Fluid energy converting method and apparatus

• US 4,347,036 A
• Filed: 11/16/1979
• Issued: 08/31/1982
• Est. Priority Date: 03/09/1978
• Status: Expired due to Term

• Current Assignee: Lee Arnold
• Original Assignee: Lee Arnold
• Inventors: Arnold, Lee
• Primary Examiner(s): Powell, Jr., Everette A.
• Application Number:
  US06/094,790
• Time in Patent Office: 1,019 Days
• Field of Search: 416/64-68, 416/79-83, 416/1
• US Class Current: 416/1
• CPC Class Codes: F03D 5/06 the wind-engaging parts swinging to-and-fro and not rotating
• CPC Class Codes: F05B 2210/16 Air or water being indistinctly used as working fluid, i.e. the machine can work equally with air or water without any modification
• CPC Class Codes: F05B 2240/124 Cascades, i.e. assemblies of similar profiles acting in parallel
• CPC Class Codes: Y02E 10/70 Wind energy

Abstract

There is disclosed a method and apparatus for converting the kinetic energy of a moving fluid stream into useful work by means of a cascade of thin airfoils positioned therein. In one embodiment, the airfoils are provided with at least two degrees of freedom and adjacent airfoils are movable out of phase. The airfoils are subjected to the aerodynamically induced oscillations caused by the aeroelastic phenomenon known as flutter and the oscillatory movement is then harnessed to do useful work. In an alternate embodiment, a cascade of airfoils is mechanically oscillated within a moving fluid stream to increase the propulsion of the fluid. Where the fluid is a liquid, the cascade includes a plurality of hydrofoils.

Claims

1. A method for converting the kinetic energy of a fluid stream into useful work comprising the steps of positioning a device including a cascade of thin airfoils in a moving fluid stream to define an aerodynamic system wherein the airfoils are at zero angle of attack when undisturbed and are provided with at least two degrees of freedom and wherein adjacent airfoils are movable out of phase, adjusting the system until the velocity of the fluid stream is a critical velocity for the system sufficient to induce flutter oscillations, disturbing at least one of the airfoils, and then utilizing the resultant oscillations to produce useful work.

2. A method according to claim 1, wherein the device includes means for adjusting the parameters associated with the device, and wherein said adjusting step includes operating said adjusting means.

3. A method according to claim 2, further including the step of controlling the operation of said adjusting means in response to variations in fluid velocity to maintain the system at critical velocity.

4. A method according to claim 1, further including the step of applying mechanical oscillations to the airfoils to maintain and enhance the flutter oscillations.

5. A method according to claim 1, wherein the oscillations of the airfoils are used to produce alternating current.

6. A method according to claim 1, wherein the oscillations of the airfoils are utilized to operate a pump.

7. A method according to claim 6, wherein the pump includes a second cascade of airfoils in another fluid stream and wherein the oscillations of the airfoils of the first cascade are utilized to oscillate the airfoils of the second cascade.

8. Apparatus for converting the kinetic energy of a fluid stream into useful work comprising a support structure open at opposite ends to permit fluid flow therethrough, a plurality of thin airfoils, means for mounting said airfoils within said support structure in a cascade at zero angle of attack when undisturbed and so that each airfoil has at least two degrees of freedom while adjacent airfoils are movable out of phase, and means operatively associated with said airfoils for utilizing the oscillations thereof to produce useful work.

9. Apparatus according to claim 8, wherein said airfoils have zero camber.

10. Apparatus according to claim 8, wherein said airfoils have a high aspect ratio and are rectangular in plan form.

11. Apparatus according to claim 8, further including means to disturb at least one of said airfoils.

12. Apparatus according to claim 8, further including a vane on said support structure and wherein said support structure is pivotally mounted upon a support within a fluid stream.

13. Apparatus according to claim 8, wherein adjacent airfoils are each free to oscillate in both pitch and plunge.

14. Apparatus according to claim 8, wherein each airfoil includes a pivotally mounted flap adjacent to its trailing edge.

15. Apparatus according to claim 14, wherein adjacent airfoils are each free to oscillate in plunge.

16. Apparatus according to claim 14, wherein adjacent airfoils are free to oscillate in pitch.

17. Apparatus according to claim 8, wherein said utilizing means produces alternating current.

18. Apparatus according to claim 8, wherein said utilizing means operates a pump.

19. Apparatus according to claim 18, wherein said pump includes a second cascade of airfoils positioned in a moving fluid stream and wherein said utilizing means oscillates said second cascade in plunge with adjacent airfoils oscillating substantially 180°

out of phase.

20. Apparatus according to claim 19, wherein said utilizing means also oscillates said second cascade in pitch.

21. Apparatus according to claim 8, wherein said airfoils are interconnected by said mounting means to form two subsystems with the airfoils of each subsystem being movable in phase and with adjacent airfoils in different subsystems.

22. Apparatus according to claim 21, wherein said subsystems are relatively movable in both pitch and plunge.

23. Apparatus according to claim 21, wherein said subsystems are relatively movable in pitch and wherein each airfoil is provided with a flap pivotally mounted adjacent to its trailing edge.

24. Apparatus according to claim 21, further including a mechanical oscillating means for each subsystem to disturb said airfoils and to maintain and enhance the oscillations of said airfoils when the apparatus is subjected to fluid flow at a critical velocity capable of inducing flutter oscillations.

25. Apparatus according to claim 21, wherein the subsystems are mechanically interconnected to move 180°

out of phase with each other.

26. Apparatus according to claim 25, further including mechanical oscillating means to disturb said airfoils and to maintain and enhance the oscillations of said airfoils when the apparatus is subjected to fluid flow at a critical velocity capable of inducing flutter oscillations.

27. Apparatus according to claim 8, further including means for adjusting the conditions under which said airfoils will begin to oscillate.

28. Apparatus according to claim 27, wherein said adjusting means includes at least one movable mass mounted on said mounting means.

29. Apparatus according to claim 27, further including a control means for maintaining the oscillatory movement when the velocity of the fluid stream varies, said control means including a detector and feedback means for controlling said adjusting means in response to a detection signal.

30. Apparatus according to claim 29, wherein said detector includes means for detecting the amplitude of the airfoil oscillations.

31. Apparatus according to claim 29, wherein said detector includes an anemometer.

32. Apparatus for converting the kinetic energy of a fluid stream into useful work comprising a support structure open at opposite ends to permit fluid flow therethrough, a plurality of thin airfoils of high aspect ratio and which are rectangular in plan form, means for mounting said airfoils within said support structure so that they are equally spaced in a cascade arrangement at zero angle of attack when undisturbed and so that each airfoil has at least two degrees of freedom and adjacent airfoils are movable out of phase, said airfoils being arranged in two subsystems with the airfoils of each subsystem being movable in phase, oscillating means for disturbing at least one of said subsystems and for maintaining and enhancing the oscillations of said airfoils when the fluid flowing through said device is at a critical velocity sufficient to induce harmonic oscillations due to flutter, control means responsive to variations in flow velocity to vary the parameters of said apparatus so that the prevailing velocity is a critical velocity sufficient to induce flutter oscillations, and means for utilizing the flutter oscillations to produce useful work.

33. A method for increasing the propulsion of a moving fluid stream comprising the steps of positioning a cascade of airfoils in a bounded fluid stream and applying a mechanical force thereto to oscillate said airfoils in a direction having a component substantially perpendicular to the direction of fluid flow with adjacent airfoils oscillating substantially 180°

out of phase.

34. A method according to claim 33, wherein said airfoil is oscillated in plunge.

35. A method according to claim 34, wherein said airfoil is also oscillated in pitch.

36. A method for increasing the propulsion of a moving fluid stream comprising the steps of positioning a cascade of airfoils within a moving fluid stream and applying a mechanical force to oscillate said airfoils in a direction having a component substantially perpendicular to the direction of fluid flow with adjacent airfoils oscillating substantially 180°

out of phase.

37. A method according to claim 36, wherein said airfoils are oscillated in plunge.

38. A method according to claim 37, wherein said airfoils are also oscillated in pitch.

39. Apparatus for increasing the propulsion of a moving fluid stream comprising a cascade of airfoils and mechanical driving means for oscillating said plurality of airfoils so that adjacent airfoils are oscillated substantially 180°

out of phase.