1. Field
A centrifugal fan is disclosed herein.
2. Background
A centrifugal fan is a fan that accelerates air introduced in an axial direction through a shroud and discharges the air in a radial direction through gaps between blades. Performance of the centrifugal fan is affected by various shape factors, as well as friction loss, shock loss and the like. Representative examples of factors having an effect on the performance of the centrifugal fan include a speed of the centrifugal fan, the shape, angle or number of blades, and the shape of a shroud.
Among the aforementioned factors, in particular, the shape of blades is important because it may contribute to enhancement in the performance of the centrifugal fan without a great change in an entire size or standard of the centrifugal fan. In recent years, studies to acquire desired performance by changing the shape of blades in various ways have been actively conducted.
Japanese Patent Laid-open Publication No. 2000-45997 discloses a blade formed by bending a single metal sheet. In the above patent, the blade formed by bending a single metal sheet has an airfoil cross section. More particularly, the blade has a three dimensional shape in which a leading edge of the blade has a prescribed inclination relative to a rotational axis of a centrifugal fan and a trailing edge of the blade is parallel to the rotational axis. However, as exemplarily shown in the above patent, respective airfoil cross sections of the blade taken at arbitrary layers perpendicular to the rotational axis have a common camber line. For example, although a lower edge of the blade bonded to a main plate has the longest camber line and an upper edge of the blade coming into contact with a shroud has the shortest camber line, the camber line at the upper edge completely overlaps the camber line at the lower edge. In the blade having the above-described shape, since inlet angles for outlet angles) at respective cross sections are substantially the same, enhancement in efficiency of the fan is limited, and in particular, it is difficult to compensate for a difference of flow characteristics between an upper portion and a lower portion of the blade.
It is one object to provide a centrifugal fan capable of achieving enhanced performance via improvement in the shape of a blade.
It is another object to provide a centrifugal fan capable of being applied to lamer products than in the related art.
It is another object to provide a centrifugal fan capable of achieving reduced flow resistance, more particularly, enhanced efficiency via improvement in the shape of a blade.
It is another object to provide a centrifugal fan capable of discharging an even volume of air from a shroud and from a main plate.
It is another object to provide a centrifugal fan capable of increasing static pressure beyond that in the related art.
It is another object to provide a centrifugal fan in which an upper portion of a blade includes a section that is concave toward a rotation axis and a lower portion of the blade includes a section that is convex in a direction opposite to the rotation axis, whereby airflow at the lower portion of the blade is reinforced and even airflow between the upper and lower portions of the blade is accomplished.
It is another object to provide a centrifugal fan capable of reducing noise.
It is a further object of to provide, a centrifugal fan capable of restricting flow separation from a rear edge of a blade.
In accordance with one embodiment, the above and other objects can be accomplished by the provision of a centrifugal fan including a main plate configured to be rotated about a rotation axis, a shroud having a suction opening through which air is suctioned, and a plurality of blades arranged in a circumferential direction between the main plate and the shroud to allow the air suctioned through the suction opening to flow from a front edge to a rear edge of each blade, wherein, assuming a first cross section, a second cross section, a third cross section and a fourth cross section of each blade sequentially taken at layers from the shroud to the main plate, a front edge of the first cross section is located farther from the rotation axis than a front edge of the fourth cross section, and a rear edge of the first cross section is located closer to the rotation axis than a rear edge of the fourth cross section, and wherein, among rear edges of the respective cross sections, the rear edge of the second cross section is located farthest away from the rotation axis and the rear edge of the third cross section is closest to the rotation axis.
The front edge of the first cross section of the blade may be located ahead of the front edge of the fourth cross section in a direction opposite to a rotation direction of the main plate. Among front edges of the respective cross sections, the from edge of the first cross section may be located at the foremost position in the direction opposite to the rotation direction of the main plate.
The rear edge of the first cross section may be located ahead of the rear edge of the fourth cross section in the direction opposite to the rotation direction of the main plate. Among the respective cross sections of the blade, the rear edge of the first cross section may be located at the foremost position in the direction opposite to the rotation direction of the main plate.
The front edge of the third cross section of the blade may be located ahead of the front edge of the fourth cross section in a rotation direction of the main plate. The rear edge of the third cross section of the blade may be located ahead of the rear edge of the fourth cross section in the rotation direction of the main plate.
An angle between a straight line interconnecting the front edge and the rear edge of the blade and a straight line interconnecting the rear edge and the rotation axis may have a maximum value at the first cross section among the respective cross sections.
When the respective cross sections of the blade are projected onto a common projection plane in a direction of the rotation axis, a straight line interconnecting the front edge and the rear edge of the first cross section may cross all straight lines interconnecting the front edges and the rear edges of the respective cross sections.
The first cross section may meet the shroud at the rear edge thereof.
The fourth cross section may be a portion of the blade where the blade meets the main plate.
A cross section of the blade between the front edge and the rear edge thereof may take the form of an airfoil.
In accordance with another embodiment, a centrifugal fan including a main plate configured to be rotated about a rotation axis, a shroud having a suction opening through which air is suctioned, and a plurality of blades arranged in a circumferential direction between the main plate and the shroud to allow the air suctioned through the suction opening to flow from a front edge to a rear edge of each blade, wherein, assuming a first cross section, a second cross section, a third cross section and a fourth cross section of each blade sequentially taken at planar layers, perpendicular to the rotation axis, from the shroud to the main plate, the rear edge of the blade between the first cross section and the second cross section gradually becomes farther away from the rotation axis, the rear edge of the blade between the second cross section and the third cross section gradually approaches the rotation axis, and the rear edge of the blade between the third cross section and the fourth cross section again gradually becomes farther away from the rotation axis.
Among rear edges of the respective cross sections, the rear edge of the second cross section may be located farthest away from the rotation axis.
Among rear edges of the respective cross sections, the rear edge of the third cross section may be located at the foremost position in a rotation direction of the main plate.
Among rear edges of the respective cross sections, the rear edge of the first cross section may be located at the foremost position in a direction opposite to a rotation direction of the main plate.
A distance between the second cross section and the third cross section may be greater than a distance between the first cross section and the second cross section.
In accordance with a further embodiment, a centrifugal fan including a main plate configured to be rotated about a rotation axis, a shroud having a suction opening through which air is suctioned, and a plurality of blades arranged in a circumferential direction between the main plate and the shroud to allow the air suctioned through the suction opening to flow from a front edge to a rear edge of each blade, wherein a longitudinal cross section of the blade taken in a direction of the rotation axis is convex in a direction opposite to the rotation axis at a portion of the blade near the shroud and is convex toward the rotation axis at a portion of the blade near the main plate.
The blade may include a portion in which the front edge becomes farther away from the rotation axis with decreasing distance to the shroud.
Assuming prescribed two cross sections sequentially taken at planar layers, perpendicular to the rotation axis, from the shroud to the main plate, the two cross sections projected onto a prescribed projection plane along the rotation axis may cross each other. Among the two cross sections of the blade, one cross section closer to the shroud than the other cross section may further cross a cross section having the longest distance from a rear edge thereof to the rotation axis included in the portion that is convex in the direction opposite to the rotation axis and a cross section having the shortest distance from a rear edge thereof to the rotation axis included in the portion that is convex toward the rotation axis. Among the two cross sections of the blade, a front edge of the cross section closer to the shroud may be located farther from the rotation axis than a front edge of the other cross section closer to the main plate, and the rear edge of the cross section closer to the shroud may be located closer to the rotation axis than the rear edge of the other cross section closer to the main plate. The rear edge of the cross section closer to the shroud may be located ahead of the rear edge of the other cross section closer to the main plate in a direction opposite to a rotation direction of the main plate.
The blade may include a positive pressure surface forming member configured to form a positive pressure surface and a negative pressure surface forming member configured to form a negative pressure surface.
According to embodiments, a centrifugal fan has the effect of achieving enhanced performance through improvement in the shape of a blade. In particular, the centrifugal fan has the effect of achieving enhanced efficiency owing to less flow resistance than in the related art.
In addition, through enhancement in the efficiency of the fan, lower speed operation of the centrifugal fan than in the related art on the basis of the same air volume is possible. This has the effect of facilitating application of the centrifugal fan to large products.
In addition, as a portion of the blade close to a shroud and a portion of the blade close to a main plate have different shapes, it is possible to deal with different airflow characteristics between the blade portion close to the shroud and the blade portion close to the main plate in an optimized manner. This has the effect of enhancing the efficiency of the fan. Furthermore, the centrifugal fan has the effect of achieving a more even air velocity at the shroud and at the main plate than in the related art and, consequently, achieving noise reduction.
In addition, the centrifugal fan has the effect of increasing static pressure beyond that in the related art.
In addition, the centrifugal fan has the effect of implementing lower speed operation than in the related art on the basis of the same air volume
In addition, the centrifugal fan has the effect of achieving an even air volume between an upper portion and a lower portion of the blade via guidance of airflow to the main plate and reinforcing airflow to a negative pressure surface at the upper portion of the blade, thereby restricting flow separation.
In addition, the centrifugal fan has the effect of preventing flow separation at a rear edge of the blade, more particularly, at a portion of the blade close to the shroud.