JP2018178769A - Multistage fluid machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multistage fluid machine capable of improving revolution removal performance in a return channel while reducing rotor-stator blade interference with a blade of a subsequent stage of impeller.SOLUTION: With respect to a height of a revolution removal member 13 in a width direction of a return channel 10, a value H2 on a rear edge 15 of the revolution removal member 13 is smaller than a value H1 on a front edge 14 of the revolution removal member 13. Moreover, the height of the revolution removal member 13 decreases broadly monotonously as going to the downstream side of a flow of fluid. A distance in the width direction between a member center line A which presents a center of the revolution removal member 13 in the width direction of a return channel 10 and a wall surface 16 of the shroud side on the return channel 10 is as follows. That is, with respect to the distance, a value D2 on the rear edge 15 of the revolution removal member 13 is smaller than a value D1 on the front edge 14 of the revolution removal member 13 and decreases broadly monotonously as going to the downstream side.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a multi-stage fluid machine having a plurality of impellers such as centrifugal impellers and mixed flow impellers.

  In a multi-stage fluid machine in which a plurality of impellers, such as centrifugal impellers and mixed flow impellers, are mounted on one rotation shaft, working fluid (hereinafter also referred to simply as “fluid”) pressurized by the impellers of each stage is swirled. While being discharged radially outward. For this reason, in the multi-stage fluid machine, a return flow path for guiding the fluid discharged radially outward to the inlet of the next-stage impeller which is axially downstream and radially inward of the rotation shaft. A return channel is provided.

  When the fluid passes through the return channel of each stage, if the swirl component (pre-rotation) in the same direction as the impeller rotation direction in the flow can not be removed sufficiently, the efficiency and pressure rise in the impeller of the next stage decrease. It is generally known. Therefore, in order to realize high performance of the multi-stage fluid machine, it is effective to guide the fluid to the inlet of the next stage impeller after sufficiently removing the pre-swing in the return channel. Therefore, return vanes, which are vanes aligned at equal intervals in the circumferential direction, are installed in the return channel.

Patent Literatures 1 and 2 describe techniques for improving the fluid flow characteristics in the return channel.
For example, in the technology described in Patent Document 1, a splitter vane is provided between adjacent return vanes, and the trailing edge of the splitter vane extends downstream of the trailing edge of the return vane. With this configuration, the extension portion of the splitter vane can suppress displacement of the fluid in the separation direction at the downstream end of the return vane, and the fluid can flow along the return vane.

  Further, in the technology described in Patent Document 2, a straightening vane extending radially inward from the trailing edge of the return vane is provided in part of the plurality of return vanes. By this configuration, the backflow from the impeller of the next stage is rectified.

JP, 2015-135068, A JP 2005-330878 A

  In the techniques described in Patent Documents 1 and 2, a splitter vane and a straightening vane extending downstream of the trailing edge of the return vane are disposed downstream of the return vane. And both of the techniques described in Patent Literatures 1 and 2 have the ability to remove pre-swirling in the return channel by installing such splitter vanes or straightening vanes (hereinafter, also referred to as “swirl removal performance”). I am aiming for improvement.

  The members having swirl removal performance such as the splitter vanes and the flow straightening plates described in Patent Documents 1 and 2 (hereinafter referred to as "swirl removal members") have an improved removal performance for pre-swirl as the amount of extension to the downstream side increases. Do. Thereby, the efficiency and pressure rise in the impeller of the next stage can be improved. However, as the trailing edge of the turning removal member approaches the leading edge of the blade of the next stage impeller, the flow from the trailing edge of the turning removal member interferes with the blade of the next stage of rotating impeller, so-called Rotor-stationary interference will be intensified. For this reason, the stress fluctuation of the root which is the installation part to the wall surface of the turning removal member accompanying a noise and unsteady pressure fluctuation will increase. Although the splitter vanes and the straightening vanes described in Patent Documents 1 and 2 intend to remove the swirling component of the flow, the suppression of the dynamic and stationary blade interference that increases when the amount of extension to the downstream side increases is considered. It could not be said that it was considered enough.

  In addition, at the outlet of the return vane in the multistage fluid machine, in practice, the distribution of the swirling component of the flow is often attached in the vane height direction (the width direction of the return channel). However, it can not be said that the splitter vanes and the flow straightening plates described in Patent Documents 1 and 2 fully consider the distribution of the swirl component of the flow in the vane height direction.

  The present invention has been made in view of the above-described circumstances, and provides a multistage fluid machine capable of improving the turning removal performance in the return channel while reducing the dynamic and stationary blade interference with the blade of the next stage impeller. To be a task.

  In order to achieve the above-mentioned subject, a multistage fluid machine concerning the present invention is provided with a plurality of impellers, and a rotating shaft to which a plurality of the above-mentioned impellers are attached, respectively. The multi-stage fluid machine further includes a diffuser provided radially outward of the impeller, and a return channel provided downstream of the diffuser and guiding fluid from the diffuser to the downstream impeller. In addition, a multi-stage fluid machine is provided in the return channel, and includes a plurality of return vanes spaced along the circumferential direction. The return channel is provided with a pivoting removal member having a trailing edge located downstream of the trailing edge of the return vane. The height of the turning removal member in the width direction of the return channel is smaller at the trailing edge of the turning removal member than the value at the leading edge of the turning removal member and as it goes downstream It is monotonically decreasing in a broad sense. The distance in the width direction between the member center line indicating the center of the turning removal member in the width direction of the return channel and the wall surface positioned on the downstream side in the axial direction of the rotation axis in the return channel is as follows is there. That is, the value at the trailing edge of the turning removal member is smaller than the value at the leading edge of the turning removal member, and the distance monotonically decreases in the downstream direction.

  According to the present invention, it is possible to provide a multi-stage fluid machine capable of improving the turning removal performance in the return channel while reducing the dynamic and stationary blade interference with the blade of the next stage impeller.

1 is a meridional cross-sectional view showing a multi-stage fluid machine according to an embodiment of the present invention. FIG. 2 is a partial enlarged cross-sectional view of the multi-stage fluid machine shown in FIG. It is the figure which looked at the return vane periphery shown by FIG. 1 and FIG. 2 from the downstream of the axial direction of a rotating shaft. It is an expanded sectional view of a turning removal member periphery of FIG. It is a partial expanded sectional view of the multistage fluid machine which concerns on the conventional general comparative example in which the turning removal member shown in FIGS. 1-4 is not provided. An example of the contour figure of the flow angle in the exit of the return channel of the multistage fluid machine concerning a comparative example is shown with a return vane. In the cross-sectional view of an arbitrary stage of a general multi-stage fluid machine, the distribution of the flow direction direction of the flow near the outlet of the impeller and near the front edge of the return vane is schematically overlapped. is there. FIG. 8A is a view for explaining the inflow vector to the return vane and the flow line between the return vane in the vicinity of the wall on the hub side in the return vane of any stage of a general multistage fluid machine. FIG. 8 (b) is a view for explaining the inflow vector to the return vanes and the flow lines between the return vanes in the vicinity of the wall surface on the shroud side in the return vanes of arbitrary stages of a general multistage fluid machine. An example of the contour figure of the flow angle in the exit of the return channel of the multistage fluid machine concerning this embodiment is shown with a return vane. Fig.10 (a)-(d) is an expanded sectional view of a turning removal member periphery which concerns on a modification. FIGS. 11 (a) and 11 (b) are views of the periphery of the turning and removing member according to the modification viewed from the downstream side in the axial direction of the rotation shaft. Fig.12 (a) is an expanded sectional view of a turning removal member periphery which concerns on a modification. FIG. 12B is a view of the periphery of the turning removal member shown in FIG. 12A as viewed from the downstream side in the axial direction of the rotation axis. Fig.13 (a)-(c) is the figure which looked at the turning removal member which concerns on a modification from the downstream of the axial direction of a rotating shaft.

Embodiments of the present invention will be described in detail with reference to the drawings as appropriate.
In addition, in each figure, about the same component and the same component, the same code | symbol is attached | subjected and those duplicate description is abbreviate | omitted suitably.

FIG. 1 is a meridional cross-sectional view showing a multi-stage fluid machine 100 according to an embodiment of the present invention. Here, the meridional plane cross section refers to a cross section obtained by cutting each part of the multi-stage fluid machine 100 along a plane including the central axis of the rotation axis 4. FIG. 2 is a partial enlarged cross-sectional view of the multi-stage fluid machine 100 shown in FIG. FIG. 3 is a view of the area around the return vane 11 shown in FIG. 2 as viewed from the downstream side in the axial direction of the rotation shaft 4 (right side in FIG. 2). However, in FIG. 3, the illustration of the central and outer portions in the radial direction is omitted.
Hereinafter, an example in which the multi-stage fluid machine 100 is a single-shaft multi-stage centrifugal compressor will be described.

  As shown in FIG. 1, in the multi-stage fluid machine 100, a plurality of centrifugal impellers (hereinafter, also simply referred to as "impellers") 2 for imparting rotational energy to the working fluid and a plurality of impellers 2 are respectively attached And a rotating shaft 4. A diffuser 3 for converting the dynamic pressure component of the fluid delivered from the impeller 2 into a static pressure component is provided on the radially outer side of the impeller 2. Further, on the downstream side of the diffuser 3, a return channel 10 for guiding the fluid from the diffuser 3 to the impeller 2 at the subsequent stage is provided.

  As shown in FIG. 2, the impeller 2 has a disk-shaped hub 22 and a plurality of blades 21 disposed at intervals in the circumferential direction on the hub 22. Further, a shroud (side plate) 23 is disposed to face the hub 22 with the wing 21 interposed therebetween. The hub 22 is fastened to the rotating shaft 4. The plurality of wings 21 are located between the hub 22 and the shroud 23. In addition, in FIG. 2, an example of the closed type impeller 2 which has the shroud 23 is shown. However, an open type impeller without the shroud 23 may be used.

  In the present embodiment, as shown in FIG. 2, the diffuser 3 is a vane (vane) diffuser having a plurality of vanes arranged at substantially equal pitches in the circumferential direction. However, although not shown in FIG. 2, a vaneless diffuser without wings may be used.

  As shown in FIGS. 2 to 3, the return channel 10 is provided with a plurality of return vanes 11 which are a plurality of vanes arranged at equal intervals along the circumferential direction. In many cases, the return vane 11 is configured as an airfoil that faces substantially in the radial direction near the trailing edge 111, and is used to remove the swirling component of the flow of fluid passing through the impeller 2 and the diffuser 3 while rotating. It is an element. By removing the swirling component of the flow by the return vanes 11 and rectifying the flow flowing into the blades 21 of the impeller 2 of the next stage, the pressure rise amount and efficiency of the impeller 2 of the next stage are increased.

  As shown in FIG. 1, the multistage fluid machine 100 is configured such that the compression stages shown in FIG. 2 are stacked in the axial direction of the multistage rotary shaft 4. Radial bearings 7 rotatably supporting the rotating shaft 4 are disposed at both ends of the rotating shaft 4. Further, at one end of the rotating shaft 4, a thrust bearing 8 for supporting the rotating shaft 4 in the axial direction is disposed.

  The impeller 2 (five impellers 2 in FIG. 1) of the multistage compression stage is fixedly attached to the rotating shaft 4. As described above, the diffuser 3 and the return channel 10 are provided on the downstream side of each impeller 2. The impeller 2, the diffuser 3 and the return channel 10 are accommodated in a casing 9. A suction flow path 5 is provided on the suction side of the casing 9, and a discharge flow path 6 is provided on the discharge side of the casing 9.

  In the multi-stage fluid machine 100 configured in this way, the fluid drawn from the suction port 1 of the impeller 2 is boosted each time it passes through the impeller 2 of each stage, the diffuser 3 and the return channel 10, and the next stage Sent to the compression stage of Then, the compressed fluid finally reaches a predetermined pressure and is discharged to the discharge flow path 6.

  As shown in FIGS. 2 to 3, the return channel 10 is provided with a swirl removing member 13 having a trailing edge 15 located downstream of the trailing edge 111 of the return vane 11. The turning removal member 13 is provided between two adjacent return vanes 11 in the circumferential direction (here, the central position in the circumferential direction). In the present embodiment, the turning removal member 13 is a flat plate whose outer peripheral shape is formed in a specific shape described later, and has a constant thickness.

FIG. 4 is an enlarged cross-sectional view around the turning removal member 13 of FIG.
As shown in FIG. 4, in the meridional plane cross section, the height of the turning removal member 13 in the width direction of the return channel 10 is the trailing edge 15 of the turning removal member 13 than the value H1 at the front edge 14 of the turning removal member 13. The value H2 at is smaller. Moreover, the height of the swirl removing member 13 monotonously decreases in a broad sense as it goes downstream in the fluid flow. Here, the broad monotonous decrease means decreasing or maintaining the same value, that is, not increasing. That is, the height of the turning removal member 13 is generally smaller toward the downstream side.

  Further, the distance in the width direction between the member center line A indicating the center of the turning removal member 13 in the width direction of the return channel 10 and the wall surface 16 on the shroud side of the return channel 10 is as follows. That is, the distance D2 is smaller at the trailing edge 15 of the turning removal member 13 than the value D1 at the leading edge 14 of the turning removal member 13 and decreases monotonously in a broad sense as going downstream There is. Thereby, the length of the swirl removing member 13 in the direction along the flow channel of the return channel 10 becomes longer near the wall surface 16 on the shroud side and becomes shorter near the wall surface 17 on the hub side. The wall surface 16 on the shroud side refers to the wall surface on the side where the fluid passing through the shroud 23 (see FIG. 2) side of the impeller 2 mainly flows, and in the return channel 10, is located on the downstream side in the axial direction of the rotating shaft 4 It corresponds to the wall surface (the wall surface on the right side in FIG. 4). Further, the wall surface 17 on the hub side refers to the wall surface on the side on which the fluid passing through the hub 22 (see FIG. 2) side of the impeller 2 mainly flows, and in the return channel 10 on the upstream side in the axial direction of the rotating shaft 4 It corresponds to the located wall surface (the left wall surface in FIG. 4).

  Immediately downstream of the trailing edge 111 of the return vane 11, the height of the swirl removal member 13 matches the width of the return channel 10, ie, is approximately equal. Further, an end edge 131 located on the downstream side in the axial direction of the rotation shaft 4 in the turning removal member 13 is joined to the wall surface 16 on the shroud side in the return channel 10 and provided.

  The leading edge 14 of the swirl removing member 13 is located immediately downstream of the trailing edge 111 of the return vane 11. The end edge 132 located on the upstream side in the axial direction of the rotation shaft 4 in the turning removal member 13 exhibits a convex curve toward the wall surface 17 on the hub side in the return channel 10 in the meridional plane cross section. Further, the member center line A also exhibits a convex curve toward the wall surface 17 on the hub side in the return channel 10 in the meridional plane cross section.

  Next, the effect by installing the turning removal member 13 in the multistage fluid machine 100 configured as described above will be described.

  FIG. 5 is a partially enlarged cross-sectional view of a multistage fluid machine 200 according to a conventional general comparative example in which the swirl removing member 13 shown in FIGS. 1 to 4 is not provided. FIG. 6 shows an example of a contour diagram of the flow angle α at the outlet (equivalent to the suction port 1 of the impeller 2) of the return channel 10 of the multi-stage fluid machine 200 according to the comparative example, together with the return vane 11. The contour diagram of the flow angle α was obtained by numerical fluid analysis. Here, the flow angle α is an angle at which the flow is inclined with respect to the axial direction of the rotation axis 4. In the contour diagram, the region where α is positive (regions P1 to P6) is a region where the flow has a turning component (pre-rotation) in the same direction as the rotation direction of the impeller 2, while the region where α is negative (region N1 to N6) are regions where the flow has a turning component (reverse turning) in the direction opposite to the rotation direction of the impeller 2. In other words, the flow angle α is 0 in the case of the flow along the axial direction of the rotary shaft 4 and becomes “positive” in the case of the flow that inclines in the pre-rotation direction as it goes downstream, and pre-rotation as it goes downstream It becomes negative in the case of the flow which inclines in the direction opposite to the direction.

From FIG. 6, at the outlet of the return channel 10, it is the region on the radially outer side of the shroud 16 side on the side of the wall surface 16 on the radially outer side; It can be seen that it is the wall surface 17 side of the hub side.
The reason (mechanism) will be described with reference to FIGS. 7 to 8. FIG. 7 is a distribution E of the flow direction speed Cm of the flow direction in the vicinity of the outlet 24 of the impeller 2 and the front edge 112 of the return vane 11 in any meridional section of a general multi-stage fluid machine. Is a diagram schematically drawn on top of one another. Here, the direction of the flow meridional plane means the direction along the flow path in the meridional plane cross section. FIG. 8 (a) illustrates the inflow vector to the return vane 11 and the flow line between the return vane 11 in the vicinity of the wall surface 17 on the hub side in the return vane 11 of any stage of a general multi-stage fluid machine FIG. FIG. 8 (b) illustrates the inflow vector to the return vanes 11 and the streamlines between the return vanes 11 near the shroud-side wall surface 16 in the return vanes 11 of any stage of a general multi-stage fluid machine FIG.

  In the internal flow path of the impeller 2 of the multi-stage fluid machine, it is generally known that the low energy fluid is accumulated on the shroud 23 side due to the influence of the secondary flow. Therefore, as shown in FIG. 7, the distribution direction E of the flow which has flowed out from the outlet 24 of the impeller 2 is slow near the wall surface 16 on the shroud side, and is faster near the wall surface 17 on the hub side. It becomes. The distribution E of the flow's meridional direction velocity Cm is basically maintained as it passes through the diffuser 3 and flows into the return channel 10. Therefore, as shown in FIG. 7 and FIG. 8, in the inflow to the return vane 11 as well, the velocity in the direction of the meridional plane Cm of the flow is large near the wall surface 17 on the hub side and decreases near the wall surface 16 on the shroud side. On the other hand, the distribution of the swirling velocity Cu of the flow does not become a distribution having a large difference between the hub side and the shroud side as the velocity in the meridional direction Cm of the flow. Accordingly, the inflow angle β to the return vane 11 is large near the wall surface 17 on the hub side as shown in FIG. 8A, and is small near the wall surface 16 on the shroud side as shown in FIG. 8B.

  For this reason, as shown in FIG. 8B, in the vicinity of the wall surface 16 on the shroud side, the flow flows in the F direction from the direction of the antinode 113 of the return vane 11, and the flow is on the back 114 side of the return vane 11. It becomes difficult to flow along. Therefore, the fluid flows out of the return vane 11 while having a large component in the pre-swirl direction B.

  On the other hand, as shown in FIG. 8A, in the vicinity of the wall surface 17 on the hub side, the flow flows in the F direction along the front edge 112 of the return vane 11. However, the pre-swirling flow generated in the vicinity of the wall surface 16 on the shroud side collides with the adjacent return vane 11, and along the antinode 113 side of this return vane 11 head toward the wall surface 17 near the hub side again A return secondary flow G occurs. Due to the influence of the secondary flow G, as shown in FIG. 8A, the fluid flows out of the return vane 11 while basically having a reverse swirl component.

  The swirl component (residual swirl) remaining in the flow at the outlet of the return channel 10 described above is obtained by installing a swirl removal member such as a splitter vane or a flow straightening plate described in Patent Documents 1 and 2 downstream of the return vane 11. It can be reduced. In this case, the more the trailing edge of the turning removal member is extended to the downstream side, the more the remaining turning can be removed. However, this also simultaneously shortens the distance between the trailing edge of the turning removal member and the leading edge 25 of the blade 21 of the impeller 2 of the next stage, and increases the rotor-vane interference.

  So, in this embodiment, as shown to FIG. 2, FIG. 4, the height of the turning removal member 13 is generally made small as it goes downstream. By configuring in this manner, a region in which the distance between the rear edge 15 of the turning removal member 13 and the front edge 25 of the blade 21 of the impeller 2 of the next stage is reduced is reduced. Therefore, it is possible to suppress the increase in the interference of the moving and stationary blades while removing the remaining turning at the outlet of the return channel 10 (the suction port 1 of the impeller 2).

By the way, the decrease amount ΔH _th of the theoretical head of the impeller 2 of the next stage caused by the remaining turning is expressed by the equation (1).

  Here, U is the rotational peripheral speed of the impeller 2 at an arbitrary radial position R, and is expressed by equation (2), where the rotational angular velocity of the impeller 2 is ω.

Further, Cu _{1 n} is a swirl component of the flow at the front edge 25 of the blade 21 in the impeller 2 of the next stage, and takes a positive value in the pre-swirl direction and a negative value in the reverse swirl direction. From equations (1) and (2), the larger the pre-swirl component of the flow and the more radially outward, the larger the ΔHth caused by the remaining swing, and the theoretical head of the next-stage impeller lowers.

As described above, in the conventional general multi-stage fluid machine, the flow at the outlet of the return channel 10 has a reverse swirl component near the wall surface 17 on the hub side and has a pre-swirl component near the wall surface 16 on the shroud side. The radial position R of the front edge 25 of the blade 21 of the impeller 2 of the next stage is larger on the shroud side than on the hub side. Therefore, the influence of the pre-rotation component in the vicinity of the wall surface 16 of the shroud side becomes remarkable for [Delta] H _th. Therefore, in the conventional general multi-stage fluid machine, the pressure rise in the impeller 2 of the next stage is reduced.

  On the other hand, in the present embodiment, the length of the swirl removing member 13 in the direction along the flow channel of the return channel 10 can be increased near the wall surface 16 on the shroud side. Since the area near the wall surface 16 on the shroud side tends to have a large pre-swirl and has a large effect on lowering the theoretical head of the impeller 2 of the next stage, the long portion along the flow path of the swirl removing member 13 It is possible to enhance. On the other hand, the length of the swirl removing member 13 in the direction along the flow channel of the return channel 10 becomes short near the wall surface 17 on the hub side. However, as described above, the flow near the wall surface 17 on the hub side originally has a reverse turning component, and does not cause the theoretical head of the impeller 2 of the next stage to be lowered. In addition, even if the reverse rotation component remains, the radial position R on the hub side of the front edge 25 of the blade 21 of the impeller 2 of the next stage is small, so the influence on the performance of the impeller 2 of the next stage is small. As a result, the performance of the multi-stage fluid machine 100 is improved because only the pre-swirling near the shroud-side wall surface 16 that causes a large head drop is selectively removed.

  FIG. 9 shows an example of a contour diagram of the flow angle α at the outlet (the suction port 1 of the impeller 2) of the return channel 10 of the multi-stage fluid machine 100 according to the present embodiment, together with the return vanes 11. In the present embodiment, the turning removal member 13 is installed at a circumferentially central position between two adjacent return vanes 11. The contour diagram of the flow angle α was obtained by numerical fluid analysis.

  If FIG. 6 and FIG. 9 are compared, when the turning removal member 13 according to the present embodiment is installed, the absolute value of the value of α is larger than that of the conventional comparative example (see FIG. 6) over the entire flow path. It turns out that it is reducing. In particular, when the swirl removing member 13 according to the present embodiment is installed in the pre-swirling region α indicated by P5 to P6 near the shroud-side wall surface 16 that was remarkable in the comparative example of FIG. It can be seen that it is reduced.

As described above, in the present embodiment, the return channel 10 is provided with the turning removal member 13 which is set to be substantially smaller as the height goes downstream. As a result, it is possible to reduce the area where the distance between the trailing edge 15 of the turning removal member 13 and the front edge 25 of the blade 21 of the impeller 2 of the next stage is short. Therefore, it is possible to suppress the increase in the dynamic and stationary blade interference while removing the remaining turning at the outlet of the return channel 10.
Further, the length of the swirl removing member 13 in the direction along the flow channel of the return channel 10 is long near the wall surface 16 on the shroud side and short near the wall surface 17 on the hub side. As a result, a sufficient length of the swirl removing member 13 can be secured in the vicinity of the wall surface 16 on the shroud side where the pre-swirl component from the outlet of the return vane 11 particularly increases. Therefore, the turning removal performance of the turning removal member 13 can be effectively improved while suppressing the dynamic and stationary blade interference.
That is, according to the present embodiment, it is possible to provide the multistage fluid machine 100 capable of improving the turning removal performance in the return channel 10 while reducing the rotor-blade interference with the blades 21 of the impeller 2 of the next stage.

  Further, in the present embodiment, the height of the swirl removing member 13 is substantially equal to the width (flow passage width) of the return channel 10 immediately downstream of the trailing edge 111 of the return vane 11. In this configuration, it is possible to ensure the turning removal performance of the return channel 10 as large as possible.

  Further, in the present embodiment, the turning removal member 13 is joined to the wall surface 16 on the shroud side of the return channel 10 and installed. In this configuration, it is possible to increase the bonding area of the turning removal member 13 to the wall surface. Therefore, the installation of the turning removal member 13 on the wall surface is facilitated, and the strength of the root, which is the installation portion of the turning removal member 13 on the wall surface, is improved.

  Further, in the present embodiment, the turning removal member 13 is provided between two adjacent return vanes 11 in the circumferential direction. According to the numerical fluid analysis, it has been found that the turning removal performance in the return channel 10 can be further improved in this configuration.

  Further, in the present embodiment, since the turning removal member 13 is a flat plate, it can be easily manufactured even if the outer shape of the peripheral edge has the above-described specific shape.

  As mentioned above, although this invention was demonstrated based on embodiment, this invention is not limited to above-described embodiment, A various modified example is included. For example, the above-described embodiments are described in detail to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the described configurations. It is possible to add, delete, and replace other configurations for some of the configurations of the above-described embodiment.

  Fig.10 (a)-(d) is an expanded sectional view of turning removal member 13a-13d periphery which concerns on a modification. As shown to Fig.10 (a), the edge 132a located in the upstream of the axial direction of the rotating shaft 4 in the turning removal member 13a may be presenting the straight line in the meridional section. Further, as shown in FIG. 10 (b), the end edge 132b of the swirl removing member 13b located on the upstream side in the axial direction of the rotary shaft 4 may be constituted by a plurality of straight lines in the meridional section. Further, as shown in FIG. 10C, the end 132c of the swirl removing member 13c located on the upstream side in the axial direction of the rotary shaft 4 exhibits a curve in the meridional section. Here, the curve of the edge 132c is formed of a convex curve and a concave curve toward the wall surface 17 on the hub side of the return channel 10, but may be formed of only a concave curve. . Further, as shown in FIG. 10 (d), an end 132d of the swirl removing member 13d located on the upstream side in the axial direction of the rotary shaft 4 has a portion exhibiting a straight line and a portion 133 exhibiting a curve in the meridional section. You may have. The portion 133 exhibiting a curve of the end edge 132d is convex toward the wall surface 17 on the hub side of the return channel 10, and the height of the turning removal member 13d is maintained and constant.

  Moreover, in the embodiment described above, the turning removal member 13 is provided at the circumferential center position between two adjacent return vanes 11 in the circumferential direction, but the present invention is not limited to this. For example, as shown to Fig.11 (a), the turning removal member 13e may be provided close to the one return vane 11 in the circumferential direction between two return vanes 11 adjacent in a circumferential direction. Alternatively, a plurality of the turning removal members may be provided between two adjacent return vanes 11 in the circumferential direction. Further, as shown in FIG. 11B, the swirl removing member 13 f may be provided so as to extend radially inward from the rear edge 111 of the return vane 11.

  Further, in the above-described embodiment, the front edge 14 of the turning removal member 13 is located immediately downstream of the trailing edge 111 of the return vane 11, but this is not a limitation. As shown in FIG. 12, the leading edge 14 g of the swirl removing member 13 g may be located upstream of the trailing edge 111 of the return vane 11. In this case, the end edge 132g of the turning removal member 13g located on the upstream side in the axial direction of the rotary shaft 4 may be joined to the wall surface 17 on the hub side of the return channel 10 because the joining area can be secured.

  Further, in the above-described embodiment, the turning removal member 13 is a flat plate having a constant thickness, but is not limited to this and may be a wing shape. For example, a swirl removing member 13h having a symmetrical wing shape as shown in FIG. 13 (a), a swirl removing member 13i having a symmetrical wing shape on the front and back and front and back as shown in FIG. 13 (b), or As shown in FIG. 13 (c), a swirl removing member 13j may be used which exhibits a wing shape having a concave antinode and a convex back.

  In the above-described embodiment, an example in which the multistage fluid machine 100 is a single-shaft multistage centrifugal compressor has been described, but the present invention is not limited to this. The present invention can also be applied to other multistage fluid machines such as multistage centrifugal pumps, multistage mixed flow compressors, multistage mixed flow pumps and the like.

Reference Signs List 2 impeller 3 diffuser 4 rotation shaft 10 return channel 11 return vane 111 return vane trailing edge 112 return vane leading edge 13, 13a to 13 j swirl removing member 131 axially located downstream of the rotating shaft in the swirl removing member Edge 14, 14g Leading edge of the pivoting removal member 15 Trailing edge of the pivoting removal member 16 Wall surface on the shroud 17 Wall surface on the hub 100 Multi-stage fluid machine A Component centerline

Claims (5)

With multiple impellers,
A rotating shaft on which a plurality of said impellers are respectively mounted;
A diffuser provided radially outward of the impeller;
A return channel provided downstream of the diffuser for directing fluid from the diffuser to the downstream impeller;
A plurality of return vanes provided in the return channel and spaced along the circumferential direction;
The return channel is provided with a pivoting removal member having a trailing edge located downstream of the trailing edge of the return vane,
The height of the turning removal member in the width direction of the return channel is smaller at the trailing edge of the turning removal member than the value at the leading edge of the turning removal member and as it goes downstream In a broad sense monotonous decrease,
The distance in the width direction between the member center line indicating the center of the turning removal member in the width direction of the return channel and the wall surface positioned on the downstream side in the axial direction of the rotation axis in the return channel is the turning removal member A multi-stage fluid machine characterized in that the value at the trailing edge of the swirl removing member is smaller than the value at the leading edge of the swirl elimination member and monotonously decreases in a broad sense toward the downstream side.   The multi-stage fluid machine according to claim 1, wherein the height of the swirl removing member matches the width of the return channel immediately downstream of the trailing edge of the return vane.   The edge of the turning removal member located on the downstream side in the axial direction of the rotation shaft is joined to the wall surface on the downstream side of the rotation shaft in the return channel. The multistage fluid machine according to Item 1.   The multistage fluid machine according to claim 1, wherein the turning removal member is provided between two adjacent return vanes in a circumferential direction.   The multistage fluid machine according to any one of claims 1 to 4, wherein the turning removal member is a flat plate.

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