Patent Grant
11339793
The present disclosure relates generally to fans, such as those used for cooling electronics, and, more particularly, to flow directing features for mitigating a recirculation of backflow air through such fans.
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
One or more fans (e.g., axial fans) are commonly included in various electronic devices such as, for example, computers (e.g., servers, desktop computers), or a variety of other stationary or portable electronic devices. The fans are typically used to direct a working fluid (e.g., air) through an enclosure of the electronic device and across certain components (e.g., a central processing unit, a power supply unit, a graphics processing unit) within the enclosure that may generate thermal energy (e.g., heat). Accordingly, the working fluid may absorb the generated thermal energy (e.g., via convective heat transfer) and transfer the thermal energy to an ambient environment (e.g., the atmosphere) surrounding the electronic device. In this manner, the fans may ensure that an operational temperature of components included in the electronic device remains below a target value or within a desired range.
In many cases, operation of the fan(s) may generate audible noise (e.g., acoustic energy) that propagates from the fans. Unfortunately, the generated noise may be unpleasant to a user operating the electronic device and/or other persons located in proximity to the fan(s).
A summary of certain embodiments disclosed herein is set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of these certain embodiments and that these aspects are not intended to limit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects that may not be set forth below.
The present disclosure relates generally to flow directing features for a fan (e.g., an axial fan) of an electronic device. In particular, the flow directing features discussed herein are configured to mitigate or substantially reduce the recirculation of backflow air within the fan and, thus, mitigate formation of flow structures that may disturb air flow upstream of fan blades of the fan. Flow disturbances of this sort may lead to the generation of broadband and tonal noise when interacting with the fan blades, as well as a reduction in net air flow through the fan. For example, typical fans generally include a rotor that is disposed within a channel of a fan housing and configured to rotate about a central axis of the channel. The rotor includes a plurality of fan blades that are configured to engage with a fluid (e.g., air) surrounding the fan and direct the air through the channel in an intended direction of air flow (e.g., a first flow direction). In certain cases, a shroud may be disposed about and coupled to the fan blades. Accordingly, the shroud may rotate with and form an outer perimeter of the rotor. A radial gap (e.g., a shroud gap) often extends between the shroud and a wall of the channel to enable unrestricted rotational motion of the rotor relative to the housing. In many cases, operation of the fan generates a pressure differential on opposing sides of the housing (e.g., a lower pressure at the inlet and a higher pressure at the outlet), which induces a backflow of air that flows through the radial gap in a direction opposite to the intended direction air flow through the housing. The backflow of air may discharge near an inlet of the housing and generate disturbances near the fan blades that may interact with the fan blades and disturb air flow through the fan. That is, a region of disturbed or non-uniform air flow may be created near and/or within the fan housing, which often generates unpleasant audible noise.
Accordingly, embodiments of the present disclosure are directed toward various flow directing features that may be included in the fan to mitigate (e.g., redirect) the recirculation of backflow air (e.g., high pressure air discharged from the radial gap) through the fan blades and/or block a discharge of the backflow air from the fan housing. By way of example, embodiments of the present disclosure include a rotating inlet flange (e.g., on the rotating shroud of the fan) that forms an upstream end portion of the fan (e.g., of the rotor) and guides backflow air discharging from the radial gap in a direction diverging away from an inlet of the fan. In this manner, the rotating inlet flange may reduce or substantially eliminate recirculation of backflow air through the housing of the fan. Embodiments of the present disclosure also include backflow mitigation feature(s) that extend radially from the rotating shroud of the rotor and project into the radial gap between the rotor and stationary housing. As described in detail below, these backflow mitigation features may increase an aerodynamic resistance (e.g., an aerodynamic impedance) or a static pressure within the radial gap to counter-act the pressure differential generated between the inlet and an outlet of the fan housing, thus mitigating air recirculation through the radial gap. As such, the backflow mitigation features may generate a stagnation of air within the radial gap that blocks a discharge of backflow air from the fan housing back to the inlet region of the fan. By employing the aforementioned techniques alone or in any combination, air flow disturbances resulting from the backflow of air may be inhibited from forming near and/or around the fan blades, thus reducing a magnitude of audible noise that may be generated during operation of the fan.
Various refinements of the features noted above may exist in relation to various aspects of the present disclosure. Further features may also be incorporated in these various aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to one or more of the illustrated embodiments may be incorporated into any of the above-described aspects of the present disclosure alone or in any combination. The brief summary presented above is intended only to familiarize the reader with certain aspects and contexts of embodiments of the present disclosure without limitation to the claimed subject matter.
Various aspects of this disclosure may be better understood upon reading the following detailed description and upon reference to the drawings in which:
One or more specific embodiments of the present disclosure will be described below. These described embodiments are only examples of the presently disclosed techniques. Additionally, in an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.
When introducing elements of various embodiments of the present disclosure, the articles “a,” “an,” and “the” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Additionally, it should be understood that references to “one embodiment” or “an embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.
As briefly discussed above, one or more flow generating devices (e.g., fans) are typically used to direct an air flow or other working fluid across certain components of an electronic device that may generate and release thermal energy. For example, a fan may be coupled to an enclosure of an electronic device and configured to circulate a continuous flow of cooling air through the enclosure, thereby preventing an accumulation of heated air within the enclosure. The fan typically includes a rotor disposed within a housing of the fan. The housing defines a channel (e.g., a flow path) along which air may flow through the housing. The rotor is configured to rotate about a central axis of the channel. Specifically, the rotor may include an electric motor or other suitable actuator that is configured to impart a torque on the rotor, thereby inducing rotation of the rotor relative to the housing of the fan. The rotor includes a hub having a plurality of angled fan blades extending radially therefrom. A circular shroud or ring may be disposed about and coupled to the fan blades, thereby forming an outer perimeter of the rotor. The fan blades engage with air surrounding the fan when the hub rotates, thereby forcing the air through the channel from an inlet to an outlet of the fan. In fans having a shrouded rotor, a radial gap extends between the rotating shroud and the housing to enable unobstructed rotation motion of the fan relative to the housing.
Operation of the fan generates a pressure differential between the inlet (e.g., low/ambient pressure) and the outlet (e.g., higher pressure) of the fan. This pressure differential may generate a backflow of air that flows through the radial gap between the rotating shroud and the housing from the outlet of the fan toward the inlet. In certain cases, this backflow air may be re-drawn into the inlet of the fan and disrupt air flow (e.g., cause fluidic disturbances to the air flow) around the fan blades. As noted above, this recirculation of backflow air through the fan may significantly increase audible noise that may be generated during operation of the fan.
Accordingly, the fan may be equipped with a rotating inlet flange that forms an upstream end portion (e.g., an inlet portion) of the rotor and directs backflow air in a direction away from the inlet. That is, the rotating inlet flange may include a contoured profile that redirects backflow air in a direction extending radially outward from the fan inlet as the backflow air is discharged from the housing. As such, the rotating inlet flange may enable the backflow air to discharge about a circumference of the housing in a direction away from the inlet, thereby reducing or substantially eliminating a likelihood of backflow air being drawn into the inlet of the fan. In some embodiments, a width of the radial gap between a terminal interface of the housing and the rotating inlet flange, referred to hereinafter as an axial gap or a vertical gap, may vary about a circumference of the housing. Width variations of the axial gap may be used to adjust a flow rate of backflow air discharging near certain portions of the housing. That is, a flowrate of backflow air may be biased toward particular side(s) (e.g., end portions) of the fan (e.g., or a fan array). As described in detail below, this flow biasing technique may reduce an amount of backflow air that may be transferred between fans disposed in close proximity to one another.
In certain embodiments, the fan may include a backflow mitigation feature, or multiple backflow mitigation features, that are included in the fan in addition to, or in lieu of, the rotating inlet flange. As discussed below, the backflow mitigation feature may reduce or substantially eliminate a backflow of air through the radial gap. For example, in some embodiments, the backflow mitigation feature may include a helical protrusion that extends from an outer surface the shroud and projects into the radial gap. Similar to the fan blades, the helical protrusion may engage the air within the radial gap and force the air in a flow direction toward the outlet of the fan. In some embodiments, the backflow mitigation feature may thereby generate a pressure within the radial gap that may partially or fully counter-act the pressure differential generated between the inlet and the outlet during operation of the fan. By reducing or mitigating the pressure difference from the fan outlet to the radial gap, air backflow into the radial gap may be mitigated or substantially prevented. In this manner, the backflow mitigation feature may mitigate a likelihood of air recirculation between the radial gap and the fan, thereby reducing audible noise that may be emitted by the disturbed air flow through the fan.
In further embodiments, one or more of the fan blades may be configured to protrude through the shroud of the fan to form a portion of, or all of, the backflow mitigation feature. That is, the fan blades may extend radially past the shroud and protrude into the radial gap, thereby engaging with the air within the radial gap and blocking (e.g., counteracting) a flow of backflow air in a similar manner as discussed above. These and other features will be described in detail below with reference to the drawings.
With the foregoing in mind,
With the preceding in mind,
For example, the rotor assembly 56 may include a hub 64 that is configured to rotate about the vertical axis 44 or a centerline 66 (e.g., a central axis) of the channel 52. That is, the hub 64 may be coupled to a motor 68, as shown in
As shown in the illustrated embodiment of
Each of the fan blades 80 includes a pressure surface 90, as shown in
In some embodiments, the housing 48 may include a mounting flange 100 that extends from the outer wall 50 and enables the fan 40A to couple to a suitable portion of the enclosure 12. For example, the mounting flange 100 may include one or more apertures 102 defined therein, which enable fasteners to extend through the mounting flange 100 and facilitate coupling the fan 40A the enclosure 12. Accordingly, the fan 40A may be used to circulate an air flow through the enclosure 12 (e.g., via an inlet and outlet of the enclosure 12) to remove thermal energy from certain components of the electronic device 10 that may generate heat, as noted above. Although the mounting flange 100 extends from the outer wall 50 near the outlet 60 of the housing 48 in the illustrated embodiment, it should be noted that the mounting flange 100 may be situated near any other portion of the housing 48 (e.g., near the inlet 58) in other embodiments of the fan 40A.
In some embodiments, the housing 48 includes an inner wall 130 that extends from a second end portion 132 of the outer wall 50 toward the rotor assembly 56. The inner wall 130 may form an outlet ring 134 that is disposed proximate a downstream end portion 136 of the shroud 82. Similar to the inlet flange 122 discussed above, an inner diameter of the outlet ring 134 may be substantially equal to the inner diameter of the shroud 82. Accordingly, the inner wall 130 may guide air discharging from the fluid passages 84 toward the outlet 60 of the housing 48.
It is important to note that vertical gaps extend between the inlet flange 122 and the shroud 82, and the shroud 82 and the outlet ring 134, respectively. That is, a first vertical gap 140 extends between the inlet flange 122 and an upstream end portion 142 of the shroud 82, and a second vertical gap 146 extends between the downstream end portion 136 of the shroud 82 and the inner wall 130. As with the radial gap 120, the first and second vertical gaps 140, 146 may ensure that physical contact between the shroud 82, the inlet flange 122, and the inner wall 130 is precluded, thereby enabling the rotor assembly 56 to rotate freely within the housing 48. As a non-limiting example, in some embodiments, a width of the first vertical gap 140, a width of the second vertical gap 146, or both, may be between about 0.5 mm and about 2 mm.
As noted above, operation of the fan 40A may generate a region of high pressure air proximate the outlet 60 of the housing 48 and a region of low pressure air proximate the inlet 58 of the housing 48. In other words, an air pressure near the outlet 60 may be greater than an air pressure near the inlet 58. This pressure differential may generate a secondary air flow, or a backflow of air (e.g., as indicated by arrow 150), which enters the radial gap 120 via the second vertical gap 146 and flows through the radial gap 120 toward the inlet 58. That is, the backflow of air may flow in a second direction 152, which is generally opposite to the first direction 96 of air flow along the fluid passages 84 of the fan blades 80. The backflow of air may discharge from the radial gap 120 via the first vertical gap 140 and re-enter the fluid passages 84. As such, a portion of the air flowing through the channel 52 may be recirculated about a perimeter of the shroud 82.
Unfortunately, this stream of air circulating through the radial gap 120 may disturb a flow of mainstream air entering the inlet 58 (e.g., increase turbulence of the air flow entering the inlet 58), thereby generating and/or increasing audible aero-acoustic noise (e.g., acoustic energy) that may be unpleasant to users operating the electronic device 10. As discussed in detail below, this audible noise may be particularly prominent within certain harmonic frequency ranges of the fan 40A. Accordingly, embodiments of the present disclosure are directed toward a rotating inlet flange that is configured to reduce or substantially eliminate a recirculation of backflow air through the radial gap 120 and the fluid passages 84 of the rotor assembly 56. As such, the rotating inlet flange may lower a magnitude (e.g., a decibel level) of audible tonal (e.g., harmonic) noise that may be generated during operation of the fan 40A.
With the preceding in mind,
To facilitate the subsequent discussion,
It is important to note that the rotating inlet flange 160 includes a profile 172 (e.g., a curved profile) that diverges radially from the generally cylindrical section of the shroud 82 to an outer edge (e.g., a distal end) of the rotating inlet flange 160. Accordingly, air flowing through the radial gap 120 may be guided along the profile 172 of the rotating inlet flange 160 prior to discharging from the housing 48. As such, the profile 172 may redirect air discharging from the radial gap 120 generally along the radial axis 42, away from the centerline 66 of the channel 52. That is, the backflow air discharges from the radial gap 120 in a direction diverging from the centerline 66. In this manner, the rotating inlet flange 160 may mitigate a likelihood of the fan 40B re-ingesting backflow air via the rotor assembly 56, thereby reducing or substantially eliminating air recirculation between the radial gap 120 and the fluid passages 84. As such, the rotating inlet flange 160 may significantly reduce audible noise that may be generated during operation of the rotor assembly 56.
For example,
Accordingly, sequential harmonic frequencies of the fans 40A, 40B may be determined by calculating multiples of the blade pass frequency (e.g., multiples of the fundamental harmonic frequency). With the foregoing in mind, the graph 180 illustrates a magnitude of acoustic energy that may be generated by the fans 40A, 40B at various harmonic frequencies. In particular, line 182 illustrates acoustic energy that may generated by the fan 40A, while line 184 illustrates acoustic energy that may be generated by the fan 40B.
As shown in the graph 180 of
As another example,
Returning to
In certain embodiments, the rotating inlet flange 160 may be configured to discharge the backflow air in a direction substantially similar to an intended direction of air flow through the fan 40B (e.g., along the first direction 96). By way of example,
In certain embodiments, the fan 40B may be configured to discharge the backflow air non-uniformly (e.g., non-axisymmetric) about a circumference of the outer wall 50. In other words, the fan 40B may be configured to discharge the backflow air along a first portion of the outer wall 50 at a flow rate that is less than or greater than a flow rate of backflow air discharged along a second portion of the outer wall 50. As discussed in detail below, this configuration may enable multiple fans 40B to be positioned in close proximity to one another while mitigating a transfer of backflow air between adjacent fans 40B. Accordingly, this flow biasing technique may reduce audible noise that may be generated due to the recirculation of backflow air between neighboring fans 40B.
To facilitate discussion,
It is important to note that such height variations along the outer wall 50 (e.g., variations in a circumferential height profile of the outer wall 50) may vary a width of the vertical gap 170 at various locations about the outer wall 50. That is, the width of the vertical gap 170 may increase or decrease about a circumference of the outer wall 50 proportionally to a decrease or increase, respectively, in a local height of the outer wall 50. As such, in the present example, a first width of the vertical gap 170 may be relatively small at the first point 206 (e.g., a constricted section) of the outer wall 50, while a second width of the vertical gap 170 is relatively large at the second point 210 (e.g., an expanded section) of the outer wall 50.
Adjusting a local width of the vertical gap 170 may facilitate regulating flow parameters (e.g., flow rate, dynamic pressure) of the backflow air discharging from the radial gap 120. For example, restricting a width of the vertical gap 170 along a particular section of the outer wall 50 may decrease the flow rate of backflow air discharging near this section of the outer wall 50. Conversely, enlarging the width of the vertical gap 170 along a section of the outer wall 50 may increase the flow rate of the backflow air discharging near this section of the outer wall 50. Accordingly, height variations along the outer wall 50 may be used to bias a discharge of backflow air to certain portion(s) of the fan 40. Specifically, in the present example, a flow rate of the backflow air near the first point 206 may be relatively small, as indicated by arrow 216, while a flow rate of the backflow air is relatively large near the second point 210, as indicated by arrow 218.
As another clarifying example,
In the exemplary embodiment of the flow generation unit 220 discussed herein, the first outer wall 50B1, the second outer wall 50B2, and the third outer wall 50B3 each include respective maximum heights at crest points 244, which are positioned along the centerline 242, and crest points 246, which are position along respective axes 248 extending generally orthogonal to the centerline 242. Respective minimum heights of the first outer wall 50B1, the second outer wall 50B2, and the third outer wall 50B3 are located at respective trough points 250, which may be positioned between (e.g., at a midpoint of) respective crest points 244, 246.
The respective heights (e.g., respective height profiles) of the first, the second, and the third outer walls 50B1, 50B2, 50B3 may vary uniformly or non-uniformly between the crest points 244, 246 and the respective trough points 250. In this manner, the fans 40B1, 40B2, 40B3 may each include constricted sections 252 along which respective vertical gaps 170 of the fans 40B1, 40B2, 40B3 are relatively small at the crest points 244, 246 and expanded sections 254 along which the respective vertical gaps 170 are relatively large at the trough points 250.
As shown in the illustrated embodiment, the constricted sections 252 may be disposed between each of the fans 40, while the expanded sections 254 are located near portions the outer walls 50B1, 50B2, 50B3 that are oriented away from one another. In this manner, each of the fans 40B1, 40B2, 40B3 may discharge a majority of their respective backflow air in a radial direction that is oriented away from neighboring fans 40B1, 40B2, 40B3 of the flow generation unit 220. This flow biasing configuration may therefore decrease a quantity of backflow air that may be discharged from one fan (e.g., the first fan 40B1) and ingested by and recirculated through an adjacent fan (e.g., the second fan 40B2).
For clarity,
In some embodiments, backflows of air of adjacent fans 40B may be discharged at different elevations, thereby reducing a likelihood of backflow air interaction between the fans 40B. For example,
In any case, the differences in height between the first outer wall 50B1 and the second outer wall 50B2 may enable a first backflow of air 270 discharging from the first fan 40B1 to impinge upon a circumferential end face 272 of the protrusion 266, while a second backflow of air 274 discharging from the second fan 40B2 may impinge upon an exterior surface 276 of the first outer wall 50B1. In this manner, the first and second backflows of air 270, 274 may be dispersed into an ambient environment, while a negligible amount of backflow air is directed toward and re-ingested by the first fan 40B1 and/or the second fan 40B2.
In some embodiments, the fans 40A, 40B, and/or 40C may include a backflow mitigation feature, or multiple backflow mitigation features, which are configured to reduce or substantially eliminate a flow of backflow air through the radial gap 120. For example,
The backflow mitigation feature 300 may engage with air occupying the radial gap 120 when the rotor assembly 56 rotates about the centerline 66 (e.g., in the counter-clockwise direction 94), such that the backflow mitigation feature 300 may attempt to partially block the flow of air in the second direction 152 or force the air in the first direction 96. In some embodiments, the backflow mitigation feature 300 may thereby generate a pressure within the radial gap 120 that is sufficient to fully or partially counteract the pressure differential generated between the vertical gap 170 and the second vertical gap 146 during operation of the fan 40D and, thus, result in substantially reduced or eliminated air backflow in the radial gap 120. Accordingly, the backflow mitigation feature 300 may generate a stagnation of air within the radial gap 120 that substantially blocks additional air from entering the radial gap 120 via the second vertical gap 146, or discharging from the radial gap 120 via the vertical gap 170. In this manner, the backflow mitigation feature 300 may reduce, or substantially eliminate a flow of backflow air through the radial gap 120.
In some embodiments, the backflow mitigation feature 300 may include a single helical protrusion that extends continuously about a circumference of the shroud 82. However, in other embodiments, the backflow mitigation feature 300 may include multiple separated features or protrusions that may be spaced equally (e.g., in an axisymmetric or uniform manner) about the circumference of the shroud 82 (e.g., as shown in the illustrated embodiment of
As an example, in some embodiments, the backflow mitigation feature 300 may include a first group of features that are positioned on the shroud 82 near the inlet 58 and have a first cross-sectional shape and a first protrusion width, while a second group of features are positioned on the shroud 82 near the outlet 60 and have a second cross-sectional shape (e.g., a different cross-sectional shape) and a second protrusion width (e.g., a different protrusion width). It should be appreciated that the geometry and/or the protrusion width of the backflow mitigation feature 300 may be tuned to minimize air backflow through the radial gap 120 at particular operational speeds of the fan 40D.
In certain embodiments, the backflow mitigation feature 300 may include a portion of the fan blades 80. For example, in some embodiments, the rotor assembly 56 may be manufactured (e.g., via an injection molding process) such that one or more of the fan blades 80 protrude radially through the shroud 82, thereby forming the backflow mitigation feature 300. Accordingly, during operation of the fan 40D, a portion of the fan blades 80 protruding radially past the shroud 82, referred to herein as a protruding portion, may engage the air within the radial gap 120 (e.g., via the pressure surface 90 of the fan blades 80) and thereby attempt to force the air in the first direction 96. Similar to the discussion above, in this manner, the protruding portion of the fan blades 80 may generate a static pressure rise in the first direction 96 within the radial gap 120 that may be sufficient to counteract the pressure differential between the vertical gap 170 and the second vertical gap 146 of the fan 40D, thus blocking a backflow of air through the radial gap 120.
In some embodiments, the rotor assembly 56 may be manufactured as a single piece component via an injection molding process. For example, to form the rotor assembly 56, a heated (e.g., liquid) polymeric material may be injected into a mold (e.g., a negative mold) having the shape of the rotor assembly 56. Upon cooling of the polymeric material, the mold may be split (e.g., into two or more individual pieces), thereby enabling removal of the rotor assembly 56 from the mold. However, due to its shape, mold lines may form on certain portions of the rotor assembly 56 that were adjacent to seams of the mold during the injection molding process. Specifically, mold lines may be formed on the inner surface of the shroud 82 and outer surface of the hub 64. Unfortunately, such mold lines may cause turbulent air flow during operation of the fan 40 (e.g., any of the fans 40A, 40B, 40C, 40D), which may generate acoustic energy (e.g., audible noise) during operation of the fans 40A, 40B, 40C, and/or 40D.
In some embodiments, to facilitate manufacture of the rotor assembly 56 and prevent the formation of mold lines on certain portions of the rotor assembly 56 (e.g., the fan blades 80), the hub 64 and the fan blades 80 may be formed as a single-piece component that is separate of the shroud 82 (e.g., in a two-piece design). For example, as shown in the illustrated embodiment of
To facilitate discussion,
In some embodiments, radial dimensions extending between the protrusions 346 and a center of the blade assembly 340 may exceed respective radial dimensions extending between the recesses 350 and a center of the shroud 82 (e.g., by approximately 0.5 mm). Accordingly, the shroud 82, the blade assembly 340, or both, may temporarily deform while the blade assembly 340 is inserted into the shroud 82.
For example, in some embodiments, the blade assembly 340 may be constructed of a relatively rigid material, such as glass-filled plastic, while the shroud 82 may be constructed of an elastically deformable material, such as a non-glass filled polymeric material. Accordingly, the shroud 82 may temporarily deform (e.g., flex, bend) while the blade assembly 340 is inserted into the shroud 82.
The blade assembly 340 may be rotated relative to the shroud 82 until the protrusions 346 of the blade tips 344 engage with respective apertures 360 defined within the shroud 82. Accordingly, upon proper alignment of the blade assembly 340 within the shroud, the shroud 82 may snap (e.g., lock) into place (e.g., return to its pre-deformed state, via a snap fit), and thus, couple the blade assembly 340 to the shroud 82.
In some embodiments, an adhesive (e.g., an epoxy resin) may be disposed within the grooves 342 prior to the mating process of the blade assembly 340 and the shroud 82. This adhesive may lubricate the interface between the blade tips 344 and the grooves 342 during this mating process and facilitate translating the blade tips 344 along the grooves 342, thus facilitating insertion of the blade assembly 340 within the shroud 82. Moreover, the adhesive will harden (e.g., cure) after installation of the blade assembly 340, thereby bonding the blade assembly 340 to the shroud 82 and enhancing a structural rigidity of the rotor assembly 54.
In some embodiments, a diametric dimension between opposing fan blades 80 may be marginally greater than (e.g., by 0.2-0.5 mm) a diametric dimension between opposing grooves 342 of the shroud 82. In this manner, a compressive force may remain between the shroud 82 and the blade tips 344 after installation of the blade assembly 340, which may facilitate forming an air-tight seal (e.g., a fluidic seal) at an interface 361 (e.g., as shown in
In some embodiments, certain of the grooves 342 may be slots that fully extend through a thickness of the shroud 82. In such embodiments, certain of the fan blades 80 corresponding to these slots (e.g., referred to herein as protruding blades) may be sized to include a radial dimension that exceeds a radial dimension of the shroud 82. Accordingly, upon complete insertion of the blade assembly 340 within the shroud 82, the protruding blades may align with the slots and extend through the slots (e.g., radially past an exterior surface 352 of the shroud 82). The remaining fan blades 80 corresponding to the grooves 342 may concentrically align the blade assembly 340 within the shroud 82 to ensure that the blade assembly 340 is centered within the shroud 82. In this manner, the protruding blades may act as the backflow mitigation feature 300 discussed above, and thereby prevent or substantially reduce a flow of backflow air through the radial gap 120.
The forward sweeping design of the fan blades 80 may reduce a radial velocity component of air flowing across the fan blades 80 during operation of the fan 40. In some embodiments, reducing radial air flow across the fan blades 80 may diminish broadband noise (e.g., audible noise) that is generated due to turbulent air flow across respective leading edges, trailing edges, and or tip regions of the fan blades 80 (e.g., generated due to separation of airflow from the suction surface 92 and/or tip leakage vortices around the fan blades 80 of shroudless fans). Accordingly, the forward sweeping blade design of the rotor assembly 54 may be used in conjunction with any one or combination of the aforementioned flow directing features to reduce an amount of acoustic energy (e.g., audible noise) generated during operation of the fan 40.
In some embodiments, the fans 40A, 40B, 40C, and/or 40D may include a flow impedance feature, or multiple flow impedance features, which are configured to impede or reduce a flow of backflow air through the radial gap 120. For example,
As shown in the illustrated embodiment, the stationary flow impedance ribs 384 may constrict several portions of the radial gap 120 to impede a backflow of air along these portions of the radial gap 120. Indeed, by constricting portions of the radial gap 120, the stationary flow impedance ribs 384 may generate a pressure drop along the radial gap 120 in the second direction 152, and thus, impede the flow of backflow air through the radial gap 120 in the second direction 152. In some embodiments, an axial distance between each of the stationary flow impedance ribs 384 (e.g., with respect to the centerline 66) may be substantially equal. In other embodiments, the axial distance between certain of the stationary flow impedance ribs 384 may be different. For example, in some embodiments, the stationary flow impedance ribs 384 positioned near the first end portion 124 of the outer wall 50 may be spaced closer together (e.g., with respect to an axial distance between adjacent stationary flow impedance ribs 384) or further apart to one another as compared to the stationary flow impedance ribs 384 positioned near the second end portion 132 of the outer wall 50. Moreover, in certain embodiments, a radial width (e.g., with respect to the centerline 66) of one or more of the stationary flow impedance ribs 384 may be substantially equal to one another or different from one another. It should be appreciated that the stationary flow impedance ribs 384 may be formed integrally with the outer wall 50.
Similar to the stationary flow impedance ribs 384, the rotating flow impedance ribs 390 may constrict several portions of the radial gap 120 to impede a backflow of air along these portions of the radial gap 120. That is, by constricting portions of the radial gap 120, the rotating flow impedance ribs 390 may generate a pressure drop along the radial gap 120 in the second direction 152, and thus, impede the flow of backflow air through the radial gap 120 in the second direction 152. In some embodiments, an axial distance between each of the rotating flow impedance ribs 390 (e.g., with respect to the centerline 66) may be substantially equal. In other embodiments, the axial distance between certain of the rotating flow impedance ribs 390 may be different. For example, in some embodiments, the rotating flow impedance ribs 390 positioned near the rotating inlet flange 160 may be spaced closer together (e.g., with respect to an axial distance between adjacent rotating flow impedance ribs 390) or further apart to one another as compared to the rotating flow impedance ribs 390 positioned near the downstream end portion 136 of the shroud 82. Moreover, in certain embodiments, a radial width (e.g., with respect to the centerline 66) of one or more of the rotating flow impedance ribs 390 may be substantially equal to one another or different from one another.
It should be appreciated that the rotating flow impedance ribs 390 may be formed integrally with the shroud 82. Accordingly, in some embodiments, the rotating flow impedance ribs 390 may stiffen the shroud 82 to reduce vibration of the shroud 82 and the rotor assembly 56 during operation of the fan 40E. Indeed, in certain embodiments, the rotating flow impedance ribs 390 may reduce or substantially mitigate vibrations that may occur at a natural vibrational frequency of the rotor assembly 56.
In some embodiments, the fan 40E may include both the stationary flow impedance ribs 384 and the rotating flow impedance ribs 390. To better illustrate and to facilitate the following discussion,
It should be appreciated that, in some embodiments, the stationary flow impedance ribs 384 may be axially aligned (e.g., with respect to the centerline 66) with the rotating flow impedance ribs 390. That is, the stationary flow impedance ribs 384 may be configured to extend along the radial axis 42 toward the rotating flow impedance ribs 390. In this manner, the stationary flow impedance ribs 384 and the rotating flow impedance ribs 390 may cooperate to constrict particular portion(s) of the radial gap 120.
The specific embodiments described above have been shown by way of example, and it should be understood that these embodiments may be susceptible to various modifications and alternative forms. It should be further understood that the claims are not intended to be limited to the particular forms disclosed, but rather to cover all modifications, equivalents, and alternatives falling within the spirit and scope of this disclosure.
The techniques presented and claimed herein are referenced and applied to material objects and concrete examples of a practical nature that demonstrably improve the present technical field and, as such, are not abstract, intangible or purely theoretical. Further, if any claims appended to the end of this specification contain one or more elements designated as “means for [perform]ing [a function] . . . ” or “step for [perform]ing [a function] . . . ”, it is intended that such elements are to be interpreted under 35 U.S.C. 112(f). However, for any claims containing elements designated in any other manner, it is intended that such elements are not to be interpreted under 35 U.S.C. 112(f).
This application claims priority from and the benefit of U.S. Provisional Application Ser. No. 62/756,859, entitled “FAN FLOW DIRECTING FEATURES, SYSTEMS AND METHODS”, filed Nov. 7, 2018, which is hereby incorporated by reference in its entirety for all purposes.
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