JP2010001868A - Centrifugal compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a centrifugal compressor capable of surely preventing contact between an impeller and a casing. <P>SOLUTION: This centrifugal compressor 1 has the casing 2 and the centrifugal impeller 3 arranged in this casing 2 and compressing air. The impeller 3 has a substantially conical hub part 4 integrally fixed to a rotary shaft (unillustrated). A plurality of blades 5 forming a flow passage of main flow air sucked in the casing 2 is arranged at an equal interval in the peripheral direction on an outer peripheral surface of this hub part 4. An air passage 9 for introducing high temperature-high pressure air on the back face side of the impeller 3 to the front face side of the impeller 3 by penetrating in the longitudinal direction of the impeller 3, is arranged in the hub part 4 of the impeller 3. The air passage 9 is composed of an annular groove part 10 opening on a front face of the hub part 4 and a plurality of through-holes 11 extending up to a bottom part of the groove part 10 from a rear surface (a back face) of the hub part 4. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a centrifugal compressor provided with an impeller rotatably disposed in a casing.

As a conventional centrifugal compressor, for example, as described in Patent Document 1, an impeller formed by mounting a plurality of blades in a radial shape on a substantially conical hub and a casing for housing the impeller What you have is known.
JP 2006-9748 A

  However, the following problems exist in the prior art. That is, the air outlet portion of the impeller may be deformed to the front side and come into contact with the casing due to the centrifugal force generated when the impeller rotates and the high-temperature and high-pressure air existing on the back side of the impeller. In order to solve this problem, it is conceivable to predict the deformation amount of the air outlet portion of the impeller and adjust the position of the impeller so that the gap (tip clearance) between the impeller and the casing becomes a predetermined amount. However, since the shape of the back surface of the impeller, the blades, the temperature distribution of the impeller, and the like are complicated, it is difficult to adjust the tip clearance by predicting the deformation amount of the impeller.

  The objective of this invention is providing the centrifugal compressor which can prevent the contact with an impeller and a casing reliably.

  The present invention relates to a centrifugal compressor including a casing and an impeller rotatably disposed in the casing. The impeller includes a hub portion integrally fixed to the rotation shaft, and a circumferential direction on the outer peripheral surface of the hub portion. A plurality of blades provided along the front side of the impeller, and is configured to send out the air sucked from the front side of the impeller to the outer side in the radial direction of the impeller. An air passage for guiding the air on the back side of the impeller to the front side of the impeller is provided.

  In such a centrifugal compressor of the present invention, since the high-pressure air on the back side of the impeller is guided to the front side of the impeller through the air passage, the back pressure of the impeller is lowered. Thereby, since the air outlet part of the impeller located in the vicinity of the back part of the impeller is suppressed from being deformed to the front side of the impeller, the contact between the air outlet part of the impeller and the casing can be prevented.

  Preferably, the air passage has a groove portion opened to the front surface of the hub portion, and a through hole extending from the rear surface of the hub portion to the groove portion.

  In this case, since the high-temperature air on the back side of the impeller is introduced into the groove portion through the through hole, the temperature in the groove portion rises, and the groove portion expands due to thermal expansion. It moves to the back side of the impeller. Thereby, contact with the air outlet part of the impeller and the casing can be further prevented.

  According to the present invention, contact between the impeller and the casing can be reliably prevented, and damage to the impeller can be avoided.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a centrifugal compressor according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view showing a main part of an embodiment of a centrifugal compressor according to the present invention. In the figure, a centrifugal compressor 1 of the present embodiment includes a casing 2 and a centrifugal impeller (impeller) 3 that is disposed in the casing 2 and compresses air.

  The impeller 3 has a substantially conical hub portion 4 that is integrally fixed to a rotating shaft (not shown), and air sucked into the casing 2 (mainstream air) is provided on the outer peripheral surface of the hub portion 4. A plurality of blades 5 forming the flow path are provided at equal intervals in the circumferential direction. A connecting portion 6 is fixed to the front surface of the hub portion 4, and the connecting portion 6 is rotatably supported by the casing 2 via a bearing 7. A predetermined gap (chip clearance) is provided between the blade 5 and the shroud 8 of the casing 2.

  When the impeller 3 rotates at a high speed, the mainstream air is sucked in from the front side of the impeller 3 and is sent out radially outward of the impeller 3. A diffuser (not shown) that converts the velocity energy of the high-speed air produced by the impeller 3 into pressure is discharged outside the impeller 3 in the radial direction. The back surface of the impeller 3 communicates with the outlet of the diffuser. For this reason, the high-temperature air sent out from the impeller 3 exists in the high pressure state on the back side of the impeller 3.

  The hub portion 4 of the impeller 3 is provided with an air passage 9 that penetrates in the front-rear direction of the impeller 3 and guides high-temperature and high-pressure air on the back side of the impeller 3 to the front side of the impeller 3. The air passage 9 includes an annular groove 10 that opens to the front surface of the hub portion 4, and a plurality of through holes 11 that extend from the rear surface (back surface) of the hub portion 4 to the bottom of the groove portion 10. The groove portion 10 extends substantially parallel to the axial direction of the impeller 3 from the bottom portion to the opening portion. The through-hole 11 extends obliquely with respect to the axial direction of the impeller 3 from the rear surface of the hub portion 4 to the annular groove 10 in correspondence with the hub portion 4 being formed in a substantially conical shape.

  In addition, as a shape of the groove part provided in the hub part 4, it does not need to be especially cyclic. For example, while providing the some groove part extended along the circumferential direction of the hub part 4, you may provide the some through-hole 11 so that it may connect with each groove part.

  FIG. 2 is a schematic cross-sectional view showing a conventional general centrifugal impeller as a comparative example. In the figure, the same reference numerals are assigned to the same elements as those of the centrifugal compressor 1 described above. In the centrifugal compressor 50 shown in FIG. 2, the air passage 9 is not provided in the hub portion 4 of the impeller 3. With such a structure, the following problems occur.

  That is, the air outlet 3b of the impeller 3 may be deformed to the front side and contact the shroud 8 due to the centrifugal force generated by the high speed rotation of the impeller 3 and the high temperature and high pressure air existing on the back side of the impeller 3. In order to avoid this, the deformation amount of the air outlet 3b of the impeller 3 is predicted, and the position of the impeller 3 is adjusted so that the tip clearance between the impeller 3 and the shroud 8 becomes a predetermined amount. However, since the shape of the back surface of the impeller 3 and the blades 5 and the temperature distribution of the impeller 3 are complicated, it is very difficult to predict the deformation amount of the impeller 3. For this reason, even if the tip clearance is adjusted, the air outlet 3b of the impeller 3 comes into contact with the shroud 8. Further, since the air pressure (air density) is high at the air outlet 3b of the impeller 3, the sensitivity to the performance of the chip clearance variation is high, and the slight variation in the chip clearance greatly affects the performance.

  Further, since the pressure (back pressure) applied to the back surface of the impeller 3 by the high-pressure air on the back surface side of the impeller 3 is increased, the thrust force applied to the front side of the impeller 3 is increased and the bearing 7 is damaged.

  On the other hand, in the present embodiment, since the air passage 9 is formed in the hub portion 4 of the impeller 3, the following operational effects are obtained.

  That is, since the high temperature air on the back side of the impeller 3 is introduced into the groove portion 10 through the through hole 11, the temperature of the inner wall surface of the hub portion 4 forming the groove portion 10 rises as shown in FIG. The opening side of the groove 10 is expanded by the thermal expansion of the inner wall surface of the portion 4. Therefore, the front end portion of the hub portion 4 is deformed outward in the radial direction of the impeller 3, and the air outlet portion 3b of the impeller 3 moves to the rear side along with this (see arrow). In addition, since the high-pressure air on the back side of the impeller 3 flows to the front side of the impeller 3 through the through hole 11 and the groove portion 10, the back pressure of the impeller 3 decreases, and the air outlet 3 b of the impeller 3 moves to the front side. Deformation itself is suppressed. As described above, the air outlet 3b of the impeller 3 is prevented from coming into contact with the shroud 8 of the casing 2, so that the impeller 8 can be prevented from being damaged. Moreover, since the deformation | transformation to the front side of the air outlet part 3b of the impeller 3 is suppressed, adjustment of the tip clearance between the impeller 3 and the shroud 8 becomes unnecessary.

  At this time, the air inlet 3a of the impeller 3 is deformed in the same direction as the front end of the hub 4 is deformed radially outward of the impeller 3, but the deformation mechanism is simple and easy to calculate. The deformation amount of the air inlet 3a of the impeller 3 can be predicted easily and accurately. Moreover, since the air pressure (air density) is relatively low in the air inlet portion 3a of the impeller 3 compared to the air outlet portion 3b of the impeller 3, the sensitivity to the performance of chip clearance variation is low. For this reason, the influence on the performance degradation by chip clearance variation is reduced, and the performance variation at the time of mass production can be reduced. Accordingly, the influence of the deformation of the air inlet 3a of the impeller 3 is extremely small.

  Furthermore, since the high-pressure air on the back side of the impeller 3 flows into the front side of the impeller 3 through the through-holes 11 and the grooves 10, the back pressure of the impeller 3 is reduced, so that the back pressure is applied to the front side of the impeller 3. Thrust force is reduced. Therefore, since damage to the bearing 7 is reduced, the impeller 3 can be smoothly rotated at a high speed.

  The present invention is not limited to the above embodiment. For example, in the above embodiment, the air passage 9 including the groove portion 10 and the through hole 11 is formed in the hub portion 4 of the impeller 3, but the hole portion penetrating in the front-rear direction of the impeller 3 is not particularly provided, and the hub portion 4 is provided. You may just form in. Even in this case, since the high-pressure air on the back side of the impeller 3 flows to the front side of the impeller 3 through the hole, deformation of the air outlet portion 3b of the impeller 3 is suppressed by a decrease in the back pressure of the impeller 3. . Thereby, it is possible to prevent contact between the impeller 3 and the casing 2.

It is a schematic sectional drawing which shows the principal part of one Embodiment of the centrifugal compressor concerning this invention. It is a schematic sectional drawing which shows the conventional general centrifugal impeller as a comparative example. FIG. 2 is a schematic cross-sectional view showing a state when high-temperature and high-pressure air on the back side of the impeller shown in FIG. 1 flows to the front side of the impeller 3 through an air passage.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Centrifugal compressor, 2 ... Casing, 3 ... Impeller, 4 ... Hub part, 5 ... Blade | wing, 9 ... Air passage, 10 ... Groove part, 11 ... Through-hole.

Claims (2)

In a centrifugal compressor including a casing and an impeller rotatably disposed in the casing,
The impeller has a hub portion that is integrally fixed to a rotation shaft, and a plurality of blades that are provided along the circumferential direction on the outer peripheral surface of the hub portion, and the air sucked from the front side of the impeller is It is configured to feed out the radial direction of the impeller,
The centrifugal compressor characterized in that the hub portion is provided with an air passage that penetrates in the front-rear direction of the impeller and guides air on the back side of the impeller to the front side of the impeller. 2. The centrifugal compressor according to claim 1, wherein the air passage includes a groove portion that opens to a front surface of the hub portion, and a through hole that extends from the back surface of the hub portion to the groove portion.

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