JP2006057487A - Centrifugal compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a centrifugal compressor effectively suppressing force exciting a rotary shaft system. <P>SOLUTION: An impeller 4 rotating with a main shaft 3 consists of a shroud 5 and a disk 6 forming a flow passage of fluid between inner surfaces thereof and a profile 7 provided between both of the inner surfaces. Regular roughness is included on an opposing surface 2a to an outer surface 5a of the shroud 5 in a casing 2. The roughness on the opposing surface 2a is formed by a plurality of radial projections 10 having a center on the main shaft 3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a centrifugal compressor that sucks fluid from the front in the axial direction and feeds it in a centrifugal direction while increasing the pressure by an impeller that rotates with a main shaft.

  As shown in FIG. 10, the conventional general centrifugal compressor 1 has an outer shape constituted by a casing 2. In the casing 2, a main shaft 3 to which an impeller 4 is integrally attached is supported by a bearing or the like. It is rotatably supported. The impeller 4 includes a shroud 5 and a disk 6 that form a fluid flow path between the inner surfaces thereof, and a profile 7 provided between the inner surfaces of the shroud 5 and the disk 6. A driving force for rotating the shaft is applied to the main shaft 3 from the driving motor, and the impeller 4 rotates together with the main shaft 3. Then, due to the shaft rotation of the impeller 4, fluid is sucked into the machine from the suction port of the casing 2, and flows into the impeller 4, that is, between the inner surfaces of both the shroud 5 and the disk 6 from the front in the axial direction. The fluid that has flowed into the impeller 4 is sent out in the centrifugal direction while being pressurized by the lift and centrifugal force from the profile 7, and finally discharged from the discharge port of the casing 2 to the outside of the machine. In FIG. 10, such a main fluid flow is indicated by white arrows.

  By the way, in such a centrifugal compressor 1, in order to realize smooth axial rotation of the impeller 4 in the casing 2 while maximizing the above-described main fluid flow path, A gap is formed in the inner surface of the casing 2. Here, for convenience of the following description, the inner surface of the casing 2 that is in a relationship of being opposed to the outer surface 5a of the shroud 5 is referred to as a first facing surface 2a, and the outer surface 5a of the shroud 5 and the first facing of the casing 2 are opposed to each other. A gap formed by the surface 2a is referred to as a first gap S1. Further, the inner surface of the casing 2 in a relationship of facing the outer surface 6a of the disk 6 is referred to as a second facing surface 2b, and is formed by the outer surface 6a of the disk 6 and the second facing surface 2b of the casing 2. The gap is referred to as a second gap S2.

  Naturally, fluid exists in the first gap S1 and the second gap S2, but the fluid in these gaps S1 and S2 is inevitably associated with the shaft rotation of the impeller 4. Therefore, a swirling flow in the same direction as the rotation direction of the fluid axis around the main shaft 3, that is, a so-called swirl is generated. Such a swirl applies an unstable reaction force to the impeller 4 with respect to the shaft vibration, and induces an excitation force that promotes the shaft vibration of the rotating shaft system in which the main shaft 3 and the impeller 4 are integrated. In particular, in recent centrifugal compressors 1 that are small and lightweight and require a large amount of output of high-pressure fluid, the shaft rotation of the impeller 4 is high and the swirl turning speed is high. As a result, the excitation force by the swirl also increases. In this case, an unstable shaft vibration is caused in the rotating shaft system by the excitation force, which may cause noise and damage to various parts.

  In addition, since the first gap S1 opens at the upstream and downstream ends of the main fluid flow path in the impeller 4, the first gap S1 has a figure in the first gap S1 due to the pressure difference of the main fluid at the upstream and downstream ends. 10, a part of the main fluid flows from the outer peripheral side of the outer surface of the shroud 5 which is the downstream end side of the impeller 4 and flows out from the inner peripheral side to the upstream end side of the impeller 4 In addition, a so-called recycle flow occurs in which the main fluid is rejoined. In such a recycle flow, the first gaps S1 at positions symmetrical in the radial direction fluctuate widely and narrowly with the axial vibration of the rotating shaft system. As a result, torque fluctuation occurs in the minute impeller 4 due to the difference in flow rate, and as a result, an unstable force is applied to the impeller 4. That is, the recycle flow is also a factor of the above-described excitation force, and this excitation force causes unstable shaft vibration in the rotating shaft system.

In the conventional centrifugal compressor 1, the inner peripheral surface 2 c of the casing 2 facing the outer peripheral surface 5 b of the shroud 5, which is an inlet for fluid into the first gap S 1, A plurality of grooves are formed on the inner peripheral surface 2d of the casing 2 facing the outer peripheral surface 6b of the disk 6 which is the inlet of the fluid to the two clearances S2, and the first clearance S1 or The swirl speed of the fluid (recycle flow) flowing into the second gap S2 is reduced, and as a result, the excitation force to the rotating shaft system by the swirl is suppressed (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 9-177597

  However, the swirl reducing groove in the conventional centrifugal compressor 1 described above is effective in reducing the swirl with respect to the fluid at the fluid inlet of the first gap S1 or the second gap S2, but actually the first It does not directly contribute to the fluid existing in the gap S1 or the second gap S2. Therefore, the swirl reduction is substantially insufficient, and it cannot be said that the excitation force to the rotating shaft system can be effectively suppressed.

  Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide a centrifugal compressor that can effectively suppress the excitation force to the rotating shaft system.

  In order to achieve the above object, a centrifugal compressor according to the present invention has a main shaft integral with an impeller supported so as to be capable of rotating in a casing, and the impeller rotates together with the main shaft so that fluid can flow from the front in the axial direction. In a centrifugal compressor that sucks and pressurizes and sends in a centrifugal direction, an impeller includes a shroud and a disk that form a fluid flow path between the inner surfaces of each other, and a profile provided between the inner surfaces of the shroud and the disk; And having regular irregularities on the surface of the casing facing the outer surface of the shroud. Thus, when the impeller rotates axially, regular irregularities on the first facing surface are generated with respect to the fluid existing in the first gap formed by the outer surface of the shroud and the first facing surface of the casing. Direct and uniform fluid resistance results, and swirl generation is suppressed.

  Here, based on practicality, the concavity and convexity of the facing surface is formed by forming a plurality of radial ridges around the main axis, or a plurality of spiral ridges around the main axis. It is preferable that it consists of. In particular, when the unevenness of the first facing surface is a spiral protrusion, a force in the direction opposite to the flow of the recycle flow can be exerted on the fluid existing in the first space. There is an advantage that deterrence can be realized at the same time.

  Moreover, the unevenness | corrugation of the said opposing surface may consist of many protrusions, many holes may be formed, or a hole may be formed in the shape of a honeycomb.

  In addition, for the purpose of suppressing swirl with respect to the fluid existing in the second gap formed by the outer surface of the disk and the second facing surface of the casing, the outer surface of the disk in the casing is further provided. It is preferable to have regular irregularities on the surface facing the surface.

  According to the centrifugal compressor of the present invention, regular irregularities on the first facing surface and the second facing surface of the casing are directly and uniformly applied to the fluid existing in the first gap and the second gap. Therefore, the generation of swirl can be suppressed, and as a result, the excitation force to the rotating shaft system can be effectively suppressed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, the centrifugal compressor which is 1st Embodiment of this invention is demonstrated. FIG. 1 is a longitudinal sectional view showing a main part of the centrifugal compressor of the first embodiment, and FIG. 2 is a plan view showing a surface of the centrifugal compressor casing facing the impeller. In the figure, parts having the same names and performing the same functions as those in FIG. 10 are denoted by the same reference numerals, and redundant description is omitted. The same applies to the second to fourth embodiments described later.

  In the present embodiment, as shown in FIGS. 1 and 2, in the first gap S <b> 1 formed by the outer surface 5 a of the shroud 5 and the first facing surface 2 a of the casing 2, the first facing surface in the casing 2. A plurality of radial ridges 10 centering on the main shaft 3 (the impeller 4) rotating around the shaft are formed at 2a at uniform intervals in the circumferential direction. That is, the first facing surface 2a has regular irregularities. In FIG. 2, eight ridges 10 are formed, but the number is not limited as long as they are arranged at a uniform interval in the circumferential direction. Incidentally, such unevenness of the first facing surface 2a can be easily manufactured by weaving the shape of the unevenness in the mold of the manufacturing action because the casing 2 is generally a cast product.

  With such a configuration, when the impeller 4 rotates with the main shaft 3, the irregularities on the first facing surface 2a (in the present embodiment, each of the irregularities in the first gap S1) Since the ridges 10) have a direct and uniform fluid resistance, the generation of swirl is suppressed. As a result, the excitation force to the rotating shaft system can be effectively suppressed.

  In addition to the configuration of the first facing surface 2a, the second facing in the casing 2 is performed in the second gap S2 formed by the outer surface 6a of the disk 6 and the second facing surface 2b of the casing 2. If the same radial protrusion 10 is formed also on the surface 2b, it is effective in that swirl can be suppressed even for the fluid existing in the second gap S2.

  Next, a second embodiment of the present invention will be described with reference to FIG. The feature of the second embodiment is that the aspect of the ridge 10 in the first embodiment is modified and the excitation force is also suppressed by the recycle flow.

  In the present embodiment, as shown in FIG. 3, the protrusion 10 on the first facing surface 2 a in the casing 2 is formed in a spiral shape around the main shaft 3 that rotates about the axis. Even with such a configuration, when the impeller 4 rotates together with the main shaft 3, the swirling ridges 10 suppress the generation of swirl with respect to the fluid existing in the first gap S1, At the same time, it is possible to exert a force opposite to the flow of the recycle flow, so that the recycle flow can be suppressed at the same time. As a result, the excitation force to the rotating shaft system can be more effectively suppressed. In FIG. 3, the rotation direction of the impeller 4 is indicated by a broken line arrow.

  Moreover, it is preferable to form the same spiral protrusion 10 on the second facing surface 2 b of the casing 2. This is because swirl can be suppressed even with respect to the fluid existing in the second gap S2.

  Next, a third embodiment of the present invention will be described with reference to FIGS. The feature of this 3rd Embodiment exists in the point which deform | transformed the uneven | corrugated aspect of the opposing surface of the casing 2 in 1st Embodiment.

  In the present embodiment, as shown in FIGS. 4 to 6, a large number of protrusions 11 are formed on the first facing surface 2 a of the casing 2 in a uniform arrangement. Even with such a configuration, when the impeller 4 rotates together with the main shaft 3, regular irregularities on the first facing surface 2 a (in the present embodiment, each of the irregularities in the first gap S 1) Since the protrusion 11) has a direct and uniform fluid resistance, the generation of swirl is suppressed.

  Moreover, it is preferable to form the same protrusion 11 also on the 2nd opposing surface 2b in the casing 2 from a viewpoint of suppressing a swirl also with respect to the fluid which exists in 2nd clearance gap S2.

  Next, a fourth embodiment of the present invention will be described with reference to FIGS. The feature of the fourth embodiment is that, as in the third embodiment, the unevenness of the facing surface of the casing 2 in the first embodiment is modified.

  In the present embodiment, as shown in FIGS. 7 to 9, a large number of holes 12 are formed in the first facing surface 2 a of the casing 2 in a uniform arrangement. Even with such a configuration, when the impeller 4 rotates together with the main shaft 3, regular irregularities on the first facing surface 2 a (in the present embodiment, each of the irregularities in the first gap S 1) Since the holes 12) have a direct and uniform fluid resistance, the generation of swirl is suppressed.

  Moreover, it is preferable to form the same hole 12 also in the 2nd opposing surface 2b in the casing 2 from a viewpoint of suppressing a swirl also with respect to the fluid which exists in 2nd clearance gap S2.

  The holes 12 of the first facing surface 2a and the second facing surface 2b may be formed in a honeycomb shape as a whole.

  In addition, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention.

  The present invention is useful for suppressing the excitation force to the rotating shaft system in a centrifugal compressor.

It is a longitudinal cross-sectional view which shows the principal part of the centrifugal compressor which is 1st Embodiment of this invention. It is a top view which shows the opposing surface with the impeller in the casing of the centrifugal compressor of 1st Embodiment. It is a top view which shows the opposing surface with the impeller in the casing of the centrifugal compressor which is 2nd Embodiment of this invention. It is a longitudinal cross-sectional view which shows the principal part of the centrifugal compressor which is 3rd Embodiment of this invention. It is a top view which shows the opposing surface with the impeller in the casing of the centrifugal compressor of 3rd Embodiment. It is a top view which shows the modification of an opposing surface with the impeller in the casing of the centrifugal compressor of 3rd Embodiment. It is a longitudinal cross-sectional view which shows the principal part of the centrifugal compressor which is 4th Embodiment of this invention. It is a top view which shows the opposing surface with the impeller in the casing of the centrifugal compressor of 4th Embodiment. It is a top view which shows the modification of the surface facing the impeller in the casing of the centrifugal compressor of 4th Embodiment. It is a longitudinal cross-sectional view which shows the principal part of the conventional centrifugal compressor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Centrifugal compressor 2 Casing 2a Opposite surface (1st opposing surface) with the outer surface of shroud in a casing
2b The facing surface of the casing to the outer surface of the disk (second facing surface)
3 Spindle 4 Impeller 5 Shroud 5a Outer surface of shroud 6 Disc 6a Outer surface of disc 7 Profile 10 Projection 11 Projection 12 Hole S1 Clearance between outer surface of shroud and facing surface of casing (first clearance)
S2 Gap between the outer surface of the disk and the facing surface of the casing (second gap)

Claims (7)

In the centrifugal compressor, the main shaft integral with the impeller is supported so as to be capable of rotating in the casing, and the impeller rotates with the main shaft so that fluid is sucked from the front in the axial direction and is pumped in the centrifugal direction.
The impeller is composed of a shroud and a disk that form a fluid flow path between the inner surfaces of each other, and a profile provided between the inner surface of the shroud and the disk, and is regularly arranged on a surface of the casing facing the outer surface of the shroud. Centrifugal compressor characterized by having unevenness.   2. The centrifugal compressor according to claim 1, wherein the concavity and convexity of the opposing surface is formed with a plurality of radial protrusions centered on a main axis.   2. The centrifugal compressor according to claim 1, wherein the concavity and convexity on the opposing surface is formed with a plurality of spiral protrusions centered on a main axis.   The centrifugal compressor according to claim 1, wherein the concavity and convexity on the opposing surface is formed with a plurality of protrusions.   The centrifugal compressor according to claim 1, wherein the concavity and convexity on the opposing surface is formed with a plurality of holes.   The centrifugal compressor according to claim 1, wherein the concavities and convexities on the facing surface are formed with holes in a honeycomb shape.   The centrifugal compressor according to any one of claims 1 to 6, further comprising regular irregularities on a surface of the casing facing the outer surface of the disk.

Images