System and Method for Marine Propulsion With Low Acoustic Noise

Abstract

A propulsion system for a marine vessel in a body of water includes an water intake formed in the hull, a impeller disc rotatable about a vertical axis for raising water and increasing the momentum of water in a plenum chamber, and a plurality of control gates located around the periphery of the hull. The impeller disc has a large outer diameter and is formed to enable efficient rotation by an electric motor. One or more of the water intake, the plenum chamber, the impeller disc and the control gates is designed to reduce acoustic noise generated by the marine vessel, direct the acoustic noise to avoid broadband acoustic noise, increase efficiency of the propulsion system and provide additional safety to passengers on the marine vessel and marine life in the body of water.

What is claimed is: 
     
         1 . A propulsion system for a marine vessel, the propulsion system comprising:
 a water intake formed in a hull, the water intake open to ambient water;   an impeller disc rotatable about a vertical axis, the impeller disc comprising:
 a top surface orthogonal to the vertical axis, the top surface extending radially outward to a top surface outer edge; and 
 a bottom surface separated from the top surface by a distance and extending radially outward to a bottom surface outer edge; and 
 an angled surface extending between the bottom surface outer edge to the top surface outer edge, the angle surface comprising a plurality of blades; 
   a plenum chamber for containing the impeller disc, the plenum chamber comprising
 an upper wall extending radially outward of the top surface outer edge; 
 a bottom wall having a bottom wall outer diameter radially inward of the water intake; and 
 a lower wall extending from the bottom wall radially inward of the water intake to the upper wall to the upper wall radially outward of the water intake, the lower wall having an opening in fluid communication with the water intake; 
   a plurality of control gates in fluid communication with the plenum chamber and located near the periphery of the hull; and   a control system configured to:
 rotate the impeller disc to cause water flow from the water intake to the plurality of control gates; and 
 open one or more of the plurality of control gates, wherein water exiting the one or more of the plurality of control gates flows into the ambient water to generate thrust. 
   
     
     
         2 . The propulsion system of  claim 1 , wherein the impeller disc comprises a hollow structure. 
     
     
         3 . The propulsion system of  claim 1 , wherein a separation distance between the angled surface of the impeller disc and the lower wall of the plenum chamber is substantially constant at all radii. 
     
     
         4 . The propulsion system of  claim 1 , wherein a separation distance between the angled surface of the impeller disc and the lower wall of the plenum chamber decreases radially outward. 
     
     
         5 . The propulsion system of  claim 1 , wherein one or more of the plenum chamber and the impeller disc is configured for neutral buoyancy in water. 
     
     
         6 . The propulsion system of  claim 1 , wherein one or more of the plenum chamber and the impeller disc is configured for positive buoyancy in water. 
     
     
         7 . The propulsion system of  claim 1 , wherein one or more of the plurality of control gates is at least partially above a surface of the ambient water. 
     
     
         8 . The propulsion system of  claim 1 , wherein one or more of the plenum chamber and the impeller disc is proportioned and configured to deflect acoustic noise away from the water intake. 
     
     
         9 . The propulsion system of  claim 1 , wherein the water intake comprises a plurality of narrow slots oriented relative to a length of the vessel. 
     
     
         10 . The propulsion system of  claim 1 , wherein each control gate is configurable to direct water exiting the control gate at an angle selected from a range of ninety degrees. 
     
     
         11 . A marine vessel comprising:
 a hull comprising an outer surface;   a water intake formed in the outer surface of the hull in a substantially vertically downward direction;   an impeller disc rotatable about a vertical axis, the impeller disc comprising:
 a top surface orthogonal to the vertical axis, the top surface extending radially outward to a top surface outer edge; and 
 a bottom surface separated from the top surface by a distance and extending radially outward to a bottom surface outer edge; and 
 an angled surface extending between the bottom surface outer edge to the top surface outer edge, the angle surface comprising a plurality of blades; 
   a plenum chamber for containing the impeller disc, the plenum chamber comprising
 an upper wall extending radially outward of the top surface outer edge; 
 a bottom wall having a bottom wall outer diameter radially inward of the water intake; and 
 a lower wall extending from the bottom wall radially inward of the water intake to the upper wall to the upper wall radially outward of the water intake, the lower wall having an opening in fluid communication with the water intake; 
   a plurality of control gates in fluid communication with the plenum chamber and located near the periphery of the hull; and   a control system configured to:
 rotate the impeller disc to cause water flow from the water intake to the plurality of control gates; and 
 open one or more of the plurality of control gates, wherein water exiting the one or more of the plurality of control gates flows into the ambient water to generate thrust. 
   
     
     
         12 . The marine vessel of  claim 11 , comprising:
 an electric motor coupled to the impeller disc; and   the electric motor is configured to rotate the impeller disc at low rotational speed.   
     
     
         13 . The marine vessel of  claim 11 , wherein a diameter of an outer edge of the impeller disc is greater than 25% of a width of the marine vessel. 
     
     
         14 . The marine vessel of  claim 11 , wherein a diameter of the upper wall of the plenum chamber is greater than 25% of a width of the marine vessel. 
     
     
         15 . The marine vessel of  claim 11 , wherein:
 the hull comprises a flat bottom; and   the water intake is configured to open substantially in a downward direction.