Propeller Design for Hydrogen-Electric Aircraft

With increasing interest in hydrogen aviation over the past several years, Proton Exchange Membrane Fuel Cell (PEMFC) powertrains have become a leading candidate for propelling short to medium haul flights. PEMFCs facilitate an electro-chemical reaction between hydrogen and oxygen to power electric motor driven-propellers. Existing powertrain modeling workflows typically employ generic look-up surfaces called propeller maps for propulsor performance. These are often unrepresentative of real blade geometries and assume equal performance across propeller diameters and rotation rates. In this study, Blade Element Momentum Theory (BEMT) is coupled to a PEMFC powertrain model developed in OpenConcept to afford an improvement in simulation fidelity and -- critically -- overall performance of the powertrain. A regional aircraft (DHC-8) with a PEMFC powertrain was modeled with a default propeller map from OpenConcept to serve as a performance baseline. Subsequently, BEMT was used to develop a propeller map where the geometry of the propeller and its performance at prescribed flight conditions are known. This map was evaluated against the baseline with and without a safety margin penalty and showed that powertrain optimization is sensitive to propeller design: an increase in weight margin of 2 tonnes combined with reductions in Balance of Plant and fuel masses of 1.2 tonnes and 89 kg were observed. Additional fidelity for thermal, structural and acoustic models unlocked by BEMT are presented. An extension of the modeling to incorporate aeroacoustic analysis is included to demonstrate the far-reaching impacts of including low-order propeller simulation into the design framework.