JP2004353607A - Centrifugal compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a centrifugal compressor capable of increasing an assembly performance and an efficiency by effectively reinforcing an impeller by a shroud. <P>SOLUTION: In this centrifugal compressor, air sucked by the rotation of the impeller 2 pivotally supported on a casing 1A is compressed and exhausted mainly by a centrifugal force. Spaces between the tips of the blades 6 of the impeller 2 are reinforced by the annular shroud 7, and the position of the trailing edge of the shroud 7 in the axial direction of the impeller is set to the intermediate part of a meridian length in a range from the air inlet part 3 of the impeller 2 to the air outlet part 4 of the impeller 2 along the tips of the blades. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a centrifugal compressor used for a supercharger, a gas turbine, an industrial compressor, or the like, and more particularly, to a centrifugal compressor provided with an impeller in which a tip of each blade is reinforced by an annular shroud. .
[0002]
[Prior art]
As shown in FIG. 3, the impeller (impeller) of this type of centrifugal compressor has a plurality of blades 101 arranged on the outer periphery of a hub 100 at predetermined intervals, and is sucked into the impeller by rotation. Gas (gas) such as air is compressed mainly by centrifugal force and discharged (discharged) to the outside.
[0003]
As shown in FIG. 3, the impeller is usually manufactured by integral machining (open impeller) by machining (for example, see Non-Patent Document 1), and particularly, the impeller has an outer diameter of 1 m or more. In the case of a large-diameter impeller, the blades are sometimes manufactured with a welded structure because the integral shaving increases the cost.
[0004]
In such an impeller, in order to secure the strength of the blade, an annular shroud 102 is fixed to the tip of the blade 101 over the entire meridional length of the tip of each blade as shown in FIG. (See, for example, Non-Patent Document 1).
[0005]
If the shroud 102 is fixed over the entire length of the meridional plane at the tip of each wing, the rotational speed of the impeller cannot be increased due to an increase in vibration or the like. Therefore, as shown in FIG. The length of the meridional plane at the tip of each wing is set to be shorter than about 30% from the leading edge of the wing, so that the wing is strengthened as before, vibration is suppressed, and efficiency is increased by increasing the speed of the impeller. (For example, see Non-Patent Document 2).
[0006]
[Non-patent document 1]
Journal of Turbomachinery JANUARY 1987, Vol. 109 (p. 42, FIG. 2 (b), FIG. 2 (a))
[Non-patent document 2]
Hitachi Review Vol. 79 No. 12 (1997-12) (p. 72, Table 2)
[0007]
[Problems to be solved by the invention]
By the way, in the impeller as shown in FIG. 5, a step is formed at the trailing edge of the shroud 102, and as it is, gas leaks from the pressure surface side of the blade 101 to the negative pressure surface side through the relevant portion, and the efficiency is reduced. Will drop.
[0008]
Therefore, the inner surface of the casing 103 is cut down (see the cut-down portion 103a) so as to fill the above-mentioned portion. However, in this case, when the casing 103 is formed by integral casting to improve the assemblability, the casing 103 is formed from the impeller axial direction. Since the casing 103 cannot be fitted, it is necessary to assemble a half casing 103, and there is a problem that it is not possible to reduce the manufacturing cost and improve the assembling property.
[0009]
As a countermeasure, it is conceivable to divide the shroud 102 in the circumferential direction and install the shroud 102 between the respective wings 101 without protruding outward from the wing tip. However, in this case, a separation flow occurs on the rear surface of each shroud 102, Since this is added to the separation flow originally generated at the tip of each blade 101, it cannot be adopted at all.
[0010]
Therefore, an object of the present invention is to provide a centrifugal compressor in which the impeller can be effectively reinforced with a shroud to improve assemblability and increase efficiency.
[0011]
[Means for Solving the Problems]
A centrifugal compressor according to the present invention for achieving this object is a centrifugal compressor that compresses and discharges gas mainly by centrifugal force by rotation of an impeller supported by a casing. An annular shroud was reinforced between the tips, and the position of the trailing edge with respect to the impeller axial length of the shroud was set from the impeller inlet to the middle part of the meridional plane length from each impeller tip to the impeller outlet. It is characterized by the following.
[0012]
Further, the rear edge of the shroud is in contact with each of the blade tips with as few steps as possible.
[0013]
Further, the intermediate portion of the meridional plane length is located at a position of 30% to 60% from the leading edge of the wing.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a centrifugal compressor according to the present invention will be described in detail using embodiments with reference to the drawings.
[0015]
[Example]
FIG. 1 is a cross-sectional view of a main part of a centrifugal compressor showing one embodiment of the present invention, and FIG. 2 is a pressure distribution diagram along the inner surface of the casing along the meridional length of the blade.
[0016]
As shown in FIG. 1, an impeller (impeller) 2 is rotatably supported in one casing 1 </ b> A, and the air sucked from an air (gas) inlet 3 into the impeller 2 by the rotation of the impeller 2. It is compressed and discharged mainly to the air (gas) outlet 4 of the impeller 2 by centrifugal force, and is sent from there to a predetermined external device.
[0017]
The impeller 2 has a plurality of blades 6 made of a thin plate which are fixed to the outer periphery of a hub 5 by welding or the like at predetermined intervals in the circumferential direction, and the tip of each blade 6 is reinforced by an annular shroud 7. Be done.
[0018]
The position of the trailing edge with respect to the length of the shroud 7 in the impeller axial direction is the middle of the meridional plane length from the impeller inlet (air inlet 3) to the impeller outlet (air outlet 4) along the tip of each blade 6. Portion (at a position of 30% to 60% from the leading edge of the blade, which is approximately 45% in the illustrated example. This position is a portion where the loss between the impeller blades due to the separation flow is the largest). A circulation path 8 through which a fluid flows through a gap between the shroud 7 and the other casing 1B is formed with a gap between the rear edge and the other casing 1B as an inlet A and a gap between the front edge of the shroud 7 and the other casing 1B as an outlet B. ing.
[0019]
Further, the inner peripheral surface 7a of the shroud 7 is formed in an arc shape along the meridional shape of the tip of each blade 6, and the outer peripheral surface 7b is formed to be flat so as to eliminate the steps as much as possible. 6 Touching the tip.
[0020]
With such a configuration, the low-energy fluid C generated in the middle part of the meridional plane length at the tip of each blade 6 causes the low pressure fluid ΔP between the inlet a and the outlet B of the circulation path 8 shown in FIG. It will be sucked out from the entrance a and returned to the exit b.
[0021]
Thereby, the loss between the impeller blades in the latter half from the middle part of the meridional plane length at the tip of each blade 6 is reduced, and the efficiency of the centrifugal compressor is effectively improved. In other words, the low-energy fluid generated in the middle part of the meridional plane length at the tip of each blade 6 is effectively circulated in consideration of other performances such as compression efficiency, which are in a trade-off relationship in terms of circulation amount and the like. It is done.
[0022]
Further, since the outer peripheral surface 7b of the shroud 7 is formed flat and is in contact with the tip of each of the blades 6 with as few steps as possible, even if the other casing 1B is formed by integral casting, the impeller The other casing 1B can be fitted from the axial direction 2 and easily bolted to one casing 1A.
[0023]
This eliminates the necessity of assembling a half casing or the like, and can reduce the manufacturing cost and improve the assemblability by using the casing 1B formed by casting.
[0024]
Of course, each wing 6 is effectively reinforced by the annular shroud 7. That is, even if the impeller 2 has a large diameter of 1 m or more and the impeller 2 is manufactured in a welded structure, the strength of each impeller 6 is sufficiently ensured.
[0025]
It is needless to say that the present invention is not limited to the above embodiments, and various changes can be made without departing from the scope of the present invention. In addition, when the present invention is applied to a tandem wing in which the impeller is divided into two along the wing tip at the midpoint of the meridional plane from the inlet to the outlet, in addition to increasing the strength of the wing, one part of the twisted wing is also provided. This has the advantage of being easier to manufacture because the size is smaller.
[0026]
【The invention's effect】
As described above in detail based on the embodiments, the invention according to claim 1 of the present invention is a centrifugal compressor that compresses / discharges gas sucked by rotation of an impeller supported by a casing mainly by centrifugal force. In the impeller, between the tips of the blades of the impeller is reinforced with an annular shroud, and the position of the trailing edge with respect to the length of the shroud in the axial direction of the impeller is defined as the meridional plane length from the impeller inlet to the impeller outlet along each blade tip. Since the impeller is set up to the middle part, the impeller can be effectively reinforced with a shroud to improve the assemblability and increase the efficiency.
[0027]
In the invention according to claim 2, the trailing edge of the shroud is in contact with each blade tip with as little step as possible, so that gas leakage from the pressure side to the suction side of the blade is prevented. As a result, a decrease in the efficiency of the centrifugal compressor can be avoided.
[0028]
Further, in the invention according to claim 3, since the middle part of the meridional plane length is located at 30% to 60% from the leading edge of the wing, the low energy generated in the middle part of the meridional plane length of each wing tip. The fluid can be effectively circulated in balance with other performances that are in a trade-off relationship in terms of the amount of circulation and the like.
[Brief description of the drawings]
FIG. 1 is a sectional view of a main part of a centrifugal compressor showing one embodiment of the present invention.
FIG. 2 is a pressure distribution diagram along an inner surface of a casing along a meridional plane length of the blade.
FIG. 3 is an explanatory view of a conventional open impeller.
FIG. 4 is a perspective view of a conventional impeller with a shroud.
FIG. 5 is a sectional view of a conventional centrifugal compressor having different shrouded impellers.
[Explanation of symbols]
1A One casing 1B The other casing 2 Impeller (impeller)
3 air inlet 4 air outlet 5 hub 6 wing 7 shroud 8 circulation path

Claims (3)

In a centrifugal compressor which compresses and discharges gas sucked by rotation of an impeller supported by a casing mainly by centrifugal force, a tip end of each blade of the impeller is reinforced by an annular shroud, and an impeller axial direction of the shroud is used. A centrifugal compressor wherein a position of a trailing edge of the centrifugal compressor is set from the inlet of the impeller to an intermediate portion of a meridional length from the impeller outlet to the impeller outlet along each blade tip. The centrifugal compressor according to claim 1, wherein a trailing edge of the shroud is in contact with each of the blade tips with as few steps as possible. The centrifugal compressor according to claim 1 or 2, wherein the intermediate portion of the meridional plane length is located at 30% to 60% from the leading edge of the blade.

Images