Research on a smallest blade area propeller

This paper concerns results of model tests and full scale measurements of the propeller designed for inland ship (749 GT chemical tanker) aiming 3% increase of propulsive efficiency comparing with the present conventional propeller.Three concepts, namely (1)small blade area, (2)decrease of hub-vortex, and (3)consideration of ship wake distribution are applied for the propeller design. NHV (Non Hub-Vortex) propeller, of which the blade area was decreased by 20% from the conventional propeller, was designed and towing tank tests (propeller open test and self propulsion test) and cavitation tests (cavitation observation, paint erosion test, and fluctuating pulse measurement) were carried out with the conventional propeller and the SBA-NHV propeller (Small Blade Area NHV propeller). The model test results showed that the propulsive efficiency of SBA-NHV propeller is about 4% higher than that of the conventional propeller and the risk of cavitation erosion and the fluctuating pressure of both propellers are almost equivalent. Finally, sea trial of 749 GT chemical tanker was performed with the SBA-NHV propeller which was newly manufactured. Results of the sea trials and the service performance demonstrated about 4% deduction of engine output without any problem of the ship vibration and cavitation erosion after 15 months operation.