US2754919A

US2754919A - Propeller

Info

Publication number: US2754919A
Application number: US351303A
Authority: US
Inventors: John R Blue
Original assignee: Individual
Current assignee: Individual
Priority date: 1953-04-27
Filing date: 1953-04-27
Publication date: 1956-07-17
Anticipated expiration: 1973-07-17

Description

July 17, 1956 J. R. BLUE 2,754,919

PROPELLER Filed April 27, 1953 3 Sheets-Sheet l I N VEN TOR, JOHN ,Q. EZUE J. R. BLUE July 17, 1956 PROPELLER 5 Sheets-Sheet 2 Filed April 27, 1953 [9'62 INVENTOR,

JOHN e. 6405 J. R. BLUE July 17, 1956 PROPELLER Filed April 27. 1953 3 Sheets-Sheet 3 INVENTOR. 1/0 ae. BZUE h fih United States Patent Office 2,754,919 Patented July 17, 1956 PROPELLER John R. Blue, Lakewood, Calif.

Application April 27, 1953, Serial No. 351,303

Claims. (Cl. 170-159) This invention relates to propellers for use in fluids either gaseous or liquid. While hereinbelow the use of the subject propeller will be described principally in connection with the propulsion of boats, the advantages obtainable from use of the propeller as an air fan will be apparent, and development of an efiicient fan is one of the objects of the invention.

This application is a continuation of my application Serial No. 239,150, filed July 28, 1951 and now abandoned.

Much effort and time has been expended by designers of propellers to produce high efficiency in one direction of rotation, that is, the direction which effects normal forward propulsion of the propelled object, and the resultant designs have been carefully correlated to proposed speeds, and modified in accord with considerations of revolutions per minute, peripheral speed, density of the surrounding fluid, and hull resistance as a factor producing cavitation. The propeller for a racing aquaplane presents problems quite different from those presented by the propeller of a tug-boat. Generally speaking, the effort has been applied to reducing cavitation, to reducing tip-loss, and to building up a concentrated cylinder ofpropelled fluid coaxial with the propeller, such a cylinder of fluid having the strongest and most enduring jet action. Little, if any, consideration has been given to efficiency in going astern, a matter of great importance to tug-boats, fishing-boats, and all types of vessels approaching slips, docks, and other fixed or moving objects. Many collisions could be averted if full speed astern actually produced a sternward force anything like the force of full speed ahead. The ordinary forwardly-efficient propeller directs, when in reverse, a strong flow directly against the vessels hull, in effect trying to drag the vessel upstream against a strong current created by its own agency.

It is an object of this invention to provide a propeller of great efficiency in the direction of rotation related to forward propulsion of the propelled vessel or vehicle, and ofgreat efficiency in the direction of rotation related to rearward propulsion of such vessel.

More specifically it is an object of this invention to provide a propeller which develops a strong co-axial cylindrical jet of fluid, with a minimum of tip-loss, cavitation,

and turbulence, when rotated in the direction of forward propulsion, and which develops a co-axial cone of fluid when rotated in the direction of rearward propulsion.

In the accompanying drawings, illustrative of an embodiment of my invention,

Fig. 1 is an elevational view of my improved propeller, from the rearward or driving side thereof when the propeller is rotated for forward movement,

Fig. 2 is a side elevational view illustrating the manner of development of the aforesaid co-axial cylindrical jet of fluid, in forward propulsion;

Fig.-3- is another side elevational view illustrating the -rnanner of development of-the aforesaid co-axial cone of fluid, in rearward propulsion;

Fig. 4 is an elevational view from the same aspect as Fig. 1 but on a slightly enlarged scale, of a single blade of my propeller, showing successive surface contour lines in relation to a base plane perpendicular to the axis of the propeller;

Fig. 5 is a side or profile elevation of the same blade, the aforesaid contour lines being shown as a succession of parallel planes; and

Figs. 6A, 6B, and 6C being cross-sectional views on the planes perpendicular to the axis of the propeller corresponding to said contour lines in sequence from the root at the trailing edge.

It is customary in describing propellers to speak of the pressure and suction sides of the blades, and of the leading and trailing edges of the blades, these terms being related to the propeller as if the propeller invariably turned in one direction, that is, the direction which drives a boat forward which is usually termed the direction of rotation. These terms, when used hereinafter, are used in the above-stated sense in which they are commonly understood by those skilled in the art, although not entirely appropriate for describing a propeller having high efiiciency in rearward propulsion and for which rotation' in the reversed direction may also be considered normal.

As shown generally in Figs. 1, 2, and 3, my improved propeller has a hub 17 upon which a plurality of blades 18 are mounted, having pressure faces l9and suction faces 20, the roots 21 of the blades being oblique to the axis of the hub. The hub 17 is in general cylindrical so that a standard shaft and nut (not shown) may be used to support and to secure it, the advantages of cylindrical jet flow from the propeller being obtained from the shape of the blades rather than fromany unorthodox shape of the hub.

The blades 18 are, of course, alike, to obviate vibration. The leading edge 22 of each blade departs-from the root 21 in a direction nearly tangential to the hub 17, and curves concavely in the direction of rotation. The trailing edge 23 departs from the root 21 nearly radially to the hub 17, takes a short curve 24 concavely oppositely to the direction of rotation and then curves convexly in a wide sweep 25 of diminishing curvature in the direction of rotation until it reaches a point 26 at substantially maximum radial distance from the hub 17 and well beyond the radius R1 bisecting the root 21. From the point 26 the trailing edge follows a more gradual curve 27, approximately a circle around the hub 17, to a point 28 where it curves sharply inward to join the leading edge 22 at 29. The tip 30, so formed, extends in the direction of rotation well beyond a radius R2 of the propeller tangent to the leading edge 22, the edge'22 being both of less length and less curvature than the edge 23.

The above-described course of the leading edge 22 and trailing edge 23 produces a blade which, as viewed in Figs. 1 and 4 and considered as in one plane, is noteworthy in two respects: the large area of the tip 30, particularly beyond the point 26, and the large blunt area 31 defined by the

trailing edge curves

24 and 25 and lying relatively close to the root 21 and extending outwardly of a radius R3 tangent to the concave curve 24. The blade is, however, not in one plane, but is characterized by a dihedral formation, dividing the blade along the dihedral angle line 32 into an inward portion' 33 and an outward portion 34. The dihedral line 32 is a gentle curve extending from a point on the trailing edge 23 about medial of the blunt rounded portion 31 diagonally hub 17, and intersects the leading edge 22 relatively distant from the hub, and the chord of the line 32 if extended would pass close to the junction of the convex and concave curves at the point 29. The dihedral angle is an exterior angle on the suction face 20 of the blade, and an interior angle on the pressure face 19, and is more pronounced, that is to say, more acute on the pressure face 19, at its intersection 35 with the leading edge 22 than at the trailing edge 23.

It will be seen from Fig. 1 that the outward blade portion 34 has considerably more area than the inward portion 33 and that the larger part of this outward portion 34 lies between the concave leading edge 22 and the radius R1 of the hub 17 bisecting the inward portion 33. Thus the blade has a large driving area remote from the hub, this area being the zone of maximum speed and leverage. The concave curvature of the leading edge 22 displaces the tip 30 from the radius R2 of the propeller tangent to the edge 22 in the direction of outward curvature of the edge 22, so that the tip 30 is projected in the direction of normal rotation into clean fluid. The tip 30 is also displaced inwardly from the radially outermost part of the blade defined by the curve 27, so that by virtue of the hereinafter described concave-convex structure of the outer portion 34, the tip 30 may direct fluid centripetally in one direction of rotation and centrifugally in the other direction.

Both the inward blade portion 33 and the outward blade portion 34 are concave-convex, as can best be observed from the blade-sections 1 to 16 illustrated in Figs. 6A, 6B, and 6C, and corresponding to the like-numbered contours shown in Figs. 4 and 5 the contours being at equal intervals from a datum plane normal to the hub axis. The inward portion 33 is concave on the suction face of the blade and convex on the pressure face 19. The root 21 is thin adjacent the trailing edge 23 and is relatively thick adjacent the leading edge 22, as seen by comparing the sections on lines 1-7. The root 21 is faired concavely to the hub 17 on the suction face 20, the concavity showing in the curve 24 of Fig. 1, and in the curves 36 of the sections 1--7. These curves reverse from concavity to convexity to form the exterior angle of the dihedral line 32 which in this area of the blade is close to the hub and lies just beyond the concave fairing on the same suction face 20. The concavity 36 on the suction face continues, but in less degree, through the sections 810, gradually approaching the dihedral line 32 and becoming imperceptibly shallow. Thus there is formed on the suction face 20, a channel which begins shallowly and close to the dihedral at the leading edge 22 and becomes deeper and more pronounced and further from the dihedral as it approaches the trailing edge 23. Very little corresponding channel is found close to the hub 17 on the pressure side 19, as the increased thickness of the root 21 near the leading edge 22 causes all the section lines to depart from the hub nearly tangentially thereto and they almost immediately develop a convexity 37 corresponding to the opposite concavity or channel 36.

The dihedral on the line 32 forms another channel across the blade, but on the pressure face 19, most pronounced at the leading edge 22.

The outward portion 34 of the blade is concave on the pressure face 19 and convex on the suction face 20. It will be seen in Figs. 4 and 5 that the contour plane 7 intersects the periphery of the blade approximately at the point 26 and that the contour plane 8 intersects the periphery at approximately the greatest radial distance from the hub 17. It will also be observed that the equidistant contour planes of Fig. 5 converge in the elevational view of Fig. 4 as they approach the periphery of the blade in the vicinity of the contour plane 7, and are spaced progressively further apart from the contour plane '7 of Fig. 4 to the contour plane 16. Therefrom it will be evident that the inclination of the blade relative to the axis of the hub 17 increases as the blade extends from the contour plane 7 to the tip 30, although never attaining a plane perpendicular to the axis of the hub 17. The same fact will be evident from the decreasing curvature of the section lines 10-l6 in Fig. 6C. The effect of this increasing inclination to the axis of the hub 17 is to produce a tip area 30 extending outwardly from approximately a line between

points

26 and 35 which has an easy angle of attack to the fluid in which it operates. The angle of attack of the whole outward portion 34 increases gradually from the tip 30 to the blunt trail ing area 31, as will be evident from the spacing of the contour lines 1-16 between 30 and 31 in Fig. 4.

When my improved propeller is rotated in the normal direction, to propel a vessel ahead, as illustrated in Fig. 2, the tip 30 cuts the water easily and the increasing angle of attack of the following part of the outer portion 34 drives the water inwardly and across the pressure face 19 towards the dihedral line 32. At the same time, the inward portion of the leading edge 22 cuts the water at an angle of attack somewhat greater than that of the tip, and because of the convex surface 37 drives the water outwardly and across the pressure face 19 towards the dihedral line 32. The two currents are convergent in a rearward direction and join to form one rearwardly directed current. The radial distance from the hub 17 to the point 35 is sutficiently great to create a current of large volume, generated by the inward portion 33 but the current generated by the outward portion 34 is subject to greater forcing area and greater forcing velocity and so overcomes the inner volume and the net result is a flow of very high compression and very high velocity in a cylindrical rearward jet of water which tends to have a diameter about equal to that of the inward portion of the propeller at the trailing edges of the blades. The rearward velocity of this jet, which is the desired result, naturally has a direct relationship to the pressure which creates it. With most propellers a considerable part of the end velocity is rotary, or turbulent, and a considerable part of the applied energy is so consumed. The convergence of two currents at the diagonal dihedral of my propeller creates such a rearward pressure that the rearward jet velocity minimizes turbulence and conserves ene1 gy. There is no tendency for water to leave the trailing edge 23 in a centrifugal direction at any point from the inwardly displaced tip 30 to the dihedral 32, so that tip loss does not become a factor to consider.

When the propeller is reversed, a large volume of water is cut by the long outer convex edge 25 and a small volume of water is cut by the short inner concave edge 24. Water cut by the edge 24 tends to seek escape from pressure along the channel 36 which widens and diverges from the hub 17 in the direction of flow. The much larger volume of water cut by the outer portion of the blade is thrown outwardly and forwardly at much higher velocity and naturally draws the smaller and less accelerated central volume after it. The combined volume is thrown, not in a centralized jet, but in an expanding cone. The outward flow is such that water between the boat-hull and the propeller immediately around the propeller hub and shaft is drawn towards the propeller and then moved outward along the channels 36 as shown by arrows in Fig. 3. The fiow is directed against water, at the sides of the hull and not against the hull itself. Consequently the hull moves readily astern, following the pulling propeller. Also the boat is much more maneuverable, and its stem is not thrown to one side or the other by propeller torque and conflicting currents but more readily obeys the set of the rudder.

It will be obvious from the foregoing description that my propeller is designed for etficient operation in any fluid, and while I have described its operation in connection with a boat, it may also be used as an air-fan, for example in a ventilator with a reversible motor, either to draw air into a room or to expel airtherefrom.

I claim:

1. A propeller having a hub and blades joining said hub at an angle oblique to the axis of said hub, said blades individually having an outward portion and inward portion forming a dihedral angle, in which the out Ward portion is inclined at a greater inclination to the axis of said hub than said inward portion, the inward portion of the blade being concave-convex and having its convex surface on the pressure-surface of the blade, the outward portion of the blade being concavo-convex and having its concave surface on the pressure surface of the blade, the line at which said portions join extending diagonally across the blade from a position on the trailing edge of the blade relatively close to said hub to a position on the leading edge of said blade relatively distant from said hub, the interior dihedral angle becoming more acute toward said position on said leading edge, said outward portion being of larger area than said inward portion.

2. A propeller comprising a hub and a plurality of blades each having an inward portion connected to said hub at an angle oblique to the axis of said hub and having an outward portion connected to said inward portion at an increased inclination to the axis of said hub, and having one convex edge and one concave edge, said blade being formed so that the larger part of said outward portion extends between said concave edge and a radius of said hub bisecting said inward portion, the angle line at which said outer portion and said inner portion are connected intersecting said convex edge at a point substantially closer to said hub than the point of intersection of said angle line with said concave edge.

3. In a propeller, a blade set obliquely to the axis of said propeller and having a convex edge marginally defining a blunt rounded area in that portion of the blade close to said axis and then extending with less curvature to a tip, and having a concave edge extending in more gradual curvature to said tip, said tip being beyond a radius of said blade tangent to said concave edge in the direction of outward curvature of said concave edge, said blade having inward and outward portions forming a dihedral angle from a point substantially medial of said concave edge to a point on said convex edge substantially medial of said blunt rounded portion, said outward portion having an inclination to the axis of said propeller greater than said inward portion, said inclination decreasing toward said dihedral angle.

4. In a propeller, a hub and a plurality of blades having roots oblique to the axis of said hub, each of said blades having a first area defined by its trailing edge adjacent the root of said blade and extending in a trailing direction beyond a radius of the hub tangent to said trailing edge at the root thereof and having a second area adjacent its tip extending in leading direction beyond a radius of the hub tangent to the leading edge of the blade at a mid-point thereof, said areas being joined to form an interior angle on the pressure surface of said blade beginning at the leading edge of said blade inwardly from said second area and extending diagonally inwardly across said blade to said first area, said angle being more acute adjacent said leading edge than adjacent said trailing edge, each of said blades having a concavity on its suction surface inwardly of said angle and extending diagonally across said blade from a position at said leading edge adjacent said angle to a position at the trailing edge of said blade adjacent the root of said blade, said concavity being most pronounced adjacent said trailing edge.

5. In a propeller, a hub and a plurality of blades having root portions set obliquely to the axis of said hub, each of said blades having a convex edge and a concave edge joining to form a tip extending outwardly of and beyond said concave edge in the direction of curvature of said concave edge, said convex edge extending around said tip and joining said concave edge inwardly from said tip, each of said blades having inward and outward portions forming a dihedral angle, that surface of said inward portion on the side of said blade having the exterior angle of said dihedral angle being faired concavedly into said hub, the angle line of said dihedral angle being a curve extending from a position on said convex edge close to said concave fairing diagonally and outwardly across said blade to a position on said concave edge further from said hub than said first mentioned position.

References Cited in the file of this patent UNITED STATES PATENTS 17,943 Swartz Aug. 4, 1857 1,123,202 Amnelius Dec. 29, 1914 1,146,121 Amnelius July 13, 1915 1,612,028 Kincaid Dec. 28, 1926 1,933,948 Weber Nov. 7, 1933 2,008,957 Hueglin July 23, 1935 2,269,287 Roberts Jan. 6, 1942 FOREIGN PATENTS 10,067 Great Britain of 1888 OTHER REFERENCES Baughmans Aviation Dictionary, 3d edition, 1951, Aero Publishers, Inc., Los Angeles, Calif., page 80.