Propeller blade performance in low-pressure environments

There have been increasing applications of propeller-driven flyers in non-Earth environments where significantly lower ambient pressures are present. This work experimentally studies the performance of rotor propeller blades of an airfoil profile in low-pressure environments by varying the aspect ratio ( ), angle of attack (α), and rotational speed of the blade. The experiments are performed in a vacuum chamber to investigate performance at various ambient pressures ranging from 3 to 96 kPa, resulting in a Reynolds number range of 300–27 500. Thrust and torque on a two-blade rotor are measured. The thrust (CT) and power (CP) coefficients of the propeller increased with α and [ ] while they were not influenced by ambient pressure levels, except for the lowest pressure tested here (3 kPa). The thrust to power ratio (CT/CP), however, decreases with the ambient pressure and α, suggesting a reduction in performance. At lower ambient pressures (<16 kPa), both CT/CP and figure of merit are higher for blades operating at higher angles of attack and lower . This increase in performance of lower rotors at high α can likely be attributed to low Reynolds number effects, which play a significant role at lower ambient pressures. These findings highlight the significant variations in performance due to reduced ambient pressures and will be useful for understanding the design requirements based on the aerodynamic performance of propellers in extraterrestrial environments.