Except for those specials applications where requirements dictate the use of counterrotating propellers, the choice between a single propeller and counterrotating propellers involves a tradeoff related to the higher efficiency of the counterrotating propellers and the greater complexity of the counterrotating machinery. The favorable effect of tangential velocity cancellation achieved by a counterrotating propeller system can be realized without counterrotating machinery by placing upstream of a propeller a stator that generates tangential velocities which are exactly canceled out by the propeller. The results of theoretical calculations show that, using the single propeller as a baseline, the increase in efficiency for SIPUP is 50% of that achieved by counterrotating propellers. The feasibility SIPUP for marine propulsion was demonstrated by the design and at sea testing of a SIPUP propulsor. The comparison of SIPUP’s at sea data and design predictions shows good agreement in both propulsive coefficient and vehicle speed.
Investigation of the SIPUP (Swirl Inducing Stator Upstream of Propeller) Concept for Marine Propulsion
Mautner, T. S. , Nelson, D. M. , and M. C. Gillerist. "Investigation of the SIPUP (Swirl Inducing Stator Upstream of Propeller) Concept for Marine Propulsion." Paper presented at the SNAME Propellers '88 Symposium, Virginia Beach, Virginia, USA, September 1988. doi: https://doi.org/10.5957/PSS-1988-02
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