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Air Flow inside Rotating Electrical Machines: A Comparison between Finite Volume and SPH Method
Mälardalen University, School of Business, Society and Engineering, Future Energy Center. (FEC, Track 3, Modeling and Simulation)ORCID iD: 0000-0002-9490-9703
ABB AB, Corporate Research.
Mälardalen University, School of Business, Society and Engineering, Future Energy Center.ORCID iD: 0000-0001-8849-7661
2017 (English)In: Conference Proceedings of NAFEMS World Congress 2017 (NWC17), 2017Conference paper, Published paper (Refereed)
Abstract [en]

A general, sufficiently accurate, applicable and reasonably fast approach to thermal analysis of rotating electrical machines is of high interest for motor and generator developers and manufacturers. The thermal performance and the lifetime of a machine is limited by the temperature distribution and the hot spot temperature. The most commonly encountered cooling medium is air and the temperature distribution is driven by the air flow pattern inside the machine. Two different Computational Fluid Dynamics methods, the mesh based Finite Volume Method (FVM) and the mesh free particle based Smoothed Particle Hydrodynamics (SPH) method are employed in this paper to model the airflow inside a rotating machine. Mesh based methods are quite robust, however, they are very expensive in terms of meshing effort and CPU time to be used extensively in R&D. Analysing and optimizing products with complex geometrical shapes need mesh generation for every specific design change and this may be the major part of the modelling process. This challenging task is not necessary for the SPH method. SPH method can also provide high quality 3D visualization that can improve the design process.

This work investigates the usability of the SPH method when applied to rotating machinery for rotor speeds normally encountered in motors and generators. A comparison with an FVM based approach is also performed. Both the FVM and the SPH solvers show good agreement for the overall flow pattern inside the machine with some disagreement for the airflow inside the air-gap between the rotor and the stator. The FVM solver successfully captures the Taylor vortex flow inside the annulus air-gap which is in general a great modelling challenge. The SPH solver on the other hand shows great capability to couple rotation of the rotor and well represent the overall flow pattern inside the machine. However, the 3D SPH solver could not capture the complex Taylor vortices inside the air-gap which may be due to the limited number of particles used for the simulation. An increase in the number of particles would certainly improve the accuracy of the results as confirmed by the 2D SPH simulation. The present study shows that the SPH solver can be used to predict the air flow pattern inside rotating machines within an acceptable accuracy.

Place, publisher, year, edition, pages
2017.
Keywords [en]
Air-gap flow; Rotating machines; CFD simulation; SPH method; Taylor vortices
National Category
Energy Engineering
Research subject
Energy- and Environmental Engineering
Identifiers
URN: urn:nbn:se:mdh:diva-36522OAI: oai:DiVA.org:mdh-36522DiVA, id: diva2:1144769
Conference
NAFEMS World Congress 2017 (NWC17)
Projects
MR-OMDOAvailable from: 2017-09-27 Created: 2017-09-27 Last updated: 2018-11-01Bibliographically approved
In thesis
1. Fluid Flow and Heat Transfer Simulations for Complex Industrial Applications: From Reynolds Averaged Navier-Stokes towards Smoothed Particle Hydrodynamics
Open this publication in new window or tab >>Fluid Flow and Heat Transfer Simulations for Complex Industrial Applications: From Reynolds Averaged Navier-Stokes towards Smoothed Particle Hydrodynamics
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Optimal process control can significantly enhance energy efficiency of heating and cooling processes in many industries. Process control systems typically rely on measurements and so called grey or black box models that are based mainly on empirical correlations, in which the transient characteristics and their influence on the control parameters are often ignored. A robust and reliable numerical technique, to solve fluid flow and heat transfer problems, such as computational fluid dynamics (CFD), which is capable of providing a detailed understanding of the multiple underlying physical phenomena, is a necessity for optimization, decision support and diagnostics of complex industrial systems. The thesis focuses on performing high-fidelity CFD simulations of a wide range of industrial applications to highlight and understand the complex nonlinear coupling between the fluid flow and heat transfer. The industrial applications studied in this thesis include cooling and heating processes in a hot rolling steel plant, electric motors, heat exchangers and sloshing inside a ship carrying liquefied natural gas. The goal is to identify the difficulties and challenges to be met when simulating these applications using different CFD tools and methods and to discuss the strengths and limitations of the different tools.

The mesh-based finite volume CFD solver ANSYS Fluent is employed to acquire detailed and accurate solutions of each application and to highlight challenges and limitations. The limitations of conventional mesh-based CFD tools are exposed when attempting to resolve the multiple space and time scales involved in large industrial processes. Therefore, a mesh-free particle method, smoothed particle hydrodynamics (SPH) is identified in this thesis as an alternative to overcome some of the observed limitations of the mesh-based solvers. SPH is introduced to simulate some of the selected cases to understand the challenges and highlight the limitations. The thesis also contributes to the development of SPH by implementing the energy equation into an open-source SPH flow solver to solve thermal problems. The thesis highlights the current state of different CFD approaches towards complex industrial applications and discusses the future development possibilities.

The overall observations, based on the industrial problems addressed in this thesis, can serve as decision tool for industries to select an appropriate numerical method or tool for solving problems within the presented context. The analysis and discussions also serve as a basis for further development and research to shed light on the use of CFD simulations for improved process control, optimization and diagnostics.

Place, publisher, year, edition, pages
Västerås: Mälardalen University, 2018
Series
Mälardalen University Press Dissertations, ISSN 1651-4238 ; 282
Keywords
Computational Fluid Dynamics, Heat transfer, Industrial applications, Reynolds Averaged Navier-Stokes, Smoothed Particle Hydrodynamics, Energy enginnering, Thermal Management, Process control
National Category
Energy Engineering
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-41277 (URN)978-91-7485-415-2 (ISBN)
Public defence
2018-12-14, Delta, Mälardalens högskola, Västerås, 13:00 (English)
Opponent
Supervisors
Available from: 2018-11-02 Created: 2018-11-01 Last updated: 2018-11-12Bibliographically approved

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