WO1997048599A1

WO1997048599A1 - Symmetrical foil for moving fluids

Info

Publication number: WO1997048599A1
Application number: PCT/US1997/010251
Authority: WO
Inventors: David J. P. Horrigan
Original assignee: Horrigan David J P
Priority date: 1996-06-17
Filing date: 1997-06-12
Publication date: 1997-12-24
Also published as: AU3390997A

Abstract

A method and apparatus for continuously moving fluids, said method comprising the steps of inserting a symmetrical foil (5) in said fluid such that the leading edge of the foil (5) is perpendicular to the direction of selected movement; and imparting a linear motion to the foil perpendicular to direction of selected movement.

Description

SYMMETRICAL FOIL FOR MOVING FLUIDS

FIELD OF THE INVENTION

The present invention generally relates to the movement of fluids under the influence of an impeller, and more specifically, movement of a fluid under the influence of a foil, and more specifically, movement of the fluid under the influence of a foil when such foil is subjected to linear oscillatory motion.

BACKGROUND OF THE INVENTION

A foil is any body whose shape causes it to receive a useful reaction from a fluid stream moving relative to it, or alternatively, to impart useful movement to fluid when the foil is moved relative to the fluid. The term is usually associated with a foil of the shape shown in Fig. 1. Fig. 1 is a three-dimensional view of a foil showing a profile or chord wise 6 section of the foil. The longitudinal axis a intersects the center of gravity of the foil. A person of ordinary skill in the naval arts will understand the term "longitudinal axis" to be an axis which has its origin at the center of gravity of the body or the centroid of the midships section of the foil, or wing. The leading edge d and the trailing edge e of the foil are oriented perpendicular to the selected movement of fluid. The dimension perpendicular to the chord is called the span c when the foil is a wing. Fig. 2 depicts the side view of a symmetrical, nonflexural foil in normal position, Figs. 2(a) and 2(b), and symmetrical flexural foils under flexure, Figs 2(c), 2(d) and 2(e). The horizontal arrow depicts the direction of flow of a fluid around the leading edge of the foil, and the arrow pointing down depicts the direction of movement of the foil relative to the fluid. The angle of attack a of Fig. 2 can be expressed as the attitude between the geometric cord of the airfoil and the direction of flow of the fluid stream. The present invention performs essentially the same whether the foil is in air or immersed in water. A linear movement of such a foil in a fluid causes a perpendicular flow of the fluid similar to the flow of air over an airfoil. If the airfoil is symmetrical, then reciprocating movement of the airfoil creates constant fluid flow. The caudal fins of fish and marine animals have the cross section of foils. It is known that the caudal fin of some high speed fish and marine mammals frequently outperform rotary propellers, utilizing very little horsepower in achieving remarkable speeds. The energy efficiency brings with it other benefits such as silent operation and reduced drag. The simplicity and reliability of the rotary propeller as well as the ability to handle large amounts of horsepower has made it the preferred propeller in use today even though slip, noise and cavitation are becoming a larger significant concern. As needs for efficient quiet propulsors or impellers evolve there will be an increasing demand for alternate means of propulsion, such as the foil.

The prior art is replete with devices attempting to use the movement of a fluid over a wing or a foil to create energy. In many cases such art endeavors to use the known physical properties of lift in order to provide the energy. U.S. Patent No. 4,595,336 to Grose discloses the use of a canard wing as a means of harnessing wind power to impart mechanical motion to a lever arm. The Grose device utilizes control surfaces to create lift in the wings. The device is limited in that it requires at least two wing surfaces to function. It is pertinent to note that if linear reciprocation motion was imparted on the canard wing it would be incapable of moving air.

U.S. Patent No. 3,204,699 to Gongwer, discloses a swimming propeller/vane, in the shape of foils, which enables the swimmer to more easily propel himself through the water. The device requires two vanes, one on each side of the swimmer, is attached to the legs of the swimmer by means of a frame, and propulsion of the swimmer is effected through pivotal oscillation of the vanes. In application, this Gongwer device has limited efficiency because the frame moves relative to the body of the swimmer, decreasing the amount of effective thrust. The Gongwer device does not positively control the angle of attack of the two vanes, In addition, Gongwer teaches that the pivot point of the foil should be forward of the longitudinal axis of the foil. The intent of the device is to enhance the capabilities of the swimmer, however, it also imparts a porpoising effect on the movement of the swimmer, thereby reducing efficiency.

U. S. Patent No. 3,111,110 to Van Der Putten discloses the use of a pair of foils, disposed on both sides of a boat, to propel the boat through the water. Each foil is operated independently by a lever arm, with movement of the foil through water in a semi-circular direction. The device is limited in that the thrust imparted by the lever is determinate of the angle of attack of the foils. The angle of attack cannot be precisely set for maximum effect.

The prior art has endeavored to replicate the actions of a caudal fin, however the prior art has failed in this regard because of a misperception of the fluid dynamics relating to the reaction of the fluid in relation to the action of the fin, and the propulsion effect created by the vortices generated as the fin moves through water. The present invention overcomes the disadvantages of the prior art by efficiently increasing the energy developed in linearly oscillating a foil in a perpendicular direction relative to the selected direction of movement of a fluid. Such linear perpendicular oscillatory movement increases the efficiency of the foil in the fluid while consuming less energy and producing less noise and cavitation.

SUMMARY OF THE INVENTION

The foil of the invention, a symmetrical foil designed for low drag and maximum angle of deterioration (7-7.5°), moves in a linear fashion at right angles to the flow to be induced^{^}and works on the "path of least resistance" principal in that as it is forced through the fluid in a peφendicular direction, the fluid will "squirt" in the easiest flow direction, that being along the planar surface of the foil in the direction of leading edge to trailing edge. When the foil is not fixed relative to the fluid, such peφendicular movement will propel the foil in a direction peφendicular to the direction of force.

The four components to accomplish efficiency are described as: 1) a symmetrical foil moved in an essentially linear motion at approximately right angles to the desired direction of fluid movement; 2) a flexural quality to direct thrust at slower speeds and to continue thrusting while the foil is reversing direction in its cycle, and to follow fair, to reduce drag at higher speeds; 3) an adjustable angle of attack relative to relative speed of fluid passing, and thrust from the drive mechanism (this adjustment should be self- centering); and 4) a compacted stroke relative to speed. At slow fluid speed the angle of attack needs to be coarse so the stroke also needs to be long and slow. As the flow accelerates the angle of attack becomes shallower and stroke reduces drag and facilitates higher stroke speed. With the above attributes in use, a high aspect ratio, slow speed, high efficiency propeller/impeller will result.

A flexible linear foil propeller/impeller, for more efficient fluid movement or propulsion, relies on a closer duplication of the mechanics of a caudal fin as used by high speed fish and marine mammals. This is accomplished using four variables to essentially maintain a foil at optimum direction to a flow to induce thrust or energy transfer relative to the speed of the flow of surrounding fluid, and to store and deliver energy at the stroke extremes to extend the percent of the cycle during which thrust is delivered, and to increase the speed and decrease the length of the stroke and pitch as speed increases and coarse angle of pitch is no longer necessary. This can be tuned to eliminate poφoising and improved energy transfer. In thin fluids in a controlled environment a simple one- speed flexible foil with no adjustment for angle of pitch or compacted stroke, could be designed to be less efficient and more slowly move the fluid up to the harmonic speed of the foil. A flexural foil allows a directed thrust when the medium in which the foil is positioned is static, or slow moving, and the flexural quality also allows a continued thrust at the extremes of the linear cycle evening out the thrust on the duty cycle. The directed thrust also reduces "poφoising" or cycle induced vibration.

A controlled angle of attack of the foil, which provides the same benefits as above but more precisely and firmly and based on the idea that a coarse angle for slow speeds of the fluid and a shallow angle (or no angle) for high speeds of the fluid, this provides the optimum transfer of energy with the least disturbance to the fluid. Fig. 2 will be discussed in terms of moving the hull of a boat through water, although the same principles apply for moving air over an airfoil for fan applications. Fig. 2(a) depicts the application of a controlled angle of attack α of the foil wherein the angle of attack α is not greater than 42.5° for slow speeds, to 6 knots. Fig. 2(b) depicts a foil with angle of deterioration a not greater than 7° for achieving and maintaining high speeds of 20 knots and above. Fig. 2(c) depicts a flexural foil with a maximum deflection of 30° which enables maximum acceleration of a static fluid. The arrow of Fig. 2(d) depicts the resulting combination of the flexural foil moved slowly in a linear direction inducing smooth and efficient flow of the fluid. As the fluid flow is increased, the angle of attack a of the flexural foil is decreased, Fig. 2(e).

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a three dimensional view of an airfoil.

Fig. 2 is a side view of an airfoil demonstrating angle of attack.

Fig. 3 is a side view of a flexural airfoil during oscillation.

Fig. 4 is a side elevation of a foil apparatus for linear oscillation.

Fig. 5 is a side view of an apparatus for oscillating a foil and for varying angle of attack.

Fig. 6 is a side view of an alternate oscillating apparatus with a flexural foil.

Fig. 6(c) is a plan view of the apparatus of Fig. 6.

Fig. 7 is a side view of a hand powered canal pump utilizing a foil.

Fig. 8 is a side view of a rotary pump utilizing a foil. Fig. 9 is a plan view of the rotary pump of Fig. 8.

DETAILED DESCRIPTION

Referring now to the drawings wherein like numerals designate like parts throughout the various views, in a first embodiment, Fig. 4, a symmetrical foil of Fig. 1 was mounted on a shaft-which was attached to a means of imparting reciprocating linear motion in a peφendicular direction. Various means for imparting linear motion are well known in the art. In the first embodiment, a standard electric motor 1 was used to drive the foil 5. The motor 1 was connected to crankshaft 3 on which was mounted connecting rod 4. Crankshaft 3 imparted generated linear motion fn the range of .2 to 10 hertz on rod 4, thereby imparting linear reciprocation motion on foil 5. On the upward cycle, pressure was created on the upper surface of foil 5, with an accompanying reduction of pressure on the lower surface of the foil, resulting in a positive airflow toward the trailing edge of foil 5. In the downward cycle, pressure was created on the lower surface of foil 5, with an accompanying reduction of pressure on the upper surface of foil 5, again resulting in a positive airflow toward the trailing edge of foil 5. The continuous linear oscillations of the foil resulted in a continuous and positive airflow over the foil, well adapted for use in applications such as fans. The equivalent effects were found to be the same when foil 5 was immersed in water, in creating a flow of water in the direction of the trailing edge of the foil. Rotary to linear force conversion is a known and predictable science that includes cams, crankshafts, rack and pinion gears, winches, scissor links, spooling gears, hydraulic and gas rams and others. Alternatively, a solenoid motor for driving a speaker, or a device where in the rotary motor spins an unbalanced weight while suspended in springs vibrating the foil in the desired direction at the desired speed could be utilized.

In a second embodiment, Fig. 5, the apparatus of the first embodiment was utilized, with crankshaft 3 having pin 8 travelling in a transverse direction in slot 9 (Fig. 5(b)) of connecting rod 4, thereby imparting an oscillatory motion to connecting rod 4, and hence to foil 5. In addition, motor 1 also imparts rotary motion to crankshaft 6, constructed similarly to crankshaft 3, having pin 8 which travels in a transverse direction in slot 9 (Fig. 5(a)) of connecting rod 7. Foil 5 was again constructed to be of symmetrical design, however, as the foil 5 was in the upward cycle, the angle of attack of foil 5 was manually adjusted positively by rod 7 following on cam 6. At the apex of the cycle, the cam 6 and rod 7 caused the angle of attack of foil 5 to be reversed for the downward cycle. At the bottom of the downward cycle, the angle of attack of foil 5 was again manually adjusted positively for the upward cycle. Such adjustment of the angle of attack pi foil 5 resulted in an increased flow of air over the surface of the foil, increasing the efficiency of the device. The maximum angle of attack of the foil for moving fluid was approximately 42 degrees. As the speed of the flow of fluid over the foil increased, the angle of attack was reduced, however, the flow of the fluid continued to increase, demonstrating a continued increase in efficiency. The most obvious method of controlling the angle of attack is to have the foil directly moved into position by a linkage that is timed to the linear drive tilting the foil just before each linear thrust, as employed in this embodiment, however, all of the methods for linear drive listed above could accommodate this technique. More novel methods would be useful in some applications such as a weight positioned on the trailing edge of foil 5 to cause foil 5 to pivot with the trailing edge going farther but slower due to its greater mass and setting up and holding the angle of attack of the foil through its cycle. In a third embodiment, Fig. 6, the foil 5 of the first and second embodiments was constructed to be flexural, i.e., the foil was constructed such that it was pliable, capable of variable, predictable form when under variable loads, returning to its symmetrical form when loads were reduced, and capable of repeating the deformation cycle. Fig. 6(b) depicts foil flex and angle of attack of the foil at high fluid flows. In Fig. 6, components performing similar functions to those components of Fig. 5 are similarly numbered. Motor 1 imparts rotary motion to cams 3 and 6, cogs on steering motor 2 mesh with cogs on steering gear 8, imparting rotational motion to foil 5, enabling directional change in the movement of the fluid. It was found that on the initial, slow power strokes of the flexural foil through a fluid, the foil flexes to a maximum degree, tending to return to its symmetrical position at the end of the cycle, thereby imparting additional thrust. As the flow of fluid increased, the stroke of the arm was reduced, the angle of attack reduced and the flex of the foil decreased, increasing the efficiency of the device while continuing to accelerate the flow of fluid over the foil. The reason for the increased efficiency of the foil of the invention is due to the storing of energy of the foil as it is flexed under the force of thrust, and the release and imparting of the stored energy to the fluid at the time the foil reaches its maximum displacement point in a cycle and at the time the angle of attack of the foil is being adjusted for the next cycle. Materials which can be utilized in flexural foils include rubber, flexible epoxies, urethane, resilient metals, and the like. Most obvious is that the foil is cast in a reinforced rubber or plastic composition but that method has limitations for power handling and durability. Such limitations could be overcome by utilizing two plates that form the skin of the foil but they are not secured at the trailing end or sides, and which are allowed to slide against each other, one supporting the other on its flexed extreme. Such a foil could be fabricated of most any sheet material from paper to steel depending on the application, permitting reinforcement or stiffening of the foil by adding layers on the inside cavity. With the availability of highly pliable plastics foils can be fabricated that would combine the cast composite and the sliding plate types to form a more efficient foil.

In a fourth embodiment, Fig. 7, the foil of the invention was utilized in a hand powered canal pump/boat propeller in order to propel a boat through water. Sleeve 16 included a mounting bracket 16a for attachment to the gunwale of a boat and a flange 17 for attachment to an operating handle 18. Rod 4 extended through sleeve 16 to a point below the surface of the water and connected to foil 5. The distal end of rod 4 pivotally attached to connector 19, which pivotally attached to handle 18, one end of which was used to operate the handle, and the second end of which was pivotally attached to flange 17. Connector 19 attached to handle 18 at a point approximately two-thirds the distance of the handle from the operating end. The boat was propelled through the water by an operator moving the handle in a linear cyclic motion, thereby imparting a linear oscillatory motion to the foil in a vertical direction. It was found that long, slow oscillations initially propelled the boat from a standing position, and as the speed of the boat increased, oscillations of smaller amplitude maintained and further increased the speed. Employment of a flexible foil further increased the rate of acceleration, speed and efficiency of the foil. It is contemplated that any human or mechanical means for generating the linear oscillatory motion of the foil can be employed to power the foil. Additionally, sleeve 16 and rod 4 can be adapted to enable the pivoting of the foil in the horizontal plane, thereby enabling the boat to be steered. Employed in a submersible, varying the attitude of the foil, the angle of attack, permits adjusting the depth of the submersible in the water (see Fig. 6(b). The embodiment in Fig. 6 could be utilized where the apparatus not only propels but steers 360 degrees and controls angle of thrust for hull attitude or pitch or dive properties.

A fifth, embodiment, Fig. 8, describes the use of the invention as a pump for raising a fluid to a higher level. In this embodiment, a conical vat 10 is constructed which has a water inlet conduit 11 and a water outlet conduit 12. A standard electric motor 1 is connected to gear 13 which drives a connecting rod 14 in an oscillatory manner peφendicular to the conical surface of vat 10. Attached to connecting rod 14 and extending interior to vat 10 is foil 15. Foil 15 is similarly constructed to foil 5 of the above embodiments, and is disposed parallel and adjacent to the conical surface of vat 10. As foil 15 is caused to be moved in an oscillatory manner by motor 1, the movement of the fluid, depicted by the directional arrows in Fig. 9, is generated by foil 15 until the velocity of the fluid causes it to raise along the sides of vat 10 to the level of outlet conduit 12, thereby exiting vat 10 at an elevated level. While the present description contains many specificities, these should not be construed as limitations on the scope of the invention, but rather as an exemplification of one/some preferred embodiment/s thereof. Many other variations are possible, for example, a foil could be designed that would be mechanically held in either flex extreme to induce drag for propulsion, or impeller breaking or steering. This could be accomplished by retracting a cable through links along the inside centerline of each foil plate with stops crimped to contact the outermost link first pulling it into an arc and then contacting each link in sequence pulling and bending a greater arc at each link. In a marine application the above foil could induce a drag, effectively braking or slowing the vessel. Accordingly, the scope of the invention should not be determined by the specific embodiment/s illustrated herein, but the full scope of the invention is further illustrated by the claims appended hereto.

Claims

I claim:

1. A method for continuously moving fluids, said method comprising the steps of:

(a) inserting a symmetrical foil in said fluid such that the leading edge of the foil is peφendicular to the direction of selected movement; and

(b) imparting a linear motion to the foil peφendicular to direction of selected movement.

2. The method of claim 1 wherein step (b) includes: (i) oscillating the foil in the direction of linear motion.

3. The method of claim 2 which includes the step: (c) varying the angle of attack of the foil during each cycle of oscillation.

4. The method of claim 2 wherein the foil is flexural.

5. A method for continuously moving fluids, said method comprising the steps of:

(b) imparting an oscillating, linear motion to the foil peφendicular to direction of selected movement; and

(c) varying the angle of attack of the foil during each cycle of oscillation.

6. The method of claim 5 wherein the foil is flexural.

7. Apparatus for continuously moving fluids relative to an object, the apparatus comprising:

(a) means having a drive for imparting linear motion to a symmetrical foil; (b) the symmetrical foil having a longitudinal axis extending the length of the foil; and (c) a connector, having two ends, one end affixed to the drive and the distal end affixed to the foil at the midpoint of the longitudinal axis of the foil.

8. The apparatus of claim 7 wherein the drive imparting linear motion includes means for imparting oscillatory motion to the foil in the axis of linear motion.

9. The apparatus of claim 7 wherein the connector includes means for adjusting the angle of attack of the foil during the oscillatory cycle.

10. The apparatus of claim 7 wherein the foil is flexural.

1 1. Apparatus for continuously moving fluids relative to an object, the apparatus comprising:

(a) means having a drive for imparting linear motion to a symmetrical foil; (b) the symmetrical foil having a longitudinal axis extending the length of the foil; (c) a connector, having two ends, one end affixed to the drive and the distal end affixed to the foil at the midpoint of the longitudinal axis of the foil; and (d) means, attached to the connector for adjusting the angle of attack of the foil during the oscillatory cycle.

12. The apparatus of claim 11 wherein the drive for imparting linear motion includes means for imparting oscillatory motion to the foil in the axis of linear motion.

13. The apparatus of claim 11 wherein one wherein the foil is flexural.

14. Apparatus for continuously moving a fluid relative to an object, the apparatus comprising:

(a) means having a drive for imparting linear motion to a symmetrical, flexural foil;

(b) the drive having means for imparting oscillatory motion to the foil in the linear axis;

(c) the foil having a longitudinal axis extending the length of the foil; (d) a connector, having two ends, one end affixed to the drive and the distal end affixed to the foil at the midpoint of the longitudinal axis of the foil for oscillating the foil in the linear axis; and

(e) means, attached to the connector for adjusting the angle of attack of the foil during the oscillatory cycle.

15. The apparatus of claims 7, 11 or 15 wherein the means for imparting linear motion is a motor.