Automated dynamic propeller testing at low Reynolds numbers

Scope and Method of Study. Experiments were conducted on small propellers using a motor dynamometer in a wind tunnel. The effects at different Reynolds numbers were observed. To maintain the Reynolds number and consistent test procedures, the wind tunnel speed and propeller RPM was dynamically controlled using a PI controller. The propeller diameters ranged from 14 inches to 18 inches with local Reynolds numbers between 20,000 and 400,000 at advance ratios from 0 to 1.;Findings and Conclusions. The experiments validated that the performance of small propellers are affected by low Reynolds numbers. The efficiency of small propellers varied based on their rotational speed. The results demonstrated an efficiency dependence on non-dimensional propeller constants, including the Reynolds number. The Reynolds number also affects the design pitch of a propeller. Additionally, a pitch based advance ratio definition found that the propellers tested have a constant ratio. At this constant ratio, a propeller achieves peak efficiency.