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RESEARCH PAPERS

Sea Trials of the Ducted Tip Propeller

[+] Author and Article Information
Ivar Hordnes, Sheldon I. Green

Department of Mechanical Engineering, University of British Columbia, 2324 Main Mall, Vancouver, British Columbia V6T 1Z4 Canada

J. Fluids Eng 120(4), 808-817 (Dec 01, 1998) (10 pages) doi:10.1115/1.2820742 History: Received July 15, 1997; Revised June 11, 1998; Online December 04, 2007

Abstract

Sea trials of a 45 ft seine boat, fitted first with a conventional tip, and subsequently with a ducted tip, 36 in. diameter propeller have been conducted. The trials consisted of careful propeller efficiency measurements at a number of advance ratios, and underwater video imaging of the different propellers under Bollard pull conditions. The trials have shown that flow-through ducts installed at the blade tips suppress the tip vortex roll-up, thus resulting in a substantial delay in the onset of tip vortex cavitation. The cavitation inception index for the ducted tip propeller is 50 percent lower than for the conventional propeller. This cavitation improvement comes without any efficiency penalty. In fact, the efficiency of the ducted tip propeller is up to 6 percent higher (at high advance ratios) than the efficiency of the same propeller fitted with conventional tips. The ducted tip propeller was originally thought to be useful only for boats with heavily loaded propellers, such as tug boats and trawlers. The current research has shown that the ducted tips may have much broader application.

Copyright © 1998 by The American Society of Mechanical Engineers
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