For typical rotorcraft missions such as medical emergencies and search and rescue, time is a critical factor that requires high-speed helicopters. Therefore, expanding the flight envelope towards higher cruising speeds would be an important innovation in the rotorcraft field, a prerequisite of the EU-funded FURADO project.
Proving ground for new-concept rotorcrafts
Clean Sky 2, the largest ever European aeronautics research programme, is dedicated to complete aircraft demonstrators and integrates technologies into viable, innovative conceptual configurations. Two very different types of rotorcraft are in the planning, one of which is called Rapid And Cost-Effective Rotorcraft (RACER). It combines a rotor with a supplementary form of propulsion, usually additional thrust engines or propellers. Introducing high-speed rotorcraft to the civil rotorcraft market promises a variety of advantages compared to conventional rotorcraft concepts. Innovation directly translates to building industrial leadership in Europe. FURADO directly contributed to the development of the RACER demonstrator. The demonstrator combines the beneficial characteristics of both fixed-wing aircraft and rotorcraft. It enables fast and efficient forward flight and performs short or vertical take off and landing. Due to its high cruising speed, aerodynamic efficiency was one of the major challenges in developing the demonstrator. Aerodynamic efficiency also reduces fuel consumption and emissions. Rotor head fairings can provide a significant reduction in aerodynamic drag. “Fully fairing the rotor head’s structural components as a whole delivers significant drag reduction potential,” notes Patrick Pölzlbauer, leading project scientist. “FURADO contributed to improving the performance of low-impact, fast and efficient helicopters thanks to a rotor head full fairing concept that applies advanced design and computational fluid dynamics (CFD) methods.”
Achieving automatic aerodynamic optimisation
Project partners created a versatile optimisation tool that enables fully automated aerodynamic shape development by means of CFD simulations. They defined a workflow for the aerodynamic design optimisation of rotor head fairings and successfully applied it to the development of the RACER full fairing. The FURADO team then focused on the pre-development of potential rotor head full fairing configurations. It concentrated on the preliminary aerodynamic design optimisation of the blade sleeves, the beanie and the pylon fairing for cruise flights. The next development phase involved a refined aerodynamic optimisation of promising full fairing configurations under the rotor rotation effect. It also dealt with the aerothermal risk assessment of the full fairing rotor head configuration. For this purpose, team members investigated helicopter external flow and the internal flow through the RACER upper deck. The newly developed FURADO fairing was compared to the current RACER blade-sleeve fairing. A drag reduction of 5 % and a lift increase of 24 % was obtained on the isolated rotor head with truncated rotor blades. Lastly, they integrated the developed software packages into the workflow and established a comprehensive database for full fairing rotor head design and analysis. “FURADO advanced the maturity of full fairing concepts for future helicopter designs, and the results will be of great value to the helicopter industry in supporting new solutions for very efficient vehicles in terms of fuel consumption, emissions and noise,” concludes Pölzlbauer. “All drag reduction efforts will have a significant impact on new helicopter developments.”
FURADO, fairing, rotorcraft, aerodynamics, helicopter, rotor head, RACER, air transport