Abstract:
A device for reducing the drive power requirement of a ship and even for not very quick ships of all types, in particular for slow, wide ships, such as tankers, bulkers and tugboats, and for improving the propeller blower stream as well as for producing a pretwist includes a front nozzle fixedly installed on the hull with fins or hydrofoils placed in the inner space thereof.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
       [0001]    This invention relates to a device for reducing the drive power requirement of a single or multiple propeller ship. 
       SUMMARY OF THE INVENTION 
       [0002]    The aim of this invention is to create a device which serves for reducing the drive power requirement of a ship. 
         [0003]    This aim is achieved by a device which is fixedly installed on the hull in front of the propeller and includes a front nozzle and fins or hydrofoils placed inside the front nozzle. 
         [0004]    Accordingly, the device according to the invention for reducing the drive power requirement of a single or multiple propeller ship is configured in such a manner that the device which is fixedly installed on the hull in front of the propeller consists of a front nozzle and fins or hydrofoils placed inside the front nozzle. 
         [0005]    Using such a device, it is possible to reduce the drive power requirement of a ship. The possible gain increases with an increasing thrust loading factor of the propeller. The device is appropriate in particular for slow wide ships such as tankers, bulkers and tugboats and even for not very quick ships of all types. The device itself is fixedly installed on the hull in front of the propeller of the ship and consists of the two functional elements front nozzle and fins or hydrofoils. 
         [0006]    The working principle of the front nozzle resides in the increase of the propeller velocity in the blower stream in areas with very high co-current and in the reduction of the propeller velocity in blower stream in areas of low co-current and that of the fins or hydrofoils placed within the front nozzle in producing a pretwist, whereby both functional elements aim at different sources of losses, namely the front nozzle at a reduction of the effective thrust load and the fins or hydrofoils at a reduction of the twist losses in the propeller jet. Due to both effects, the efficiency of the propulsion system is increased. 
         [0007]    In accordance with a feature of the invention, the front nozzle is placed with a symmetrical rotation with the upwards offset axle, preferably above the propeller axle, wherein the inner diameter of the front nozzle is maximally 90% of the propeller diameter. 
         [0008]    Preferably, four fins or hydrofoils are placed asymmetrically inside the front nozzle and radially to the propeller axle, wherein the fins or hydrofoils connect the hull with the front nozzle and are placed at the rear end of the front nozzle, wherein the vaulted side of the hydrofoil-shaped and also lens-shaped cross-sectional profile of the fin or of the hydrofoil is oriented upwards on the upwardly striking side of the propeller and downwards on the downwardly striking side of the propeller. The arrangement of four fins or hydrofoils in the inner space of the front nozzle does not constitute any limitation, all the more since a lower or higher number of fins or hydrofoils can also be provided. 
         [0009]    The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0010]    In the drawing: 
           [0011]      FIG. 1  is a starboard side view of the device according to the invention consisting of a front nozzle with fins or hydrofoils placed in the inner space thereof; 
           [0012]      FIG. 2  is a rear view of the device, whereby the fins or hydrofoils are represented being not adjusted; 
           [0013]      FIG. 3  is an enlarged cross-section through the profile of a fin or of an hydrofoil; 
           [0014]      FIG. 4  is a side view of the stern contour; 
           [0015]      FIG. 5  is a body plan of the after-body; and 
           [0016]      FIG. 6  shows the front nozzle with fins or hydrofoils placed in the inner space thereof according to  FIG. 1  with position arrangements of the fins. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    According to  FIG. 1 , the device  10  for reducing the drive power requirement of a ship consists in that a front nozzle  20  with a cylindrical configuration or a differently configured shape or cross-sectional form is provided directly in front of the propeller (which is not represented on the drawing) of a ship  100 , this nozzle being fixedly installed on the hull. Fins or hydrofoils  30  are placed in the inner space  20   a  of the front nozzle  20 . The front nozzle  20  is placed on the hull so as to have a symmetrical rotation with an upwards offset axle  21 . 
         [0018]    For the embodiment represented in  FIG. 2 , four fins or hydrofoils  30   a ,  30   b ,  30   c ,  30   d  are placed star-shaped with different fin or hydrofoil lengths in the inner space  20   a  of the front nozzle  20 . These four fins or hydrofoils are placed asymmetrically inside the front nozzle and radially to the propeller axle PA. This being, the fins or hydrofoils  30   a ,  30   b ,  30   c ,  30   d  connect the front nozzle  20  with the hull  100  and are placed at the rear end of the front nozzle  20  which is turned to the propeller, whereby the vaulted side  32  of the hydrofoil-shaped or lentiform cross-sectional profile  31  of the fins or hydrofoils  30 ,  30   a ,  30   b ,  30   c ,  30   c  is orientated upwards on the aport side of the ship or on the upwards striking side of the propeller and downwards on the starboard side of the ship or on the downwards striking side of the propeller. Moreover, the fins or hydrofoils  30   a ,  30   b ,  30   c ,  30   d  are orientated at the front upwards on the aport side and at the front downwards on the starboard side ( FIGS. 2 and 3 ). The sense of rotation of the propeller is in direction of the arrow X ( FIG. 1 ). The fins or hydrofoils  30  or  30   a ,  30   b ,  30   c ,  30   d  placed in the inner space  20   a  of the front nozzle  20  are adjustable in their angular positions and lockable in the angular positions which have been set. 
         [0019]    According to an embodiment with a propeller rotating upwards to the starboard side, the fins or hydrofoils  30   a ,  30   b ,  30   c ,  30   d  take on the following preferred radial angular positions and initial angular positions: 
         [0000]                                                              Fin angle   Angle of attack                                    Aport (BB)   lower fin (30a)   247.5°   14°       Aport (BB)   middle fin (30b)   292.5°   12°       Aport (BB)   upper fin (30c)   337.5°    8°       Starboard (SB)   fin (30d)    90.0°   10°                    
namely for a fin angle definition: seen from behind: 12 o&#39;clock=0°, increasing clockwise, whereby the fin angles and the angles of attack can differ from the indicated values.
 
         [0020]    According to the embodiment represented in  FIGS. 1 ,  3  and  6 , the fins or hydrofoils have a lentiform cross-sectional profile  31  with a vaulted side wall  32  and with a straight base surface  33 . The arrangement and the position, for example, of both fins  30  to the propeller axle PA is such that the upper fin is with its base surface  33  approximately parallel to the propeller axle PA, whereas the lower fin takes on a position for which its base surface  33  is in an angle α of at least 5°, preferably of 10° to the propeller axle PA. Other angular positions of the fins are possible. On the whole, the fins  30   a ,  30   b ,  30   c ,  30   d  have preferably the positions shown in  FIG. 2 . 
         [0021]    The front nozzle  20  according to  FIGS. 1 and 6  is formed by a moulded body  25  with a cross-sectional profile  26  with an outside situated wall section  2   a  which is oblique with an angle to the propeller axle PA and with an inside situated straight wall section which is parallel to the propeller axle PA, this wall section having an arc-shaped wall section  26   c  in the area turned away from the propeller, this wall section being converted into the outside wall section  26   a . The outside situated wall section  26   a  can also be configured arc-shaped. The propeller side is indicated by PS in  FIG. 6 . 
         [0022]    While specific embodiments of the invention have been shown and described in detail to illustrate the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principle.