Ship propeller

Abstract

A ship propeller includes a hub having an outer periphery, a first blade set including a plurality of first blades each having a span-chord ratio substantially in a range of 3 to 8 and a second blade set including a plurality of second blades each having a span-chord ratio substantially in a range of 3 to 8. The first blade set and the second blade set are situated in different planes of rotation and working at the same rotation direction and the same rotation speed. Furthermore, the distance between the first blade set and the second blade set is 30 percent less than the mean blade radius. Specifically, the ship propeller has a total expanded area ratio substantially no less than 0.7.

What is claimed is: 
     
         1 . A ship propeller, comprising:
 a hub having an outer periphery; and   a plurality of blade sets, wherein each of the plurality of blade sets comprises a plurality of blades, wherein each blade has a span-chord ratio substantially in a range of 3 to 8 and projects outward from the outer periphery of the hub, wherein the plurality of blade sets are situated in different planes of rotation and working at the same rotation direction and the same rotation speed, wherein the ship propeller has a total expanded area ratio substantially no less than 0.7.   
     
     
         2 . A ship propeller according to  claim 1 , wherein the distance between two adjacent blade sets is 30 percent less than the mean blade radius. 
     
     
         3 . A ship propeller, comprising:
 a hub having an outer periphery;   a first blade set comprising a first plurality of blades, wherein each of the first plurality of blades has a span-chord ratio substantially in a range of 3 to 8 and projects outward from the outer periphery of the hub; and   a second blade set comprising a second plurality of blades, wherein each of the second plurality of blades has a span-chord ratio substantially in a range of 3 to 8 and projects outward from the outer periphery of the hub, wherein the first blade set and the second blade set are situated in different planes of rotation and working at the same rotation direction and the same rotation speed, wherein the ship propeller has a total expanded area ratio substantially no less than 0.7.   
     
     
         4 . A ship propeller according to  claim 3 , wherein the distance between the first blade set and the second blade set is  30  percent less than the mean blade radius. 
     
     
         5 . A ship propeller according to  claim 3 , wherein the cross-section of each of the first plurality of blades and the cross-section of each of the second plurality of blades are streamlined foil shape respectively. 
     
     
         6 . A ship propeller according to  claim 3 , wherein the second plurality of blades are disposed without overlapping the first plurality of blades from rotation axis view angle. 
     
     
         7 . A ship propeller according to  claim 3 , wherein the second plurality of blades are disposed at least partially overlapping the first plurality of blades from rotation axis view angle. 
     
     
         8 . A ship propeller according to  claim 3 , wherein the first plurality of blades and the second plurality of blades are evenly distributed around the outer periphery of the hub respectively. 
     
     
         9 . A ship propeller according to  claim 3 , wherein each of the first plurality of blades is forwardly skewed. 
     
     
         10 . A ship propeller according to  claim 3 , wherein each of the first plurality of blades is backwardly skewed. 
     
     
         11 . A ship propeller according to  claim 3 , wherein each of the first plurality of blades is backwardly skewed in the region adjacent to the root portion and forwardly skewed in the region adjacent to the tip portion. 
     
     
         12 . A ship propeller according to  claim 3 , wherein each of the first plurality of blades is forwardly skewed in the region adjacent to the root portion and backwardly skewed in the region adjacent to the tip portion. 
     
     
         13 . A ship propeller according to  claim 3 , wherein each of the second plurality of blades is forwardly skewed. 
     
     
         14 . A ship propeller according to  claim 3 , wherein each of the second plurality of blades is backwardly skewed. 
     
     
         15 . A ship propeller according to  claim 3 , wherein each of the second plurality of blades is backwardly skewed in the region adjacent to the root portion and forwardly skewed in the region adjacent to the tip portion. 
     
     
         16 . A ship propeller according to  claim 3 , wherein each of the second plurality of blades is forwardly skewed in the region adjacent to the root portion and backwardly skewed in the region adjacent to the tip portion.