C.P. PROPELLERS-THE NEED FOR MODEL TESTING
Controllable-pitch propellers now hold a very large share of the propeller market, and propeller suppliers are giving them increased attention. The Author discusses some of the mechanical and hydrodynamic aspects of the design of these propellers, with particular reference to the work of his company (SMM Engineering) and that done in the cavitation tunnel at Newcastle University. Among the matters discussed are: (i) loads in the hub body due to thrust, centrifugal force, pitch-holding, and pitch-changing (the hub body is not, however, loaded by pitch-changing forces in some double-acting designs such as SMME's XX); (ii) model work associated with these loads; (iii) hub design to allow the hydrodynamicist the largest blade-palm, with its attendant advantages; (iv) blade area ratio; (v) boss diameter ratio; (vi) pitch-changing behaviour of ducted c.p. propellers during manoeuvring; (vii) spindle torque of ducted propellers (the work needed for one c.p. propeller is more than that needed for seven f.p. propellers); (ix) the strain-gauge blade dynamometer. Today's needs are for high efficiency (to minimise fuel consumption) and operational reliability, and for low first cost, which is largely a matter of having the smallest hub size. Minimum blade-width not only increases efficiency but minimises spindle torque and hence reduces the hub size. A further requirement is for large-diameter propellers running at low rpm. Current and future needs relating to c.p. propeller design and construction are further discussed, and it is mentioned that blades designed for more exacting loadings will require careful maintenance and that it could become the practice to change the blades at survey periods and repair them ready for the next docking. Future ships must have underwater hulls designed with more attention to improving the wake. Long slender blades of slow-running c.p. propellers will give the designer similar freedom in blade outline to that enjoyed by the designer of f.p. propellers. Blade-tip vortices are among the other matters considered. Feathering propellers (the small demand for these has recently tended to grow) are also discussed, together with some results of tests on them. Finally, the Author briefly discusses priorities for future cavitation-tunnel work on c.p. propellers. Although investigations relating to individual ship applications will always be important and may require short-term priority, in the long run it is the steady process of refinement and extension of standard information that will do most to help British c.p. propeller design. Order from BSRA as No. 53,402.
- From the Proceedings of the Stone Manganese Marine/Newcastle University Conference "Model Experiments as an Aid to Advanced Propulsion", 24-27 September 1979.
Newcastle upon Tyne University, EnglandClaremont Tower, Claremont Road
Newcastle NE1 7RU, Tyne and Wear, England
- May, E R
- Publication Date: 1979
- Features: References;
- Pagination: 7 p.
- TRT Terms: Controllable pitch propellers; Ducted propellers; Mechanical loads; Pitch (Dynamics); Propeller blades; Propellers; Vehicle design
- Old TRIS Terms: Model testing; Propeller design; Propeller efficiency; Propeller hubs; Propeller loading; Propeller pitch
- Subject Areas: Design; Marine Transportation; Vehicles and Equipment;
- Accession Number: 00316633
- Record Type: Publication
- Source Agency: British Ship Research Association
- Report/Paper Numbers: Paper No. 11 Conf Paper
- Files: TRIS
- Created Date: Oct 8 1980 12:00AM