Abstract
This article describes the underpinning research, development, construction, and testing of a 4-MW multithree 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 tradeoffs, together with the experimental testing of this electrical machine connected to an active rectifier, are presented. A time-efficient analytical approach to the downselection 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 the 3-D 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.
Highlights
INTRODUCTIONWith air transport being amongst the least green forms of passenger transportation, over the past two decades, the aerospace industry and related bodies have been working intensively on defining aircraft technology roadmaps for the reduction of the net carbon emissions [1]
With air transport being amongst the least green forms of passenger transportation, over the past two decades, the aerospace industry and related bodies have been working intensively on defining aircraft technology roadmaps for the reduction of the net carbon emissions [1].Various ambitious aircraft emission reduction targets are set, such as those within the EU’s Flightpath 2050 program which seeks reductions of CO2 and NOx emissions per passenger kilometre by 75% and 90%, respectively, relative to the year 2000 [2]
One prominent example in this area was the E-Fan X ground demonstrator, which has brought together two key European companies, namely Airbus and Rolls-Royce, jointly developing a hybridelectric propulsion system involving a 2 MW electric drive supplied from a 2.5 MW generator that is powered by a gas turbine situated in the fuselage [5]
Summary
With air transport being amongst the least green forms of passenger transportation, over the past two decades, the aerospace industry and related bodies have been working intensively on defining aircraft technology roadmaps for the reduction of the net carbon emissions [1]. To make hybrid-electric aircraft fly, the continuous power density and efficiency of the electrical machines used for propulsion and generation both need to be pushed beyond the current state of the art [8]. Taking into account the technology readiness and high requirements for efficiency, power density and reliability, electrical machines with permanent magnets (PM) are a promising topology to fit the criteria for hybrid-electric propulsion systems [16], [17]. This work aims to present and demonstrate the challenges in developing a 4 MW (5 MVA), 15,000 rpm, electrical machine suitable for the future hybrid-electric aircraft on-board generating systems, by targeting a record power-density of 18 kW/kg (including active and passive components). The novelty of the paper is a demonstration of a breakthrough power density at the MW power-levels reached by using innovative machine optimisation methodologies, which exploit improved material properties and advanced thermal management techniques
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