Fan modules and server equipment

Inactive Publication Date: 2013-02-28
HITACHI LTD
0 Cites 8 Cited by

AI-Extracted Technical Summary

Problems solved by technology

In addition, since the conventional technology premises the series configuration of the two axial flow fans, there is a ...
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Method used

[0048]The axial flow fan mounted in the information instrument is used under the conditions different from originally assumed conditions. Therefore, an amount of airflow and static pressure are reduced.
[0049]If the fan module 1 shown in FIG. 1 is used to cool a variety of information instruments similarly to the conventionally used axial flow fan, airflow disturbed by the resistor bodies (specific examples are described later but they mean objects to be cooled in e.g. server equipment) located on the upstream side of the fan module is straightened by the stator 2. Thereafter, the airflow thus straightened enters the axial flow fan 3. In this way, disturbed airflow does not enter the axial flow fan 3. Thus, possible noise can be suppressed. Even in the state where the axial flow fan is mounted in the information instrument, the axial flow fan is improved to meet the inflow conditions assumed when designing the axial flow fan. Thus, the amount of airflow and static pressure of the axial flow fan mounted in the information instrument are increased compared with an axial flow fan not provided with a stator on the upstream side thereof.
[0051]To address the concern noise, a second embodiment focuses on a positional relationship between the stator vanes 22 and the rotor vanes 32. This suppresses increase in the noise of frequencies resulting from the number of the rotor vanes 32 or the stator vanes 22.
[0056]With this configuration, the rotor vane 32 constantly passes the stator vane 22 only at a single point. Therefore, an area where the interference between the rotor vane and the stator vane occurs simultaneously can be minimized. This can produce an effect of suppressing an increase in the sound pressure level of each frequency component of noises resulting from the number of the rotor vanes 32 or the stator vanes 22. FIG. 8 is a graph showing the effect of the second embodiment. FIG. 8 can confirm the fact that the fan module of the second embodiment shown in FIG. 7 can reduce the noise of vane passing frequency (the sound pressure level) resulting from the number of the rotor vanes or the stator vanes. If the second embodiment is implemented, the sound pressure level is lowered as a whole compared with the case that the second embodiment is not implemented. Incidentally, if “order of vane passing frequency” of the horizontal axis in FIG. 8 is n-order, a relationship is such that “noise frequency”/(“the rotation number of the axial flow fan”דthe number of vanes”)=n.
[0057]In a third embodiment, a configuration in which the direction of airflow is changed by stator van...
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Benefits of technology

[0022]The present invention can provide a fan module that can achieve a balance between...
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Abstract

A fan module and server equipment are provided that can achieve a balance between increased airflow and noise reduction when an axial flow fan is mounted in the server equipment.
The fan module for taking in and discharging air includes a stator located on an upstream side with respect to airflow and an axial flow fan located on the downstream side. When the fan module is viewed from the rotational-axial direction of the axial flow fan, if a leading edge of a rotor vane constituting part of the axial flow fan passes a trailing edge of a stator vane constituting part of the rotor, a skew is formed in which the leading edge of the rotor vane constantly intersects the leading edge of the rotor vane at a single point.

Application Domain

Pump componentsStators +9

Technology Topic

Trailing edgeAirflow +6

Image

  • Fan modules and server equipment
  • Fan modules and server equipment
  • Fan modules and server equipment

Examples

  • Experimental program(10)

Example

First Embodiment
[0046]A first embodiment is described with reference to FIGS. 4, 5 and 6. FIG. 4 is an explanatory view showing a state of airflow entering the axial flow fan exposed to the atmosphere. FIG. 5 is an explanatory view showing a state of airflow entering the axial flow fan mounted in an information instrument. FIG. 6 is a graph showing a comparison in velocity distribution of airflow entering the axial flow fan between when the axial flow fan is exposed to the atmosphere and when it is mounted in the information instrument.
[0047]In cooling a variety of information instruments, resistor bodies such as boards which disturb airflow are generally located on the upstream side of a cooling fan. If the airflow thus disturbed by these resistor bodies enters the cooling fan mounted in an information instrument, noises are generated. As shown in FIG. 4, general-purpose small-sized axial flow fans are presupposed to be used under atmosphere-exposure conditions; therefore, they are designed under the assumption that airflow a1 enters the axial flow fan not only from a rotational-axial direction but from a direction perpendicular to the rotational-axial direction. On the other hand, the axial flow fan mounted in the information instrument has a restricted flow passage; therefore, airflow a2 enters the axial flow fan only from the rotational-axial direction as shown in e.g. FIG. 5. If distributions in airflow velocity in the rotational-axial direction are compared between the conditions of airflow into the axial flow fan as described above, the results are as shown in FIG. 6. In FIG. 6, an intersection between a vertical axis and a transverse axis corresponds to the position of radius 0 of the axial flow fan (i.e., the position of the center of the axial flow fan). As seen from FIG. 6, in the case of the axial flow fan mounted in the information instrument (the solid line in FIG. 6), the velocity of airflow in a rotational-axial direction is averagely increased because of the restricted flow passage. In other words, the average value of the velocity distribution of airflow entering the axial flow fan mounted in the information instrument is greater than that of the airflow entering the axial flow fan exposed to the atmosphere.
[0048]The axial flow fan mounted in the information instrument is used under the conditions different from originally assumed conditions. Therefore, an amount of airflow and static pressure are reduced.
[0049]If the fan module 1 shown in FIG. 1 is used to cool a variety of information instruments similarly to the conventionally used axial flow fan, airflow disturbed by the resistor bodies (specific examples are described later but they mean objects to be cooled in e.g. server equipment) located on the upstream side of the fan module is straightened by the stator 2. Thereafter, the airflow thus straightened enters the axial flow fan 3. In this way, disturbed airflow does not enter the axial flow fan 3. Thus, possible noise can be suppressed. Even in the state where the axial flow fan is mounted in the information instrument, the axial flow fan is improved to meet the inflow conditions assumed when designing the axial flow fan. Thus, the amount of airflow and static pressure of the axial flow fan mounted in the information instrument are increased compared with an axial flow fan not provided with a stator on the upstream side thereof.

Example

Second Embodiment
[0050]As shown in FIG. 1, the fan module 1 has the stator 2 disposed immediately in front of the axial flow fan 3. The rotor vanes 32 are rotated along with the rotation of the boss 31 to which the motor of the axial flow fan 3 is attached. The rotation of the rotor vanes 32 causes interference with the stator vanes 22 of the stator. Thus, there is concern about increased noise of frequencies resulting from the number of the rotor vanes 32 or of the stator vanes 22.
[0051]To address the concern noise, a second embodiment focuses on a positional relationship between the stator vanes 22 and the rotor vanes 32. This suppresses increase in the noise of frequencies resulting from the number of the rotor vanes 32 or the stator vanes 22.
[0052]FIG. 7 partially shows the fan module 1 as viewed from the upstream side of airflow in the rotational-axial direction of the rotor vanes 32. As described earlier, the interference between the rotor vanes 32 and the stator vanes 22 occurs when the rotor vane 32 rotating in the direction of an arrow in FIG. 7 passes the stator vane 22 at rest.
[0053]In FIG. 7, circles 41, 42 have different radii and are concentric with the boss 21 of the stator 2. A point of intersection between the circle 41 and the stator vane 22 is assumed as a point 43. A point of intersection between the circle 42 and the stator vane 22 is assumed as a point 44. A point of intersection between the circle 41 and the rotor vane 32 is assumed as a point 45. A point of intersection between the circle 42 and the rotor vane 32 is assumed as a point 46. A line segment connecting the point 43 with the point 44 is assumed as a line 47, and a line segment connecting the point 45 with the point 46 is assume as a line 48. The fan module in the second embodiment is configured such that if the point 43 and the point 45 are superimposed on each other on the circle 41 or the point 44 and the point 46 are superimposed on each other on the circle 42, the line 47 is not coincident with the line 48. This non-coincident configuration means a state where as shown in e.g. FIG. 7, if the point 46 on the rotor vane 32 shifts to a position superimposed on the point 44 on the stator vane, another point 45′ on the rotor vane 32 is not superimposed on the point 43 on the stator vane.
[0054]More specifically, the fan module taking in and discharging air is characteristically configured as below. The fan module includes the stator located on the upstream side with respect to airflow and the axial flow fan located on the downstream side. When the fan module is viewed from the rotational-axial direction of the axial flow fan, if two virtual concentric circles having different radii are assumed, a trailing edge of a stator vane constituting part of the stator and a leading edge of a rotor vane constituting part of the axial flow fan each have two points of intersections with the two concentric circles. A straight line connecting the two points of intersection on the trailing edge of the stator vane and a straight line connecting the two points of intersection on the leading edge of the rotor vane are configured as below. If, on one of the two concentric circles, one point of intersection on the trailing edge of the stator vane is superimposed on the point of intersection on the leading edge of the rotor vane, on the other of the two concentric circles, the other point of intersection on the trailing edge of the stator vane is not coincident with the other point of intersection on the leading edge of the rotor vane.
[0055]Further, when the leading edge of the rotor vane passes the trailing edge of the stator vane, a skew is formed in which the leading edge of the rotor vane constantly intersects the leading edge of the rotor vane at a single point.
[0056]With this configuration, the rotor vane 32 constantly passes the stator vane 22 only at a single point. Therefore, an area where the interference between the rotor vane and the stator vane occurs simultaneously can be minimized. This can produce an effect of suppressing an increase in the sound pressure level of each frequency component of noises resulting from the number of the rotor vanes 32 or the stator vanes 22. FIG. 8 is a graph showing the effect of the second embodiment. FIG. 8 can confirm the fact that the fan module of the second embodiment shown in FIG. 7 can reduce the noise of vane passing frequency (the sound pressure level) resulting from the number of the rotor vanes or the stator vanes. If the second embodiment is implemented, the sound pressure level is lowered as a whole compared with the case that the second embodiment is not implemented. Incidentally, if “order of vane passing frequency” of the horizontal axis in FIG. 8 is n-order, a relationship is such that “noise frequency”/(“the rotation number of the axial flow fan”דthe number of vanes”)=n.

Example

Third Embodiment
[0057]In a third embodiment, a configuration in which the direction of airflow is changed by stator vanes is added to that of the first or second embodiment to thereby increase the amount of airflow in a fan module mounted in server equipment such as an information instrument. FIG. 9 is a schematic cross-sectional view of a fan module of the third embodiment, showing a positional relationship between a stator vane 22 and a rotor vane 32. The stator vane 22 of a stator and the rotor vane 32 of an axial flow fan are arranged from the upstream side of airflow. The rotor vane 32 is rotated in a rotational direction R. The stator vane 22 is warped in a U-shape in cross-section relative to the rotational direction R.
[0058]A velocity component 51 of airflow entering the fan module is changed in direction by the stator vane 22 and turned to a velocity component 52 of the airflow, which enters the rotor vane 32. In other words, because of the presence of the stator vane 22, the airflow having a velocity component 54 which is a circumferential velocity in a direction reverse to the rotational direction R enters the rotor vane 32. In short, the stator vane applies a reverse pre-swirl to the rotor vane. In general, an axial flow fan is designed under the assumption that the airflow entering the rotor vane has no circumferential velocity component. However, if the axial flow fan is mounted in a variety of information instruments or the like for use, airflow is disturbed; therefore, the airflow having a circumferential velocity component which has the same direction as the rotational direction of the axial flow fan enters the axial flow fan. Incidentally, a velocity component 53 of the airflow has the same direction and magnitude as those of the velocity component 51 of airflow entering the fan module.
[Expression 1]
Pth=ρ(Cu2u2−Cu1u1)  expression 1
[0059]Pth: Theoretical total pressure
[0060]ρ: Density
[0061]Cu1: Swirl velocity at rotor vane inlet
[0062]Cu2: Swirl velocity at rotor vane outlet
[0063]u1: Circumferential velocity at rotor vane inlet
[0064]u2: Circumferential velocity at rotor vane outlet
[0065]Expression 1 is an expression representing the theoretical total pressure of the axial flow fan. According to this expression, the theoretical total pressure of the axial flow fan is obtained by multiplying a value by the air density ρ, such a value being obtained by reducing the product of the swirl velocity Cu1 which is the circumferential velocity component at the axial flow fan inlet and the rotating velocity u1 from the product of the swirl velocity Cu2 which is the circumferential velocity component at the axial flow fan outlet and the rotating velocity u2. This expression shows that if the airflow entering the axial flow fan has a circumferential velocity component in the same direction as the rotational direction of the axial flow fan, the total pressure of the axial flow fan is lowered. On the other hand, the stator vane 22 of the third embodiment allows the airflow having the circumferential velocity component in a direction reverse to the rotational direction R of the rotor vane 32 to enter the rotor vane 32. According to expression 1, such airflow increases the theoretical total pressure of the axial flow fan, which leads to increased static pressure and also to the increased amount of airflow.

PUM

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Description & Claims & Application Information

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