Propeller slipstream enhancer

Abstract

The invention relates a fluid or air propeller propulsion apparatus using modified state of the art propeller that reduces the typical propeller slipstream disc contraction at the propeller tips, by simply adding a novel channel or trough on the back surface spanwise midway between the leading edge and trailing edge. A portion of the air or fluid flowing over the back face of propeller blade is raked off and collected in the channel during rotation of the propeller, wherein the fluid or air is acted upon by centrifugal force varying directly with the propeller speed causing the fluid or air to be accelerated thru the channel or trough to the trailing edge of the propeller. This additional flow increases the propeller capacity additional jetting action bootstrapping causing the propeller to turn more easily, all of which increases the propeller thrust and efficiency as much as 10 percent.

1 . In apparatus characterized as a foil having a back surface extending from the leading edge to the trailing edge of said foil and an opposite camber surface extending from the leading edge to the trailing edge of said foil, between the opposite back surface and a fluid of which relative movement can occur, the improvement which comprises
 an area completely smooth on the cambered side, and the back surface smooth except for a channel or trough extending spanwise midway of the leading edge and the trailing edge subtended on a straight line to the trailing edge of said foil devoid of any indentations causing the fluid stream not to collect in the channel allowing the centrifugal force of the foil rotation to produce a flow to the foil tip to enhance the slipstream, improve performance and efficiency of the foil as contrasted with a foil otherwise similar except that it contains no channel, indentations, or projections in the area between the leading edge and the trailing edge.   
     
     
         2 . The apparatus of  claim 1  wherein the foil is a hydrofoil and the fluid is water. 
     
     
         3 . The apparatus of  claim 1  wherein the foil is an airfoil and the fluid is air. 
     
     
         4 . The apparatus of  claim 3  wherein the airfoil is a propeller blade. 
     
     
         5 . The apparatus of  claim 3  wherein the airfoil is a propeller with blades of which are provided with a single channel or trough spanwise on each blade back surface opposite the cambered surface spanwise midway between the leading edge and trailing edge of said propeller. 
     
     
         6 . The apparatus of  claim 1  wherein the depth of the channel or trough ranging 0.0714 times the maximum chord of the foil from edge to edge. 
     
     
         7 . The apparatus of  claim 1  wherein the foil which is provided with a channel or trough extending from a location wherein the inner ends of the blades are joined via a hub at the outer terminal ends of the blades. 
     
     
         8 . The apparatus of  claim 1  wherein the channel or trough trailing subtended by a direct from the 10 percent position measured from the leading edge to the trailing edge boundary of the channel intersecting the back surface midway to the trailing edge, the said channel approximately 65 percent of the foil length and terminating approximately 5 percent of the foil length from the foil tip. 
     
     
         9 . The apparatus of  claim 1  wherein a portion the flow of air or fluid passing at right angle to the leading edge of the foil raking off a portion of the flow which accumulates in the channel or trough and exits the said foil tip at the trailing edge parallel to the cambered face of the foil and at an angle measured from the tip of approximately 45 degrees to the longitudinal axis of the foil. 
     
     
         10 . The apparatus in  claim 4 , wherein the channel or trough at right angle to the air or fluid flow, rakes off a portion of the flow wherein accumulated during the rotation of the propeller apparatus the air is further propelled by centrifugal force via the said channel, reducing slipstream disc contraction at the propeller tips at zero or low forward speed, and at greater speeds, and inducing flow over the cambered face of the propeller apparatus increasing propulsion, plus bootstrapping by the jetting effect of the air exiting the trailing edge at the tip of the propeller apparatus.