JPH11173299A - Centrifugal compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce pressure loss at return flow passage part of a centrifugal compressor and improve efficiency of the centrifugal compressor. SOLUTION: A return flow passage 6 which guides fluid fed from the front stage impeller to the rear stage impeller is provided between plural impellers provided for a rotation shaft 2. Plural return vanes 21 are provided in a return flow passage part 6a between a return bend part which constitutes the return flow passage 6 and is bent in the U-shape in the cross section view with distance circumferencially of the rotation shaft 2. The inlet end 22 on the return bend part side of the return vanes 21 is positioned at substantially intermediate part which is inclined about 45 deg. to a bending part on the downstream side of the bending central position C of the return bend part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a centrifugal compressor which can be used, for example, for industrial centrifugal compressors, gas turbine centrifugal compressors and the like.

[0002]

2. Description of the Related Art FIG. 6 shows a conventional five-stage centrifugal compressor 1 used in general industries. In this figure, reference numeral 2 denotes an impeller rotary shaft, and reference numeral 3 denotes an impeller rotary shaft 2. A plurality of impellers (impellers) coaxially mounted on the housing, reference numeral 4 denotes a housing for accommodating a rotating body (rotor) composed of the impeller rotating shaft 2 and the impeller 3, and reference numerals 5a and 5b denote suction formed in the housing 4. And a discharge unit. In the housing 4 described above, return flow paths 6 are provided in regions between the impellers 2 adjacent to each other along the impeller rotation shaft 2, and these return flow paths 6
It is formed so as to surround the periphery of the impeller rotation shaft 2.

The return passage 6 serves to send the fluid compressed by the impeller 3 at the front stage to the impeller 3 at the rear stage, and is located downstream of the diffuser members 7 and 8 as shown in FIG. Return bend members 11, 1
2 and return flow path walls 9, 10 located downstream of the return bend members 11, 12, and a plurality of return vanes 13 between the return flow path walls 9, 10.
Is provided. These return vanes 13 are arranged over the entire width between the return flow path wall 9 and the return flow path wall 10, and extend along the circumferential direction of the impeller rotating shaft 2 as shown in FIG. They are arranged at equal intervals and radially around the impeller rotation shaft 2.

In the conventional centrifugal compressor 1 described above, an inlet end (return vane inlet) 14 which is an outer peripheral end of the plurality of return vanes 13 is connected to the return bend member 1.
A portion on the downstream side of the return bend portion 15 (bend portion of the return flow path 6) composed of the U-shaped section 1 and 12, that is, a pair of return flow path walls 9 on the downstream side of the return bend portion 15. , Between 10 and the return bend member 11,
12 and at a downstream location (see FIGS. 7 and 8).

[0005]

However, the conventional return channel structure of the centrifugal compressor 1 as described above has the following problems. That is, the return bend members 11, 1
Return bend 1 which is a curved flow path composed of 2
In FIG. 5, as shown in FIG. 9, due to the curvature, the pressure on the inner peripheral side of the flow channel is lower than the flow at the center of the flow channel, and the flow velocity Cm
Increases, the frictional loss increases, and at the point where the curvature of the outlets of the return bend members 11 and 12 disappears, the energy of the fluid flowing against the pressure increase in the downstream portion is insufficient, and the flow is separated. A region H occurs, and the uniformity of flow at the inlet end 14 of the return vane 13 is hindered, pressure recovery in the downstream portion becomes insufficient, and the efficiency of the centrifugal compressor 1 is impaired. .

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a centrifugal compressor capable of reducing pressure loss in a return flow path portion of the centrifugal compressor and improving efficiency. And

[0007]

According to a first aspect of the present invention, there is provided a centrifugal compressor according to the first aspect of the present invention, in which a plurality of impellers provided on a rotating shaft transfer a fluid sent out from a preceding impeller to a subsequent impeller. A centrifugal compressor provided with a return flow path for guiding, wherein the return flow path is a return bend portion bent in a U-shape in cross section, and a return flow between the return bend portion and a rear-stage impeller. A path portion, and a plurality of return vanes provided in the return flow passage portion at intervals in a circumferential direction of the rotating shaft, and the return vane has an end on the return bend portion side, It is characterized in that it is located substantially at the middle of the bent portion on the downstream side of the bent center position of the return bend portion. As a result, even in the case of a return vane having a two-dimensional shape, the flow angle of the fluid on the inner peripheral side of the return bend at the end of the return vane is increased, and separation on the inner peripheral side of the return bend is prevented. Flow uniformity is ensured.

[0008]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a centrifugal compressor according to an embodiment of the present invention. FIG. 1 shows a return flow path structure of the centrifugal compressor according to the present embodiment, in which a fluid compressed by the impeller 3 and sent between the diffuser members 7 and 8 returns to the return bend member 1.
The return vanes provided between the return flow path walls 9 and 10 are fed through the return flow path sections 6a including the return flow path walls 9 and 10 through the return bend section 15 having a U-shaped cross section including the return flow path walls 1 and 12. 21 guides and guides the impeller 3 at the subsequent stage.

As shown in FIG. 2, the return vane 21 has an inlet end 22 on the return vane 15 side.
In the return bend portion 15 composed of the return bend members 11 and 12, approximately in the middle of the bend point on the downstream side from the bend center position C, specifically, about 45 degrees downstream from the center point O of the arc of the return bend portion 15. The inlet end 22 of the return vane 21 is disposed at a position inclined to the side. Accordingly, the flow path inclination angle αh on the side of the return bend member 11 at the inlet end 22 of the return vane 21, that is, on the hub side, which is the inner circumferential side of the flow path, is set to about 45 degrees.

Here, as described above, the return vane 2
1 is disposed such that the flow path inclination angle αh on the hub side, which is the return bend member 11 side, is about 45 degrees, so that the shroud on the return bend member 12 side, that is, the outer peripheral side of the flow path. A relationship of αh <αs occurs between the flow path inclination angle αs on the side.

As shown in FIG. 3, the inlet angle at which the fluid flows into the inlet end 22 of the return vane 21 has a fixed relationship between the shroud-side inlet angle βBs and the hub-side inlet angle βBh. That is, the inlet end 22 of the return vane 21
Is established from the shroud-side flow channel inclination angle αs and the hub-side flow channel inclination angle αh at which is located.

TanβBh · sinαh = tanβBs · sinαs

Here, tan βBh and tan β
βBs is represented by the following equations.

TanβBh = △ mh / △ l = (△ r / sinαh) / △ l = tanβr / sinαh tanβBs = △ ms / △ l = (△ r / sinαs) / △ l = tanβr / sinαs ...

Here, βr: the angle formed by the center plane B of the return vane 21 on a plane perpendicular to the impeller rotating shaft 2 Δl: the circumferential length forming the angle Δr: the radial length forming the angle Δ m: Flow direction length forming an angle Δmh: Flow direction length forming an angle on the hub side Δms: Flow direction length forming an angle on the shroud side That is, the above equation is derived from the equation.

Here, as described above, between the flow path inclination angle αh on the hub side and the flow path inclination angle αs on the shroud side, α
Since there is a relationship of h <αs, the following relationship is established from the equation between the inlet angle βBh on the hub side of the inlet end 22 of the return vane 21 and the inlet angle βBs on the shroud side.

ΒBh> βBs

This relationship is defined by the return bend unit 1
5 indicates that the flow angle of the fluid flowing through 5 is as follows. That is, as shown in FIG. 4, when the swirling speed Cuh on the hub-side surface and the swirling speed Cus on the shroud-side surface are made substantially equal (Cuh ≒ Cus), the hub effect occurs due to the curvature effect of the fluid flow. Meridional velocity Cmh on the side surface and meridional velocity C on the shroud side surface
Since the relationship of ms is Cmh> Cms, tanβh> tanβs, and therefore, the flow angle βh on the hub-side surface and the flow angle βs on the shroud-side surface are βh> βs.

That is, since the flow angle is large on the hub side and small on the shroud side, even if the return vane 21 has a two-dimensional shape, as shown in FIG. Can be reliably prevented, and the inlet end 22 of the return vane 21
, It is possible to ensure the uniformity of the flow, and therefore, it is possible to reduce the pressure loss in the return flow path portion. As a result, the performance of the multi-stage centrifugal compressor can be significantly improved at low cost.

[0020]

As described above, according to the centrifugal compressor of the present invention, the following effects can be obtained. According to the centrifugal compressor of the first aspect, since the end of the return bend on the side of the return bend is located substantially at the middle of the bent portion on the downstream side from the center of the return bend, the return vane is formed. Has a two-dimensional shape, the flow angle of the fluid on the inner peripheral side of the return bend portion at the end of the return vane increases, and separation on the inner peripheral side of the return bend portion can be prevented.
The uniformity of the flow at the inlet of the return vane can be ensured, so that the pressure loss in the return flow path can be reduced. As a result, the performance of the multi-stage centrifugal compressor can be significantly improved at low cost.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a return flow path for explaining a return flow path structure of a centrifugal compressor according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view illustrating a return flow path structure of the centrifugal compressor according to the embodiment of the present invention, as viewed from an arrow X direction in FIG.

FIG. 3 is a diagram illustrating each angle of a return vane for explaining a return channel structure of the centrifugal compressor according to the embodiment of the present invention.

FIG. 4 is a diagram illustrating each speed and flow angle of a fluid of a return vane for explaining a return channel structure of the centrifugal compressor according to the embodiment of the present invention.

FIG. 5 is a diagram schematically showing a flow of a fluid in a return flow path of the centrifugal compressor according to the embodiment of the present invention.

FIG. 6 is a cross-sectional view of the centrifugal compressor illustrating a schematic configuration of the centrifugal compressor.

FIG. 7 is a schematic cross-sectional view of a return flow path for explaining a return flow path structure of a conventional centrifugal compressor.

FIG. 8 is a schematic cross-sectional view illustrating a return channel structure of a conventional centrifugal compressor viewed from the direction of arrow Y in FIG.

FIG. 9 is a diagram schematically showing a flow of a fluid in a return channel structure of a conventional centrifugal compressor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Centrifugal compressor 2 Rotating shaft 3 Impeller 6 Return flow path 6a Return flow path part 15 Return bend part 21 Return vane 22 End part on return bend part side C bending center position

Claims (1)

[Claims] 1. A centrifugal compressor provided with a return flow path between a plurality of impellers provided on a rotating shaft for guiding a fluid sent out from a preceding impeller to a subsequent impeller, wherein the return flow path comprises: A return bend portion bent in a U-shape in cross section, a return flow path portion between the return bend portion and the impeller on the subsequent stage, and a space in the return flow path portion in the circumferential direction of the rotating shaft. And a return vane having a plurality of return vanes, the return vane having an end on the return bend portion side located substantially at the middle of a bent portion on the downstream side of a bent center position of the return bend portion. A centrifugal compressor, characterized in that: