WO2023009436A1

WO2023009436A1 - Blower fan assembly

Info

Publication number: WO2023009436A1
Application number: PCT/US2022/038182
Authority: WO
Inventors: SaiGeetha PADIRI; Vijay Kambhammettu
Original assignee: Regal Beloit America, Inc.
Priority date: 2021-07-26
Filing date: 2022-07-25
Publication date: 2023-02-02
Also published as: US20230026923A1

Abstract

A blower fan assembly comprising a scroll housing, a forward curved blower wheel, and a blower motor adapted to rotate the blower wheel about a blower wheel axis. The forward-curved blower wheel comprises a plurality of fan blades circumferentially spaced about the blower wheel axis. Each of the fan blades has a leading edge with a leading edge angle and a trailing edge with a trailing edge angle. The leading edge angle is at least 50° and not more than 80°. The trailing edge angle is at least 5.5° and not more than 18.5°. The outer radius is not more than 4 inches (101.6 mm).

Description

BLOWER FAN ASSEMBLY

Cross-Reference to Related Applications [0001] This patent application claims priority to U.S. patent application

17/384,926, filed July 26, 2021, and entitled “Blower Fan Assembly,” the entire disclosure of which is incorporated herein by reference.

Statement Regarding Federally Sponsored Research or Development [0002] Not Applicable.

Appendix

[0003] Not Applicable.

Background of the Invention

Field of the Invention

[0004] This invention pertains to a blower fan assembly.

SUMMARY

[0005] One aspect of the disclosure is a blower fan assembly comprising a scroll housing, a forward curved blower wheel, and a blower motor adapted to rotate the blower wheel about a blower wheel axis. The forward-curved blower wheel comprises a plurality of fan blades circumferentially spaced about the blower wheel axis. Each of the fan blades has a leading edge and a trailing edge. The blower wheel has an inner radius. The inner radius of the blower wheel is the radial distance between the blower wheel axis and the leading edge of each fan blade. The blower wheel has an outer radius. The outer radius of the blower wheel is the radial distance between the blower wheel axis and the trailing edge of each fan blade. The leading edge of each fan blade has a leading edge angle. The leading edge angle is the angle between a first tangent line and a first reference line. The first tangent line is a line tangent to the camber line at the leading edge. The first reference line intersects the leading edge and is perpendicular to a first radial line extending from the blower wheel axis to the leading edge. The first tangent line and the first reference line are in a plane perpendicular to the blower wheel axis. The trailing edge of each fan blade has a trailing edge angle. The trailing edge angle is the angle between a second tangent line and a second reference line. The second tangent line is tangent to the camber line at the trailing edge. The second reference line intersects the trailing edge and is perpendicular to a second radial line extending from the blower wheel axis to the trailing edge. The second tangent line and the second reference line are in a plane perpendicular to the blower wheel axis. The leading edge angle is at least 50° and not more than 80°. The trailing edge angle is at least 5.5° and not more than 18.5°. The outer radius is not more than 4 inches (101.6 mm). The blower wheel is within the scroll housing.

[0006] Another aspect of the disclosure is a blower fan assembly comprising a scroll housing, a forward curved blower wheel, and a blower motor adapted to rotate the blower wheel about a blower wheel axis. The scroll housing has a blower wall and opposite axial sides. The blower wall has a scroll profile as viewed in a plane perpendicular to the blower wheel axis. The blower wall extends axially from one of the axial sides to the other of the axial sides. The scroll profile of the blower wall extends circumferentially from a first scroll end to a second scroll end. The blower wall has a cut-off at the first scroll end. The scroll housing has a cut-off angle. The cut-off angle is an angle between a first radial scroll line extending from the blower wheel axis to the first scroll end and a second radial scroll line extending from the blower wheel axis to the second scroll end. The cut-off angle is 68° ± 10°. The blower wall has an exhaust wall portion extending generally straight from the second radial scroll line and an exhaust angle. The exhaust angle is the angle between the exhaust wall portion and an exhaust line. The exhaust line is perpendicular to the second radial scroll line and intersects the second scroll end. The exhaust angle is 5° ± 3°. The blower wall has an angle at cut-off. The angle at cut-off is the angle between a cut-off reference line and the cut-off. The cut-off reference line is perpendicular to the second radial scroll line and extends from the second radial scroll line through the cut-off. The angle at cut-off is 25° ± 5°. The blower wheel is within the scroll housing.

[0007] Another aspect of the disclosure is a scroll housing. The scroll housing has a blower wall and opposite axial sides. The blower wall has a scroll profile as viewed in a plane perpendicular to the blower wheel axis. The blower wall extends axially from one of the axial sides to the other of the axial sides. The scroll profile of the blower wall extends circumferentially from a first scroll end to a second scroll end. The blower wall has a cut-off at the first scroll end. The scroll housing has a cut-off angle. The cut-off angle is an angle between a first radial scroll line extending from the blower wheel axis to the first scroll end and a second radial scroll line extending from the blower wheel axis to the second scroll end. The cut off angle is 68° ± 10°. The blower wall has an exhaust wall portion extending generally straight from the second radial scroll line and an exhaust angle. The exhaust angle is the angle between the exhaust wall portion and an exhaust line. The exhaust line is perpendicular to the second radial scroll line and intersects the second scroll end. The exhaust angle is 5° ± 3°. The blower wall has an angle at cut-off. The angle at cut-off is the angle between a cut-off reference line and the cut-off. The cut-off reference line is perpendicular to the second radial scroll line and extends from the second radial scroll line through the cut-off. The angle at cut off is 25° ± 5°.

[0008] Another aspect of the disclosure is a forward-curved blower wheel. The forward-curved blower wheel comprises a plurality of fan blades circumferentially spaced about the blower wheel axis. Each of the fan blades has a leading edge and a trailing edge. The blower wheel has an inner radius. The inner radius of the blower wheel is the radial distance between the blower wheel axis and the leading edge of each fan blade. The blower wheel has an outer radius. The outer radius of the blower wheel is the radial distance between the blower wheel axis and the trailing edge of each fan blade. The leading edge of each fan blade has a leading edge angle. The leading edge angle is the angle between a first tangent line and a first reference line. The first tangent line is a line tangent to the camber line at the leading edge. The first reference line intersects the leading edge and is perpendicular to a first radial line extending from the blower wheel axis to the leading edge. The first tangent line and the first reference line are in a plane perpendicular to the blower wheel axis. The trailing edge of each fan blade has a trailing edge angle. The trailing edge angle is the angle between a second tangent line and a second reference line. The second tangent line is tangent to the camber line at the trailing edge. The second reference line intersects the trailing edge and is perpendicular to a second radial line extending from the blower wheel axis to the trailing edge. The second tangent line and the second reference line are in a plane perpendicular to the blower wheel axis. The leading edge angle is at least 50° and not more than 80°. The trailing edge angle is at least 5.5° and not more than 18.5°. The outer radius is not more than 4 inches (101.6 mm). [0009] Further features and advantages, as well as the operation, are described in detail below with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS [0010] FIG. 1 is a perspective view of a blower fan assembly.

[0011] FIG. 2 is a perspective view of the forward curved blower wheel of the blower fan assembly shown in Figure 1.

[0012] FIG. 3 is a side view of the forward curved blower wheel shown in Figure 2.

[0013] FIG. 4 is a magnified side view of one of the blades of the forward curved blower wheel shown in Figure 3.

[0014] FIG. 5 is a perspective view taken along the plane of line 5-5 of Figure 1.

[0015] FIG. 6 is a perspective view similar to Figure 5, but with components removed.

[0016] FIG 7. is a perspective view of a scroll housing of the blower fan assembly shown in Figure 1.

[0017] FIG. 8 is a schematic view of the scroll profile of the scroll housing shown in Figure 7.

[0018] FIG. 9 is a computer generated plot of the scroll profile design compared with prior art fan assemblies of comparable size.

[0019] Reference numerals in the written specification and in the figures indicate corresponding items. DETAILED DESCRIPTION

[0020] An embodiment of a blower fan assembly, generally indicated by the reference number (20), is shown in Figures 1 and 5-6. The blower fan assembly (20) comprises a scroll housing (22), a forward curved blower wheel (24), and a blower motor (26). The blower motor (26) is adapted to rotate the blower wheel (24) about a blower wheel axis (X). The blower wheel (24) is within the scroll housing (22).

[0021] Referring to Figures 2-4, the forward-curved blower wheel (24) comprises a plurality of fan blades (28) circumferentially spaced about the blower wheel axis (X). Each of the fan blades (28) has a leading edge (30) and a trailing edge (32). The plurality of blades (28) may comprise 40 blades.

[0022] The blower wheel has an inner radius (Ri). The inner radius (Ri) of the blower wheel (24) is the radial distance between the blower wheel axis (X) and the leading edge (30) of each fan blade (28). The inner radius (Ri) is at least 2.3 inches, and the inner radius (Ri) is preferably 83.82 mm (approximately 3.3 inches).

[0023] The blower wheel (24) has an outer radius (Ro). The outer radius (Ro) of the blower wheel (24) is the radial distance between the blower wheel axis (X) and the trailing edge (32) of each fan blade (28). The outer radius (Ro) is not more than 4 inches (101.6 mm), and the outer radius (Ro) is preferably 98 mm (approximately 3.86 inches).

[0024] The leading edge (30) of each fan blade (28) has a leading edge angle (OLE). The leading edge angle (OLE) is the angle between a first tangent line (LTI) and a first reference line (Li). The first tangent line (LTI) is a line tangent to a camber line (LCAMBER) at the leading edge (30). As used herein, camber line is the mean line of the blade profile. The first reference line (Li) intersects the leading edge (30) and is perpendicular to a first radial line (LRI) extending from the blower wheel axis (X) to the leading edge (30). The first tangent line (LTI) and the first reference line (Li) are in a plane perpendicular to the blower wheel axis (X). The leading edge angle (OLE) is at least 50° and not more than 80°. For example, in one embodiment the leading edge angle (OLE) may be 60°, while in another embodiment, the leading edge angle (OLE) may be 70°.

[0025] The trailing edge (32) of each fan blade (28) has a trailing edge angle (OTE). The trailing edge angle (OTE) is the angle between a second tangent line (LT2) and a second reference line (L2). The second tangent line (LT2) is tangent to the camber line (LCAMBER) at the trailing edge (32). The second reference line (L2) intersects the trailing edge (32) and is perpendicular to a second radial line (LR2) extending from the blower wheel axis (X) to the trailing edge (32). The second tangent line (LT2) and the second reference line (L2) are in a plane perpendicular to the blower wheel axis (X). The trailing edge angle (OTE) is at least 5.5° and not more than 18.5°. For example, in one embodiment the trailing edge angle (OTE) may be 6.5°, while in another embodiment, the trailing edge angle (OTE) may be 18.25°.

[0026] Each fan blade (28) has a stagger angle (OSA) and a chord line (LCHORD). The stagger angle (OSA) is the angle between the chord line (LCHORD) and a radial line (LR3) extending from the axis of rotation (X) and intersecting the leading edge (30). The stagger angle (OSA) is 30° ± 15°. For instance, the stagger angle (OSA) may be 30° in an embodiment.

[0027] The blower wheel (24) may further comprise a blower wheel inlet (34) and an internal cavity (36). The blower wheel inlet (34) is axially aligned with the fan axis (X). The internal cavity (36) is bounded by the blower wheel inlet (34) and the leading edges (30) of the fan blades (28).

[0028] The blower wheel inlet (34) may comprise a first blower wheel inlet (38), and the blower wheel (24) may further comprise a second blower wheel inlet (40). The internal cavity (36) is further bounded by the second blower wheel inlet (40). [0029] The blower fan assembly (20) may further comprise a center disc (42). The center disc (42) is axially between and axially spaced from the first and second blower wheel inlets (38 and 40, respectively), and is at least partially within the blower wheel. Additionally, the internal cavity (36) may comprise a first internal cavity portion (44), and a second internal cavity portion (46). The first internal cavity portion (44) is between the first blower wheel inlet (38) and the center disc (42), and the second internal cavity portion (46) is between the second blower wheel inlet (40) and the center disc (42).

[0030] Referring to Figures 5-8, the scroll housing (22) has a blower wall (48) and opposite axial sides (50). The blower wall (48) has a scroll profile (52) as viewed in a plane perpendicular to the blower wheel axis (X). The blower wall (48) extends axially from one of the axial sides (50) to the other of the axial sides (50). The scroll profile of the blower wall (48) extends circumferentially from a first scroll end (54) to a second scroll end (56). The blower wall has a cut-off (58) at the first scroll end (54).

[0031] The scroll housing (22) has a cut-off angle (0co). The cut-off angle (0co) is an angle between a first radial scroll line (Lsi) extending from the blower wheel axis (X) to the first scroll end (54) and a second radial scroll line (I_s2) extending from the blower wheel axis (X) to a second scroll end (56). The cut off angle (Geo) is 68° ± 10°, and more preferably 68° ± 5°. [0032] The blower wall (48) has an exhaust wall portion (60) and an exhaust angle (QEC). The exhaust wall portion (60) extends generally straight from the second radial scroll line (I_s2). The exhaust angle is the angle between the exhaust wall portion (60) and an exhaust line (LEX). The exhaust line (LEX) extends from the second scroll end (56) and is perpendicular to the second radial scroll line (Ls2). The exhaust angle is 5° ± 3°, and may be 5° ± 1°.

[0033] The blower wall (48) has an angle at cut-off (OACO). The angle at cut-off (OACO) is the angle between a cut-off reference line (Leo) and the cut-off (58). The cut-off reference line (Leo) is perpendicular to the second radial scroll line (Ls2) and extends from the second radial scroll line (Ls2) through the cut-off (58). The angle at cut-off (OACO) is 25° ± 5°, and may be 25° ± 3°.

[0034] In operation, the blower motor (26) rotates the blower wheel (24) at 1400- 1600 rpm with a flow rate between 500 and 1500 cubic feet per minute (CFM). The above-described characteristics of the scroll housing (22) and the blower wheel (24) enable the blower fan assembly (20) to have a static blower efficiency at least 15% higher than prior art blower fan assemblies of comparable size. Additionally, the present blower fan assembly (20) may be up to 4 dB(A) quieter than prior art blower fan assemblies of comparable size. Figure 9 shows the present invention (New Design) as compared with two prior art blower fan assemblies of comparable size (Standard Designs 1 and 2).

[0035] In view of the foregoing, it should be appreciated that the invention has several advantages over the prior art.

[0036] It should also be understood that when introducing elements of the present invention in the claims or in the above description of exemplary embodiments of the invention, the terms "comprising," "including," and "having" are intended to be open-ended and mean that there may be additional elements other than the listed elements. Additionally, the term "portion" should be construed as meaning some or all of the item or element that it qualifies. Moreover, use of identifiers such as first, second, and third should not be construed in a manner imposing any relative position or time sequence between limitations.

[0037] As various modifications could be made in the constructions and methods herein described and illustrated without departing from the scope of the invention, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative rather than limiting. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims appended hereto and their equivalents.

Claims

What is claimed is:

1. A blower fan assembly comprising: a scroll housing; a forward curved blower wheel; a blower motor adapted to rotate the blower wheel about a blower wheel axis; the forward-curved blower wheel comprising a plurality of fan blades circumferentially spaced about the blower wheel axis, each of the fan blades having a leading edge and a trailing edge, the blower wheel having an inner radius, the inner radius of the blower wheel being the radial distance between the blower wheel axis and the leading edge of each fan blade, the blower wheel having an outer radius, the outer radius of the blower wheel being the radial distance between the blower wheel axis and the trailing edge of each fan blade, the leading edge of each fan blade having a leading edge angle, the leading edge angle being the angle between a first tangent line and a first reference line, the first tangent line being a line tangent to the camber line at the leading edge, the first reference line intersecting the leading edge and being perpendicular to a first radial line extending from the blower wheel axis to the leading edge, the first tangent line and the first reference line being in a plane perpendicular to the blower wheel axis, the trailing edge of each fan blade having a trailing edge angle, the trailing edge angle being the angle between a second tangent line and a second reference line, the second tangent line being tangent to the camber line at the trailing edge, the second reference line intersecting the trailing edge and being perpendicular to a second radial line extending from the blower wheel axis to the trailing edge, the second tangent line and the second reference line being in a plane perpendicular to the blower wheel axis, the leading edge angle being at least 50° and not more than 80° and the trailing edge angle being at least 5.5° and not more than 18.5°, the outer radius being not more than 4 inches (101.6 mm); the blower wheel being within the scroll housing.

2. The blower fan assembly of claim 1 , wherein each fan blade has a stagger angle and a chord line, the stagger angle being the angle between the chord line and a radial line extending from the axis of rotation and intersecting the leading edge, the stagger angle being 30° ± 15°.

3. The blower fan assembly of claim 2 wherein the inner radius is at least 3.3 inches.

4. The blower fan assembly of claim 3 wherein the leading edge angle is 65° ± 5° and the trailing edge angle is 12° ± 3°.

5. The blower fan assembly of claim 4 wherein the plurality of fan blades comprises 40 blades.

6. The blower fan assembly of claim 4 wherein the scroll housing has a blower wall and opposite axial sides, the blower wall having a scroll profile as viewed in a plane perpendicular to the blower wheel axis, the blower wall extending axially from one of the axial sides to the other of the axial sides, the scroll profile of the blower wall extending circumferentially from a first scroll end to a second scroll end, the blower wall having a cut-off at the first scroll end, the scroll housing having a cut off angle, the cut-off angle being an angle between a first radial scroll line extending from the blower wheel axis to the first scroll end and a second radial scroll line extending from the blower wheel axis to the second scroll end, the cut-off angle being 68° ± 10°.

7. The blower fan assembly of claim 6 wherein the blower wall has an exhaust wall portion and an exhaust angle, the exhaust wall portion extending generally straight from the second radial scroll line, the exhaust angle being the angle between the exhaust wall portion and an exhaust line, the exhaust line extending from the second scroll end and being perpendicular to the second radial scroll line, the exhaust angle being 5° ± 3°.

8. The blower fan assembly of claim 7 wherein the blower wall has an angle at cut-off, the angle at cut-off being the angle between a cut-off reference line and the cut-off, the cut-off reference line being perpendicular to the second radial scroll line and extending from the second radial scroll line through the cut-off, the angle at cut-off being 25° ± 5°.

9. The blower fan assembly of claim 8 wherein the blower wheel further comprises a blower wheel inlet and an internal cavity, the blower wheel inlet being axially aligned with the fan axis, the internal cavity being bounded by the blower wheel inlet and the leading edges of the fan blades.

10. The blower fan assembly of claim 9 wherein the blower wheel inlet comprises a first blower wheel inlet and the blower wheel further comprises a second blower wheel inlet, the internal cavity being further bounded by the second blower wheel inlet.

11. The blower fan assembly of claim 10 further comprising a center disc axially between and axially spaced from the first and second blower wheel inlets, and wherein the internal cavity comprises a first internal cavity portion and a second internal cavity portion, the first internal cavity portion being between the first blower wheel inlet and the center disc, the second internal cavity portion being between the second blower wheel inlet and the center disc.

12. A blower fan assembly comprising: a scroll housing; a forward curved blower wheel; a blower motor adapted to rotate the blower wheel about a blower wheel axis; the scroll housing having a blower wall and opposite axial sides, the blower wall having a scroll profile as viewed in a plane perpendicular to the blower wheel axis, the blower wall extending axially from one of the axial sides to the other of the axial sides, the scroll profile of the blower wall extending circumferentially from a first scroll end to a second scroll end, the blower wall having a cut-off at the first scroll end, the scroll housing having a cut-off angle, the cut-off angle being an angle between a first radial scroll line extending from the blower wheel axis to the first scroll end and a second radial scroll line extending from the blower wheel axis to the second scroll end, the cut-off angle being 68° ± 10°; the blower wall having an exhaust wall portion extending generally straight from the second radial scroll line and an exhaust angle, the exhaust angle being the angle between the exhaust wall portion and an exhaust line, the exhaust line being perpendicular to the second radial scroll line and intersecting the second scroll end, the exhaust angle being 5° ± 3°; the blower wall having an angle at cut-off, the angle at cut-off being the angle between a cut-off reference line and the cut-off, the cut-off reference line being perpendicular to the second radial scroll line and extending from the second radial scroll line through the cut-off, the angle at cut-off being 25° ± 5°; the blower wheel being within the scroll housing.

13. The blower fan assembly of claim 12 wherein the scroll housing as a cut-off angle of 68° ± 5°, an exhaust angle of 5° ± 1 °, and an angle at cut-off of 25° ± 3.

14. The blower fan assembly of claim 12, wherein the forward-curved blower wheel comprises a plurality of fan blades circumferentially spaced about the blower wheel axis, each of the fan blades having a leading edge and a trailing edge, the blower wheel having an inner radius, the inner radius of the blower wheel being the radial distance between the blower wheel axis and the leading edge of each fan blade, the blower wheel having an outer radius, the outer radius of the blower wheel being the radial distance between the blower wheel axis and the trailing edge of each fan blade, the leading edge of each fan blade having a leading edge angle, the leading edge angle being the angle between a first tangent line and a first reference line, the first tangent line being a line tangent to the camber line at the leading edge, the first reference line intersecting the leading edge and being perpendicular to a first radial line extending from the blower wheel axis to the leading edge, the first tangent line and the first reference line being in a plane perpendicular to the blower wheel axis, the trailing edge of each fan blade having a trailing edge angle, the trailing edge angle being the angle between a second tangent line and a second reference line, the second tangent line being tangent to the camber line at the trailing edge, the second reference line intersecting the trailing edge and being perpendicular to a second radial line extending from the blower wheel axis to the trailing edge, the second tangent line and the second reference line being in a plane perpendicular to the blower wheel axis, the leading edge angle being at least 50° and not more than 80° and the trailing edge angle being at least 5.5° and not more than 18.5°, the outer radius being not more than 4 inches (101.6 mm).

15. The blower fan assembly of claim 14 wherein the plurality of fan blades comprises 40 blades.

16. The blower fan assembly of claim 14 wherein the blower wheel further comprises a first blower wheel inlet, a second blower wheel inlet, a first internal cavity, a second internal cavity, and a center disc, the first blower wheel inlet being axially aligned with the fan axis, the first internal cavity being bounded by the first blower wheel inlet and the leading edges of the fan blades, the second blower wheel inlet being axially aligned with the fan axis, the second internal cavity being bounded by the second blower wheel inlet and the leading edges of the fan blades, the center disc being axially between and axially spaced from the first and second blower wheel inlets and separating the first internal cavity from the second internal cavity.

17. A scroll housing having a blower wall and opposite axial sides, the blower wall having a scroll profile as viewed in a plane perpendicular to the blower wheel axis, the blower wall extending axially from one of the axial sides to the other of the axial sides, the scroll profile of the blower wall extending circumferentially from a first scroll end to a second scroll end, the blower wall having a cut-off at the first scroll end, the scroll housing having a cut-off angle, the cut-off angle being an angle between a first radial scroll line extending from the blower wheel axis to the first scroll end and a second radial scroll line extending from the blower wheel axis to the second scroll end, the cut-off angle being 68° ± 10°; the blower wall having an exhaust wall portion extending generally straight from the second radial scroll line and an exhaust angle, the exhaust angle being the angle between the exhaust wall portion and an exhaust line, the exhaust line being perpendicular to the second radial scroll line and intersecting the second scroll end, the exhaust angle being 5° ± 3°; the blower wall having an angle at cut-off, the angle at cut-off being the angle between a cut-off reference line and the cut-off, the cut-off reference line being perpendicular to the second radial scroll line and extending from the second radial scroll line through the cut-off, the angle at cut-off being 25° ± 5°.

18. A forward curved blower wheel comprising a plurality of fan blades circumferentially spaced about the blower wheel axis, each of the fan blades having a leading edge and a trailing edge, the blower wheel having an inner radius, the inner radius of the blower wheel being the radial distance between the blower wheel axis and the leading edge of each fan blade, the blower wheel having an outer radius, the outer radius of the blower wheel being the radial distance between the blower wheel axis and the trailing edge of each fan blade, the leading edge of each fan blade having a leading edge angle, the leading edge angle being the angle between a first tangent line and a first reference line, the first tangent line being a line tangent to the camber line at the leading edge, the first reference line intersecting the leading edge and being perpendicular to a first radial line extending from the blower wheel axis to the leading edge, the first tangent line and the first reference line being in a plane perpendicular to the blower wheel axis, the trailing edge of each fan blade having a trailing edge angle, the trailing edge angle being the angle between a second tangent line and a second reference line, the second tangent line being tangent to the camber line at the trailing edge, the second reference line intersecting the trailing edge and being perpendicular to a second radial line extending from the blower wheel axis to the trailing edge, the second tangent line and the second reference line being in a plane perpendicular to the blower wheel axis, the leading edge angle being at least 50° and not more than 80° and the trailing edge angle being at least 5.5° and not more than 18.5°, the outer radius being not more than 4 inches (101.6 mm).

19. The forward curved blower wheel of claim 18 wherein the leading edge angle is 60°, the trailing edge angle is 18.25°, and wherein each fan blade has a stagger angle and a chord line, the stagger angle being the angle between the chord line and a radial line extending from the axis of rotation and intersecting the leading edge, the stagger angle being 30°.

20. The forward curved blower wheel of claim 18 wherein the leading edge angle is 70° and the trailing edge angle is 6.5°, and wherein each fan blade has a stagger angle and a chord line, the stagger angle being the angle between the chord line and a radial line extending from the axis of rotation and intersecting the leading edge, the stagger angle being 30°.