Free-tipped axial fan assembly
A free-tipped axial fan assembly includes fan having a blade tip geometry which provides a desired blade loading in the presence of a tip gap. The maximum camber exhibits a sudden and significant increase as the blade tip radius R is closely approached in the direction of increasing radial position. In some constructions, the maximum camber at the blade tip radius R is at least 10 percent greater than the maximum camber at a radial position r where r/R=0.95. In some constructions, the blade angle increases by more than 0.01 radians from a radial position r where r/R=0.95 to the blade tip radius R. The maximum camber at the blade tip radius R is at least 0.06 times the chord length in some constructions.
1. A free-tipped axial fan assembly comprising:
a fan comprising a plurality of generally radially extending blades, each of the plurality of blades having a leading edge, a trailing edge, and a blade tip; and
a shroud comprising a shroud barrel surrounding at least a portion of the blade tips with a tip gap being defined between the shroud barrel and the blade tips;
wherein the fan has a blade tip radius R and a diameter D equal to twice the blade tip radius R;
wherein each of the plurality of blades has a sectional geometry which at every radial position has a mean line, the mean line having a chord length, a blade angle, and a camber distribution, the camber distribution having a maximum camber;
characterized in that the maximum camber at the blade tip radius R is at least 10 percent larger than the maximum camber at a radial position r where r/R=0.95, and that from a radial position r where r/R=0.95 to the blade tip radius R, the blade angle increases by at least 0.01 radians.
2. The free-tipped axial fan assembly of claim 1 further characterized in that the maximum camber at the blade tip radius R is at least 20 percent larger than the maximum camber at a radial position r where r/R=0.95.
3. The free-tipped axial fan assembly of claim 1 further characterized in that the maximum camber at the blade tip radius R is at least 30 percent larger than the maximum camber at a radial position r where r/R=0.95.
4. The free-tipped axial fan assembly of claim 1 further characterized in that the maximum camber divided by the chord length at the blade tip radius R is at least 0.06.
5. The free-tipped axial fan assembly of claim 1 further characterized in that from a radial position r where r/R=0.95 to the blade tip radius R, the blade angle increases by at least 0.02 radians.
6. The free-tipped axial fan assembly of claim 5 further characterized in that from a radial position r where r/R=0.95 to the blade tip radius R, the blade angle increases by at least 0.04 radians.
7. The free-tipped axial fan assembly of claim 1 further characterized in that the shroud barrel is flared, and the blade tip leading edge is at a larger radius than the blade tip trailing edge.
8. The free-tipped axial fan assembly of claim 1 further characterized in that the tip gap is greater than about 0.007 times the fan diameter D and less than about 0.02 times the fan diameter D.
9. A free-tipped axial fan assembly comprising:
a fan comprising a plurality of generally radially extending blades, each of the plurality of blades having a leading edge, a trailing edge, and a blade tip; and
a shroud comprising a shroud barrel surrounding at least a portion of the blade tips with a tip gap being defined between the shroud barrel and the blade tips;
wherein the fan has a blade tip radius R and a diameter D equal to twice the blade tip radius R;
wherein each of the plurality of blades has a sectional geometry which at every radial position has a mean line, the mean line having a chord length, a blade angle, and a camber distribution, the camber distribution having a maximum camber;
characterized in that the maximum camber at the blade tip radius R is at least 10 percent larger than the maximum camber at a radial position r where r/R=0.95, and that the maximum camber at the blade tip radius R is greater than or equal to the maximum camber at all other radial positions along the blade.
10. The free-tipped axial fan assembly of claim 9 further characterized in that the maximum camber at the blade tip radius R is at least 20 percent larger than the maximum camber at a radial position r where r/R=0.95.
11. The free-tipped axial fan assembly of claim 9 further characterized in that the maximum camber at the blade tip radius R is at least 30 percent larger than the maximum camber at a radial position r where r/R=0.95.
12. The free-tipped axial fan assembly of claim 9 further characterized in that the maximum camber divided by the chord length at the blade tip radius R is at least 0.06.
13. The free-tipped axial fan assembly of claim 9 further characterized in that from a radial position r where r/R=0.95 to the blade tip radius R, the blade angle increases by at least 0.01 radians.
14. The free-tipped axial fan assembly of claim 9 further characterized in that from a radial position r where r/R=0.95 to the blade tip radius R, the blade angle increases by at least 0.02 radians.
15. The free-tipped axial fan assembly of claim 9 further characterized in that from a radial position r where r/R=0.95 to the blade tip radius R, the blade angle increases by at least 0.04 radians.
16. The free-tipped axial fan assembly of claim 9 further characterized in that the shroud barrel is flared, and the blade tip leading edge is at a larger radius than the blade tip trailing edge.
17. The free-tipped axial fan assembly of claim 9 further characterized in that the tip gap is greater than about 0.007 times the fan diameter D and less than about 0.02 times the fan diameter D.