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Optimal Integrated Design of the Propulsion System of a Hybrid-electric Regional Aircraft

par Laurence Laffont - publié le , mis à jour le

Matthieu PETTES-DULER’s thesis defense, intitled "Conception intégrée optimale du système propulsif d’un avion régional hybride-électrique" (Optimal Integrated Design of the Propulsion System of a Hybrid-electric Regional Aircraft) will be taking place on Friday, 23rd of April, 2021 at 10 am.

The work thesis has been supervized by Xavier ROBOAM and Bruno SARENI. This thesis happens within Project HASTECS (CleanSky2 - H2020).

Link : :


In 2019, transportation was the fastest growing sector, contributing to environmental degradation. Finding sustainable solutions that pollute less is a key element in solving this problem, particularly for the aviation sector, which accounts for around 2% of global CO2 emissions. With the advent of Covid-19, air traffic seems to have come to a fairly permanent halt, but this pandemic reinforces the need to move towards a "cleaner sky" and respect for the environment, which is the objective of the Clean Sky2 program (H2020 EU), the context in which the HASTECS project and our thesis are set.

The main objective of HASTECS (Hybrid Aircraft Academic reSearch on Thermal and Electrical Components and Systems) is to couple thermal and electrical studies within the hybrid electric propulsion chain of a regional aircraft, by integrating the environmental constraints (in particular partial discharges) specific to the aviation sector. The aim is to identify the most promising technologies and breakthroughs and to develop the tools that will significantly increase the compactness and efficiency of the electrical processes within the hybrid propulsion chain. In our case, only series hybrid electric architecture was studied in this project, as it leads to a high dimensioning power maximizing the technological constraints on the chain.

The technological targets set in HASTECS, considered under two horizons (2025 then 2035), are the following :

eMotor + cooling system

2025 Target 2035 Target
Specific power 5 kW /kg 10 kW/kg
Cruise efficiency 96% 98.5%
Maximal design point 94.5% 97%
Power Electronics + cooling system

2025 Target 2035 Target
Specific power 15 kW /kg 25 kW/kg
Cruise efficiency 98% 99.5
Maximal design point 96.5% 99%

In the framework of this project, our thesis aims at the design by optimization of the complete propulsion chain integrating in particular the models resulting from the technological developments of the major components (power electronics, wiring and distribution architecture, actuation) while considering, from a simplified energy management, the hybridization of a main (thermal) and auxiliary (electrical) source.

A first objective of our thesis concerned the development of an environment model. Once these conditions are set, the system integration consists in building a suite of scale models whose granularity allows the global (systemic) evaluation of the energy yields and masses of each component up to the complete propulsion chain. The propulsion system is designed via an iterative process estimating, according to the design choices, the mass variations and their consequences on thrust : this integrated design approach allows, among other things, to evaluate the snowball effects, which have a major influence in aeronautics. Indeed, the addition of mass on a device has consequences on both the structure and onboard fuel.

After a state of the art and context study, we propose a series of "scale models" that can be integrated into an optimization process of the complete chain (with a reasonable computing time). These models are derived from :

Previous studies : gas turbines, auxiliary electrical sources (batteries, fuel cells), speed reducer, propeller ;
Or from an adaptation (reduction) of technological models from HASTECS work packages : power electronics and their cooling, electric motors and their cooling, partial discharge constraints.
Before moving on to system integration and design optimization, a chapter is devoted to sensitivity analysis, the objective of which is to specify the most sensitive degrees of freedom (decision variables) with respect to the main objectives (mass and loss reduction) of the design. Sensitivity analysis techniques based on Sobol indices are used in particular.

Finally, the last part and the final objective of this project concerns the optimal design of the complete chain integrating clean energy management in hybrid electric architecture. This study starts with local studies on the major components (drive chain) in order to progress towards system integration and the complete chain. Many results highlight the emergence of system couplings that do not appear in the assembly of local optima.