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Research Papers

Characteristics of the Convective Heat Transfer Coefficient at the End Winding of a Hydro Generator

[+] Author and Article Information
Stephan Klomberg

Institute for Fundamentals
and Theory in Electrical Engineering,
Christian Doppler Laboratory
for Multiphysical Simulation,
Analysis and Design of Electrical Machines,
Inffeldgasse 18, Graz A-8010, Austria
e-mail: stephan.klomberg@tugraz.at

Ernst Farnleitner

Andritz Hydro GmbH,
Dr.-Karl-Widdmann-Strasse 5,
Weiz A-8160, Austria
e-mail: ernst.farnleitner@andritz.com

Gebhard Kastner

Andritz Hydro GmbH,
Dr.-Karl-Widdmann-Strasse 5,
Weiz A-8160, Austria
e-mail: gebhard.kastner@andritz.com

Oszkár Bíró

Institute for Fundamentals
and Theory in Electrical Engineering,
Christian Doppler Laboratory
for Multiphysical Simulation,
Analysis and Design of Electrical Machines,
Inffeldgasse 18, Graz A-8010, Austria
e-mail: biro@tugraz.at

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF THERMAL SCIENCE AND ENGINEERING APPLICATIONS. Manuscript received November 7, 2013; final manuscript received October 24, 2014; published online November 25, 2014. Assoc. Editor: Jovica R. Riznic.

J. Thermal Sci. Eng. Appl 7(1), 011011 (Mar 01, 2015) (8 pages) Paper No: TSEA-13-1197; doi: 10.1115/1.4028978 History: Received November 07, 2013; Revised October 24, 2014; Online November 25, 2014

The focus of this paper is a computational fluid dynamics (CFD) analysis of the end winding region of a hydro generator as basis for development of correlations between the convective wall heat transfer coefficient (WHTC) and speed and flow rate parameters. These correlations are used as boundary conditions for thermal networks. Furthermore, there is also a focus on the influence of the numerical settings on the correlations. This work deals with a reduced numerical model which is designed to calculate a hydro generator fast and accurately by using a steady-state simulation with the mixing plane (MP) method.

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Figures

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Fig. 1

Longitudinal section of the hydro generator with (a) inlet, (b) air guide inlet, (c) end winding bar bottom, (d) end winding bar top, (e) salient pole, (f) air-gap, (g) stator ducts, (h) air guide outlet, (i) outlet

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Fig. 2

Schematic model of one axial half of a hydro generator: (a) inlet, (b) air guide inlet, (c) end winding bar bottom, (d) end winding bar top, (e) salient pole, (f) air-gap, (g) stator ducts, (h) air guide outlet, (i) outlet, (j) axial symmetry

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Fig. 3

Reduced slot sector model a hydro generator: (a) inlet, (b) air guide inlet, (c) end winding bar bottom, (d) end winding bar top, (e) salient pole, (f) air-gap, (g) stator ducts, (h) air guide outlet, (i) outlet, (j) axial symmetry

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Fig. 4

Sketch of simple RSI-MP

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Fig. 5

Front view reduced model

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Fig. 6

Comparison of the two used grids around the end winding bar

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Fig. 7

Mesh of the domain end winding bars. y+ ≈ 1.

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Fig. 8

Classification of an end winding bar

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Fig. 9

Characterization of the WHTC along an end winding bar

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Fig. 10

Typical flow condition at the inlet area

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Fig. 11

Flow velocity distribution at the end winding cross section

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Fig. 12

Distribution of the radial outflow and inflow, and axial outflow through the end winding bars

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Fig. 13

Comparison of the WHTC with the radial velocity in the evaluation zones

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Fig. 14

Comparison of the WHTC for different rotational speed

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