US20060237169A1

US20060237169A1 - Aerodynamically enhanced cooling fan

Info

Publication number: US20060237169A1
Application number: US11/263,351
Authority: US
Inventors: John Franz; Wade Vinson; Yousef Jarrah
Original assignee: Hewlett Packard Development Co LP
Current assignee: Hewlett Packard Development Co LP
Priority date: 2005-04-21
Filing date: 2005-10-31
Publication date: 2006-10-26
Also published as: TW200639628A; US20060237168A1

Abstract

A cooling fan comprising a fan housing that connects to a chassis supporting an electronic device. A motor is disposed within the fan housing. A blade assembly is rotatably coupled to the motor. The fan housing has a length at least 10 mm longer than a distance between a leading edge and a trailing edge of the blade assembly.

Description

BACKGROUND

Computer systems include numerous electrical components that draw electrical current to perform their intended functions. For example, a computer's microprocessor or central processing unit (“CPU”) requires electrical current to perform many functions such as controlling the overall operations of the computer system and performing various numerical calculations. Generally, any electrical device through which electrical current flows produces heat. The amount of heat any one device generates generally is a function of the amount of current flowing through the device.
Typically, an electrical device is designed to operate correctly within a predetermined temperature range. If the temperature exceeds the predetermined range (i.e., the device becomes too hot or too cold), the device may not function correctly, thereby potentially degrading the overall performance of the computer system. Thus, many computer systems include cooling systems to regulate the temperature of their electrical components. One type of cooling system is a forced air system that relies on one or more cooling fans to blow air over the electronic components in order to cool the components.
The cubic feet per minute (“CFM”) of air that can be moved across an electric device is an important factor in how much heat can be removed from the device. Thus, the capacity of a cooling fan is a critical factor in selecting an air mover for use in a cooling application. The CFM that a cooling fan can produce is governed a number of factors including: the total area of the blades generating the airflow, the free area provided for airflow through the fan, the design of the blades, and the power generated by the electric motor.
Axial flow fans generally comprise a plurality of radial blades rotating within a housing. Increasing performance demands on axial flow fans have required that fans provide increased volumes of air while, at the same time, reducing the size of the fan. One solution to increasing fan performance is simply to increase the speed at which the fan rotates. Increasing fan speed can also be accompanied by increased acoustic emissions, increased vibration, and decreased component life. Therefore, as can be appreciated, there remains a need in the art for cooling fans that provide high volumes of airflow by designs and improvements that increase performance without necessitating an increase in the speed at which fan operates.

BRIEF SUMMARY

The problems noted above are solved in large part by a cooling fan comprising a fan housing that connects to a chassis supporting an electronic device. A motor is disposed within the fan housing. A blade assembly is rotatably coupled to the motor. The fan housing has a length at least 10 mm longer than a distance between a leading edge and a trailing edge of the blade assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of exemplary embodiments of the invention, reference will now be made to the accompanying drawings in which:
FIG. 1 shows a computer system including cooling fans constructed in accordance with embodiments of the invention;
FIG. 2 shows a cross-sectional view of a cooling fan having a conical hub constructed in accordance with embodiments of the invention;
FIG. 3 shows a cross-sectional view of cooling fan having an extended intake as constructed in accordance with embodiments of the invention;
FIG. 4 shows a cross-sectional view of cooling fan having an extended length motor constructed in accordance with embodiments of the invention;
FIG. 5 shows a cross-sectional view of cooling fan having aerodynamically optimized stator blades constructed in accordance with embodiments of the invention;
FIG. 6 shows a cross-sectional view of cooling fan having forward swept blades as constructed in accordance with embodiments of the invention;
FIG. 7 shows a cross-sectional view of cooling fan having an asymmetric trailing edge constructed in accordance with embodiments of the invention;
FIG. 8 shows a cross-sectional view of cooling fan having a variable chord length constructed in accordance with embodiments of the invention;
FIG. 9 shows a cross-sectional view of cooling fan having an extended housing constructed in accordance with embodiments of the invention; and
FIG. 10 shows a cooling fan having a rippled housing constructed in accordance with embodiments of the invention.

NOTATION AND NOMENCLATURE

Certain terms are used throughout the following description and claims to refer to particular system components. As one skilled in the art will appreciate, computer companies may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . .” Also, the term “couple” or “couples” is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection, or through an indirect connection via other devices and connections.

DETAILED DESCRIPTION

The following discussion is directed to various embodiments of the invention. Although one or more of these embodiments may be preferred, the embodiments disclosed should not be interpreted, or otherwise used, as limiting the scope of the disclosure, including the claims. In addition, one skilled in the art will understand that the following description has broad application, and the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to intimate that the scope of the disclosure, including the claims, is limited to that embodiment.
Many computer cooling applications utilize cooling fans that have been designed to minimize the size of the fan. This design methodology results in small fans that face performance limitations, have inherent aerodynamic inefficiencies, and unwanted acoustic emissions. The embodiments described herein illustrate aerodynamic enhancements that can be made to a cooling fan in order to improve performance, efficiency, and/or acoustic emissions. Many of the embodiments described herein will utilize more space than a conventional fan design but the increase in size can be offset by an increase in efficiency of the fan. As it is used herein, an aerodynamically enhanced cooling fan is a cooling fan used in an electronics cooling application that has been designed for aerodynamic performance as opposed to compactness. Aerodynamically enhanced cooling fans are characterized by features that improve aerodynamic performance but also increase the length of the fan including, but not limited to, a conical hub, a recessed blade assembly, an elongated motor, stator and impeller blades, shaped blades, tapered inlet, tapered outlet, and other features that reduce pressure disturbances.
Referring now to FIG. 1, a computer assembly 10 comprises chassis 12, motherboard 14, heat sinks 16, electronic components 18, and aerodynamically enhanced cooling fans 20. Each aerodynamically enhanced cooling fan 20 comprises a housing 22 that extends past and surrounds blade assembly 24. Cooling fans 20 are arranged so as to generate an airflow that cools electronic components 28. Heat sinks 26 may be arranged so as to be directly in the airflow generated by fans 20. Heat sinks 26 are coupled to electronic components so that the heat generated by the electronic component is dissipated to the airflow through the increased surface area of the heat sink.
Cooling fans 20 comprise features that improve the performance of the fan but also increase the length of the fans as compared to conventional fans having the same diameter blades. Conventional fans often maximize the area of the blades by extending the blades to the edge of the housing. Cooling fans 20 incorporate one or more aerodynamic improvements that necessitate the housing 22 extending past the leading edge and/or the trailing edge of the blades. In certain embodiments, housing 22 has a length that is at least 10 mm longer than the distance between the leading edge and the trailing edge of the blades.
FIG. 2 illustrates cooling fan 100 comprising housing 102, blades 104, and conical hub 106. Conical hub 106 projects in front of blades 104 and provides a smooth transition that eliminates pressure disturbances within the flow moving toward the blades. This smooth transition increases pressure performance of the fan. In certain embodiments, hub 106 has length 107 at least twice its diameter 108. Hub 106 may have a smoothly curved tip 109 or may have a more sharply pointed tip but avoids any flat surfaces or abrupt corners that may cause disturbances in the flow. Housing 102 also projects in front of blades 104 so that conical hub 106 is also surrounded by the housing.
FIG. 3 illustrates cooling fan 110 comprising housing 112 and blade assembly 114 that is recessed from housing inlet 116. Blade assembly 114 is recessed a distance 117 of at least one blade diameter 118 from inlet 116. In certain embodiments, a recessed distance 117 of at least two blade diameters 118 is desired. Recessing blade assembly 114 reduces flow disruptions and pressure disturbances at inlet 116 by allowing the flow to straighten and stabilize before contacting the blade assembly. Reducing the flow disruptions also aids in reducing acoustic emissions.
FIG. 4 illustrates cooling fan 120 comprises housing 122, motor 124, and blades 126. The motor diameter 125 is limited by the diameter of hub 121. In order to increase the power provided by motor 124, the length 127 of the motor can be increased. Thus, motor 124 can have a smaller diameter 125 and longer length 127 than a motor with equivalent power in a conventional fan. In certain embodiments, motor 124 has a length at least twice as long as its diameter. Housing 122 extends past the trailing edge of blades 126 so as to surround motor 124. Reducing diameter 125 allows for a reduction in the diameter of hub 121 and a greater area within housing 122 for the surface area of blades 126. Increasing the surface area of blades 126 increases the differential pressure that can be developed by the fan.
FIG. 5 illustrates cooling fan 130 comprising housing 132, motor 134, impeller blades 136 and stator blades 138. Stator blades 138 are offset from impeller blades 136 so that flow moves efficiently between the trailing edge of the impeller blades to the leading edge of the stator blades. The performance of cooling fan 130 may also be improved by impeller blades 136 having a forward swept leading edge 140 and stator blades 138 having a backward sweeping trailing edge 142. FIG. 6 illustrates one shape of a blade 144 having a sweeping edge 146. Other examples of variations in blade shapes are shown in FIGS. 7 and 8. FIG. 7 illustrates a blade 150 having an asymmetrical edge 152. FIG. 8 illustrates a blade 160 having an expanded mid-section 162.
In certain embodiments, multiple blade designs may be used in combination on a single impeller assembly. The number of blades used may also be varied depending on factors such as the speed at which the fan will be operated. These, and various other blade designs and configurations, seek to improve aerodynamic performance of the blades so as to increase fan performance and/or decrease acoustic emissions. It is also understood that the blade designs described herein can be used with other fan configurations, including conventionally sized cooling fans.
Aerodynamic improvements may also be realized by varying the configuration of a fan housing. FIG. 9 illustrates a cooling fan 170 having a tapered inlet 172 and a tapered outlet 174. Tapered inlet 172 acts to converge the flow moving toward blades 176. The convergence of flow through tapered inlet 172 increases the pressure of the flow as it approaches blades 176 and allows the fan to operate at a higher pressure. Tapered inlet 172 also provides a smooth, gradual transition that can reduce acoustic emissions by reducing sudden pressure disturbances. Pressure disturbances can also cause pressure losses that reduce the efficiency of the fan. Therefore, reducing sudden pressure disturbances may help to reduce acoustic emissions and increase the efficiency of the fan by reducing losses caused by the pressure disturbances.
On the opposite end of fan 170, outlet 174 provides a gradual transition in diameter that allows the flow to smoothly expand as it moves away from blades 176. The smooth, gradual transition can help reduce acoustic emissions by reducing sudden pressure disturbances. Pressure disturbances can also cause pressure losses that reduce the efficiency of the fan. Therefore, reducing sudden pressure disturbances may help to reduce acoustic emissions and increase the efficiency of the fan by reducing losses caused by the pressure disturbances.
In another embodiment, as shown in FIG. 10, housing 180 may have “ripples” 182 near the edges of the housing. Ripples 182 reduce sudden pressure disturbances in the flow as it exits housing 180. Pressure disturbances can cause unwanted acoustic emissions may create pressure losses that reduce the efficiency of the fan. Therefore, reducing sudden pressure disturbances may help to reduce acoustic emissions and increase the efficiency of the fan by reducing losses caused by the pressure disturbances.
The above discussion is meant to be illustrative of the principles and various embodiments of the present invention. Numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. For example, the aerodynamic features described herein may be applied to other types of axial fans used to cool electronic components. It is intended that the following claims be interpreted to embrace all such variations and modifications.

Claims

1. A cooling fan comprising:

a fan housing that connects to a chassis supporting an electronic device;

a motor disposed within said fan housing; and

a blade assembly rotatably coupled to said motor, wherein said fan housing has a length at least 10 mm longer than a distance between a leading edge and a trailing edge of said blade assembly.

2. The cooling fan of claim 1 wherein the conical hub has a diameter at least twice its length.

3. The cooling fan of claim 1 wherein said blade assembly is recessed from an inlet disposed on said housing.

4. The cooling fan of claim 3 wherein said blade assembly is recessed from the inlet a distance at least equal to a diameter of said blade assembly.

5. The cooling fan of claim 1 wherein said motor has a length at least twice its diameter.

6. The cooling fan of claim 1 further comprising a plurality of stator blades fixably disposed within said housing such that an airflow generated by said blade assembly passes over said stator blades.

7. The cooling fan of claim 6 wherein said stator blades have a backward sweeping trailing edge and the blades of said blade assembly have a forward swept leading edge.

8. The cooling fan of claim 1 wherein the blades of said blade assembly have an asymmetrical trailing edge.

9. The cooling fan of claim 1 wherein the blades of said blade assembly have an expanded mid-section.

10. The cooling fan of claim 1 wherein said fan housing has a tapered inlet.

11. The cooling fan of claim 1 wherein said fan housing has a tapered outlet.

12. The cooling fan of claim 1 wherein said fan housing comprises disturbance reducing ripples disposed near an outlet.

13. A computer system comprising:

a chassis;

an electronic component disposed within said chassis; and

an aerodynamically enhanced cooling fan disposed within said chassis, wherein said cooling fan comprises a fan housing that connects to said chassis, wherein said fan housing said fan housing has a length at least 10 mm longer than a distance between a leading edge and a trailing edge of a blade assembly disposed within the housing.

14. The computer system of claim 13 wherein the blade assembly is rotatably coupled to a motor and comprises a plurality of blades extending radially from a conical hub having a diameter at least twice its length.

15. The computer system of claim 13 wherein said blade assembly is recessed from an inlet disposed on said housing a distance at least equal to a diameter of said blade assembly.

16. The computer system of claim 13, wherein said aerodynamically enhanced cooling fan comprises further comprises a plurality of stator blades fixably disposed within said housing such that an airflow generated by said blade assembly passes over said stator blades.

17. The computer system of claim 13, wherein said fan housing has a tapered inlet and a tapered outlet.

18. A cooling fan comprising:

means for connecting the fan to a chassis supporting an electronic device;

means for rotating a blade assembly; and

means for reducing pressure disturbances in a flow of air through the fan, wherein said means for reducing pressure disturbances comprises a fan housing having a length at least 10 mm longer than a distance between a leading edge and a trailing edge of the blade assembly.

19. The cooling fan of claim 18 wherein said means for reducing pressure disturbances comprises at least one aerodynamic enhancement to the blade assembly selected from the group consisting of a blade having a sweeping edge, a blade having an asymmetrical edge, and a blade having an expanded mid-section.

20. The cooling fan of claim 18 wherein said means for reducing pressure disturbances comprises an aerodynamic enhancement to the fan housing selected from the group consisting of a tapered inlet, a tapered outlet, and ripples in an edge of the housing at an outlet.