JP2004027894A - Open impeller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an open impeller for realizing high efficiency by reducing clearance flow with a simple means. <P>SOLUTION: A plurality of blades 2 are constantly spaced at prescribed intervals on an outer periphery of a hub 1, and gas taken in the impeller due to rotation of the blades is mainly compressed by a centrifugal force and discharged to the outside. An outside free end (blade end) 3 of the blade 2 is formed in a manner that thickness t<SB>2</SB>of a latter half part (downstream side of gas flow) is thicker than thickness t<SB>1</SB>of a first half part (upstream side of gas flow). <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an open impeller used for a centrifugal compressor, a blower, and the like.
[0002]
[Prior art]
As shown in FIG. 3, this type of impeller has a plurality of blades 101 arranged on an outer periphery of a hub 100 at a predetermined interval, and the rotation of the blade 101 allows a gas sucked from a gas inlet portion 103 of a housing 102 to be removed. It is compressed mainly by centrifugal force and is discharged from the flow path 104 of the housing 102 to the outside.
[0003]
In the open impeller, a clearance is provided between the inner wall surface 102a of the housing 102 and the outer free edge (wing tip) 101a of the wing 101 because there is no side plate (cover) inevitably in structure.
[0004]
[Problems to be solved by the invention]
Therefore, during operation, due to the pressure difference between the pressure surface P side and the suction surface S side of the blade 101, the leakage flow flowing through the clearance (see the arrow near the outer free edge 101a in FIG. However, there is a problem that the loss increases due to interference with the mainstream and the efficiency decreases.
[0005]
As a countermeasure against this, it is conceivable to reduce the clearance as much as possible. However, there is naturally a limit in preventing contact (interference) between the outer free edge 101a of the wing 101 and the inner wall surface 102a of the housing 102 during operation. Further, a coating having high machinability may be applied to the inner wall surface 102a of the housing 102, or a device for adjusting the clearance during operation may be used, but these have a disadvantage that the cost increases.
[0006]
The present invention has been proposed in view of such circumstances, and an object of the present invention is to provide an open impeller that can reduce the clearance flow by simple means and achieve high performance.
[0007]
[Means for Solving the Problems]
An open impeller according to the present invention for achieving the above object has a thickness of an outer free edge of the wing in the open impeller having a plurality of blades arranged on an outer periphery of a hub at predetermined intervals. Is characterized by the fact that the latter half is thicker than the first half as the blade load increases.
[0008]
The wing is thickened at 30% or more of the meridian length of the wing.
[0009]
Also, the wing is characterized in that it is two to three times thicker in the latter half than in the first half.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an open impeller according to the present invention will be described in detail using embodiments with reference to the drawings.
[0011]
[Example]
FIG. 1 is a structural explanatory view of an open impeller showing an embodiment of the present invention. FIG. 1 (a) is a side sectional view, FIG. 1 (b) is a front view, and FIG. FIG.
[0012]
As shown in FIG. 1, a plurality of blades 2 are equally arranged on the outer periphery of a hub 1 at predetermined intervals, and the gas sucked into the impeller by its rotation is compressed mainly by centrifugal force and discharged to the outside. Has become.
[0013]
The outer free edge of the blade 2 (tip) 3, as shown in FIG. 2, among which, (upstream of the gas flow) rear half thickness t ₂ is the first half of the (gas downstream side of the flow) It is thicker than the thickness t ₁ of the.
[0014]
In the illustrated example, the formed to be thicker at 30% since the meridian length _{m s} of the blade _{2 (m> 0.3m s),} 2 times than less than 30% of its thickness even meridian length _{m s} to 3 (T ₂ > _{2 to} 3t ₁ ).
[0015]
With this configuration, when the open impeller is operated, the flow is diverted from the axial direction to the radial direction, and the gas is pressurized using centrifugal force. At this time, in the latter half of the impeller (where the flow changes from the axial direction to the radial direction), the pressure difference between both sides (the pressure surface side and the suction surface side) of the blade 2 is large, and the clearance flow tends to be strong.
[0016]
Accordingly, in this embodiment, it is formed to be thicker at 30% since the meridian length m _s of the blade 2 has a two to three times more than 30% of its thickness even meridian length m _s Therefore, the passage resistance of the above-described clearance (see the clearance between the inner wall surface 102a of the housing 102 and the outer free edge (wing tip) 101a of the wing 101 in FIG. 3) increases.
[0017]
As a result, the clearance flow is reduced by a simple means of changing the blade thickness, and the performance of the open impeller is improved.
[0018]
It is needless to say that the present invention is not limited to the above embodiment, and various changes can be made without departing from the spirit of the present invention. For example, in the above embodiment, the thickness is changed only at a predetermined portion of the outer free edge (wing tip) 3 of the wing 2, but the thickness may be changed to the full height of the wing 2. Further, the thickness may be provided by another member.
[0019]
【The invention's effect】
As described above in detail based on the embodiments, the invention according to claim 1 of the present invention relates to an open impeller having a plurality of blades arranged on a periphery of a hub at predetermined intervals. The thickness of the outer free edge of the wing is made thicker in the latter half than in the first half as the wing load increases, so that the clearance flow can be reduced by simple means to achieve higher performance.
[0020]
Further, in the invention according to claim 2, since the thickness is increased after 30% of the meridian length of the wing, the same operation and effect as in claim 1 can be more effectively obtained.
[0021]
In the invention according to claim 3, since the thickness of the wing is two to three times larger in the latter half than in the first half, the same operation and effect as in claim 1 can be obtained more effectively.
[Brief description of the drawings]
FIG. 1 is a structural explanatory view of an open impeller showing an embodiment of the present invention, wherein FIG. 1 (a) is a side sectional view and FIG. 1 (b) is a front view.
FIG. 2 is a view taken in the direction of arrows BB in FIG.
FIG. 3 is a structural explanatory view of a conventional open impeller, wherein FIG. 3 (a) is a side sectional view, and FIG. 3 (b) is a sectional view taken along line AA of FIG. 3 (a).
[Explanation of symbols]
1 the thickness of the hub 2 wings 3 outer free edges m _s meridian length t ₁ the first half of the blade of the blade in the thickness t ₂ wing (gas upstream side of the flow), the second half portion (the downstream side of the gas flow)

Claims (3)

In an open impeller having a plurality of blades arranged at predetermined intervals on the outer periphery of a hub, the thickness of the outer free edge of the blade is larger in the latter half than in the first half while the blade load is increased. An open impeller characterized by: 2. The open impeller according to claim 1, wherein the thickness is increased after 30% of the meridian length of the wing. The open impeller according to claim 1, wherein the wing has a thickness that is two to three times greater in a rear half part than in a front half part.

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