temperature difference between the pre-swirl and blade-cooling air were made for a range of flow rates and for rotational Reynolds numbers up to Reθ = 1.8 × 106. Considering the experimental errors in measuring the small temperature differences, good agreement between theory and experiment was achieved.

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.

Flow in a “Cover-Plate” Preswirl Rotor–Stator System

1999 ◽  
Vol 121 (1) ◽  
pp. 160-166 ◽  
Author(s):  
H. Karabay ◽  
J.-X. Chen ◽  
R. Pilbrow ◽  
M. Wilson ◽  
J. M. Owen
Keyword(s):  
Vortex Flow ◽  
Rotating Disk ◽  
Reynolds Numbers ◽  
Tangential Component ◽  
Cover Plate ◽  
Rotating Disc ◽  
Blade Cooling ◽  
Rotating Cavity ◽  
Cooling Air ◽  
Nondimensional Temperature

This paper describes a combined theoretical, computational, and experimental study of the flow in an adiabatic preswirl rotor–stator system. Preswirl cooling air, supplied through nozzles in the stator, flows radially outward, in the rotating cavity between the rotating disk and a cover-plate attached to it, leaving the system through blade-cooling holes in the disk. An axisymmetric elliptic solver, incorporating the Launder–Sharma low-Reynolds-number k–ε turbulence model, is used to compute the flow. An LDA system is used to measure the tangential component of velocity, Vφ, in the rotating cavity of a purpose-built rotating-disc rig. For rotational Reynolds numbers up to 1.2 × 106 and preswirl ratios up to 2.5, agreement between the computed and measured values of Vφ is mainly very good, and the results confirm that free-vortex flow occurs in most of the rotating cavity. Computed values of the preswirl effectiveness (or the nondimensional temperature difference between the preswirl and blade-cooling air) agree closely with theoretical values obtained from a thermodynamic analysis of an adiabatic system.

Experimental Study on Racetrack-Shaped Holes Impingement Cooling With Bump Type Roughening Element

2012 ◽  
Author(s):  
Chiyuki Nakamata ◽  
Yoji Okita ◽  
Takashi Yamane ◽  
Yoshitaka Fukuyama ◽  
Toyoaki Yoshida
Keyword(s):  
Experimental Study ◽  
Flow Condition ◽  
Reynolds Numbers ◽  
Main Flow ◽  
The Other ◽  
Relative Location ◽  
Target Plate ◽  
Cooling Effectiveness ◽  
Impingement Cooling ◽  
Cooling Air

Cooling effectiveness of an impingement cooling with array of racetrack-shaped impingement holes is investigated. Two types of specimens are investigated. One is a plain target plate and the other is a plate roughened with bump type elements. Sensitivity of relative location of bump to impingement hole on the cooling effectiveness is also investigated. Experiments are conducted under three different mainflow Reynolds numbers ranging from 2.6×105 to 4.7×105, with four different cooling air Reynolds numbers for each main flow condition. The cooling air Reynolds numbers are in the range from 1.2×103 to 1.3×104.

Computation of Heat Transfer in Rotating Cavities Using a Two-Equation Model of Turbulence

1990 ◽  
Author(s):  
A. P. Morse ◽  
C. L. Ong
Keyword(s):  
Heat Transfer ◽  
Turbulence Model ◽  
Radial Direction ◽  
Reynolds Numbers ◽  
Systematic Errors ◽  
Equation Model ◽  
Sufficient Accuracy ◽  
Nusselt Numbers ◽  
Radial Outflow ◽  
Cooling Air

The paper presents finite-difference predictions for the convective heat transfer in symmetrically-heated rotating cavities subjected to a radial outflow of cooling air. An elliptic calculation procedure has been used, with the turbulent fluxes estimated by means of a low Reynolds number k-ε model and the familiar ‘turbulence Prandtl number’ concept. The predictions extend to rotational Reynolds numbers of 3.7 × 106 and encompass cases where the disc temperatures may be increasing, constant or decreasing in the radial direction. It is found that the turbulence model leads to predictions of the local and average Nusselt numbers for both discs which are generally within ± 10% of the values from published experimental data, although there appear to be larger systematic errors for the upstream disc than for the downstream disc. It is concluded that the calculations are of sufficient accuracy for engineering design purposes, but that improvements could be brought about by further optimization of the turbulence model.

Heat Transfer in a “Cover-Plate” Pre-Swirl Rotating-Disc System

1998 ◽  
Author(s):  
Robert Pilbrow ◽  
Hasan Karabay ◽  
Michael Wilson ◽  
J. Michael Owen
Keyword(s):  
Heat Transfer ◽  
Reynolds Numbers ◽  
Cover Plate ◽  
Swirl Ratio ◽  
Rotating Disc ◽  
Blade Cooling ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer ◽  
Turbine Disc ◽  
Cooling Air

In most gas turbines, blade-cooling air is supplied from stationary pre-swirl nozzles that swirl the air in the direction of rotation of the turbine disc. In the “cover-plate” system, the pre-swirl nozzles are located radially inward of the blade-cooling holes in the disc, and the swirling air flows radially outwards in the cavity between the disc 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 disc” are compared with measured values obtained from a rotating-disc rig. Comparisons are presented, for a wide range of coolant flow rates, for rotational Reynolds numbers in the range 0.5 × 106 to 1.5 × 106, and for 0.9 < βp < 3.1, where βp is the pre-swirl ratio (or ratio of the tangential component of velocity of the cooling air at inlet to the system to that of the disc). 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.

Heat Transfer From Air-Cooled Contrarotating Disks

1997 ◽  
Vol 119 (1) ◽  
pp. 61-67 ◽  
Author(s):  
J.-X. Chen ◽  
X. Gan ◽  
J. M. Owen
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flow Rate ◽  
Reynolds Numbers ◽  
The Other ◽  
Reynolds Analogy ◽  
Flow Rates ◽  
Nusselt Numbers ◽  
Radial Outflow ◽  
Equivalent Conditions

A superposed radial outflow of air is used to cool two disks that are rotating at equal and opposite speeds at rotational Reynolds numbers up to 1.2 × 106. One disk, which is heated up to 100°C, is instrumented with thermocouples and fluxmeters; the other disk, which is unheated, is made from transparent polycarbonate to allow the measurement of velocity using an LDA system. Measured Nusselt numbers and velocities are compared with computations made using an axisymmetric elliptic solver with a low-Reynolds-number k–ε turbulence model. Over the range of flow rates and rotational speeds tested, agreement between the computations and measurements is mainly good. As suggested by the Reynolds analogy, the Nusselt numbers for contrarotating disks increase strongly with rotational speed and weakly with flow rate; they are lower than the values obtained under equivalent conditions in a rotor–stator system.

Computation of Flow Between Two Disks Rotating at Different Speeds

2003 ◽  
Vol 125 (2) ◽  
pp. 394-400 ◽  
Author(s):  
Muhsin Kilic ◽  
J. Michael Owen
Keyword(s):  
Boundary Layers ◽  
Gas Turbines ◽  
Reynolds Numbers ◽  
Internal Cooling ◽  
Rotating Disks ◽  
Measured Velocity ◽  
Layer Flow ◽  
Radial Outflow ◽  
Cooling Air ◽  
Good Agreement

Disks rotating at different speeds are found in the internal cooling-air systems of most gas turbines. Defining Γ as the ratio of the rotational speed of the slower disk to that of the faster one then Γ=−1, 0 and +1 represents the three important cases of contra-rotating disks, rotor-stator systems and co-rotating disks, respectively. A finite-volume, axisymmetric, elliptic, multigrid solver, employing a low-Reynolds-number k-ε turbulence model, is used for the fluid-dynamics computations in these systems. The complete Γ region, −1⩽Γ⩽+1, is considered for rotational Reynolds numbers of up to Reϕ=1.25×106, and the effect of a radial outflow of cooling air is also included for nondimensional flow rates of up to Cw=9720. As Γ→−1, Stewartson-flow occurs with radial outflow in boundary layers on both disks and between which is a core of nonrotating fluid. For Γ≈0, Batchelor-flow occurs, with radial outflow in the boundary layer on the faster disk, inflow on the slower one, and between which is a core of rotating fluid. As Γ→+1, Ekman-layer flow dominates with nonentraining boundary layers on both disks and a rotating core between. Where available, measured velocity distributions are in good agreement with the computed values.

scholarly journals Flow in a Rotating Cavity With a Peripheral Inlet and Outlet of Cooling Air

1996 ◽  
Author(s):  
Xiaopeng Gan ◽  
Iraj Mirzaee ◽  
J. Michael Owen ◽  
D. Andrew S. Rees ◽  
Michael Wilson
Keyword(s):  
Boundary Layers ◽  
Turbulence Model ◽  
Laser Doppler Anemometry ◽  
Axial Direction ◽  
Reynolds Numbers ◽  
Recirculation Region ◽  
Rotating Disc ◽  
The Core ◽  
Radial Outflow ◽  
Cooling Air

In some engines, corotating gas–turbine discs are cooled by air introduced at the periphery of the system. The air enters through holes in a stationary peripheral casing and leaves through the rim seals between the casing and the discs. This paper describes a combined computational and experimental study of such a system for a range of flowrates and for rotational Reynolds numbers of up to Reϕ = 1.5 × 106. Computations are made using an axisymmetric elliptic solver, incorporating the Launder–Sharma low–Reynolds–number k–ε turbulence model, and velocity measurements are obtained using laser–Doppler anemometry. The stationary peripheral casing creates a recirculation region: there is radial outflow in boundary layers on the discs and inflow in the core between the boundary layers. The radial extent of the recirculation region increases as the flow rate increases and as the rotational speed decreases. In the core, the radial and tangential components of velocity, Vr and Vϕ, are invariant in the axial direction, and the measured values of Vϕ conform to a Rankine–vortex flow. The agreement between the computed and measured velocities is not as good as that found for other rotating–disc systems, and deficiencies in the turbulence model are believed to be responsible.

CFD Investigation of Vane Nozzle and Impeller Design for HPT Blade Cooling Air Delivery System

2013 ◽  
Author(s):  
Shuqing Tian ◽  
Qin Zhang ◽  
Hui Liu
Keyword(s):  
Delivery System ◽  
Pressure Loss ◽  
Aerodynamic Performance ◽  
Blade Cooling ◽  
System Pressure ◽  
Total Temperature ◽  
Swirl Vane ◽  
Radial Outflow ◽  
Cooling Air ◽  
Main Factor

In the design of a HPT blade cooling air delivery system, sufficient supply pressure and lower relative total temperature are required to guarantee HPT blades working properly in the high temperature environment. The pre-swirl vane nozzles and the radial impellers are used in the delivery system with lower radial location of pre-swirl nozzle to achieve the requirements. In this paper, CFD analysis is utilized for designing the vane nozzles and the radial impellers. Two HPT blade cooling air delivery systems were explored. The baseline is a system without impellers, and the alternative is a system with impellers. The results show that the impeller contributes to the delivery system by pumping effectiveness thus decreasing the extracted air pressure. The parity of swirl ratio between the flow and the broach slots is a main factor that decreases the system pressure loss, which can be improved by the radial impellers. The well-designed contoured radial-impeller vane with 30° front angle and 20° trailing angle is recommended in the blade cooling air delivery system design because of its good aerodynamic performance and closely radial outflow. The cascade vane nozzle with more than 70° angle turn is recommended in the pre-swirl nozzle design. It has a good aerodynamic performance with discharge coefficient greater than 0.99 and deviation angle less than 1.3°. The well-designed radial impeller pays big contributions to the blade cooling air delivery system with 11.4% increase of the thermal effectiveness and 10.2% decrease of the pressure loss versus the system without impellers.

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