Power extraction from a propeller's wake

Abstract

A propeller obtains the forward propulsive force, or thrust, by increasing the rearward momentum of a quantity of the fluid in which it is submerged. The fluid leaving the propeller also has rotary (swirl) motion and this represents a waste of energy. The idea behind this project was thus to investigate the possibility of extracting power from the wake of a propeller. The test rig was set out to include a motor driven propeller followed by a suitably sized 'wind turbine', the power absorbed by the propeller being measured via a floating field arrangement and the power developed by the turbine being measured via a brake dynamometer. In the provided wind tunnel conditions were not set to be dynamically similar to those in real-life situations, however the project was made to assume an academic nature in that working with one Reynolds number is 'similar' to working with other Reynolds numbers. Thus the results of this project could also be extended further such that more practical use of this same idea of extracting power from a propeller's wake can be found in real-life situations.