Thermal optimisation of the stator vent design for a synchronous generator

Bersch, Kevin (2019) Thermal optimisation of the stator vent design for a synchronous generator. PhD thesis, University of Nottingham.

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An appropriate cooling of electrical machines is essential for safe, reliable and efficient operation and to address the growing demand for highly power-dense machines. Conventional thermal design optimisation procedures have traditionally relied on simple analytical correlations, which are not well suited to investigate complex and novel designs. Computational Fluid Dynamics (CFD) enables a more accurate prediction of fluid flow and heat transfer. But to date, the high complexity of the geometry, mesh and solver setup have required the model setup to be updated manually when the machine design is changed.

Within this thesis, a novel methodology for the thermal optimisation of electrical machines is developed based on a 3-D Conjugate Heat Transfer CFD model of a synchronous generator. It enables the automated optimisation of multiple design parameters without requiring any additional user input after the initial model setup. The impact the design changes have on the electromagnetic performance was taken into account through analytical correlations developed from electromagnetic 2-D FEA. By implementing these correlations into the thermal optimisation procedure, an optimal machine design considering the thermal as well as the electromagnetic performance can be achieved.

The developed methodology was applied to improve the stator cooling of an air-cooled synchronous generator with a power rating of several hundred kVA used for continuous industrial power generation. Initially, a model of the current machine design was created to gain insight into its thermal performance. As the machine hot spot is located in the stator core windings, venting the stator was identified as a beneficial design change. Subsequently, five vent design parameters were optimised, reducing peak and average stator winding temperatures.

Based on the outcome of the design optimisation, a vented stator-casing arrangement was built and tested experimentally. In comparison to the original machine design, the peak stator winding temperature rise was reduced by 20.1 %, while the average stator winding temperature rise decreased by 12.3 %.

The investigated generator and the designed prototype were validated experimentally by torque, mass flow, rotor and stator winding temperature measurements. The temperature measurements were taken at various loads, including full load, while the machine was connected to the grid. This enabled an accurate prediction of the generator's thermal performance under normal operating conditions. Good agreement between CFD and experimental data was found, validating the design methodology.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Eastwick, Carol N.
Connor, Peter H.
Galea, Michael
Keywords: Electrical machines, Cooling, Thermal Management, Generator, Fluid Dynamics, CFD, Energy, Efficiency
Subjects: T Technology > TK Electrical engineering. Electronics Nuclear engineering
Faculties/Schools: UK Campuses > Faculty of Engineering
Item ID: 56829
Depositing User: Bersch, Kevin
Date Deposited: 30 Jul 2019 08:19
Last Modified: 07 May 2020 11:15

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