Propeller Design and Loss Mechanisms in Low-Reynolds-Number Flows

To develop a highly efficient propeller for small-scale unmanned aerial vehicles, the influences of induced and profile losses determined by design parameters are investigated at Re<104. The propeller blade shapes, such as chord length and twist angle distributions in the spanwise direction, are determined using the Adkins–Liebeck method. For a fixed designated thrust value and a forward velocity, the influences of a propeller normalized radius, a blade number, and a tip speed ratio on the propeller performance are discussed. Results show that the profile loss can be larger than the induced loss. For such a case, it is beneficial to reduce the blade number and the propeller rotational speed to increase the blade chord length and the Reynolds number; consequently, the propeller efficiency increases even if the induced drag increases.