Design and performance evaluation of a full turboelectric, distributed electric propulsion aircraft: preliminary results of EU project IMOTHEP (2022)

This project has received funding from the European Unions Horizon 2020 research and innovation programme under grant agreement No 875006 IMOTHEP. This paper presents intermediate results obtained in the scope of the European project Investigation and Maturation of Technologies for Hybrid Electric Propulsion or IMOTHEP. The main objective of the IMOTHEP project is to significantly improve the estimation of the potential offered by hybrid electric propulsion in order to reduce the fuel consumption and CO2 emissions of civilian transport aircraft. Four aircraft configurations are studied and compared to a reference aircraft representative of actual technology levels, as well as to a baseline aircraft using future technologies but with conventional propulsion and architecture. The four configurations are split into two segments: (i) regional transport aviation (REG) and (ii) Small to Medium Range (SMR) transport aircraft. Within each segment, a conservative and a radical aircraft configuration are studied. The conservative configuration is named after its proximity with conventional aircraft while the radical configuration explores more disruptive propulsion integration and aircraft layout. This project gathers 27 European partners, and also Russian and Canadian research institutes. Each partner brings an expertise in some of the many disciplines, from components modelling to overall aircraft evaluation, which are needed to model and analyse a hybrid electric propulsion aircraft. The work is organised in three design loops: -L0 : first conceptual design loop, independent or loosely coupled multi-disciplinary evaluation from Top Level Requirements. -L1 : first multi-disciplinary design loop integrating models provided by different work-packages, especially models of hybrid electric components (electric motor, cables, converters, turboshaft, generator,). -L2 : second multi-disciplinary design loop integrating refined and higher fidelity models, and addressing transient effects. This paper reports the overall aircraft performances for the SMR conservative aircraft, complemented with a safety evaluation of the propulsive architecture both taken at the end of L0 design loop. The SMR conservative aircraft is based on the DRAGON concept, a fully turboelectric propulsive architecture with distributed electric fans. Preliminary evaluations of this concept are available in [1], [2] and [3]. This concept brings a first hybrid electric propulsion architecture to all partners to quick start the project and a design process is readily available. The work performed in design loop L0 hence consisted in updating the design process with IMOTHEP Top Level Requirements (TLARs) and first feedbacks from the disciplinary work-packages, in particular concerning the failure cases to be integrated in the design process. At that stage, the performances of the Hybrid Distributed Electric Propulsion (HDEP) components (efficiencies, specific powers) were based on an initial set of assumptions from literature survey and expert judgement. A second part of the work was to produce sensitivity analysis of the overall aircraft performances with varying electric component characteristics to perform trade-offs and selection of technology for components design. Finally, the subsequent on-going activities of design loop L1 are introduced. A specific focus is done on the detailed modelling of the Electrical Propulsion Units (EPU), an integrated component including the electrical machine. Sensitivity analysis have been carried out regarding the cooling strategy (air or liquid), EPU architecture (with or without a gearbox) as well as on the potential to combine the cooling of the electrical machine (EM) and power electronics (PE) in an integrated architecture (PE close to the EM). Some preliminary results will be detailed. References [1] Peter Schmollgruber et al., \"Multidisciplinary ExplorationofDRAGON : an ONERA Hybrid Electric Distributed Propulsion Concept,\" in AIAA Scitech2019, SANDIEGO, United States, 2019, pp. -. [2] Peter Schmollgruber et al., \"Multidisciplinary Design and performance of the ONERA Hybrid Electric Distributed Propulsion concept DRAGON,\" in AIAA Scitech 2020 Forum, doi : 10.2514/6.2020-0501. [3] Michael Ridel et al., \"DRAGON : hybrid eletrical architecture for distributed fans propulsion.,\" in MEA2021, Bordeaux, 2021, pp. hal-03420612.