Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
  • B63H—MARINE PROPULSION OR STEERING
  • B63H5/00—Arrangements on vessels of propulsion elements directly acting on water
  • B63H5/07—Arrangements on vessels of propulsion elements directly acting on water of propellers
  • B63H5/08—Arrangements on vessels of propulsion elements directly acting on water of propellers of more than one propeller
  • B63H5/10—Arrangements on vessels of propulsion elements directly acting on water of propellers of more than one propeller of coaxial type, e.g. of counter-rotative type
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
  • B63H—MARINE PROPULSION OR STEERING
  • B63H1/00—Propulsive elements directly acting on water
  • B63H1/02—Propulsive elements directly acting on water of rotary type
  • B63H1/12—Propulsive elements directly acting on water of rotary type with rotation axis substantially in propulsive direction
  • B63H1/14—Propellers
  • B63H1/28—Other means for improving propeller efficiency

Definitions

• This application relates to an arrangement in a counter rotating propulsion system (CRP).
• CRP counter rotating propulsion system
• the propulsion system is normally located in after part of the marine vessel.
• the propellers are equipped with hubcap, which is normally covering the propeller fastening bolt.
• the circulation of water around each forward propeller blade forms a vortex near the hub before they joint to one hub vortex.
• This hub vortex cavitation is known to be very harmful to the propulsion unit or the rudder behind the main propeller.
• the hub vortex is itself erosive but it can also induce other harmful forms of cavitation on construction such as propulsion unit or after propeller blade.
• This invention will reduce or eliminate the above mentioned problem in CRP propulsion concept and thus protect the after propeller and entire propulsion unit itself from damage.
• the invention will increase the capability to steer the propulsion unit behind forward propeller without danger of erosive hub vortex cavitation and without dangerous cavitation on the blades after hub of forward cavitation. This will lead to longer lifetime and reduce repairing costs of the propulsion unit.
• the invention is based to an idea to break the flow of the vortex caused by the blades of the forward propeller.
• the hub cab of the propeller in detail the external appearance of the hubcap is formed so that it consists of at least two, equally distributed flow plates projecting from the outer surface of the hubcap. The number of the flow plates is in practice not higher than eight while four flow plates gives the most efficient result.
• cap itself should be well-streamlined, with relation of cap diameter and cap length not more than 2. It provides the absence of developed separation after hub cap with plates and so make it possible to eliminate blade cavitation in separation zone after fore hub when thruster is not co-axial with fore propeller.
• the absence of the hub vortex allows the safe operation of after propeller and steerable propulsion unit.
• the invention is advantageous to implement, as it requires no other modifications to the structure or to operation of the propulsion system or its peripheral devices. Further as the invention mainly is realized with a special forming of a separate component, the invention is adaptable also to the propulsion devices in use.
• the hubcap of the fore propeller will have the flow plates which are straight and similar to each other. This gives an optimal effect and a balanced structure.
• the number of the flow plates is independent of the number of the blades of the forward propeller and the position of the flow plates is independent of the position of the blades of the forward propeller.
• the diameter of the tip edges of the plates is in the range of 0,4 —2 times the maximum hub diameter. Within this range the efficiency of the invented appliance is especially advantageous.
• the flow plates are fastened to the hub cab either by fixed to the cap by welding or by with bolts.
• the size and shape of the flow plates is easy to change and vary if necessary depending of the respective requirements. If the flow plates are used with the vessels in use, this possibility might be desirable.
• the hubcap is moulded as one piece with flow plates whereby the hubcap can be handled as an integrated piece.
• the aft propeller is turnable and the aft propeller is used to propel and steer the vessel.
• Figure 1 is a schematic view of a CRP arrangement according to the invention
• FIG. 2a is side view of a hub cap according to the invention.
• FIG. 2b is front view of a hub cab of Figure 2a.
• FIG. 1 shows a propulsion arrangement 2 which is realized with counter rotating propellers (CRP), which is placed under the hull 4 of the vessel.
• the main propulsion propeller, so called forward propeller 6 is arranged onto the main driving axis 8, which is supported via bearings to the hull 4 of the ship.
• the forward propeller 6 is driven e.g. by the drive unit, like a diesel engine, directly or via a electric drive that is supplied by a diesel-generator unit by means of a frequency converter which is well-known in the art.
• the drive unit and the bearing and other features of the power transmission is utilizing conventional technique well-known in the art and there in no need to explain in detail in order to understand the invention.
• the forward propeller 6 comprises a hub 10 arranged to the driving axis 8 and propeller blades 12 fixed to the hub 10.
• the number of blades, the inclination of the blades and the size of the blades will be defined when dimensioning the propulsion system of ship and they may vary case by case.
• the inclination of the blades may also be adjustable.
• the hull 4 of the ship is designed so that the bottom of the hull curves over the forward propeller 8 and the bottom extends at higher level after the forward propeller.
• the bottom 14 at the rearmost portion of the ship is higher than the bottom 16 of the ship in front of the forward propeller.
• a rurnable steering device 18 which consists of an azimuth propeller unit, like an AZIPOD® unit, which steers and propels the vessel.
• the steering device 18 comprises a shaft 20, which is pillowed to be turnable 360 degrees around its vertical axis.
• a streamlined casing 21, which covers the driving motor of the steering propeller 22, is attached under the shaft 20.
• the steering propeller 22 is driven by the driving axis 24, which is positioned on the same level as the axis 8 of the forward propeller.
• the well-streamlined hub cap 30 of the forward propeller 6 and the hub cap 26 of the steering propeller 22 are against each other and the forward propeller 6 and the steering propeller 22 are rotating in the opposite direction when the ship is moving forwards.
• the steering device 18 is turned around the vertical axis of the shaft 20 in order to effect the desired steering action.
• the rotating planes of the forward and steering propellers are farther from each other than the double diameter of the forward propeller when the propellers are against each other.
• the hub cap 30 of the forward propeller 6 and the hub cap 26 of the steering propeller are thus positioned much closer.
• the vortex and the stress caused by it effects thus heavily to the hubcap of the forward propeller and also to the steering propeller.
• the hub vortex cavitation and the aft propeller blade cavitation with its harmful effects are minimized by arranging a well-streamlined hub 30 after the forward propeller and flow plates 28 onto the hubcap 30.
• each flow plate 28 is mounted symmetrically or with equal distance to each flow plate on the outer surface of the hubcap 30 as shown in the figures 2a and 2b.
• the figure 2a is the side view and the figure 2b is the front view when seen from the rear of the vessel.
• the hubcap has length L and diameter D, whereby the ratio D/L is not higher than 2.
• the flow plates are straight plates that are welded or fixed by bolts to the surface of the main propeller hubcap 2.
• the flow plates 2 can also be cast together with the whole propeller hubcap.
• the flow plate has been installed on the whole length of the cap surface and the flow plates link up to each other outside the cap surface extending a little over the top edge of the cap.
• the height of the flow plate does not exceed the radial dimensions of the cap.
• the flow plate does not extend over the diameter of the hubcap.
• the flow plates are projected in the radial direction from the surface of the hubcap and they are installed in the direction of the propeller axis with no inclination. It has been shown that the tip edges of the flow plates may vary in the range of 0,4 to 2 times the maximum hub diameter D. Accordingly this range corresponds about 0,12 to 0,4 times the diameter of the propeller.
• the number of the flow plates is not tied to the number of the propeller blades and it may vary from two to eight while four flow plates has been found to be advantageous. Neither the positioning of the flow plates is not bound to the position of the propeller blades but they can coincide or be aside.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• Ocean & Marine Engineering (AREA)
• Structures Of Non-Positive Displacement Pumps (AREA)
• Vehicle Body Suspensions (AREA)
• Manipulator (AREA)
• Control Of Linear Motors (AREA)
• Excavating Of Shafts Or Tunnels (AREA)
• Control Of Electric Motors In General (AREA)
• Gear-Shifting Mechanisms (AREA)
• Other Liquid Machine Or Engine Such As Wave Power Use (AREA)
• Aiming, Guidance, Guns With A Light Source, Armor, Camouflage, And Targets (AREA)
• Earth Drilling (AREA)

Priority Applications (10)

Applications Claiming Priority (2)

Publications (1)

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ID=8565138

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Citations (4)

Family Cites Families (6)

• 2002
  • 2002-12-20 FI FI20022265A patent/FI115210B/fi not_active IP Right Cessation
• 2003
  • 2003-12-19 DE DE60335026T patent/DE60335026D1/de not_active Expired - Lifetime
  • 2003-12-19 KR KR1020057011298A patent/KR101127484B1/ko not_active Expired - Fee Related
  • 2003-12-19 WO PCT/FI2003/000978 patent/WO2004056654A1/en active Application Filing
  • 2003-12-19 CN CNA2003801070571A patent/CN1729123A/zh active Pending
  • 2003-12-19 CA CA2509401A patent/CA2509401C/en not_active Expired - Fee Related
  • 2003-12-19 AU AU2003292278A patent/AU2003292278B2/en not_active Ceased
  • 2003-12-19 DK DK03767842.2T patent/DK1578662T3/da active
  • 2003-12-19 EP EP03767842A patent/EP1578662B1/en not_active Expired - Lifetime
  • 2003-12-19 JP JP2004561548A patent/JP4005601B2/ja not_active Expired - Fee Related
  • 2003-12-19 AT AT03767842T patent/ATE488427T1/de not_active IP Right Cessation
  • 2003-12-19 ES ES03767842T patent/ES2356628T3/es not_active Expired - Lifetime
  • 2003-12-19 US US10/539,089 patent/US20060172632A1/en not_active Abandoned
  • 2003-12-19 RU RU2005122954/11A patent/RU2304545C2/ru not_active IP Right Cessation
• 2005
  • 2005-07-18 NO NO20053510A patent/NO334694B1/no not_active IP Right Cessation

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