Patent EA-002323-B1 (EA)
Title: Improved fluid displacing blade and rotodynamic machine
Inventor: LEUNG CHI KEUNG
IPC: B63H1/18
Filed: 1998-04-08
Abstract: 1. In a blade in a rotodynamic machine for acting on a fluid, the blade having two surfaces, one on either side thereof, at least one surface of which acts on said fluid; a plurality of apertures extending through said blade between said two surfaces in a direction substantially normal to the radial extent of said rotodynamic machine, said plurality of apertures being located in positions spread substantially evenly throughout said blade. 2. A blade as claimed in claim 1 wherein said apertures have a cross-sectional area of up to 50% of the entire blade area. 3. A blade as claimed in claim 1 wherein said apertures have a cross-sectional area of up to 20% of the entire blade area. 4. A blade as claimed in claim 1 wherein said apertures have a cross-sectional area of up to 10% of the entire blade area. 5. A blade as claimed in claim 1 wherein said apertures have a cross-sectional area of up to 5% of the entire blade area. 6. A blade as claimed in claim 1 wherein said apertures have a cross-sectional area of between 1 % and 3% of the entire blade area. 7. A blade as claimed in claim 1 wherein said apertures have a cross-sectional area of about 2% of the entire blade area. 8. A blade as claimed in any one of the preceding claims wherein said apertures are rectangular or elliptical. 9. A blade as claimed in claim 8 wherein said apertures have a diametric aspect ratio of up to 1:10. 10. A blade as claimed in claim 8 wherein said apertures have a diametric aspect ratio of up to 1:4. 11. A blade as claimed in claim 8 wherein said apertures have a diametric aspect ratio of up to 1:2. 12. A blade as claimed in any one of claims 1 to 7 wherein said apertures are circular or square in cross-section. 13. A blade as claimed in any one of the preceding claims wherein the apertures include a bevelled leading edge on the face thereof. 14. A blade as claimed in any one of the preceding claims wherein said plurality of apertures are aligned with their axial extent extending up to 75 degree  from the direction of travel of the blade through the fluid. 15. A blade as claimed in claim 14 wherein said plurality of apertures are aligned with their axial extent extending up to 60 degree  from the direction of travel of the blade through the fluid. 16. A blade as claimed in claim 14 wherein said plurality of apertures are aligned with their axial extent extending up to 45 degree  from the direction of travel of the blade through the fluid. 17. A blade as claimed in claim 14 wherein said plurality of apertures are aligned with their axial extent extending up to 30 degree  from the direction of travel of the blade through the fluid. 18. A blade as claimed in claim 14 wherein said plurality of apertures are aligned with their axial extent extending up to 20 degree  from the direction of travel of the blade through the fluid. 19. A blade as claimed in claim 14 wherein said plurality of apertures are aligned with their axial extent extending up to 10 degree  from the direction of travel of the blade through the fluid. 20. A blade as claimed in claim 14 wherein said plurality of apertures are aligned with their axial extent extending up to 5 degree  from the direction of travel of the blade through the fluid. 21. A blade as claimed in claim 14 wherein said plurality of apertures are aligned with their axial extent extending substantially in the direction of travel of the blade through the fluid. 22. A rotodynamic machine such as a propeller or impellor or the like having at least one blade as claimed in any one of the preceding claims. 23. A rotodynamic machine as claimed in claim 22 wherein there are a plurality of blades in a dynamically balanced configuration. 24. A rotodynamic machine as claimed in claim 22 or 23 wherein the size of said apertures near the outer edge is larger than the size of said apertures nearer the hub. 25. A rotodynamic machine as claimed in claim 24 wherein the size of said apertures varies progressively or in stepwise manner, decreasing from the outer edge of the rotodynamic machine toward the hub. 26. A rotodynamic machine as claimed in claim 25 wherein the size of the apertures between the outer edge of the blade and toward the hub is determined so that the flow rate of fluid flowing through each aperture is substantially constant across the blade, so that the effect imparted is even across the entire rotodynamic machine. 27. A propeller substantially as herein described with reference to the drawings. 28. In a blade in a rotodynamic machine for acting on a fluid, a plurality of apertures substantially as herein described.