Optimisation of Proprotors for Performance and Noise

With the global drive towards more sustainable aviation, new electric aircraft platforms are being developed. These may be smaller scale battery-powered drone craft, or as large as commercial aircraft with hydrogen-electric powertrains. There is also the desire for such craft to have vertical take-off and landing capacities, for use as inter-city flying taxis. Such powertrains are most commonly driven by propellers, but there exists a lack of design and validation tools for optimising these for this new role. In addition, for commercial aircraft, the transition from turboprop to hydrogen-electric powertrains results in the scope for aeroacoustic research. Previously, the noise generated by a propeller on such an aircraft was secondary, and thus not considered as a primary design parameter. With the shift in focus towards sustainable, "silent" flight in dense urban areas, the noise disturbance to the public is becoming a significant factor. Limited research exists in the design of a propeller for noise, particularly when considering VTOL, and the transition to cruise flight. This research aims to occupy this space, through the following objectives:

Design, build, and commission a propeller test rig and compare against published data
Develop a propeller performance and geometry optimisation code (Bath BEMT software)
Validate the BEMT code by correlating its predictions to rig tests in horizontal, vertical, and transitional flight
Implement noise considerations into the design process, and validate these through acoustic testing of propellers on the rig with microphone arrays

These objectives will result in a comprehensive and validated design tool for the next generation of propeller-driven aircraft. Given mission parameters and requirements, such as for noise, thrust, torque, and efficiency, an optimal propeller will be generated. Such propellers could then be implemented onto aircraft of the types and applications listed above. This research will focus particularly on the low Reynolds number, high angle-of-attack, VTOL-cruise transition, and post-stall influences on propeller design, as these remain the least validated when applying BEMT modelling.

The ability to generate optimised propellers for these eVTOL applications will permit the advancement of the design of these novel aerospace platforms, while maximising their propulsive efficiencies, and minimising the acoustic annoyance to the public. The successful implementation of high-efficiency, quiet propellers onto commercial aircraft will accelerate the transition away from fossil-fuel powered flight by increasing the feasibility of sustainable aviation through alternative propulsive systems.