This thesis reports on a simulation-based investigation in the metallic rotor containment sleeves for high performance permanent magnet machines. Metallic sleeves are often favoured in applications such as aerospace which have the highest demands on long-term stability. However, metallic sleeves suffer from the presence of induced eddy current loss which can lead to excessive rotor heating. The research encompasses both mechanical and electromagnetic aspects of metallic containment sleeve performance and is undertaken within the context of two reference machine designs, viz. a 60.7kW machine operating at 2600rpm and a 395kW machine operating at 20,000rpm. These designs were provided by Rolls-Royce as an industry partner of this thesis.
The requirements of containment sleeves are described, and the various sleeve technologies used commercially are reviewed. Literature concerned with eddy current loss in sleeves is reviewed along with various innovations in sleeve design aimed at enhancing mechanical and/or electromagnetic performance. An extensive data gathering exercise covering 41 grades of high-strength materials processed by different manufacturing routes is reported along with details of manufacturing routes for thin-walled metallic sleeves.
Extensive use is made of structural finite element analysis to model the mechanical behaviour of metallic sleeves including consideration of interference fitting, adhesive bonding and stress distributions. Two- and three-dimensional electromagnetic finite element analysis is used to model several aspects of sleeve performance with a particular focus on rotor losses due to induced eddy currents. This investigation included the inclusion of design features to reduce eddy current losses including segmenting a sleeve into several electrically separate rings, nesting of sleeves and the introduction of grooves into the sleeve. This demonstrates that by adopting various features, significant losses in metallic sleeves to make them competitive with carbon-fibre sleeves. The issue of scaling is considered by evaluating the performance of a metallic sleeve in a MW range electrical propulsion application.
From this widespread investigation, it is concluded that using a metallic sleeve, in particular Inconel 718, provides minimal electromagnetic losses and mechanical benefits to the 60.7kW machine design. For the 395kW design, the substitution is not recommended unless manufacturing edits are to be made, however, these come with their own challenge and cost.
