THE PROPELLER AS A SPEED LOG: USING FULL SCALE THRUST MEASUREMENTS TO QUANTIFY PROPELLER EFFICIENCY AND HULL FOULING

摘要

Ships require less fuel when their hulls are clean and their propellers are smooth, so regular maintenance is needed to allow them to sail efficiently. To optimally plan maintenance to propeller and hull, the ship’s hydrodynamic performance must be monitored. Full scale thrust measurements are a very useful input for such performance monitoring. Using thrust measurements a distinction can be made between efficiency losses related to the hull, and efficiency losses related to the propeller. Moreover, when a ship is equipped with a fixed pitch propeller the combination of propeller rotation rate and thrust can be used to estimate ship speed. This paper discusses a method to determine hull and propeller fouling separately, and a method to correct faulty speed log data using thrust measurements. A case study shows that the two methods successfully provide credible estimates of relative improvements in hull resistance and propeller efficiency.