초록 ▼

A mixed flow fan assembly uses induced reverse ambient air flow through the in-line motor enclosure for motor cooling, motor segregation from primary exhaust contamination, and augmentation of volumetric flow rate. Induced ambient airflow through openings in and/or around the base of the fan housing

A mixed flow fan assembly uses induced reverse ambient air flow through the in-line motor enclosure for motor cooling, motor segregation from primary exhaust contamination, and augmentation of volumetric flow rate. Induced ambient airflow through openings in and/or around the base of the fan housing balances low pressure around the fan wheel and the inlet cone to inhibit primary exhaust recirculation and increase volumetric flow rate. Guide vanes downstream of the fan wheel are used to axially reorient radial and tangential velocity components of primary effluent flow. The geometry of the fan assembly is optimized to minimize exhaust gas recirculation and maximize overall efficiency.

대표청구항 ▼

1. A mixed flow fan assembly, comprising: a fan housing, having an axial fan housing centerline, and having a top and a base that is supported on a mounting plenum, and having an upper portion that is internally divided into an axially central motor enclosure surrounded by an annular exhaust plenum,

1. A mixed flow fan assembly, comprising: a fan housing, having an axial fan housing centerline, and having a top and a base that is supported on a mounting plenum, and having an upper portion that is internally divided into an axially central motor enclosure surrounded by an annular exhaust plenum, and having a lower portion that contains a fan wheel and an inlet bell;the fan wheel, comprising a shroud, a wheel cone, and multiple impeller blades attached to both the wheel cone and the shroud, wherein each of the impeller blades has a leading edge and a trailing edge, and wherein the shroud has an inverted bell shape and has a lower end which opens into the inlet bell, and wherein the inlet bell has a substantially frustum shape and has a lower end which opens into the mounting plenum, through which an exhaust gas flow flows upward into the fan housing;a fan motor located in the motor enclosure and rotatably coupled to the fan wheel through a motor-impeller shaft coupler, such that the fan motor imparts rotation to the fan wheel and the impeller blades, and such that the rotation of the impeller blades draws the exhaust gas flow upward through the inlet bell and the shroud and accelerates the exhaust gas flow upward into the annular exhaust plenum, from which an exhaust gas flow is discharged through the top of the fan housing;wherein multiple guide vanes are radially disposed within the annular exhaust plenum at a guide vane offset from the fan wheel, and wherein the guide vanes have a vertical profile which transitions from a lower curved leading edge to an upper substantially axial trailing edge, and wherein the guide vanes divert the exhaust gas flow in the axial direction, and increase the volumetric flow of the exhaust gas flow, thereby increasing the static efficiency of the mixed flow fan assembly; andwherein one or more inlet openings are located between the base of the fan housing and the mounting plenum, and wherein a first ambient air flow is induced through the inlet openings by a venturi effect of the exhaust gas flow expelled from the shroud of the fan wheel, and wherein the aforesaid venturi effect draws the first ambient air flow through the lower portion of the fan housing and into an area of a low pressure generated by the exhaust gas flow expelled from the shroud and surrounding the shroud and the inlet bell, and wherein the first ambient air flow around the shroud and the inlet bell offsets the low pressure generated by the exhaust gas flow expelled from the shroud, thereby reducing an efficiency loss caused by a recirculation of the exhaust gas flow within the fan wheel, and thereby increasing volumetric flow rate through the fan wheel. 2. The mixed flow fan assembly of claim 1, wherein the shroud has an impeller shroud outer diameter edge and the wheel cone has an impeller cone outer diameter edge, and wherein a line drawn between the impeller shroud outer diameter edge and the impeller cone OD outer diameter edge forms a containment angle with respect to a horizontal reference line perpendicular to the fan housing centerline, and wherein the containment angle, when rotated through a full circle around the fan housing centerline, defines a conical or planar containment boundary, and wherein a rotational locus of the trailing edges of the impeller blades about the fan housing centerline defines a conical blade boundary, and wherein an area between the shroud and the wheel cone and between the containment boundary and the blade boundary constitutes a discharge containment region, through which the exhaust gas flow passes before entering the annular exhaust plenum, thereby allowing the guide vane offset to be reduced without interfering with the exhaust gas flow. 3. The mixed flow fan assembly of claim 2, wherein the containment angle is in a range from 0 to 20 degrees. 4. The mixed flow fan assembly of claim 3, wherein the containment angle is 20 degrees. 5. The mixed flow fan assembly of claim 3, wherein a tangential line at the impeller cone outer diameter edge forms an angle in the range of 0 to 20 degrees with respect to a vertical reference line parallel to the fan housing centerline. 6. The mixed flow fan assembly of claim 4, wherein a tangential line at the impeller cone outer diameter edge forms an angle of 20 degrees with respect to a vertical reference line parallel to the fan housing centerline. 7. The mixed flow fan assembly of claim 5, wherein the trailing edge of each impeller blade forms an angle of 90 degrees with the shroud. 8. The mixed flow fan assembly of claim 7, wherein the leading edge of each impeller blade forms an angle of 45 degrees to a horizontal reference line perpendicular to the fan housing centerline. 9. The mixed flow fan assembly of claim 7, wherein the leading edge of each impeller blade forms an angle of 72.25 degrees with the shroud. 10. The mixed flow fan assembly of claim 5, wherein the wheel cone has an impeller cone plate with a radius of curvature in the range of 0.30D to 0.36D, where “D” is an impeller diameter. 11. The mixed flow fan assembly of claim 10, wherein the inlet bell has a radius of curvature of 0.25D, where “D” is the impeller diameter. 12. The mixed flow fan assembly of claim 10, wherein the impeller cone plate has a radius of curvature of 0.30D. 13. The mixed flow fan assembly of any one of claims 1-12, wherein the motor enclosure has a bottom that opens into the lower portion of the fan housing, and wherein a multi-purpose port accesses the motor enclosure from outside the fan housing through the exhaust plenum, and wherein the fan wheel further comprises a back plate, and wherein the back plate of the fan wheel has multiple back plate blades, such that rotation of the back plate blades draws a second ambient air flow through the multi-purpose port into the motor enclosure and down into the fan wheel, and wherein the first ambient air flow cools the fan motor, and wherein the second ambient air flow maintains a positive pressure in the motor enclosure so as to pneumatically segregate the fan motor from the exhaust gas flow through the annular exhaust plenum, and wherein the flow of the second ambient air flow into the fan wheel dilutes the exhaust gas flow and causes the exhaust gas flow to be expelled from the shroud with an increased volumetric flow rate, thereby increasing the static efficiency of the mixed flow fan assembly.