AUV Propellers: Optimal Design and Improving Existing Propellers for Greater Efficiency

Propeller design is a significant process that is overlooked in many design situations. Using propeller vortex lifting line code and two-dimensional analysis with Brockett diagrams, a propeller design can be optimized for an Autonomous Underwater Vehicle with a given design speed by varying blade number, propeller diameter, hub position, and chordlength distribution over a given range of RPS appropriate to the AUV´s thrusters. Initial design decisions from PVL code chose a three-bladed 0.625m diameter propeller at 2RPS, with a hub located at r/R(0.2) and an efficiency of 0.7091. Final propeller design modified the chord distribution to improve distributed lift coefficients and to ensure that shallow-water operations would not experience cavitation effects. The final design geometry used the same values of the propeller blade number, diameter, RPS and hub location as the initial design, but at an efficiency of 0.7642. While off-the-shelf propellers, such as those designed for model airplanes, can have high calculated efficiencies relative to actuator disk theory, the lift coefficient at each radial position and the resulting stalling effects must be considered. Comparison of an existing design with an optimized design improves existing propellers and contributes to the process of choosing future off-the-shelf propellers