Mixed flow cooling fan

Abstract

Described are an air-cooled machines having a housing defining an inlet and an outlet; a bearing in the housing; a shaft, the shaft defining a rotational axis that extends in a longitudinal direction; and a fan attached to the shaft, wherein the fan defines an airflow path including an intake and an exhaust, where a portion of the airflow path between the intake and the exhaust is in a direction that is not parallel to the rotational axis, the fan includes a back plate; and a plurality of impeller blades extending from an upstream surface in a direction away from the outlet of the housing; where a first fan inlet diameter ranges from 0 to 3 inches; and a first fan outlet diameter ranges from 3 to 8 inches.

Description

MIXED FLOW COOLING FANFIELD OF THE INVENTION

[0001] The field of the invention relates to mixed flow cooling fans utilized in machinery', and, more particularly, utilized in electrical generators and motors for aircraft and other aerospace applications.BACKGROUND

[0002] Machines, such as starters utilized on an aircraft to start the engine and / or generators that convert rotary motion to electrical energy, are often operated at high rotary speed. Operation of these machines can create large amounts of heat that must be removed from the machine for proper operation and increased service life, of the machine, and hence the aircraft.

[0003] To remove this heat, fans are often used. In particular, the fan can force air through the machine. The air that is moved through the machine by the fan absorbs heat generated by the machine and is subsequently discharged outside of the machine, thereby decreasing the temperature of the machine. However, existing fans used to cool the machines are inefficient.

[0004] Notably, many machines rely upon a traditional fan which does not adequately cool the machine. Instead, the traditional fans introduce swirl energy into the air which increases windage losses. This increases the air temperature and decreases the heat transfer capacity of the air. Furthermore, modem machines are compact and filled with electromagnetics, thereby leaving small spaces for the air to pass through. This increases the resistance faced by the cooling air, thereby slowing down the airflow. Since the convective heat transfer coefficient is directly proportional to the speed of the air going over the surface, this decrease in air speed results in a decrease in total heat transfer. Accordingly, a more advanced cooling fan is needed.SUMMARY

[0005] The terms “invention,” “the invention,” “this invention” and “the present invention” used in this patent are intended to refer broadly to all of the subject matter of this patent and the patent claims below. Statements containing these terms should be understood not to limit the subject matter described herein or to limit the meaning or scope of the patent claims below. Embodiments of the invention covered by this patent are defined by the claims below, not this summary. This summary is a high-level overview of various aspects of the invention and introduces some of the concepts that are further described in the DetailedDescription section below. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used in isolation to determine the scope of the claimed subject matter. The subject matter should be understood by reference to appropriate portions of the entire specification of this patent, any or all drawings and each claim.

[0006] According to certain embodiments of the present invention, an air-cooled machine includes: a housing defining an inlet for air to enter into the air-cooled machine and an outlet for the air to exit the air-cooled machine; a bearing received in the housing; a shaft rotationally supported by the bearing, the shaft defining a rotational axis that extends in a longitudinal direction; and a fan attached to the shaft so as to be coaxially aligned with the bearing, wherein the fan defines an airflow path including an intake that receives the air from the inlet of the housing and an exhaust that discharges the air from the intake toward the outlet of the housing, and wherein a portion of the airflow path between the intake and the exhaust is in a direction that is not parallel to the rotational axis, the fan comprising: a curved back plate with an upstream surface that faces the inlet and a downstream surface that faces the outlet, and wherein the upstream surface and the downstream surface face in opposite directions to one another along the rotational axis; and a plurality of impeller blades extending from the upstream surface in a direction away from the outlet of the housing; wherein a first fan inlet diameter ranges from 0 to 3 inches; and wherein a first fan outlet diameter ranges from 3 to 8 inches.

[0007] According to certain embodiments of the present inventions, an air-cooled machine includes: a housing defining an inlet for air to enter into the air-cooled machine and an outlet for the air to exit the air-cooled machine; and a fan rotatable around a rotational axis, wherein the fan defines an airflow path including an intake that receives the air from the inlet of the housing and an exhaust that discharges the air from the intake toward the outlet of the housing, and wherein a portion of the airflow path between the intake and the exhaust is in a direction that is not parallel to the rotational axis, the fan comprising: a curved back plate with an upstream surface that faces the inlet and a downstream surface that faces the outlet, and wherein the upstream surface and the downstream surface face in opposite directions to one another along the rotational axis; a plurality of impeller blades extending from the upstream surface in a direction away from the outlet of the housing; and a shroud that is integral to the fan, wherein the shroud is upstream of the curved back plate and downstream of the inlet so as to at least partially cover the plurality of impeller blades, wherein the backplate and the plurality of impeller blades cooperate to define the airflow path from the intake to the exhaust; wherein a first fan inlet diameter ranges from 1 to 2 inches, a first fan outlet diameter ranges from 3 to 6 inches, a second fan inlet diameter ranges from 2 to 4 inches, a second fan outlet diameter ranges from 4 to 7 inches, a fan height ranges from 2 to 45% of the second fan outlet diameter, a thickness of each of the plurality of impeller blades ranges from 0.01 to 0.15 inches.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 is a perspective view of a rotating machine according to certain embodiments of the present invention.

[0009] FIG. 2A is a sectional elevation view of the rotating machine of FIG. 1.

[0010] FIG. 2B is a detailed elevation view of the 2B circle of FIG. 2A.

[0011] FIG. 3A is a left elevation view of a fan of a rotating machine according to certain embodiments of the present invention.

[0012] FIG. 3B is a right elevation view of the fan of FIG. 3 A.

[0013] FIG. 3C is a front sectional elevation view of the fan of FIG. 3A along lines3C-3C.

[0014] FIG. 4A is a left elevation view of a fan without a shroud of a rotating machine according to certain embodiments of the present invention.

[0015] FIG. 4B is a right elevation view of the fan of FIG. 4A.

[0016] FIG. 4C is a front sectional elevation view of the fan of FIG. 4A along fines4C-4C.

[0017] FIG. 5A is a right elevation view of a fan of a rotating machine according to certain embodiments of the present invention.

[0018] FIG. 5B is a front sectional elevation view of the fan of FIG. 5A along lines 5B-5B.DETAILED DESCRIPTION

[0019] The subject matter of embodiments of the present invention is described here with specificity to meet statutory requirements, but this description is not necessarily intended to limit the scope of the claims. The claimed subject matter may be embodied in other ways, may include different elements or steps, and may be used in conjunction with other existing or future technologies. This description should not be interpreted as implying any particular order or arrangement among or between various steps or elements except when the order of individual steps or arrangement of elements is explicitly described.

[0020] With reference to FIG. 1, a rotating machine 10 is shown. Without departing from the scope of the disclosure, the rotating machine 10 could be an electric motor (e.g., a starter utilized on an aircraft to start the engine) or a generator that converts rotary motion to electrical energy. Alternatively, the rotating machine 10 can be a combination startergenerator that is used to start the engine of an aircraft (i.e., startup mode) and also generate electricity for usage by the aircraft (i.e., generating mode). Though the embodiments below are discussed with respect to the rotating machine 10, the embodiments may be incorporated into any suitable machine.

[0021] As shown in FIGS. 1-2, the rotating machine 10 includes a housing 12, a bearing 14, a shaft 16, and a fan 18. The rotating machine 10 can also include a heat sink 22, a rotor 24, and a stator 26. The housing 12 defines an outer surface of the rotating machine 10 and serves to contain the components together in an easily manipulatable package to aid in installation into the aircraft. The housing 12 may be made of any number of materials, including, for example, pipe stock, solid stock, etc. As illustrated, the housing 12 may be attached to a chassis 20.

[0022] The chassis 20 can be made of any number of materials, including for example, aluminum. Aluminum offers good strength, light weight, and high thermal conductivity. The chassis 20 can include a non-rotation section 20a that is downstream of the fan 18. Further, the non-rotation section 20a may be a radial passage that longitudinally extends so as to help redirect the air that leaves the fan 18 in a direction that is parallel to the rotational axis x. In some embodiments, a static flow straightener and / or guide vanes may be arranged directly downstream of the fan 18; however, these are not required.

[0023] Further, the housing 12 defines a cylindrical shape in cross-section in a plane orthogonal to the rotational axis X; however, the cross-section may be any suitable shape. The housing 12 defines an inlet 28 for air to enter into the rotating machine 10 and an outlet 32 for the air to exit the rotating machine 10. The inlet 28 and the outlet 32 can be aligned with one another along the rotational axis X or may not be aligned w’ith one another.

[0024] With continued attention to FIGS. 2A-2B, the rotating machine 10 can include the bearing 14. As illustrated, the rotating machine 10 includes a plurality of bearings 14, although for simplicity, only one is identified. However, it will be understood that any number of bearings 14 could be utilized without departing from the scope of this disclosure. An inner diameter of the bearing is sized and shaped so as to be complimentary with the shaft 16 as will be described in more detail hereinbelow. Further, the bearing 14 may have an outerdiameter that is complimentary with the housing 12 so as to be received by the housing 12 and allow rotation of the inner diameter of the bearing 14 with respect to the housing 12 as is known.

[0025] The rotating machine 10 also includes the shaft 16 that is rotatably disposed at least partially within the housing 12. The shaft 16 includes a first longitudinal end 34 and a second longitudinal end 36. The shaft 16 defines a rotational axis X that extends in a longitudinal direction. Further, the shaft 16 can be circular in cross-section in a plane orthogonal to the rotational axis X. The shaft 16 may be supported by the bearing 14. The shaft 16 can be made of any number of materials that provide sufficient strength and rigidity to support the fan 18 and the rotor 24 as will be described in more detail hereinafter.

[0026] As shown in FIGS. 2A-2B, the fan 18 is attached to the shaft 16 and can be coaxially aligned with the bearing 14. Further, the fan 18 is configured to move the air from the inlet 28 to the outlet 32 such that the air leaving the fan 18 does not travel in a path that is always parallel to the rotational axis X.

[0027] As illustrated, the fan 18 is disposed at the first longitudinal end 34 of the shaft 16. The fan 18 may be made of any number of materials that offer sufficient strength and rigidity, along with appropriate chemical resistance to segregation, including for example, aluminum, plastic, and fiber-reinforced plastic. The fan 18 can also be created by additive manufacturing, also known as 3D printing.

[0028] Notably, the fan 18 defines an airflow path 30 including an intake 40 that receives the air from the inlet 28 of the housing 12 and an exhaust 50 that discharges the air from the intake 40 toward the outlet of the housing 12. As illustrated, a portion 30a of the airflow path 30 between the intake 40 and the exhaust 50 is in a direction that is not parallel to the rotational axis X.

[0029] Rather, in a sectional view, as shown in FIG. 2B, the portion 30a extends in a direction that is nearly perpendicular to the rotational axis X. In particular, the fan 18 changes the direction of the airflow from the inlet 28, which arrives at the intake 40 in a direction that is parallel to the rotational axis X to a radially extending outward direction (vertical in the sectional view of FIG. 2B) in the portion 30a.

[0030] Although the exhaust 50 is merely illustrated in two locations in FIG. 2B, it will be understood that this is a function of the drawing being a sectional 2-D representation, Notably, the exhaust 50 is a region that serves as the exit point for the air that was in the fan 18. The exhaust 50 is a void of material in a ring shape extending around a perimeter of thefan 18 from which the air that has passed through the fan 18 is discharged. Similarly, the intake 40 is defined as the region that serves as the entry point for air from the inlet 28 into the fan 18.

[0031] The air from the inlet 28 that enters the fan 18 may exclusively enter the fan 18 through the intake 40 and exit the fan 18 through the exhaust 50. Thus, the fan 18 is configured to receive the air from the inlet 28 in a direction that is parallel to the rotational axis X and, in cooperation with the non-rotation section 20a of the chassis 20, subsequently discharge the air from the fan 18 toward the outlet 32 such that the discharged air is then again parallel to the rotational axis X.

[0032] Then, the fan 18 changes the airflow direction again after leaving the exhaust 50 to a direction that is once again generally parallel to the rotational axis X. The aforementioned changes in airflow direction offer numerous thermodynamic cooling advantages to the rotating machine 10. In particular, a minimum amount of swirl energy is imparted into the air, thereby minimizing windage losses. As such, the heat transfer capacity of the air is improved .

[0033] With specific attention to FIGS. 3A-5B, the fan 18 is shown in more detail. The fan 18 is attached to the shaft 16 so that rotation of the shaft 16 about the rotational axis X results in rotation of the fan 18. The fan 18 can include a curved back plate 38 that defines a frusto-conical shape and a plurality of impeller blades 42 and a hub 44. The back plate 38 and the plurality of impeller blades 42 cooperate to define the airflow path 30 from the intake 40 to the exhaust 50.

[0034] As shown in FIGS. 3B, 4B, and 5A, the fan 18 can have 11 impeller blades 42. This number of blades can provide the proper amount and speed of airflow so as to sufficiently cool the components within the housing 12. However, it is understood that the fan 18 may have fewer than 11 or more than 11 impeller blades 42. Because of the back plate 38 and the plurality of impeller blades 42, the fan 18 outputs an air pressure that is higher than axial fans and lower than centrifugal fans. This mid-pressure output allows the discharged air to overcome flow obstructions when traveling from the fan 18 to the outlet 32.

[0035] Further, the fan 18 can include a shroud 46. Notably, FIGS. 3A-3C and 5A-5B illustrate the fan 18 with a shroud 46 that is integral, whereas FIGS, 4A-4C illustrate the fan 18 without the shroud 46. It will be understood that the fan 18 does not require the shroud 46, but numerous operating advantages are provided by the shroud 46 as will be discussed in more detail hereinafter.

[0036] The shroud 46 can be integral to the fan 18. With the shroud 46 being integral to the fan 18. numerous advantages are provided. For example, weight savings are realized and improved performance of the fan 18 (e.g., higher flow rate) is achieved. The shroud 46 reduces complexity and part count and eliminates interface problems which could occur with multiple parts that perform the same functions. The integral shroud 46 may be attached via two piece assembly or may be machined or 3-D printed as a part of the fan 18 itself. The shroud 46 increases the structural stiffness and provides improved structural integrity with higher stress to strength margins than a non-connected shroud. Having the shroud 46 as one part also makes it easier to optimize the airflow as there are no fasteners or part interfaces which might disrupt the airflow. As will be appreciated, this is extremely desirable in an aircraft. Further, the shroud 46 reduces the blade tip losses introduced with the clearance between a non-connected shroud and the impeller blades. The shroud 46 reduces the risk of damaging the impeller blades and ease of fitment due to manufacturing tolerances because a clearance of 0.03 inches to 0.05 inches is very difficult to maintain with manufacturing tolerances. Additionally, a non-connected shroud is typically made out of sheet metal, which is difficult to maintain shape to keep the consistent clearance gap between the impeller blades and the shroud and leads to inefficiencies.

[0037] Further, the shroud 46 is disposed so as to be upstream of the bearing 14 and downstream of the inlet 28 so as to at least partially cover the plurality of impeller blades 42. The shroud 46 cooperates with the plurality of impeller blades 42 and the housing 12 to move the air from the inlet 28 to the outlet 32.

[0038] The back plate 38 defines an outer diameter 48 and includes an upstream surface 52 that faces the inlet 28 and a downstream surface 54 that faces the outlet 32. The upstream surface 52 and the downstream surface 54 face in opposite directions to one another along the rotational axis X. Further, the back plate 38 defines a bore 56 that extends through the upstream surface 52 and the downstream surface 54 to allow receipt of the shaft 16, The bore 56 can be aligned with the rotational axis X.

[0039] Additionally, the back plate 38 can extend radially outward from the bore 56 so as to provide a continuous surface between each of the plurality of impeller blades 42 so as to prevent the air from longitudinally traveling between individual blades of the plurality of impeller blades 42. This arrangement ensures that the air can sufficiently cool the rotor 24 and the stator 26.

[0040] The plurality of impeller blades 42 extend from the upstream surface 52 in a direction away from the outlet 32 of the housing 12. Further, the plurality of impeller blades 42 radially extend from the outer diameter 48 of the back plate 38 along the upstream surface 52 toward the bore 56 in a curved manner when viewing the back plate 38 along the rotational axis X. Additionally, each of the plurality of impeller blades 42 can directly contact the back plate 38 and the shroud 46, As illustrated, the plurality of impeller blades 42 each extend between the back plate 38 and the shroud 46 so as to space the back plate 38 and the shroud 46 from one another.

[0041] Each of the impeller blades 42 can include an inner curved radial surface 58 and an outer flat radial surface 62. The inner curved radial surface 58 and the outer flat radial surface 62 are connected by a free end flat face 64, The free end flat face 64 faces away from the outlet 32. Further, the outer flat radial surface 62 and the free end flat face 64 meet to define an outermost point 66 that is a first radial distance from the rotational axis X. Notably, the first radial distance is greater than a radial distance between the rotational axis X and the outer diameter 48 of the back plate 38. The inner curved radial surface and the outer flat radial surface cooperate to define a radial length of each of the plurality of impeller blades 42.

[0042] Each of the impeller blades 42 can also include a leading face 68 and a trailing face 72. The leading face 68 and the trailing face 72 cooperate to define an angular thickness of each of the plurality of impeller blades. As illustrated, each of the blades 42 has the same thickness. Notably, the radial length of each of the plurality of impeller blades 42 is greater than the angular thickness of each of the plurality of impeller blades 42. The aforementioned design of the impeller blades 42 provides numerous advantages. For example, the tensile stress subjected to the fan 18 due to rotation loads is reduced, aerodynamic performance is improved, and noise during operation is reduced.

[0043] The hub 44 of the fan 18 extends from the downstream surface 54 of the back plate 38 toward the outlet 32 of the housing 12. Further, the hub 44 defines a hole 74 for receipt of the shaft 16. As will be appreciated, the hole 74 is sized so as to allow' for passage of the shaft 16. The hole 74 and the bore 56 can be in registry so as to allow passage of the shaft 16 therethrough.

[0044] The shroud 46 defines an opening 76 that allows fluid communication between the plurality of impeller blades 42 and the inlet 28. When the fan 18 of the rotating machine 10 includes the shroud 46, the intake 40 is disposed immediately upstream andadjacent the plurality of the impeller blades 42 and immediately downstream and adjacent the opening 76 of the shroud 46. When the fan 18 does not include the shroud 46, the intake 40 is in the same location, namely immediately adjacent and upstream of the impeller blades 42.

[0045] As illustrated, the opening 76 is circular in shape and coaxially aligned with the rotational axis X. Further, the opening 76 of the shroud 46 defines a shroud opening diameter that is greater than the bore 56 of the back plate 38. Further, the shroud 46 defines a shroud outer diameter 84. The shroud outer diameter 84 is greater than the outer diameter 48 of the back plate 38. The aforementioned geometric differences help ensure proper movement of the air between the inlet 28 and the outlet 32.

[0046] The fan 18 can also include a sealing ring portion 78. As illustrated, the sealing ring portion 78 is integral to the fan 18 and to the back plate 38. The sealing ring portion 78 can be generally circular in shape and extend from the downstream surface 54 of the back plate 38 towurd the outlet 32. The sealing ring portion 78 and the plurality of blades 42 are on opposite longitudinal sides of the back plate 38. The sealing ring portion 78 defines an inner diameter 82 which is greater than the opening 76 of the shroud 46.

[0047] Various geometry parameters of the fan 18, as illustrated in FIGS. 5A-5B, may be adjusted to further optimize the efficiency of the fan 18. In some embodiments, a first fan inlet diameter 102, which may be defined as the diameter of the circle formed by connecting the points of the inner curved radial surfaces 58 of each impeller blade 42 closest to the center of the fan 18, may range from 0 to 3 inches, 0 to 4 inches, 0 to 5 inches, 1 to 3 inches, 1 to 4 inches, 1 to 5 inches, 2 to 3 inches, 2 to 4 inches, or 2 to 5 inches. The circle formed by connecting the points of the inner curved radial surfaces 58 of each impeller blade 42 closest to the center of the fan 18 is shown in FIG. 5A for illustrative purposes and may not actually be present in the fan 18. A second fan inlet diameter 104, which may be defined as the diameter of the opening 76 of the shroud 46, may range from 2 to 5 inches, 1 to 5 inches, 0 to 5 inches, 3 to 5 inches, 4 to five inches, 0 to 6 inches, 1 to 6 inches, 2 to 6 inches, 3 to 6 inches, 4 to 6 inches, 5 to 6 inches, 0 to 4 inches, 1 to 4 inches, 2 to 4 inches, 3 to 4 inches, 0 to 3 inches, 1 to 3 inches, or 2 to 3 inches.

[0048] In certain embodiments, a first fan outlet diameter 106, which may be defined as the outer diameter 48 of the back plate 38, may range from 3 to 8 inches, 4 to 8 inches, 5 to 8 inches, 6 to 8 inches, 7 to 8 inches, 2 to 9 inches, 3 to 9 inches, 4 to 9 inches, 5 to 9 inches, 6 to 9 inches, 7 to 9 inches, 8 to 9 inches, 2 to 8 inches, 2 to 7 inches, 3 to 7 inches, 4 to 7 inches, 5 to 7 inches, 6 to 7 inches, 2 to 6 inches, 3 to 6 inches, 4 to 6 inches, or 5 to 6 inches.A second fan outlet diameter 108, which may be defined as the shroud outer diameter 84 of the shroud 46, may range from 4 to 10 inches, 3 to 10 inches, 5 to 10 inches, 6 to 10 inches, 7 to 10 inches, 8 to 10 inches, 9 to 10 inches, 3 to 11 inches, 4 to 11 inches, 5 to 11 inches, 6 to 11 inches, 7 to 11 inches, 8 to 11 inches, 9 to 11 inches, 10 to 11 inches, 3 to 9 inches, 4 to 9 inches, 5 to 9 inches, 6 to 9 inches, 7 to 9 inches, 8 to 9 inches, 3 to 8 inches, 4 to 8 inches, 5 to 8 inches, or 6 to 8 inches.

[0049] In some embodiments, a fan height 110, defined as the distance between the most downstream surface of the back plate 38 to the most upstream surface of the shroud 46 may be 20 to 45%, 10 to 55%, 15 to 55%, 20 to 55%, 25 to 55%, 30 to 55%, 35 to 55%, 40 to 55%, 45 to 55%, 50 to 55%, 10 to 50%, 15 to 50%, 20 to 50%, 25 to 50%, 30 to 50%, 35 to 50%, 40 to 50%, 45 to 50 %, 10 to 45%, 15 to 45%, 25 to 45%, 30 to 45%, 35 to 45%, 40 to 45%, 10 to 40%, 15 to 40%, 20 to 40%, 25 to 40%, 30 to 40%, 35 to 40%, 10 to 35%, 15 to 35%, 20 to 35%, 25 to 35%, or 30 to 35% of the second fan outlet diameter 108.

[0050] In certain embodiments, a first blade inlet angle 112, which may be defined as the beginning of the curvature of the blade with respect to the radial line, e.g., the angle between the radial line from the fan center to the average at the inner curved radial surface 58, may be 0 to 45°, 0 to 55°, 5 to 55°, 10 to 55°, 15 to 55°, 20 to 55°, 25 to 55°, 30 to 55°, 35 to 55°, 40 to 55°, 45 to 55°, 50 to 55°, 0 to 50 °, 5 to 50°, 10 to 50°, 15 to 50°, 20 to 50°, 25 to 50°, 30 to 50 °, 35 to 50°, 40 to 50°, 45 to 50°, 5 to 45°, 10 to 45°, 15 to 45°, 20 to 45°, 25 to 45°, 30 to 45°, 35 to 45°, 40 to 45°, 0 to 40°, 5 to 40°, 10 to 40°, 15 to 40°, 20 to 40°, 25 to 40°, 30 to 40°, 35 to 40°, 0 to 35°, 5 to 35°, 10 to 35°, 15 to 35°, 20 to 35°, 25 to 35°, or 30 to 35°. A first blade outlet angle 114, which may be defined as the end of the curvature of the blade with respect to the radial line, e.g., the angle between the radial line from the fan center to the average line along the blade at the outlet, may be -5 to 66°, 0 to 66°, 5 to 66°, 10 to 66°, 15 to 66°, 20 to 66°, 25 to 66°, 30 to 66°, 35 to 66°, 40 to 66°, 45 to 66°, 50 to 66°, 55 to 66°, 60 to 66°, -5 to 60°, 0 to 60°, 5 to 60°, 10 to 60°, 15 to 60°, 20 to 60°, 25 to 60°, 30 to 60°, 35 to 60°, 40 to 60°, 45 to 60°, 50 to 60°, 55 to 60°, -5 to 70°, 0 to 70°, 5 to 70°, 10 to 70°, 15 to 70°, 20 to 70°, 25 to 70°, 30 to 70°, 35 to 70°, 40 to 70°, 45 to 70°, 40 to 70°, 45 to 70°, 50 to 70°, 55 to 70°, 60 to 70°, or 65 to 70°.

[0051] In some embodiments, a second blade inlet angle 116, which may be defined as the angle between an intake edge of the impeller blade 42 and vertical, may be 10 to 90°, 0 to 90°, 20 to 90°, 30 to 90°, 40 to 90°, 50 to 90°, 60 to 90°, 70 to 90°, 80 to 90°, 0 to 80°, 10 to 80°, 20 to 80°, 30 to 80°, 40 to 80°, 50 to 80°, 60 to 80°, 70 to 80°, 0 to 110°, 10 to 110°,20 to 110°, 30 to 110°, 40 to 110°, 50 to 110°, 60 to i 10°, 70 to i 10°, 80 to 110°, 90 to 110°, or 100 to 110°. A second blade outlet angle 118, which may be defined as the angle between an exhaust edge of the impeller blade 42 and vertical, may be 10 to 80°, 0 to 80°, 20 to 80°, 30 to 80°, 40 to 80°, 50 to 80°, 60 to 80°, 70 to 80°, 0 to 70°, 10 to 70°, 20 to 70°, 30 to 70°, 40 to 70°, 50 to 70°, 60 to 70°, 0 to 90°, 10 to 90°, 20 to 90°, 30 to 90°, 40 to 90°, 50 to 90°, 60 to 90°, 70 to 90°, or 80 to 90°.

[0052] In certain embodiments, a fan hub inlet angle 120, which may be defined as the angle between the upstream surface 52 at the intake and vertical, may be 0 to 45°, 5 to45°, 10 to 45°, 15 to 45°, 20 to 45o, 25 to 45°, 30 to 45°, 35 to 45°, 40 to 45°, 0 to 40°, 5 to40°, 10 to 40°, 15 to 40°, 20 to 40°, 25 to 40°, 30 to 40°, 35 to 40°, 0 to 50°, 5 to 50°, 10 to50°, 15 to 50°, 20 to 50°, 25 to 50°, 30 to 50°, 35 to 50°, 40 to 50°, or 45 to 50°. A fan hub outlet angle 122, which may be defined as the angle between the upstream surface 52 at the exhaust and vertical, may be 0 to 45°, 5 to 45°, 10 to 45°, 15 to 45°, 20 to 45°, 25 to 45°, 30 to 45°, 35 to 45°, 40 to 45°, 0 to 40°, 5 to 40°, 10 to 40°, 15 to 40°, 20 to 40°, 25 to 40°, 30 to 40°, 35 to 40°, 0 to 50°, 5 to 50°, 10 to 50°, 15 to 50°, 20 to 50°, 25 to 50°, 30 to 50°, 35 to 50°, 40 to 50°, or 45 to 50°.

[0053] In some embodiments, a fan shroud inlet angle 124, which may be defined as the angle between the shroud 46 at the intake and vertical, may be 25 to 90°, 15 to 90°, 20 to 90°, 30 to 90°, 35 to 90°, 15 to 80°, 20 to 80°, 25 to 80°, 30 to 80°, 35 to 80°, 15 to 85°, 20 to 85°, 25 to 85°, 30 to 85°, 35 to 85°, 15 to 95°, 20 to 95°, 25 to 95°, 30 to 95°, 35 to 95°, 15 to 100°, 20 to 100°, 25 to 100°, 30 to 100°, or 35 to 100°. A fan shroud outlet angle 126, which may be defined as the angle between the shroud 46 at the exhaust and vertical, may be 10 to 45°, 0 to 45°, 5 to 45°, 15 to 45°, 20 to 45°, 25 to 45°, 30 to 45°, 35 to 45°, 40 to 45°, 0 to 40°, 5 to 40°, 10 to 40°, 15 to 40°, 20 to 40°, 25 to 40°, 30 to 40°, 35 to 40°, 0 to 50°, 5 to 50°, 10 to 50°, 15 to 50°, 20 to 50°, 25 to 50°, 30 to 50°, 35 to 50°, 40 to 50°, or 45 to 50°.

[0054] In certain embodiments, a blade tilt angle at the leading edge, which may be defined as the angle between the average line of the inner curved radial surface 58 at the leading edge going from the back plate 38 to the shroud 46 and the back plate 38 angle at the leading edge, may be 0 to 25°, 5 to 25°, 10 to 25°, 20 to 25°, 0 to 15°, 5 to 15°, 10 to 15°, 0 to 20°, 5 to 20°, 10 to 20°, 15 to 20°, 0 to 30°, 5 to 30°, 10 to 30°, 15 to 30°, 20 to 30°, 25 to 30°, 5 to 35°, 10 to 35°, 15 to 35°, 20 to 35°, 25 to 35°, or 30 to 35°. A blade tile angle at the trailing edge, which may be defined as the angle between the average line of the outer flat radial surface 62 going from the back plate 38 to the shroud 46 and the back plate 38 angle atthe trailing edge, may be 30 to 60°, 20 to 60°, 25 to 60°, 35 to 60°, 40 to 60°, 45 to 60°, 50 to 60°, 55 to 60°, 20 to 55°, 25 to 55°, 30 to 55°, 35 to 55°, 40 to 55°, 45 to 55°, 50 to 55°, 20 to 65°, 25 to 65°, 30 to 65°, 35 to 65°, 40 to 65°, 45 to 65°, 50 to 65°, 55 to 65°, or 60 to 65°.

[0055] In some embodiments, a blade thickness of the impeller blades 42, which may be defined as the distance of the impeller blade 42 between the leading face 68 and the trailing face 72, may be 0.04 to 0.25 inches, 0.01 to 0.25 inches, 0.02 to 0.25 inches, 0.03 to 0.25 inches, 0.05 to 0.25 inches, 0.06 to 0.25 inches, 0.07 to 0.25 inches, 0.01 to 0.20 inches, 0.02 to 0.20 inches, 0.03 to 0.20 inches, 0.04 to 0.20 inches, 0.05 to 0.20 inches, 0.06 to 0.20 inches, 0.07 to 0.20 inches, 0.01 to 0.30 inches, 0.02 to 0.30 inches, 0.03 to 0.30 inches, 0.04 to 0.30 inches, 0.05 to 0.30 inches, 0.06 to 0.30 inches, or 0.07 to 0.30 inches. A blade draft angle, which may be defined as the angle the impeller blade 42 outside surface makes with the center line of the blade at a given cross-section, may be 0 to 30°, 5 to 30°, 10 to 30°, 15 to 30°, 20 to 30°, 25 to 30°, 0 to 20°, 5 to 20°, 10 to 20°, 15 to 20°, 0 to 25°, 5 to 25°, 10 to 25°, 15 to 25°, 20 to 25°, 0 to 35°, 5 to 35°, 10 to 35°, 15 to 35°, 20 to 35°, 25 to 35°, 30 to 35°, 0 to 40°, 5 to 40°, 10 to 40°, 15 to 40°, 20 to 40°, 25 to 40°, 30 to 40°, or 35 to 40°.

[0056] In certain embodiments, the various geometry parameters of the fan 18 may be a first fan inlet diameter 102 of 0 to 3 inches, a first fan outlet diameter 106 of 3 to 8 inches, a second fan inlet diameter 104 of 2 to 5 inches, a second fan outlet diameter 108 of 4 to 10 inches, a fan height 110 of 20 to 45% of the second fan outlet diameter 108, a first blade inlet angle 112 of 0 to 45°, a first blade outlet angle 114 of -5 to 66°, a second blade inlet angle 116 of 10 to 90°, a second blade outlet angle 118 of 10 to 80°, a fan hub inlet angle 120 of 0 to 45°, a fan hub outlet angle 122 of 0 to 45°, a fan shroud inlet angle 124 of 25 to 90°, a fan shroud outlet angle of 10 to 45°, a blade tilt angle at the leading edge of 0 to 25°, a blade tilt angle at the trailing edge of 30 to 60°, a blade thickness of 0.04 to 0.25 inches, and a blade draft angle of 0 to 30°.

[0057] In some embodiments, the various geometry parameters of the fan 18 may be a first fan inlet diameter 102 of 1.5 to 2 inches, a first fan outlet diameter 106 of 4 to 5 inches, a second fan inlet diameter 104 of 3 to 4 inches, a second fan outlet diameter 108 of 5 to 6 inches, a fan height 110 of 20 to 45% of the second fan outlet diameter 108, a first blade inlet angle 112 of 30 to 35°, a first blade outlet angle 114 of 45 to 55°, a second blade inlet angle 116 of 30 to 35°, a second blade outlet angle 118 of 45 to 55°, a fan hub inlet angle 120 of 25 to 30°, a fan hub outlet angle 122 of 20 to 25°, a fan shroud inlet angle 124 of 25 to 90°, a fan shroud outlet angle of 10 to 45°, a blade tilt angle at the leading edge of 0 to 25°, a blade tiltangle at the trailing edge of 30 to 60°, a blade thickness of 0.04 to 0.25 inches, and a blade draft angle of 0 to 30°.

[0058] In certain embodiments, the various geometry parameters of the fan 18 may be a first fan inlet diameter 102 of 1 to 1.5 inches, a first fan outlet diameter 106 of 3 to 4 inches, a second fan inlet diameter 104 of 2 to 3 inches, a second fan outlet diameter 108 of 4 to 5 inches, a fan height 110 of 20 to 45% of the second fan outlet diameter 108, a first blade inlet angle 112 of 30 to 35°, a first blade outlet angle 114 of 45 to 55°, a second blade inlet angle 116 of 30 to 35°, a second blade outlet angle 118 of 45 to 50°, a fan hub inlet angle 120 of 25 to 30°, a fan hub outlet angle 122 of 20 to 25°, a fan shroud inlet angle 124 of 25 to 90°, a fan shroud outlet angle of 10 to 45°, a blade tilt angle at the leading edge of 0 to 25°, a blade tilt angle at the trailing edge of 30 to 60°, a blade thickness of 0.04 to 0.25 inches, and a blade draft angle of 0 to 30°.

[0059] In some embodiments, the various geometry parameters of the fan 18 may be a first fan inlet diameter 102 of 1.5 to 2 inches, a first fan outlet diameter 106 of 5 to 6 inches, a second fan inlet diameter 104 of 3 to 4 inches, a second fan outlet diameter 108 of 6 to 7 inches, a fan height 110 of 20 to 45% of the second fan outlet diameter 108, a first blade inlet angle 112 of 30 to 35°, a first blade outlet angle 114 of 45 to 55°, a second blade inlet angle 116 of 30 to 35°, a second blade outlet angle 118 of 50 to 55°, a fan hub inlet angle 120 of 25 to 30°, a fan hub outlet angle 122 of 20 to 25°, a fan shroud inlet angle 124 of 25 to 90°, a fan shroud outlet angle of 10 to 45°, a blade tilt angle at the leading edge of 0 to 25°, a blade tilt angle at the trailing edge of 30 to 60°, a blade thickness of 0.04 to 0.25 inches, and a blade draft angle of 0 to 30°.

[0060] In some embodiments, the various geometry parameters of the fan 18 may be a first fan inlet diameter 102 of 1.5 to 2 inches, a first fan outlet diameter 106 of 4 to 5 inches, a second fan inlet diameter 104 of 3 to 4 inches, a second fan outlet diameter 108 of 5 to 6 inches, a fan height 110 of 20 to 45% of the second fan outlet diameter 108, a first blade inlet angle 112 of 30 to 35°, a first blade outlet angle 114 of 45 to 55°, a second blade inlet angle 116 of 30 to 35°, a second blade outlet angle 118 of 50 to 55°, a fan hub inlet angle 120 of 25 to 30°, a fan hub outlet angle 122 of 20 to 25°, a fan shroud inlet angle 124 of 25 to 90°, a fan shroud outlet angle of 10 to 45°, a blade tilt angle at the leading edge of 0 to 25°, a blade tilt angle at the trailing edge of 30 to 60°, a blade thickness of 0.04 to 0.25 inches, and a blade draft angle of 0 to 30°.

[0061] The dimensions of the various geometry parameters of the fan 18 may be determined based on the machine within which the fan 18 is used in. It is understood that though FIGS. 5A-5B depict a fan 18 with a shroud 46 that rotates clockwise, the described ranges for the various geometry parameters may similarly be applied to a fan without a shroud, a fan with a non-rotating shroud, or a fan that rotates counterclockwise.

[0062] The fan 18 formed with various geometry parameters falling within the ranges described herein may improve the airflow through a machine by 25 to 45% compared to traditional fans used within the machines. Such improved airflow may reduce operating temperature by 20 to 30oC and ultimately improve the lifespan of the bearing and brush of the machine. The fan 18 may also reduce the whirl introduced into the airflow at the fan exhaust 50 and may reduce windage losses. The fan 18 formed with various geometry parameters falling within the ranges described herein may consume approximately 40% less power and may reduce noise produced by the fan 18 by approximately 10 dB as compared to traditional fans used within the machines.

[0063] With reference once again to FIG. 2A, the heat sink 22 is shown. The heat sink 22 allows for cooling of adjacent electrical / electronic components (unnumbered) due to the air that enters through the inlet 28. The heat sink 22 can be disposed within the housing 12 so as to be between the fan 18 and the inlet 28. Furthermore, this location can be coaxially aligned with the fan 18 and the inlet 28.

[0064] With continued attention to FIG. 2A, the rotating machine 10 also includes the rotor 24, which is attached or coupled to the shaft 16 so that the shaft 16 and the rotor 24 rotate together. The rotor 24 is of known construction. Rotation of the rotor 24 is due to the interaction between the windings and magnetic fields which produces a torque around the rotational axis X. The rotor 24 is rotationally movable with respect to the stator 26. The rotor 24 is disposed on the shaft 16 so as to be between the heat sink 22 and the outlet 32. Additionally, the rotor 24 is received on the shaft 16 such that the fan 18 is longitudinally disposed between the rotor 24 and the inlet 28.

[0065] The stator 26 is of known construction. The stator 26 is a stationary part of the rotating machine 10, and thus is stationary with respect to the housing 12 and the rotor 24. When the rotating machine 10 is a generator, energy flows through the stator 26 to or from the rotor 24 as is known. When the rotating machine 10 is a starter, the stator 26 provides a rotating magnetic field that drives the rotating armature, as is also known in the art. When therotating machine 10 is a generator, the stator 26 converts the rotating magnetic field to electric current. The stator 26 is disposed within the housing 12.

[0066] A rotating machine has been described above with particularity. Modifications and alterations will occur to those upon reading and understanding the preceding detailed description. The invention, however, is not limited to only the embodiments described above. Instead, the invention is broadly defined by the appended claims and the equivalents thereof.

[0067] In the following, further examples are described to facilitate the understanding of the invention:

[0068] Example 1 . An air-cooled machine (which may incorporate features of any of the subsequent examples), comprising: a housing defining an inlet for air to enter into the aircooled machine and an outlet for the air to exit the air-cooled machine; a bearing received in the housing; a shaft rotationally supported by the bearing, the shaft defining a rotational axis that extends in a longitudinal direction; and a fan attached to the shaft so as to be coaxially aligned with the bearing, wherein the fan defines an airflow path including an intake that receives the air from the inlet of the housing and an exhaust that discharges the air from the intake toward the outlet of the housing, and wherein a portion of the airflow path between the intake and the exhaust is in a direction that is not parallel to the rotational axis, the fan comprising: a curved back plate with an upstream surface that faces the inlet and a downstream surface that faces the outlet, and wherein the upstream surface and the downstream surface face in opposite directions to one another along the rotational axis; and a plurality of impeller blades extending from the upstream surface in a direction away from the outlet of the housing; wherein a first fan inlet diameter ranges from 0 to 3 inches; and wherein a first fan outlet diameter ranges from 3 to 8 inches.

[0069] Example 2. The air-cooled machine of example(s) 1 or any preceding or subsequent example(s), wherein the fan further comprises a shroud that is integral to the fan, wherein the shroud is upstream of the bearing and downstream of the inlet so as to at least partially cover the plurality of impeller blades, wherein the back plate and the plurality of impeller blades cooperate to define the airflow path from the intake to the exhaust.

[0070] Example 3. The air-cooled machine of example(s) 2 or any preceding or subsequent example(s), wherein a second fan inlet diameter ranges from 2 to 5 inches, and a second fan outlet diameter ranges from 4 to 10 inches.

[0071] Example 4. The air-cooled machine of example(s) 3 or any preceding or subsequent example(s), wherein the second fan outlet diameter is greater than the first fan outlet diameter.

[0072] Example 5. The air-cooled machine of example(s) 3 or any preceding or subsequent example(s), wherein a fan height ranges from 2- to 45% of the second fan outlet diameter.

[0073] Example 6. The air-cooled machine of example(s) 3 or any preceding or subsequent example(s), wherein the second fan inlet diameter is greater than the first fan inlet diameter.

[0074] Example 7. The air-cooled machine of example(s) 2 or any preceding or subsequent example(s), wherein a thickness of each of the plurality of impeller blades ranges from 0.04 to 0.25 inches.

[0075] Example 8. The air-cooled machine of example(s) 2 or any preceding or subsequent example(s), wherein the shroud defines an opening that allows fluid communication between the plurality of impeller blades and the inlet.

[0076] Example 9. The air-cooled machine of example(s) 2 or any preceding or subsequent example(s), wherein a fan shroud inlet angle ranges from 25 to 90°.

[0077] Example 10. The air-cooled machine of example(s) 2 or any preceding or subsequent example(s), wherein a fan shroud outlet angle ranges from 10 to 45°.

[0078] Example 11. The air-cooled machine of example(s) 1 or any preceding or subsequent example(s), wherein a first blade inlet angle ranges from 0 to 45°, and a first blade outlet angle ranges from -5 to 66°.

[0079] Example 12. The air-cooled machine of example(s) 11 or any preceding or subsequent example(s), wherein a second blade inlet angle ranges from 10 and 90°, and a second blade outlet angle ranges from 10 to 80°.

[0080] Example 13. The air-cooled machine of example(s) 1 or any preceding or subsequent examplc(s). wherein a fan hub inlet angle ranges from 0 to 45°, and a fan hub outlet angle ranges from 0 to 45°.

[0081] Example 14. The air-cooled machine of example(s) 1 or any preceding or subsequent example(s), wherein a blade tilt angle at a leading edge ranges from 0 to 25°.

[0082] Example 15. The air-cooled machine of example(s) 1 or any preceding or subsequent example(s), wherein a blade tilt angle at a trailing edge ranges from 30 to 60°.

[0083] Example 16. The air-cooled machine of example(s) 1 or any preceding or subsequent example(s), wherein a blade draft angle ranges from 0 to 30°.

[0084] Example 17. An air-cooled machine (which may incorporate features of any of the preceding or subsequent examples), comprising: a housing defining an inlet for air to enter into the air-cooled machine and an outlet for the air to exit the air-cooled machine; and a fan rotatable around a rotational axis, wherein the fan defines an airflow path including an intake that receives the air from the inlet of the housing and an exhaust that discharges the air from the intake toward the outlet of the housing, and wherein a portion of the airflow path between the intake and the exhaust is in a direction that is not parallel to the rotational axis, the fan comprising: a curved back plate with an upstream surface that faces the inlet and a downstream surface that faces the outlet, and wherein the upstream surface and the downstream surface face in opposite directions to one another along the rotational axis: a plurality of impeller blades extending from the upstream surface in a direction away from the outlet of the housing; and a shroud that is integral to the fan, wherein the shroud is upstream of the curved back plate and downstream of the inlet so as to at least partially cover the plurality of impeller blades, wherein the back plate and the plurality of impeller blades cooperate to define the airflow path from the intake to the exhaust; wherein a first fan inlet diameter ranges from 1 to 2 inches, a first fan outlet diameter ranges from 3 to 6 inches, a second fan inlet diameter ranges from 2 to 4 inches, a second fan outlet diameter ranges from 4 to 7 inches, a fan height ranges from 2 to 45% of the second fan outlet diameter, a thickness of each of the plurality of impeller blades ranges from 0.01 to 0.15 inches.

[0085] Example 18. The air-cooled machine of example(s) 17 or any preceding or subsequent example(s), wherein a fan hub inlet angle ranges from 0 to 45°, and a fan hub outlet angle ranges from 0 to 45°.

[0086] Example 19. The air-cooled machine of example(s) 17 or any preceding or subsequent example(s), a first blade inlet angle ranges from 0 to 45°, a first blade outlet angle ranges from -5 to 66°, a second blade inlet angle ranges from 10 and 90°, a second blade outlet angle ranges from 10 to 80°.

[0087] Example 20. The air-cooled machine of example(s) 17 or any preceding example(s), wherein a blade tilt angle at a leading edge ranges from 0 to 25°, a blade tilt angle at a trailing edge ranges from 30 to 60°, and a blade draft angle ranges from 0 to 30°.

[0088] Different arrangements of the components depicted in the drawings or described above, as well as components and steps not shown or described are possible.Similarly, some features and sub-combinations are useful and may be employed without reference to other features and sub-combinations. Embodiments of the invention have been described for illustrative and not restrictive purposes, and alternative embodiments will become apparent to readers of this patent. Accordingly, the present invention is not limited to the embodiments described above or depicted in the drawings, and various embodiments and modifications may be made without departing from the scope of the claims below.

Claims

CLAIMSThat which is claimed is:1 . An air-cooled machine, comprising: a housing defining an inlet for air to enter into the air-cooled machine and an outlet for the air to exit the air-cooled machine; a bearing received in the housing; a shaft rotationally supported by the bearing, the shaft defining a rotational axis that extends in a longitudinal direction; and a fan attached to the shaft so as to be coaxially aligned with the bearing, wherein the fan defines an airflow path including an intake that receives the air from the inlet of the housing and an exhaust that discharges the air from the intake toward the outlet of the housing, and wherein a portion of the airflow path between the intake and the exhaust is in a direction that is not parallel to the rotational axis, the fan comprising: a curved back plate with an upstream surface that faces the inlet and a downstream surface that faces the outlet, and wherein the upstream surface and the downstream surface face in opposite directions to one another along the rotational axis; and a plurality of impeller blades extending from the upstream surface in a direction away from the outlet of the housing; wherein a first fan inlet diameter ranges from 0 to 3 inches; and wherein a first fan outlet diameter ranges from 3 to 8 inches.

2. The air-cooled machine of claim 1, wherein the fan further comprises a shroud that is integral to the fan, wherein the shroud is upstream of the bearing and downstream of the inlet so as to at least partially cover the plurality of impeller blades, wherein the back plate and the plurality of impeller blades cooperate to define the airflow path from the intake to the exhaust.

3. The air-cooled machine of claim 2, wherein a second fan inlet diameter ranges from 2 to 5 inches, and a second fan outlet diameter ranges from 4 to 10 inches.

4. The air-cooled machine of claim 3, wherein the second fan outlet diameter is greater than the first fan outlet diameter.

5. The air-cooled machine of claim 3, wherein a fan height ranges from 2- to 45% of the second fan outlet diameter.

6. The air-cooled machine of claim 3, wherein the second fan inlet diameter is greater than the first fan inlet diameter.

7. The air-cooled machine of claim 2, wherein a thickness of each of the plurality of impeller blades ranges from 0.04 to 0.25 inches.

8. The air-cooled machine of claim 2, wherein the shroud defines an opening that allows fluid communication between the plurality of impeller blades and the inlet.

9. The air-cooled machine of claim 2, wherein a fan shroud inlet angle ranges from 25 to 90°.

10. The air-cooled machine of claim 2, wherein a fan shroud outlet angle ranges from 10 to 45°.

11. The air-cooled machine of claim 1 , wherein a first blade inlet angle ranges from 0 to 45°, and a first blade outlet angle ranges from -5 to 66°.

12. The air-cooled machine of claim 11, wherein a second blade inlet angle ranges from 10 and 90°, and a second blade outlet angle ranges from 10 to 80°.

13. The air-cooled machine of claim 1, wherein a fan hub inlet angle ranges from 0 to 45°, and a fan hub outlet angle ranges from 0 to 45°.

14. The air-cooled machine of claim 1, wherein a blade tilt angle at a leading edge ranges from 0 to 25°.

15. The air-cooled machine of claim 1, wherein a blade tilt angle at a trailing edge ranges from 30 to 60°.

16. The air-cooled machine of claim 1, wherein a blade draft angle ranges from 0 to 30°.

17. An air-cooled machine, comprising: a housing defining an inlet for air to enter into the air-cooled machine and an outlet for the air to exit the air-cooled machine; and a fan rotatable around a rotational axis, wherein the fan defines an airflow path including an intake that receives the air from the inlet of the housing and an exhaust that discharges the air from the intake toward the outlet of the housing, and wherein a portion of the airflow path between the intake and the exhaust is in a direction that is not parallel to the rotational axis, the fan comprising: a curved back plate with an upstream surface that faces the inlet and a downstream surface that faces the outlet, and wherein the upstream surface and the downstream surface face in opposite directions to one another along the rotational axis; a plurality of impeller blades extending from the upstream surface in a direction away from the outlet of the housing; and a shroud that is integral to the fan, wherein the shroud is upstream of the curved back plate and downstream of the inlet so as to at least partially cover the plurality of impeller blades, ’wherein the back plate and the plurality of impeller blades cooperate to define the airflow path from the intake to the exhaust; wherein a first fan inlet diameter ranges from 1 to 2 inches, a first fan outlet diameter ranges from 3 to 6 inches, a second fan inlet diameter ranges from 2 to 4 inches, a second fan outlet diameter ranges from 4 to 7 inches, a fan height ranges from 2 to 45% of the second fan outlet diameter, a thickness of each of the plurality of impeller blades ranges from 0.01 to 0.15 inches.

18. The air-cooled machine of claim 17, wherein a fan hub inlet angle ranges from 0 to 45°, and a fan hub outlet angle ranges from 0 to 45°.

19. The air-cooled machine of claim 17, a first blade inlet angle ranges from 0 to 45°, a first blade outlet angle ranges from -5 to 66°, a second blade inlet angle ranges from 10 and 90°, a second blade outlet angle ranges from 10 to 80°.

20. The air-cooled machine of claim 17, wherein a blade tilt angle at a leading edge ranges from 0 to 25°, a blade tilt angle at a trailing edge ranges from 30 to 60°, and a blade draft angle ranges from 0 to 30°.

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