PERFORMANCE OF DUCTED PROPELLERS FITTED TO SURFACE CRAFT

The Authors examine the special problems of estimating ducted-propeller performance, both by model and full-scale procedures. A review of the literature has shown that the powering performance, cavitation and flow field within ducted propellers are strongly affected by the presence of the hull and rudder appendages. In the case of model tests it is important to include all such non-uniformities, otherwise the duct will be subjected to an unreal flow field leading to difficulties in modelling the prototype performance. Studies of ducted propeller performance are reviewed from the aspects of influence of duct geometry and influence of advance ratio. It is suggested that claims for improvement in efficiency by the use of diffusion ducts are misleading and should be treated with caution. Some alternative configurations are proposed. Considerable power losses are associated with high jet velocities and tangential swirl in the slipstream. Preliminary analysis indicates that reductions in shaft power of 8-10% could be achieved by elimination of slipstream rotation. Finally, mention is made of the development of a laser velocimeter for measuring the flow field at various stations through the ducted propeller and the open propeller. By this means data can be obtained indicating mass flow, slipstream swirl and velocity as a function of propulsor geometry and advance ratio. Order from BSRA as No. 49,611.

Media Info

  • Features: References;
  • Pagination: p. 143

Subject/Index Terms

Filing Info

  • Accession Number: 00195354
  • Record Type: Publication
  • Source Agency: British Ship Research Association
  • Files: TRIS
  • Created Date: Jul 31 1979 12:00AM