Performance of eVTOL Rotors Through Dynamic Transition

The Bath University Low-speed eVTOL Experimental Test-rig (BULLET) is a novel facility with the ability to examine the performance of eVTOL rotors under a broad variety of aerodynamic scenarios. The aim is to investigate unsteady inflow conditions due to dynamic pitching, at pitch rates representative of both transition and gust encounters. A Transition Number (Tr) has been defined to classify this change in inflow. An isolated APC 10x7E rotor has been investigated through dynamic transition from axial to edgewise flight. It has been shown that for Tr ⪆ 1.00 × 10−3, the quasi-steady assumption is invalid and the aerodynamic response is significantly influenced by the dynamic input. A near constant increase in thrust is observed throughout the transition path, demanding a decreased shaft power near conditions of edgewise flight. The mean increment in thrust is correlated with Tr, suggesting a quasi-steady effect based on unsteady inputs, i.e. rotor kinematics or gust encounters. A piece-wise linear model for this behavior is presented, informing the characterization of unsteady inflow.