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Research Papers: Gas Turbines: Heat Transfer

Buoyancy-Induced Flow and Heat Transfer in Compressor Rotors

[+] Author and Article Information
Hui Tang

Department of Mechanical Engineering,
University of Bath,
Bath BA2 7AY, UK
e-mail: h.tang2@bath.ac.uk

Mark R. Puttock-Brown

Thermo-Fluid Mechanics Research Centre,
School of Engineering and Informatics,
University of Sussex,
Farlmer, Brighton BN1 9RH, UK
e-mail: M.Puttock@sussex.ac.uk

J. Michael Owen

Department of Mechanical Engineering,
University of Bath,
Bath BA2 7AY, UK
e-mail: ensjmo@bath.ac.uk

Contributed by the Heat Transfer Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received June 7, 2017; final manuscript received October 21, 2017; published online April 25, 2018. Assoc. Editor: Riccardo Da Soghe.

J. Eng. Gas Turbines Power 140(7), 071902 (Apr 25, 2018) (10 pages) Paper No: GTP-17-1200; doi: 10.1115/1.4038756 History: Received June 07, 2017; Revised October 21, 2017

The buoyancy-induced flow and heat transfer inside the compressor rotors of gas-turbine engines affects the stresses and radial growth of the compressor disks, and it also causes a temperature rise in the axial throughflow of cooling air through the center of the disks. In turn, the radial growth of the disks affects the radial clearance between the rotating compressor blades and the surrounding stationary casing. The calculation of this clearance is extremely important, particularly in aeroengines where the increase in pressure ratios results in a decrease in the size of the blades. In this paper, a published theoretical model—based on buoyancy-induced laminar Ekman-layer flow on the rotating disks—is extended to include laminar free convection from the compressor shroud and forced convection between the bore of the disks and the axial throughflow. The predicted heat transfer from these three surfaces is then used to calculate the temperature rise of the throughflow. The predicted temperatures and Nusselt numbers are compared with measurements made in a multicavity compressor rig, and mainly good agreement is achieved for a range of Rossby, Reynolds, and Grashof numbers representative of those found in aeroengine compressors. Owing to compressibility effects in the fluid core between the disks—and as previously predicted—increasing rotational speed can result in an increase in the core temperature and a consequent decrease in the Nusselt numbers from the disks and shroud.

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References

Long, C. A. , Miché, N. D. D. , and Childs, P. R. N. , 2007, “Flow Measurements Insided a Heated Multiple Rotating Cavity With Axial Throughflow,” Int. J. Heat Fluid Flow, 28(6), pp. 1391–1404. [CrossRef]
Owen, J. M. , and Tang, H. , 2015, “Theoretical Model of Buoyancy-Induced Flow in Rotating Cavities,” ASME J. Turbomach., 137(11), p. 111005. [CrossRef]
Tang, H. , and Owen, J. M. , 2017, “Effect of Buoyancy-Induced Rotating Flow on Temperature of Compressor Discs,” ASME J. Eng. Gas Turbines Power, 139(6), p. 062506. [CrossRef]
Tang, H. , and Owen, J. M. , 2018, “Theoretical Model of Buoyancy-Induced Heat Transfer in Closed Compressor Rotors,” ASME J. Eng. Gas Turbines Power, 140(3), p. 032605.
Owen, J. M. , and Long, C. A. , 2015, “Review of Buoyancy-Induced Flow in Rotating Cavities,” ASME J. Turbomach., 137(11), p. 111001. [CrossRef]
Childs, P. R. N. , 2011, Rotating Flow, Elsevier, Oxford, UK.
Atkins, N. R. , and Kanjirakkad, V. , 2014, “Flow in a Rotating Cavity With Axial Throughflow at Engine Representative Conditions,” ASME Paper No. GT2014-27174.
Tang, H. , Shardlow, T. , and Owen, J. M. , 2015, “Use of Fin Equation to Calculate Nusselt Numbers for Rotating Discs,” ASME J. Turbomach., 137(12), p. 121003. [CrossRef]
Bohn, D. , Deuker, E. , Emunds, R. , and Gorzelitz, V. , 1995, “Experimental and Theoretical Investigations of Heat Transfer in Closed Gas-Filled Rotating Annuli,” ASME J. Turbomach., 117(1), pp. 175–183. [CrossRef]
Long, C. A. , and Childs, P. R. N. , 2007, “Shroud Heat Transfer Measurements Inside a Heated Multiple Rotating Cavity With Axial Throughflow,” Int. J. Heat Fluid Flow, 28(6), pp. 1405–1417. [CrossRef]
Grossmann, S. , and Lohse, D. , 2000, “Scaling in Thermal Convection: A Unifying Theory,” J. Fluid Mech., 407, pp. 27–56. [CrossRef]
Lloyd, J. R. , and Moran, W. R. , 1974, “Natural Convection Adjacent to Horizontal Surfaces of Various Planforms,” ASME J. Heat Transfer, 96(4), pp. 443–447. [CrossRef]
Puttock-Brown, M. , 2018, “Experimental and Numerical Investigation of Flow Structure and Heat Transfer in Gas Turbine H.P. Compressor Secondary Air Systems,” Ph.D. thesis, University of Sussex, Brighton, UK.
Atkins, N. R. , 2013, “Investigation of a Radial-Inflow Bleed as a Potential for Compressor Clearance Control,” ASME Paper No. GT2013-95768.

Figures

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Fig. 1

Schematic diagram of gas turbine high-pressure compressor rotor [1]

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Fig. 2

Simplified diagram of single compressor cavity

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Fig. 3

Simplified diagram of instrumented disk of Sussex rig (dimensions in mm)

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Fig. 4

Control volume for temperature rise of axial throughflow

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Fig. 5

Cross section of Sussex multiple-cavity rig

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Fig. 6

Comparison between theoretical and experimentally derived average disk temperatures; symbols denote experimental values

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Fig. 7

Distributions of nondimensional temperature and Nusselt numbers for case a (Ro≈0.6,Grf=2.5×1011,Reϕ=1.6×106).Solidlinesaretheoreticalcurves;brokenlinesareexperimentally−derivedcurves;shadingshowsuncertaintyinNuf; symbols denote temperature measurements

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Fig. 8

Distributions of nondimensional temperature and Nusselt numbers for Case b (Ro≈0.3). Solid lines are theoretical curves; broken lines are experimentally derived curves; shading shows uncertainty in Nuf; symbols denote temperature measurements: (a) case b1 (Grf=1.0×1012,Reϕ=3.0×106) and (b) case b2 (Grf=1.0×1012,Reϕ=3.0×106).

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Fig. 9

Distributions of nondimensional temperature and Nusselt numbers for case c (Ro≈0.2). Solid lines are theoretical curves; broken lines are experimentally derived curves; shading shows uncertainty in Nuf; symbols denote temperature measurements: (a) case c1 (Grf=4.2×1011,Reϕ=3.0×106), (b) case c2 (Grf=4.5×1011,Reϕ=3.0×106), (c) case c3 (Grf=6.8×1011,Reϕ=2.5×106), (d) case c4 (Grf=7.2×1012,Reϕ=2.7×106), (e) case c5 (Grf=7.2×1012,Reϕ=2.7×106), and (f) case c6 (Grf=7.8×1012,Reϕ=2.7×106).

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Fig. 10

Distributions of nondimensional temperature and Nusselt numbers for case d (Ro≈0.2, Grf=4.1×1011,Reϕ=2.1×106). Solid lines are theoretical curves; broken lines are experimentally—derived curves; shading shows uncertainty in Nuf; symbols denote temperature measurements

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Fig. 11

Comparison between modeled and experimental nondimensional temperature rise of axial throughflow

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