To provide a marine propulsion device capable of obtaining the high propeller efficiency in an operational state of low speed and high load irrespective of during direct advance and during making a turn by a propeller of a compact and double-end type counter rotating propeller.
The marine propulsion device 1 includes a pod 4 turnable with respect to a hull 2, front and rear propellers 5, 6 provided on the pod to constitute a counter rotating propeller, and a cylindrical duct 7 of blade-like section type mounted on the pod while accommodating the rear propeller 6. The outside diameter DR of the rear propeller is set to be in a numerical range of 86-100% of the outside diameter DF, and the spacing d of the front and rear propellers is set to be in a numerical range of 45-80% of the outside diameter DF of the front propeller. Thus, the difference between inner and outer flow speeds of the duct is increased, the forward thrust force is increased by the differential pressure attributable thereto, and the efficiency of the propeller is improved.
IGETA MASAKI
MATSUURA MASAO
| JP2008149746A | 2008-07-03 | |||
| JPS58156492A | 1983-09-17 | |||
| JPS62273194A | 1987-11-27 | |||
| JPS62149598A | 1987-07-03 | |||
| JPH08282590A | 1996-10-29 |
| US3094967A | 1963-06-25 | |||
| US20050009418A1 | 2005-01-13 | |||
| US5632658A | 1997-05-27 |
Noriyuki Suzuki