Claims
- 1. An automotive engine-cooling fan assembly comprising a shroud and a fan, said shroud comprising a barrel which surrounds said fan, and said fan comprising a central hub and a plurality of blades, each of said blades having a root portion and a tip portion, said tip portion having a leading edge and a trailing edge, said shroud being characterized in that:
the barrel comprises a flared inlet and said fan being characterized in that:
a) a portion of each blade tip is shaped to conform to the flared inlet of the shroud barrel b) the radius of the blade tip at the upstream end of the conforming portion is greater than the radius of the blade tip at the downstream end of the conforming portion.
- 2. The fan assembly of claim 1 further characterized in that the clearance gap between the conforming portion of the blade tips and the shroud, measured perpendicular to the shroud, varies by no more than plus or minus approximately 20 percent over the extent of that portion.
- 3. The fan assembly of claim 1 further characterized in that the entire axial extent of the blade tip conforms to the flared inlet.
- 4. The fan assembly of claim 1 further characterized in that the blade tip leading edge lies axially downstream of the entrance to the inlet flare.
- 5. The fan assembly of claim 4 further characterized in that the blade tip leading edge lies axially downstream of the entrance to the inlet flare by a distance less than approximately 0.04 times the fan diameter.
- 6. The fan assembly of claim 1 further characterized in that the axial extent of the portion of the blade tip which is upstream of the portion which conforms to the flared inlet is less than approximately 0.3 times the axial extent of the entire blade tip.
- 7. The fan assembly of claim 1 further characterized in that the barrel comprises an approximately cylindrical portion downstream of the flared inlet.
- 8. The fan assembly of claims 1 or 7 further characterized in that the axial extent of the portion of the blade tip which is downstream of the portion which conforms to the flared inlet is less than approximately 0.5 times the axial extent of the entire blade tip.
- 9. The fan assembly of claim 1 further characterized in that the shroud barrel comprises a stepped portion downstream of the blade tip trailing edge, and the radius of said stepped portion is less than that of the shroud barrel at the axial position of the blade tip trailing edge.
- 10. The fan assembly of claim 1 further characterized in that the difference between the radius of the shroud barrel at the axial position of the blade tip trailing edge and the minimum radius of the shroud barrel is not greater than 0.02 times the fan diameter.
- 11. The fan assembly of claim 1 further characterized in that the fan blades are approximately radial when viewed from upstream.
- 12. The fan assembly of claim 11 further characterized in that the fan blades are raked forward at the tips by less than approximately 3 percent of the fan diameter.
- 13. The fan assembly of claim 1 further characterized in that the fan blades are skewed.
- 14. The fan assembly of claim 13 further characterized in that the fan blades have rearward rake angle in regions where they are back-swept more than approximately 15 degrees and forward rake angle in regions where they are either back-swept less than approximately 5 degrees or forward-swept.
- 15. The fan assembly of claim 13 further characterized in that the fan blade is forward-swept at the root and back-swept at the tip, and has forward rake angle at the root and rearward rake angle at the tip.
- 16. The fan assembly of claim 13 further characterized in that the fan blade is back-swept at the root and forward-swept at the tip, and has rearward rake angle at the root and forward rake angle at the tip.
- 17. The fan assembly of claim 1 further characterized in that the distance between every point on the surface of the flared inlet and a corresponding point on an approximating ellipse is less than approximately 0.5 percent of the fan diameter.
- 18. The fan assembly of claim 17 further characterized in that one semi-axis is axial and one semi-axis is radial.
- 19. The fan assembly of claim 18 further characterized in that the radial semi-axis of the approximating ellipse is between approximately 0.4 and 1.0 times the axial semi-axis of that ellipse.
- 20. The fan assembly of claim 18 further characterized in that the axial semi-axis of the approximating ellipse is between approximately 0.5 and 2 times the axial extent of the blade tip.
- 21. The fan assembly of claim 18 further characterized in that the axial semi-axis of the approximating ellipse is between approximately 0.04 and 0.14 times the fan diameter.
- 22. The fan assembly of claim 18 further characterized in that the radial semi-axis of the approximating ellipse is between approximately 0.02 and 0.11 times the fan diameter.
- 23. The fan assembly of claim 1 further characterized in that the radius of the upstream end of the conforming portion of the blade tip is between approximately 2 percent and 15 percent greater than the radius of the downstream end of the conforming portion of the blade tip.
- 24. The fan assembly of claim 1 further characterized in that the minimum clearance between the blade tip and the shroud, measured perpendicularly to the shroud, is between approximately 0.007 and 0.02 times the fan diameter.
- 25. The fan assembly of claim 1 further characterized in that the minimum axial distance between the blade tip and the shroud is between approximately 0.011 and 0.034 times the fan diameter.
- 26. The fan assembly of claim 17 further characterized in that the radial and axial coordinates of the conforming portion of the blade tips form a curve, and the distance between every point on that curve and a corresponding point on an approximating ellipse is less than approximately 0.5 percent of the fan diameter.
- 27. The fan assembly of claim 26 further characterized in that the ellipse approximating the shape of the flared inlet has a semi-axis which is axial and a semi-axis which is radial and the ellipse approximating the shape of the blade tip has a semi-axis which is axial and a semi-axis which is radial, and the axial semi-axis of the ellipse approximating the shape of the blade tip exceeds the axial semi-axis of the ellipse approximating the shape of the flared inlet by an amount equal to or greater than the amount by which the radial semi-axis of the ellipse approximating the shape of the blade tip exceeds the radial semi-axis of the ellipse approximating the shape of the flared inlet.
- 28. The fan assembly of claim 1 further characterized in that the blade tip chord length is between approximately 0.2 and 0.4 times the fan diameter.
- 29. The fan assembly of claim 1 further characterized in that the shroud is mounted behind an upstream heat exchanger.
- 30. The fan assembly of claim 29 further characterized in that the shroud comprises a plenum upstream of the barrel, said plenum being mounted behind an upstream heat exchanger, where the area of heat exchanger face covered by the plenum is at least approximately 1.5 times the fan disk area.
- 31. The fan assembly of claim 1 further characterized in that the shroud is mounted in front of a downstream heat exchanger.
- 32. The fan assembly of claim 1 further characterized in that the fan and the shroud are made of injection-molded plastic.
- 33. The fan assembly of claim 32 further characterized in that the shroud is molded as a single part.
- 34. The fan assembly of claim 1 further characterized in that the axial distance between the blade tip trailing edge and the downstream edge of the shroud barrel is less than approximately 0.5 times the axial extent of the blade tip.
- 35. The fan assembly of claim 34 further characterized in that the axial distance between the blade tip trailing edge and the downstream edge of the shroud barrel is less than approximately 0.3 times the axial extent of the blade tip.
RELATED APPLICATIONS
[0001] This application claims priority to U.S. provisional application No. 60/211,988, filed on Jun. 16, 2000, the contents of which are incorporated herein by reference.
Provisional Applications (1)
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Number |
Date |
Country |
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60211988 |
Jun 2000 |
US |