As aircraft propulsion is transitioning to hydrogen fuel-cells, ensuring safe and reliable operation remains a key challenge. This thesis develops a control methodology to automate the startup and shutdown of a multi-stack hydrogen fuel-cell propulsion system for aircraft, whilst minimizing stack degradation. The work was conducted in collaboration with DLR, with contributions from Airbus, ZAL and HSU, focusing on air-cooled, open-cathode PEM fuel cells for aerospace applications.

Control-oriented models were developed using Multi-level Flow Modelling, Finite State Machine, and subsystem physical models, which were validated against experimental data in Simulink. Based on these models, subsystem controllers were designed to operate under the supervisory Finite State Machine automatic controller. The simulation results verify the defined control safety and reliability requirements, demonstrating that the multi-level control methodology is robust in automating the startup and shutdown operations, highlighting the use case in future aircraft fuel-cell propulsion systems.

Bachelor Thesis: Design Synthesis Exercise 2023
Group 13: Electric General Aircraft
in collaboration with
Group 10: Mid-Flight Recharging System

Addressing the pressing need for sustainability amid climate change, the aviation sector is under pressure to mitigate its significant carbon emissions. As aviation accounts for over 2% of global emissions, achieving zero-emissions aviation by 2050 is crucial. The challenge lies in finding alternatives to jet fuel. One option is battery-powered electric aviation, but limitations such as range constraints and emissions during production and disposal must be considered.

This report proposes a solution to extend the range of all-electric passenger aircraft. The ElectriFly aircraft can currently fly 600km at 110m/s before requiring recharging. To achieve perpetual flight capability, a mid-flight recharging system is introduced using a drogue and probe system, similar to military refueling technologies. This approach not only increases range but also reduces turn around time at airports.

Powered by four parallel-connected solid-state batteries with an energy density of 600kWh/kg, the ElectriFly aircraft features 14 propellers using distributed propulsion and potential plasma actuators. This setup improves aerodynamic performance, reduces noise, and allows for regenerative braking, easing the burden on the recharging drone. Real-time data sensors enable predictive maintenance, minimizing downtime and providing pilots with crucial flight anomaly information.

This research presents a promising solution for electric aircraft limitations through mid-flight recharging. The proposed ElectriFly aircraft offers extended range capabilities and improved operational efficiency, supporting the goal of sustainable aviation.