Experimental investigation of vortex ring state in an eVTOL propeller

This study presents an experimental investigation of the vortex ring state condition occurring in vertical descent of an eVTOL aircraft propeller. Wind tunnel tests were conducted on a propeller model representative of the tilter propeller of the Archer Maker eVTOL aircraft in 1:4 scale. The study focused on the characterization of the propeller aerodynamic performance and flow physics during descent flight conditions. With this aim, thrust and torque measurements along with Particle Image Velocimetry surveys were performed during the wind tunnel campaign reproducing both axial flight and a [Figure presented] propeller tilt angle. Multiple descent rate conditions were reproduced and analyzed with the propeller operating at different rotational speeds. Test results highlighted a significant decrease in performance during vortex ring state, occurring consistently at the same descent ratio along with the tested rotational speeds. Flow field surveys clearly reveal the topology of vortex ring generation as function of the descent ratio, allowing for a quantitative characterization of vortex ring dimensions and wandering.