Multi-row propeller (mrp) with co-rotating blades

Abstract

Propulsion devices that provide increased propeller efficiency when operating outside of an optimal advance ratio are described. In one example, a propulsion device includes a hub having a curved surface extending around and along a rotation axis of the hub. The propulsion device can further include two or more rows of blades extending radially outward from the curved surface and including a first row of blades having a first blade and a second row of blades having a second blade that is angularly and axially offset from the first blade on the curved surface. A first centerline of the first blade and a second centerline of the second blade each intersect with a helical line that extends along the rotation axis of the hub. The first blade and the second blade collectively form a helical pattern of blades that projects radially outward from the curved surface along the helical line.

Therefore, at least the following is claimed: 
     
         1 . A propulsion device, comprising:
 a hub having a curved surface extending around and along a rotation axis of the hub; and   two or more rows of blades extending radially outward from the curved surface and comprising a first row of blades having a first blade and a second row of blades having a second blade, the second blade being angularly and axially offset from the first blade on the curved surface,   wherein a first centerline of the first blade and a second centerline of the second blade intersect with a helical line that extends along the rotation axis of the hub, the first blade and the second blade collectively forming a helical pattern of blades that projects radially outward from the curved surface along the helical line.   
     
     
         2 . The propulsion device of  claim 1 , wherein the two or more rows of blades and each blade of the two or more rows of blades rotate at a same rotational rate and in a same rotational direction about the rotation axis during rotation of the propulsion device. 
     
     
         3 . The propulsion device of  claim 1 , wherein the first blade has a first leading edge and the second blade has a second leading edge, and wherein the first leading edge and the second leading edge are facing in a same rotational direction about the rotation axis. 
     
     
         4 . The propulsion device of  claim 1 , wherein a leading edge of each blade of the two or more rows of blades is facing in a same rotational direction about the rotation axis. 
     
     
         5 . The propulsion device of  claim 1 , wherein the first blade and the second blade each comprise a discrete blade that is individually coupled to the curved surface, the curved surface being a single continuous surface. 
     
     
         6 . The propulsion device of  claim 1 , wherein the first blade and the second blade each has a different blade angle with respect to a rotation plane that is normal to the rotation axis. 
     
     
         7 . The propulsion device of  claim 1 , wherein each row of the two or more rows of blades comprises an equal number of blades. 
     
     
         8 . The propulsion device of  claim 1 , wherein at least one row of the two or more rows of blades comprises a number of blades that is different from at least one other row of the two or more rows of blades. 
     
     
         9 . The propulsion device of  claim 1 , wherein each blade of the two or more rows of blades has a same geometry. 
     
     
         10 . The propulsion device of  claim 1 , wherein at least one blade of the two or more rows of blades has a geometry that is different from at least one other blade of the two or more rows of blades. 
     
     
         11 . The propulsion device of  claim 1 , wherein each row of the two or more rows of blades comprises a uniform angular distribution of blades about the rotation axis. 
     
     
         12 . The propulsion device of  claim 1 , wherein each row of the two or more rows of blades comprises a same uniform angular distribution of blades about the rotation axis. 
     
     
         13 . The propulsion device of  claim 1 , wherein at least one row of the two or more rows of blades comprises a uniform angular distribution of blades about the rotation axis that is different from at least one other row of the two or more rows of blades. 
     
     
         14 . The propulsion device of  claim 1 , wherein at least one row of the two or more rows of blades comprises a nonuniform angular distribution of blades about the rotation axis. 
     
     
         15 . The propulsion device of  claim 1 , wherein each blade of the two or more rows of blades has a same blade angle. 
     
     
         16 . The propulsion device of  claim 1 , wherein at least one blade of the two or more rows of blades has a blade angle that is different from at least one other blade of the two or more rows of blades. 
     
     
         17 . A propulsion device, comprising:
 a first hub having a first row of blades extending radially outward from a first curved surface of the first hub, the first row of blades comprising a first blade, the first curved surface extending around and along a rotation axis of the propulsion device; and   a second hub having a second row of blades extending radially outward from a second curved surface of the second hub, the second row of blades comprising a second blade that is angularly and axially offset from the first blade as measured from the rotation axis, the second curved surface extending around and along the rotation axis,   wherein a first centerline of the first blade and a second centerline of the second blade intersect with a helical line that extends along the rotation axis, the first blade and the second blade collectively forming a helical pattern of blades that projects radially outward from the first curved surface and the second curved surface along the helical line.   
     
     
         18 . The propulsion device of  claim 17 , wherein each blade of each of the first row of blades and the second row of blades rotate at a same rotational rate and in a same rotational direction about the rotation axis during rotation of the propulsion device. 
     
     
         19 . The propulsion device of  claim 17 , wherein a leading edge of each blade of each of the first row of blades and the second row of blades is facing in a same rotational direction about the rotation axis. 
     
     
         20 . A method of improving propulsion efficiency, the method comprising:
 rotating a propulsion device, the propulsion device comprising a hub having two or more rows of blades that extend radially outward from a curved surface of the hub and comprise a first row of blades having a first blade and a second row of blades having a second blade, the second blade being angularly and axially offset from the first blade on the curved surface, the first blade and the second blade collectively forming a helical pattern of blades that extends along at least a portion of the curved surface;   altering a first direction of a fluid flow over the first blade by a first amount and a second direction of the fluid flow over the second blade by a second amount that is less than the first amount based on rotating the propulsion device; and   increasing an efficiency of the propulsion device based on altering the second direction of the fluid flow over the second blade by the second amount.