PROPULSIVE ARRANGEMENTS: FINAL REPORT ON PROPULSION, CAVITATION AND PRESSURE FLUCTUATION PROPERTIES OF A LARGE SINGLE-SCREW TANKER FITTED WITH DUCTED PROPELLER

This Report summarises an investigation performed at the Swedish State Shipbuilding Experimental Tank in 1971-75 to determine the propulsion, cavitation and pressure fluctuation properties of a 300,000-dwt tanker fitted with a ducted propeller. The main part of the investigation concerned a ship model with V-shaped stern sections, but some propulsion tests were also carried out with a model with U-shaped stern sections. Both models had earlier been tested with conventional propellers. The ducted propeller used belonged to the SSPA systematic series. Self propulsion tests in the towing tank indicated that the shaft power in most cases was lower for the ducted propeller than for the conventional propeller. The gain in efficiency was, however, relatively small--3%--6% for both stern shapes. Thrust measurements in SSPA cavitation tunnel No. 2 showed that the non-dimensional thrust of the duct at the same advance ratios was about 70% higher at 4 m/s in the tunnel that at 1.2 m/s in the self propulsion tests, and that it decreased with increasing water velocity in the tunnel. A probable explanation of this unexpected result is that laminar flow separation influenced the measurements at the lower Reynolds numbers. The pressure fluctuations on the hull were measured by two transducers located at the upper part of the stern ahead of the propeller. In those cases where the cavitation was insignificant the non-dimensional pressure amplitude of the first harmonic K sub p1 was almost the same for the ducted propeller as for the conventional one. For lower cavitation numbers and advance ratios k sub p1 of the conventional propeller increased with increasing cavitation extension. No similar increase was recorded for the ducted propeller, where K sub p1 remained almost the same in the entire sigma-J range tested. The fact that the ducted propeller induced very small pressure fluctuations on the hull also when the cavitation was severe is probably due to the small circumferential variation of cavitation extension. Order from BSRA as No. 47,489

• Corporate Authors:

  Swedish State Shipbuilding Experimental Tank

  P.O. Box 24001
  S-40022 Goteborg 24,   Sweden 
• Authors:
  • Dyne, G
• Publication Date: 0

Media Info

• Features: References;
• Pagination: 40 p.

Subject/Index Terms

• TRT Terms: Atmospheric pressure; Cavitation (Mechanics); Cavitation erosion; Ducted propellers; Engine efficiency; Propellers; Propulsion; Screw propellers; Ships; Structural models; Tests
• Uncontrolled Terms: Ship models
• Old TRIS Terms: Pressure fluctuations; Propulsion tests; Propulsive efficiency
• Subject Areas: Bridges and other structures; Marine Transportation; Vehicles and Equipment;

Filing Info

• Accession Number: 00172122
• Record Type: Publication
• Source Agency: British Ship Research Association
• Report/Paper Numbers: Report K207-7
• Files: TRIS
• Created Date: Mar 14 1978 12:00AM