Abstract
In order to accurately estimate the temperature rise for high-power high-speed permanent magnet machines (HSPMMs), a novel temperature calculation method considering the non-linear variation of material properties with temperature is proposed based on multi-physics co-simulation analysis. According to the theory of computational fluid dynamics and heat transfer, the computation model of fluid–solid–heat coupling heat transfer is established, and the coupled field is calculated using finite volume method with fundamental assumptions and corresponding boundary conditions. With the influences from temperature gradient and water flow rate considered, the heat transfer coefficients of water pipe surfaces are obtained by the application of the inverse iteration method. Thus, HSPMM temperature and fluid field can be simulated numerically by the finite volume methods, while the spatial temperature distributions for the machine main components are analysed in this study. The 1.12 MW, 18,000 rpm HSPMM is prototyped with experiments conducted on it, while the test data are then compared with the calculated results, which validate the correctness of the solution method of the coupled field.
Highlights
High speed permanent magnet machines (HSPMMs) are developing towards the high power density characteristic
High power HSPMMs are characterized with strong-coupling, multi-constraints and nonlinear properties, while their temperature field calculations are more complicated than the conventional machines
Calculation steps of temperature rise for high-power HSPMM based on multi-physical field analysis can be concluded as: 1) assume the working temperature of the machine and the convection heat transfer coefficient on the surface of the waterway, and calculate the machine losses; 2) calculate the temperature distribution for the machine based on the fluid-solid-heat coupling method, and determine the convection heat transfer coefficients by the inverse iterative method; 3) if the calculated temperature is inconsistent with the assumed temperature, the iterative calculation is repeated until the requirements are met
Summary
High speed permanent magnet machines (HSPMMs) are developing towards the high power density characteristic. The surface heat dissipation coefficient of liquid-cooled for high-density PM machine is decided based on the fluid flow state, the fluid physical properties and the geometric parameters of the heat dissipation surface. Empirical methods are usually used to approximate the key parameters such as thermal conductivity and convection heat transfer coefficient [12], and there is still a gap towards the accurate calculation of machine temperature rise. The fluid-solid-heat coupling and inverse iteration method are developed to calibrate the heat transfer coefficients for the prototype in order to perform advanced thermal analyses and achieve the desirable cooling performance for the machine
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