This paper is the first in a series dedicated to investigating the airflow and thermal management of electrical machines. Due to the temperature dependent resistive losses in the machine"s windings, any improvement in cooling provides a direct reduction in losses and an increase in efficiency. This paper focuses on the airflow which is intrinsically linked to the thermal behaviour of the machine as well as the windage power consumed to drive the air through the machine. A full CFD model has been used to analyse the airflow around all major components of the machine. Results have been experimentally validated and investigated. At synchronous speed the experimentally tested mass flow rate and windage torque were under predicted by 4% and 7% respectively by the CFD. A break-down of torque by component shows that the fan consumes approximately 87% of the windage torque.

This paper is the first in a series dedicated to investigating the airflow and thermal management of electrical machines. Due to the temperature dependent resistive losses in the machine"s windings, any improvement in cooling provides a direct reduction in losses and an increase in efficiency. This paper focuses on the airflow which is intrinsically linked to the thermal behaviour of the machine as well as the windage power consumed to drive the air through the machine. A full CFD model has been used to analyse the airflow around all major components of the machine. Results have been experimentally validated and investigated. At synchronous speed the experimentally tested mass flow rate and windage torque were under predicted by 4% and 7% respectively by the CFD. A breakdown of torque by component shows that the fan consumes approximately 87% of the windage torque.

This paper describes the underpinning research, development, construction and testing of a 4MW multi-three phase generator designed for a hybrid-electric aircraft propulsion system demonstrator. The aim of the work is to demonstrate gravimetric power densities around 20 kW/kg, as required for multi-MW aircraft propulsion systems. The key design choices, development procedures and trade-offs, together with the experimental testing of this electrical machine connected to an active rectifier are presented. A time-efficient analytical approach to the down-selection of various machine configurations, geometrical variables, different active and passive materials and different thermal management options is first presented. A detailed design approach based on 3D Finite Element Analysis (FEA) is then presented for the final design. Reduced power tests are carried out on a full scale 4 MW machine prototype, validating the proposed design. The experimental results are in good agreement with simulation and show significant progress in the field of high power density electrical machines at the targeted power rating.

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Aircraft taxiing is conventionally performed using the main engines' inefficient idle thrust. Therefore, in line with greener aviation, the electrification of taxiing is the most viable option to reduce emissions, noise, and fossil fuel consumption during ground operations. This paper studies the potential of hybridising the conventional electric taxiing system, which is currently driven by the Auxiliary Power Unit, with an electrical energy storage system, comprising commercial high-energy and high-power lithium-ion batteries, for the purpose of reducing fuel consumption. Hence, a power distribution optimisation is formulated to minimise fuel consumption over a typical worst-case taxi-out profile. Three different energy management strategies are presented for a narrow-body aeroplane. The optimisation is performed for the selection of off-the-shelf batteries so that their impact on fuel savings can be evaluated in the early design stage.The study showed that a wide range of savings is achievable according to the selected strategy, the added weight allowance and the battery characteristics. Considering a 180 kg added weight allowance and covering the three investigated strategies, up to 72% of taxiing fuel is saved.

A combined electromagnetic and thermal modelling approach has been developed to optimise the design of multiple radial stator vents in an air-cooled, synchronous generator with a power rating of several hundred kVA. An experimentally validated 3-D Conjugate Heat Transfer Computational Fluid Dynamics model has been created and coupled with 2-D Electromagnetic Finite Element Analysis. Correlations between the combined vent width and rotor copper, rotor iron and stator iron losses were derived from the electromagnetic analysis. These correlations were implemented into the optimisation procedure of the parametric thermofluid model. Five parameters: vent locations, widths and the height of a baffle, were optimised simultaneously with the aim of minimising the peak stator winding temperature. The peak stator winding temperature was reduced by 11.1 %. The average stator winding temperature decreased by 6.3 %. To maintain the machine's power output, the removal of active stator material was compensated by increasing the rotor current.