SEA TRIALS OF THE DUCTED TIP PROPELLER

摘要

Sea trials of a 45 foot seine boat, fitted first with aconventional tip, and subsequently with a ducted tip, 36 inchdiameter propeller have been conducted. The trials consistedof careful propeller efficiency measurements at a number ofadvance ratios, and underwater video imaging of the differentpropellers under Bollard pull conditions. The trials haveshown that flow-through ducts installed at the blade tipssuppress the tip vortex roll-up, thus resulting in a substantialdelay in the onset of tip vortex cavitation. This cavitationimprovement comes without any efficiency penalty. In fact, theefficiency of the ducted tip propeller is up to 10% higher (athigh advance ratios) than the efficiency of the same propellerfitted with conventional tips.The ducted tip propeller was originally thought to be usefulonly for boats with heavily loaded propellers, such as tug boatsand trawlers. The current research has shown that the ductedtips may have much broader application.