US3514215A - Hydropropeller - Google Patents

Description

May 6, 1970 P. E. WILLIAMS 3,514,215

HYDROPROPELLER Filed Feb. 20, 1969 3 Sheets-Sheet 1 FIG. I.

INVENTOR P E. Williams ATTORNEY May 26, 1970 Filed Feb. 20, 1969 P. E. WILLIAMS 3,514,215

HYDROPROPELLER 3 Sheets-Sheet 5 United States Patent 3,514,215 HYDROPROPELLER Paul E. Williams, Purcellville, Va. Continuation-impart of application Ser. No. 658,532, Aug. 4, 1967. This application Feb. 20, 1969, Ser. No. 800,937

Int. Cl. B63h 1/00; B64c 11/18 US. Cl. 416-200 Claims ABSTRACT OF THE DISCLOSURE A hydropropeller characterized by a blade shape involving a particular shape relationship of adjacent blade portions, including a negative angular incidence at the blade tip which creates a recirculation of individual water particles in a cascade effect enhancing propeller efiiciency.

RELATED APPLICATIONS This application constitutes a continuation-impart of my copending application, Ser. No. 658,532 entitled Hydropropeller, filled Aug. 4, 1967, now abandoned.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to a hydropropeller or marine propeller and has as its primary object the provision of an improved and more efiicient propeller developing greater thrust in proportion to its size and speed of rotation than in hitherto known types.

Description of the prior art Marine propellers have hitherto, according to the circulation pattern of the Momentum Theory of Rankine and Froude, acted upon or handled each individual particle of water a single time. A particle, at rest in advance of a conventional rotating propeller, is impacted by a blade and moved rearwardly at an accelerated velocity. The energy imparted to the particle results in direction of thrust in reaction to the particle acceleration. The volume of water handled is a function of density, the diameter of the propeller in terms of area and acceleration, so that propeller efiiciency is a function of the ratio of the input to the output plus loss.

Loss becomes a major factor as the tip speed of the blades approaches a critical velocity in water, because cavitation is produced, thus detracting from the available power in terms of thrust and acceleration.

SUMMARY OF THE INVENTION The instant invention, as a result of the particular blade shape, modifies the circulation pattern of the movement of the individual water particles by changing the direction of flow over the outer area to recirculate such particles toward the center to add to the flow of particles over the inntr area so that in a steady state the input is multiplied through a multiplicity of stages of particle travel, in what may be termed a cascade effect. As directional changes are imparted to certain particles by the blade shape, there is a change in energy across the blade radius. Similarly, for the change of direction of an individual particle through the cascade steps, the principle of constrvation of energy applies, so that there is no material loss of energy.

As a particle having a direction so changed moves in the thrust direction, the volume multiplied by (n) cascade stages results in a materially increased velocity in order that the volume may equal the input.

Thus, in contrast to conventional propellers, the tip speed of the propeller of the instant invention is below cavitation speed, the blade moves a materially greater volume of fluid, and the ratio of forward advance to diameter and speed of revolution is extremely high.

The blade shape for achieving these results may be described as a plurality of shape relationships cross sectionally of the blade forming a substantially continuous warp in the relative angle of incidence between the leading edge and the trailing edge, culminating in a negative angle of incidence of the trailing edge at the tip. The trailing edge of the blade as viewed from the rear is thus a parabolic curve extending from a positive angle of incidence at its root corresponding to that of the leading edge, to a negative angle of incidence at its tip.

It is thus a primary object of this invention to provide a hydropropeller blade having a shape which will inherently recirculate individual particles of water in a cascade effect producing the result above set forth.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevational view of a hydropropeller constructed in accordance with the instant inventive concept.

FIG. 2 is a side elevational view thereof.

FIG. 3 is a schematic view of one blade disclosing the cross sectional configuration of the blade at sections AA, BB, CC, D-D and BE.

FIG. 4 is a schematic view showing the motion imparted to individual Water particles by the propeller of the instant invention.

FIG. 5 is a schematic view showing the motion imparted to an individual Water particle by a conventional propeller.

FIG. 6 is a longitudinal sectional view taken substantially along the center line of a slightly modified form of the invention.

FIG. 7 is a composite plan view partially broken away illustrating the diiferent angle of pitch for the forward and rear pairs of blades in the form of the invention shown in FIG. 6.

DESCRIPTION OF A PREFERRED EMBODIMENT A hydropropeller constructed in accordance with the instant invention is generally indicated at 10 in FIGS. 1 and 2, and includes a hub 11 which may be of any desired conventional type, but which is illustrated as a cylindrical member 12 having a central bore 13 for the reception of a shaft (not shown), and a transverse groove 14 extending across each end to facilitate removal and replacement of the propeller on the shaft.

Any desired number of blades 15 extend radially from hub 11; in the illustrative embodiment four are shown all of which are identical, so that only one need be described.

The invention resides specifically in the shape of the individual blades and the effect produced thereby. Each blade consists of a root 16 connected in any desired manner to hub 11, a leading edge 17, a trailing edge 19 and a tip 18. The relationship of these components to each other and the effect produced by this relationship will now be described.

The root 1-6 of each blade is integral with or secured firmly to the hub in any desired manner, with the leading edge 17 inclined with respect to a transverse plane through the hub, at any desired pitch. Leading edge 17 is sharply undercut as at 20 (see FIG. 1), and is of slightly bulbous shape as seen in FIG. 3. The cross section of the blade is similar to an air foil configuration, and the trailing edge 19, at point 19a, approximately 20% of the blade length, has a positive angle of incidence trailing relative to the leading edge as shown. The portion 19b of the trailing edge opposite undercut portion 20 extends rearwardly relative to the hub a substantial distance and is angled forwardly at 19c, approximately 30% of the blade length, so that the chord of the inboard section is greater than that of the outboard section. The cross sectional shape of the blade and the relationship of the trailing and leading edges at this point is similar to that at the root, although slightly elongated as shown in FIG. 3.

At a point between 40% and 45% of the blade length, the leading edge is warped rearwardly at an angle of about 10 relative to a transverse plane through the hub, while the trailing edge is warped to a greater degree until its angle of incidence becomes negative. Points 17a and 19d, located at substantially 43% of the blade length as shown in FIG. 3 at CC indicate the degree of warp.

Fro mpoint 17a the cross section and pitch of leading edge 17 remains substantially constant, while the warp of trailing edge 19 increases constantly as shown in FIG. 3 at DD and E-E, through points 19a and 19 taken respectively at about 70% and 80% of blade length, until a relatively large negative angle of incidence is achieved at tip 18. The trailing edge is rounded at 18a adjacent tip 18 at about 90% of the blade length. The portion of the blade between the cross section defined by points 17a and 19d and the hub may be defined as the inboard section of the blade, while the portion between this cross section and the tip may be defined as the outboard section of the blade.

This novel configuration of the blade produces a flow effect which may best be described as a cascade effect, characterized by a continuous recirculation of individual water particles which are deflected from the outboard section of the blade, beyond 43% of blade length, back into the inboard section, thus materially increasing the volume of water displaced, and increasing the effectiveness of the propeller.

It is preferred that opposite pairs of blades be located at spaced points relative to the length of the hub in order to recirculate water particles in slightly offset transverse planes relative to the hub. In the case of an odd number of blades, such as three, each blade is offset relative to the others longitudinally of the hub.

In order to explain more fully the effect produced by this novel blade construction, reference is made to FIG. 4 showing schematically the action of a conventional screw propeller according to the prior art. A particle P at rest (velocity V in advance of propeller 25 with the area of the propeller diameter designated at 26, according to the momentum theory of Rankine and Froude, is handled once and once only when producing thrust. For the purpose of this discussion the propeller will be treated as a disc in order to obviate consideration of blade section elements, power and the like, which are irrelevant to the instant theory.

The particle P is activated by the propeller, and is now given an acceleration V The velocity V drops as the particle P moves down stream. The energy imparted to particle P results in a thrust in reaction to the acceleration of the particle P The volume of water involved is a function of the mass density of the fluid involved, the diameter D of the disc in terms of area A of II/4D and the acceleration V. The efficiency of the standard screw propeller is therefore a function of the input to the output plus loss, or p, V-A /2V A as schematically shown in FIG. 4.

In the case of the instant inventive concept, a modified circulation pattern is imparted which accomplishes a modification of this momentum theory, as shown schematically in FIG. 5, where again a multiplicity of discs 31, 32, 33 n are substituted for the bladed propeller. In the theoretical discussion a particle P at input D is, at P at the point D given a change in direction by disc 31 over the outer area p V A as indicated by arrow 34, and continues at D through area p 'V 'A particle P to P ( arrows 35, 36, 3'7) and P (arrow 38) to %(P V A The particle P is thus added to 4 particle P so that in steady state the input P (P V A is added to that of P /s V A A multiplicity of discs are indicated in FIG. 5 corresponding to propeller position. indicating the transfer of particle P through stages 1 through n in what may be described as a cascade effect.

As particle P receives a change in direction, there is a corresponding change in energy across the blade radius. Similarly, in the direction change of P through (n) cascades, the principle of conservation of energy is applicable so that loss is minimized.

As particle P changes in direction moving toward P or thrust direction, the volume p 'V 'A goes through (n) stages of cascade, so that velocity V is greatly increased in order that the volume It (p 'V 'A may equal the input.

Since output must obviously equal input, the tip speed of the conventional propeller must approach the limit of cavitation in water to achieve maximum efliciency. Propeller efficiency approaches unity as a limit and ranges, with good conventional design, from 75% to 83%.

In contrast, with the blade shape of the propeller of the instant invention and the consequent recirculating cascade effect, the volume of fluid moved is much greater than the volume moved by the conventional propeller, and the tip speed may therefore be well below the cavitation limit. The ratio of thrust or forward advance V, to propeller diameter and speed of revolution is extremely low, and therefore, propeller eflficiency as hitherto determined becomes meaningless.

Performance criteria can best be measured in multiples of thrust in terms of pounds per horsepower, and tests have indicated a performance factor in these terms of 7 to 20 times that of the standard screw propeller.

Under certain conditions, particularly in high speed operation, it has been found that improved performance is provided by varying the relative pitch of the forward and rear blades or paids of blades. Such a modified form of the invention is disclosed in FIGS. 6 and 7.

FIG. 6 discloses a propeller shaft 25 having a tapered end 26 fitting in a tapered collar 27 upon which is mounted hub 28. Hub 28 carries a forward pair of blades 29 and a rear pair of blades 30, the hub being held on shaft 25 by means of lock nut 31 and provided with a tapered conical rear faring 32.

Blades 29 and 30 are identical in configuration to previously described blades 15. However, while the forward pair of blades have a relatively high pitch, illustratively 45, as seen in FIG. 7, the rear pair of blades has a lesser pitch, illustratively 37". It has been found that the acceleration of water particles created by the blade shapes of blades 29, as previously described, may be more effectively handled and reaccelerated by the rear pair of blades 30 if the pitch of the rear set of blades is reduced relative to that of the forward pair of blades 29, particularly at high speeds of rotation, in that the accelerated particles tend to produce less tip cavitation when the pitch of the rear pair of blades is somewhat less than that of the initially impacted forward pair.

From the foregoing it will now be seen that there is herein provided an improved hydropropeller characterized by a blade shape which recirculates individual water particles in a cascade effect, which accomplishes all the objects of this invention and others, including many advantages of great practical utility and commercial importance.

I claim:

1. A hydropropeller consisting of (a) a hub,

(b) a plurality of blades secured to the hub, each blade including (c) a root,

(e) a leading edge,

(f) a trailing edge,

(g) an inboard section, and

(h) an outboard section,

(i) the leading edge being pitched at a desired angle throughout the inboard section and bent to extend at an obtuse angle relative to said inboard section throughout the length of the outboard section,

(j) said trailing edge conforming in pitch to said length at its root and being gradually warped relative to said leading edge through a decreasing positive angle of incidence throughout the inboard section through an increasing negative angle of incidence through the outboard section,

(k) the leading edge being sharply undercut adjacent the hub,

(l) the trailing edge being extended lateral y of the blade length adjacent the undercut portion of the leading edge to provide a greater blade chord throughout at least a portion of the inboard section,

(In) the laterally extended portion of the trailing edge of each blade overlapping a portion of the inboard section of the leading edge of the adjacent blade, the hub being substantially cylindrical and certain blades being ollset longitudinally of the hub relative to certain other blades.

2. A hydropropeller consisting of (a) a hub,

(b) a plurality of blades secured to the hub, each blade including (0) a root,

(e) a leading edge,

(if) a trailing edge,

(g) an inboard section, and

(h) an outboard section,

(i) the leading edge being pitched at a desired angle throughout the inboard section and bent to extend at an obtuse angle relative to said inboard section throughout the length of the outboard section,

( said trailing edge conforming in pitch to said length at its root and being gradually warped relative to said leading edge through a decreasing positive angle of incidence throughout the inboard section through an increasing negative angle of incidence through the outboard section,

(k) the leading edge being sharply undercut adjacent the hub,

(1) the trailing edge being extended laterally of the blade length adjacent the undercut portion of the leading edge to provide a greater blade chord throughout at least a portion of the inboard section,

(In) the laterally extended portion of the trailing edge of each blade overlapping a portion of the inboard section of the leading edge of the adjacent blade, the hub being longitudinally extended and each blade being longitudinally offset relative to the other blades.

3. The structure of claim 1 wherein the pitch of certain of said longitudinally offset blades differs from that of certain other blades.

4. The structure of claim 1 wherein the blades are arranged in pairs and the foremost pair relative to the direction of travel of the propeller has a greater pitch than that of the pair to the rear.

5. The structure of claim 2 wherein the blades to the rear of the foremost blade have a lesser angle of pitch than that of the foremost blade relative to the direction of travel of the propeller.

References Cited UNITED STATES PATENTS EVERETTE A. POWELL, 1a., Primary Examiner US. Cl. X.R,

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