WO2020075378A1 - Centrifugal fluid machine - Google Patents

Abstract

The present invention provides a centrifugal fluid machine in which flow separation in a return flow passageway is suppressed and efficiency improvement is achieved. This centrifugal fluid machine comprises: a centrifugal impeller; a diffuser flow passageway disposed downstream of the centrifugal impeller; a curving flow passageway; and cross-over blades formed so as to provide communication between return flow passageways. The centrifugal fluid machine is characterized in that the trailing edge of the cross-over blades is inclined in the circumferential direction.

Description

Centrifugal fluid machine

The present invention relates to a centrifugal fluid machine.

Centrifugal fluid machines with rotating centrifugal impellers have been used as pumps and compressors for various plants and various equipment. In particular, in recent years, with the increasing demand for reduction of environmental load (power consumption), these fluid machines are required to have higher efficiency and wider operating range than ever before.

As background art of this technical field, there is JP-A-2016-169672 (Patent Document 1). In this publication, a diffuser flow path that guides fluid that has passed through an impeller radially outward, a return flow path formed on the second surface side of an annular partition wall on the opposite side, an annular partition wall, a diffuser flow path, and a return channel. On the outer peripheral side of the flow passage, an annular flow passage configured to guide the fluid from the diffuser flow passage to the return flow passage in the axial direction, at least a diffuser vane portion formed in the diffuser flow passage portion, and at least in the return flow passage portion And a return vane portion formed in the above, and at least one of the diffuser vane portion and the return vane portion is extended into the annular flow path (see summary).

Further, as background technology of this technical field, there is JP-A-2010-255451 (Patent Document 2). In this publication, an air guide has a substantially disk-shaped base portion, a plurality of upper surface blades and a plurality of lower surface blades sandwiching the base portion, and an outer periphery connecting the upper surface blade and the lower surface blade to an outer peripheral position of the base portion. By having a blade, the upper surface blade, the lower surface blade, and the outer peripheral blade are plate-shaped with a substantially uniform thickness, and a part of the adjacent outer peripheral blades are configured to overlap on the projection plane viewed from the rotation axis direction, It is described that it is possible to smoothly flow air from the upper surface flow path to the lower surface flow path, so that it is possible to reduce the bending loss and improve the ventilation efficiency (see the abstract).

JP, 2016-169672, A JP, 2010-255451, A

In the centrifugal pump described in Patent Document 1, at least one of the blade rows provided in the diffuser flow passage or the return flow passage is extended to the curved flow passage. Further, in the electric blower described in Patent Document 2, the blade inside the curved flow path is deformed. In each case, the loss inside the curved flow path is reduced to improve efficiency. However, Patent Document 1 and Patent Document 2 do not attempt to improve the efficiency by suppressing flow separation in the return flow passage. Further, Patent Document 1 and Patent Document 2 do not describe a centrifugal fluid machine that can maintain efficiency even when the outer diameter dimension in the radial direction of the centrifugal fluid machine is reduced.

Therefore, the present invention provides a centrifugal fluid machine that suppresses flow separation in the return flow path and improves efficiency.

In order to solve the above problems, a centrifugal fluid machine of the present invention is formed by connecting a centrifugal impeller with a diffuser flow passage, a curved flow passage, and a return flow passage that are arranged downstream of the centrifugal impeller. A crossover blade, and a trailing edge of the crossover blade is inclined in the circumferential direction.

According to the present invention, it is possible to provide a centrifugal fluid machine that suppresses flow separation in the return flow path and improves efficiency.

The problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

It is sectional drawing explaining a centrifugal fluid machine. It is a meridional surface sectional view which expanded the crossover diffuser which concerns on a present Example. It is an outline view explaining a static channel of a crossover diffuser concerning a comparative example. It is an outline view explaining the return channel side of the crossover diffuser concerning a comparative example. It is an outline view explaining the return channel side of the crossover diffuser concerning this example. 7 is a graph comparing changes in the flow passage cross-sectional area between the blades of the crossover blade according to the comparative example and the present embodiment. It is an analysis figure which compared the flow velocity distribution near the trailing edge of the crossover blade which concerns on a comparative example and this example obtained by numerical fluid analysis. It is explanatory drawing which expanded the return flow path side of the crossover diffuser which concerns on a present Example. FIG. 7 is an outline view illustrating a return flow path side of the crossover diffuser according to the second embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that the same configurations are denoted by the same reference numerals, and when the description is duplicated, the description may be omitted.

FIG. 1 is a sectional view illustrating a centrifugal fluid machine. In this embodiment, a multistage centrifugal pump will be used as the centrifugal fluid machine for description. It is also applicable to a single-stage centrifugal pump, a multi-stage centrifugal compressor, and a single-stage centrifugal compressor.

The centrifugal pump described in the present embodiment has a rotating shaft 12 that extends horizontally through the casing 11. Inside the casing 11, eight impellers 13 and seven static flow passages corresponding to seven centrifugal impellers (hereinafter, referred to as “impellers”) 13 excluding the final stage (see FIG. In FIG. 1, a flow path 21 in which the U-shape is inverted is accommodated.

The impeller 13 is fixed to the rotating shaft 12, and the stationary flow path 21 is fixed to the casing 11.
The number of impellers 13 is not limited to eight. The stationary flow passage 21 is arranged so as to correspond to the impeller 13 except the final stage.

The casing 11 includes a suction port 15 and a discharge port 16, and the suction port 15 side is the upstream side and the discharge port 16 side is the downstream side in the axial direction of the rotating shaft 12.

The rotary shaft 12 is rotated by a drive source not shown in FIG. The impeller 13 is fixed to the rotating shaft 12 and rotates together with the rotating shaft 12.

That is, the fluid flows in from the suction port 15 on the upstream side and flows out from the discharge port 16 on the downstream side via the impeller 13 and the stationary flow passage 21.

FIG. 2 is an enlarged meridional sectional view of the crossover diffuser according to the present embodiment.

The fluid flows in from the impeller inlet 13A located at the center of the impeller 13 in the radial direction and flows out from the impeller outlet 13B located at the radial outer side of the impeller 13. The fluid flowing out from the impeller outlet 13B passes through the stationary flow path 21 and flows into the next-stage impeller 13.

The flow path between the impellers 13 adjacent to each other is formed by the stationary flow path 21.
The stationary flow channel 21 is composed of a diffuser flow channel 22, a curved flow channel 23, and a return flow channel 24. When the fluid that has passed through the diffuser flow path 22 passes through the curved flow path 23, the flow direction changes from the outward direction to the inward direction. The turned fluid passes through the return flow path 24 and flows into the impeller 13 at the next stage.

In addition, the static flow passage 21 is arranged downstream of the impeller 13 and is formed in communication with the diffuser flow passage 22, the curved flow passage 23, and the return flow passage 24 so as to form a crossover blade (a stationary blade arranged in the circumferential direction). (Rows) 25, and a plurality of sheets are arranged uniformly in the circumferential direction. The crossover diffuser is composed of the stationary flow path 21 having the crossover blades 25.

The inside of the stationary flow passage 21 is referred to as a hub wall surface (hub) 26, and the outside of the stationary flow passage 21 is referred to as a shroud wall surface (shroud) 27.

The stationary flow passage 21 has an effect of decelerating the flow speed of the fluid flowing out from the impeller 13 and recovering the fluid pressure, and a swirl angle (flow angle) of the flow of the fluid flowing into the impeller 13 at the next stage. And the effect of adjusting.

FIG. 3 is an outline view illustrating a static flow path of the crossover diffuser according to the comparative example.

The left side of FIG. 3 shows the crossover diffuser from the diffuser flow path 22 side, the figure in FIG. 3 shows the crossover diffuser from the curved flow path 23 side, and the right side view of FIG. 3 shows the crossover. The diffuser is shown from the return flow path 24 side (perspectively).

The crossover blade 25 has ten blades that communicate with the diffuser flow path 22, the curved flow path 23, and the return flow path 24. Although the number of the crossover blades 25 is 10 in this embodiment, the number is not limited to 10 and may be 8 or 12.

Also, the crossover blade 25 is generally formed of a casting as an integrated body with the hub wall surface 26.

The crossover blades 25 flow between the blades in a direction indicated by an arrow (a direction from the leading edge 30 of the crossover blades 25 toward the trailing edge 31 of the crossover blades 25). It has a function of recovering the pressure of and a function of adjusting the swirling angle of the fluid flow.

It should be noted that the center line (dashed line) commonly described in the drawing on the left side of FIG. 3, the drawing in FIG. 3, and the drawing on the right side of FIG. 3 is the center of the crossover diffuser, and The center of rotation of the vehicle 13 is shown.

FIG. 4 is an outline view illustrating the return flow passage side of the crossover diffuser according to the comparative example.

FIG. 5 is an outline view illustrating the return flow passage side of the crossover diffuser according to the present embodiment.

4 and 5 show the crossover blade 25 from the return flow path 24 side, and a bird's eye view of the stationary flow path 21 from the return flow path 24 side with a line of sight parallel to the rotating shaft 12. A plurality of the crossover blades 25 shown in FIG. 4 and the crossover blades 25 shown in FIG. 5 are evenly arranged in the circumferential direction.

Comparing FIG. 4 and FIG. 5, it can be seen that the feature of the present embodiment resides in the wing-shaped structure of the stationary flow channel 21 mainly from the curved flow channel 23 to the return flow channel 24. Conversely, regarding the blade-shaped structure of the diffuser flow path 22, the blade-shaped structure described in this embodiment (may be referred to as “the shape of this embodiment” hereinafter) and the comparative example will be described. It is the same as the wing-shaped structure (may be referred to as “comparative example shape” hereinafter).

In other words, it can be seen that the blade-shaped structure described in the present example and the blade-shaped structure described in the comparative example are different in the blade-shaped structure of the trailing edge 31 of the crossover blade 25.

In the blade-shaped structure described in the comparative example, the trailing edge 31 of the crossover blade 25 is arranged parallel to the rotating shaft 12. Therefore, from the angle (line of sight) shown in FIG. 4, the pressure surface 28 of the crossover blade 25 is shown, but the suction surface 29 of the crossover blade 25 is not shown.

On the other hand, in the blade-shaped structure described in this embodiment, the trailing edge 31 of the crossover blade 25 is inclined in the circumferential direction. At this time, the trailing edge 31 of the crossover blade 25 is arranged such that the trailing edge 33 on the shroud wall surface 27 side is inclined with respect to the trailing edge 32 on the hub wall surface 26 side on the upstream side in the rotational direction of the impeller 13. To be done. That is, the trailing edge 31 of the crossover blade 25 is arranged at a position where the trailing edge 33 on the shroud wall surface 27 side is shifted to the upstream side in the rotational direction of the impeller 13 with respect to the trailing edge 32 on the hub wall surface 26 side. To be done.

Therefore, even from the angle (line of sight) shown in FIG. 5, the pressure surface 28 of the crossover blade 25 and the suction surface 29 of the crossover blade 25 are illustrated. That is, in the blade-shaped structure described in the present embodiment, the suction surface 29 of the crossover blade 25, which is not illustrated in the blade-shaped structure described in the comparative example, is illustrated.

As described above, in this embodiment, the trailing edge 31 of the crossover blade 25 is inclined in the circumferential direction to adjust the flow passage cross-sectional area between the blades of the crossover blade 25.

Further, in the centrifugal pump described in the present embodiment, since the trailing edge 31 of the crossover blade 25 arranged in the stationary flow passage 21 is inclined in the circumferential direction, separation of the fluid flow in the return flow passage 24 from the wall surface is prevented. It can be suppressed and efficiency can be improved. Then, even when the outer diameter of the centrifugal pump in the radial direction is reduced, the efficiency can be maintained.

FIG. 6 is a graph comparing changes in the flow passage cross-sectional area between the blades of the crossover blade according to the comparative example and the present embodiment.

That is, FIG. 6 shows a change in the flow passage cross-sectional area between the blades of the crossover blade 25 in the relationship between the meridional plane cross-sectional direction position and the flow passage cross-sectional area between the blades. The flow passage cross-sectional area between the blades represents a flow passage cross-sectional area on a cross section perpendicular to the flow direction of the fluid passing between the adjacent crossover blades 25 and 25. Further, the leading edge 30 of the crossover blade 25 is set to 0, and the trailing edge 31 of the crossover blade 25 is set to 1. From 0 to 1, the leading edge 30 of the crossover blade 25 to the trailing edge 31 of the crossover blade 25 is set. Represents up to.

From the diffuser flow path 22 to the first half of the curved flow path 23, there is no difference in the flow path cross-sectional area between the blades between the comparative example shape and the present example shape. However, the difference is confirmed from the middle half (intermediate position) of the curved flow path 23 where the inclination of the crossover blade 25 starts to the return flow path 24, and the shape of the present embodiment is compared with the shape of the conventional example, It can be seen that the flow passage cross-sectional area between the blades is narrow.

Therefore, it can be said that the expansion angle of the flow passage cross-sectional area between the blades from the middle half (intermediate position) of the curved flow passage 23 to the downstream (up to the return flow passage 24) is small.

Generally speaking, the larger the expansion angle of the flow passage cross section between the blades, the greater the diffuser effect and the higher the static pressure recovery rate. On the other hand, if the expansion angle of the flow passage cross-sectional area between the blades is too large, the fluid flow separates from the wall surface, increasing the loss, and conversely, the static pressure recovery rate becomes low (worse). For this reason, the design of the static flow passage 21 needs to be adjusted so that the expansion angle of the flow passage cross-sectional area between the blades is not made too large.

Further, geometrically, when the crossover blade 25 is bent in the radial direction from the circumferential direction, the flow passage cross-sectional area between the blades becomes large. Therefore, in order to adjust the flow passage cross-sectional area between the blades, it is important to bend the crossover blade 25 from the circumferential direction to the radial direction.

On the other hand, in the stationary flow passage 21, particularly the return flow passage 24, the swirling velocity component in the circumferential direction of the fluid flowing from the diffuser flow passage 22 to the return flow passage 24 through the curved flow passage 23 must be removed. . This is to reduce the influence on the impeller 13 of the next stage located downstream of the return flow path 24.

Therefore, it is necessary to bend the crossover blade 25 from the circumferential direction to the radial direction from the curved flow path 23 to the return flow path 24. By this bending, the swirling velocity component of the fluid in the circumferential direction is removed. However, when the crossover blades 25 are bent in the radial direction from the circumferential direction, the flow passage cross-sectional area between the blades increases. Therefore, it is necessary to divert the flow of the fluid from the circumferential direction to the radial direction while suppressing an excessive expansion of the flow passage cross-sectional area between the blades.

Therefore, in the present embodiment, the cross-sectional area of the flow path between the blades is adjusted by inclining the trailing edge 31 of the crossover blade 25 in the circumferential direction. When the trailing edge 31 of the crossover blade 25 is inclined in the circumferential direction, the crossover blade 25 on the shroud wall surface 27 side is sharply bent in the radial direction from the circumferential direction, while the crossover blade 25 on the hub wall surface 26 side is curved. From the direction to the radial direction. Therefore, the flow passage cross-sectional area on the hub wall surface 26 side is narrowed, and the change in the flow passage cross-sectional area between the blades is small, while the flow passage cross-sectional area on the shroud wall surface 27 side is wide and the flow between the blades is small. The change in road cross-sectional area also becomes large.

On the shroud wall surface 27 side, due to the action of centrifugal force of the flow, the flow of fluid is relatively difficult to separate from the wall surface even if the expansion angle of the flow passage cross-sectional area between the blades is large. On the other hand, on the hub wall surface 26 side, since the centrifugal force of the flow acts in the direction in which the flow separates from the wall surface, the flow of the fluid separates from the wall surface unless the expansion angle of the flow passage cross-sectional area between the blades is reduced. , Increase loss.

That is, in this embodiment, the trailing edge 31 of the crossover blade 25 is inclined in the circumferential direction to suppress the expansion of the flow passage cross-sectional area between the blades on the hub wall surface 26 side and the peeling on the hub wall surface 26 side. be able to.

As described above, in the present embodiment, the trailing edge 31 of the crossover blade 25 is formed so that the flow passage cross-sectional area on the hub wall surface 26 side is narrowed and the flow passage cross-sectional area on the shroud wall surface 27 side is widened. By inclining in the circumferential direction, it is possible to suppress separation of the fluid flow in the return flow path 24 from the wall surface, and it is possible to improve efficiency. Then, even when the outer diameter of the centrifugal pump in the radial direction is reduced, the efficiency can be maintained.

Also, looking at the change in the flow passage cross-sectional area between the blades shown in FIG. 6, it can be seen that the expansion of the flow passage cross-sectional area between the blades occurs from the middle half (intermediate position) of the curved flow passage 23. This means that the crossover blade 25 starts to be bent from the circumferential direction to the radial direction inside the curved flow path 23. Conversely, unless the crossover blade 25 is bent from this position, the swirling speed of the fluid in the circumferential direction reaches the outlet of the stationary flow passage 21 (the trailing edge 31 of the crossover blade 25 or the outlet of the return flow passage 24). It means that the components cannot be completely removed.

In particular, if the outer diameter of the centrifugal pump in the radial direction, which is one of the purposes of this embodiment, is reduced, that is, the outer diameter of the stationary flow passage 21 is reduced, the outermost diameter portion of the diffuser flow passage 22 is cut off. The area becomes smaller. As a result, the absolute value of the flow velocity at the outlet of the diffuser flow passage 22 becomes larger than that before the outer diameter of the stationary flow passage 21 is reduced. That is, it means that the swirling velocity component of the fluid in the circumferential direction increases. When the swirling velocity component of the fluid in the circumferential direction increases, the crossover blade 25 must be largely bent in the radial direction from the circumferential direction in order to turn the flow of the fluid.

On the other hand, in order to reduce the outer diameter of the static flow passage 21, the static flow shorter than that before reducing the outer diameter of the static flow passage 21 is smaller than that before the outer diameter of the static flow passage 21 is reduced. In the passage 21, the fluid of higher flow velocity must be diverted.

Further, since the static flow passage 21 becomes shorter, the flow path between the blades can be more appropriately set in the flow passage cross-sectional area of the outlet of the static flow passage 21 (the trailing edge 31 of the crossover blade 25 or the outlet of the return flow passage 24). It is necessary to set the expansion angle of the road cross-sectional area.

By reducing the outer diameter of the static flow passage 21, the effect of decelerating the fluid in the diffuser flow passage 22 is reduced, so that the flow velocity of the fluid flowing into the curved flow passage 23 is increased. In particular, as the diffuser flow path 22 becomes shorter, the effect of turning the flow, which is taken by the blade row of the diffuser flow path 22, becomes smaller, so that the swirling velocity component of the fluid in the circumferential direction increases.

The fluid flow that has flowed into the curved flow path 23 while the swirling velocity component of the fluid in the circumferential direction is large is easily separated from the blade surface of the curved flow path 23 or the blade surface of the return flow path 24. The fact that the swirling velocity component of the fluid in the circumferential direction is dominant means that the component in the direction in which the flow separates from the crossover blade 25 is dominant. Therefore, in the comparative example shape, the flow separates from the wall surface. .

When the flow separates from the wall surface, the loss increases, leading to a decrease in efficiency. In addition, since the fluid does not flow along the blade surface, the fluid reaches the outlet of the return flow passage 24 while the swirling velocity component of the fluid in the circumferential direction remains dominant, so that the fluid flows into the impeller 13 of the next stage. The angle becomes smaller, which leads to deterioration of fluid performance in the impeller 13 at the next stage.

In order to increase the diversion of the flow in the diffuser flow path 22, the blade rows of the diffuser flow path 22 are erected in the circumferential direction to obtain the same deceleration effect as before the outer diameter of the stationary flow path 21 was reduced. However, if the blade row of the diffuser flow path 22 is set up in the circumferential direction, the blade row is likely to be peeled during low flow rate operation, and stable operation may not be possible.

Therefore, in the present embodiment, in order to solve such a problem, the trailing edge 31 of the crossover blade 25 is tilted in the circumferential direction to adjust the flow passage cross-sectional area between the blades, thereby reducing the flow passage cross-sectional area between the blades. The point where the expansion starts, that is, the inclination of the crossover blade 25 starts is set inside the curved flow path 23. Furthermore, it is preferable to set the point at which the inclination of the crossover blade 25 starts to be in the middle half (intermediate position) of the curved flow path 23.

By this, it is possible to suppress the separation of the fluid flow in the return flow path 24 from the wall surface, and to improve the efficiency. Then, even when the outer diameter of the centrifugal pump in the radial direction is reduced, the efficiency can be maintained.

Also, reducing the outer diameter of the centrifugal pump in the radial direction leads to a reduction in the volume of the centrifugal pump, which directly leads to cost reduction. In this embodiment, a smaller centrifugal pump can be developed while maintaining high efficiency.

FIG. 7 is an analysis diagram comparing the flow velocity distributions near the trailing edge of the crossover blade according to the comparative example and the present example, which are obtained by numerical fluid analysis.

It can be seen that the flow velocity on the hub wall surface 26 side is low for both the comparative example shape and the present example shape. In the comparative example shape, a low flow velocity region due to the effect of flow separation can be confirmed near the suction surface 29. On the other hand, in the shape of this embodiment, this low flow velocity region is not confirmed, and it can be seen that flow separation is suppressed. This can be expected to improve efficiency.

By this, it is possible to suppress the separation of the fluid flow in the return flow path 24 from the wall surface, and to improve the efficiency. Then, even when the outer diameter of the centrifugal pump in the radial direction is reduced, the efficiency can be maintained.

FIG. 8 is an explanatory view in which the return flow passage side of the crossover diffuser according to the present embodiment is enlarged.

An intersection 36 where the camber line 34 on the hub side of the crossover blade 25 and the camber line 35 on the shroud side of the crossover blade 25 intersect is located inside the curved flow path 23.

That is, the camber line 35 on the shroud wall surface 27 of the crossover blade 25 and the camber line 34 on the hub wall surface 26 of the crossover blade 25 are curved when viewed from the rotation axis direction of the impeller 13. Will have an intersection 36 inside.

Also, this intersection 36 is preferably located downstream of the intermediate position of the curved flow path 23.

With this, it is possible to adjust the change in the flow passage cross-sectional area between the blades inside the curved flow passage portion 23. Specifically, mainly, it is possible to reduce the change in the flow passage cross-sectional area between the blades on the hub wall surface 26 side and suppress the separation of the fluid flow on the hub wall surface 26 side.

In the comparative example shape, this intersection 36 coincides with the trailing edge 31 of the crossover wing 25, and this intersection 36 does not exist. The existence of the intersection 36 is one of the structural feature points of the shape of this embodiment.

Further, as shown in FIG. 8, since the trailing edge 31 of the crossover blade 25 has an inclination in the circumferential direction, a circumferential lean angle 37 as indicated by α can be newly obtained as a shape parameter.

This circumferential lean angle 37 is because the trailing edge 31 of the crossover blade 25 has an inclination in the circumferential direction, that is, the trailing edge 33 of the shroud wall surface 27 side is smaller than the trailing edge 32 of the hub wall surface 26 side. Since it is arranged at a position shifted upstream in the rotation direction of the vehicle 13, it can be obtained.

The circumferential lean angle 37 (α) is a straight line formed from the center of the crossover diffuser to the rear edge 33 on the shroud wall surface 27 side and a straight line formed to the rear edge 32 on the hub wall surface 26 side. Is the angle between.

That is, this angle is a line segment that connects the trailing edge 33 on the shroud wall surface 27 side and the rotation center of the impeller 13 and a line segment that connects the trailing edge 32 on the hub wall surface 26 side and the rotation center of the impeller 13. And are angles formed at the center of rotation of the impeller 13.

-It is effective to set the value of the circumferential lean angle 37 (α) to 3 to 20 °. When α is 20 ° or more, the turning angle of the crossover blade 25 mainly on the shroud wall surface 27 side becomes excessively large, the fluid flow on the blade surface on the shroud wall surface 27 side is separated, and loss occurs. If α is 3 ° or less, the effect of inclining the trailing edge 31 of the crossover blade 25 in the circumferential direction may not be sufficiently exhibited. The value of the circumferential lean angle 37 (α) is more preferably 5 to 15 °.

As described above, according to the present embodiment, it is possible to provide a centrifugal pump that can be applied from a low flow rate operation to a high flow rate operation, that is, can be applied to a so-called wide operating range and that suppresses a decrease in efficiency.

Further, according to the present embodiment, even when the outer diameter of the centrifugal pump in the radial direction is reduced, it is possible to stably operate in the entire flow rate range while maintaining high efficiency.

Further, according to the present embodiment, it is possible to suppress the occurrence of loss in the stationary flow passage 21 and achieve high efficiency.

Further, according to this embodiment, the flow passage cross-sectional area between the blades can be adjusted, and in particular, in the flow passage from the curved flow passage 23 to the return flow passage 24, the change of the flow passage cross-sectional area between the blades can be suppressed. It can be made gentle and the increase in loss due to the rapid expansion of the flow passage cross-sectional area between the blades can be suppressed. Further, it is possible to suppress the separation of the fluid flow from the wall surface due to the rapid expansion of the flow passage cross-sectional area between the blades, reduce the loss, and appropriately adjust the inflow angle of the fluid to the next-stage impeller 13. be able to.

Further, according to the present embodiment, even when the radial outer diameter of the centrifugal pump is reduced, the efficiency can be maintained, so that cost reduction and improvement in operational efficiency can be expected. The installation area of the pump can also be reduced.

FIG. 9 is an external view illustrating the return flow path side of the crossover diffuser according to the second embodiment.

In this embodiment, the trailing edge 31 of the crossover blade 25 is inclined in the circumferential direction similarly to the first embodiment, but the downstream stationary blade 38 is arranged downstream of the trailing edge 31 of the crossover blade 25. To be done. The downstream vanes 38 are arranged inside the return flow passage 24, and are effective devices for further diverting the fluid flow that could not be diverted by the crossover vanes 25.

Although various arrangement positions of the downstream vanes 38 can be considered, like the crossover blade 25, they are arranged inside the return flow path 24, and with respect to the trailing edge 33 of the crossover blade 25 on the shroud wall surface 27 side. The impeller 13 is arranged so as to be located on the upstream side in the rotation direction. This maximizes the turning angle of the flow. The downstream vanes 38 are preferably arranged in the same number as the crossover blades 25.

In the present embodiment, the downstream stationary blade 38 has a two-dimensional blade structure, but various structures can be considered, and the downstream stationary blade 38 may be inclined in the circumferential direction similarly to the crossover blade 25, or three-dimensional. It may have a different wing structure.

In this way, even when the outer diameter of the centrifugal pump in the radial direction is reduced, it is possible to operate stably in the entire flow rate range while maintaining high efficiency.

Further, although these embodiments have been described on the assumption of a multi-stage centrifugal pump, any centrifugal pump having a diffuser flow passage 22, a curved flow passage 23, and a return flow passage 24 may be a single-stage centrifugal pump. Applicable. Further, it can be applied to a single-stage or multi-stage centrifugal gas machine having a similar structure.

Note that the present invention is not limited to the above-described embodiment, and includes various modifications.
For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described above.

11 ... Casing, 12 ... Rotating shaft, 13 ... Centrifugal impeller, 13A ... Impeller inlet, 13B ... Impeller outlet, 15 ... Suction port, 16 ... Discharge port, 21 ... Stationary flow path, 22 ... Diffuser flow path, 23 ... Bending flow path, 24 ... Return flow path, 25 ... Crossover blade, 26 ... Hub wall surface, 27 ... Shroud wall surface, 28 ... Crossover blade pressure surface, 29 ... Crossover blade suction surface, 30 ... Crossover blade Leading edge, 31 ... trailing edge of crossover blade, 32 ... hub wall side trailing edge, 33 ... shroud wall side trailing edge, 34 ... hub side camber line, 35 ... shroud side camber line, 36 ... intersection, 37 ... circumferential lean angle, 38 ... downstream vane

Claims (8)

1. A centrifugal impeller, and a crossover blade formed by communicating a diffuser flow passage, a curved flow passage, and a return flow passage arranged downstream of the centrifugal impeller,
   A centrifugal fluid machine, wherein a trailing edge of the crossover blade is inclined in a circumferential direction.
2. The trailing edge of the crossover blade, wherein the trailing edge on the shroud wall surface side is inclined toward the upstream side in the rotational direction of the centrifugal impeller with respect to the trailing edge on the hub wall surface side. 1. The centrifugal fluid machine according to 1.
3. The camber line on the shroud wall surface of the crossover blade and the camber line on the hub wall surface of the crossover blade have an intersection inside the curved flow path when viewed from the rotation axis direction of the centrifugal impeller. The centrifugal fluid machine according to claim 2, wherein.
4. The centrifugal fluid machine according to claim 3, wherein the intersection is located downstream of an intermediate position of the curved flow path.
5. A line segment that connects the trailing edge of the shroud wall surface and the rotation center of the centrifugal impeller and a line segment that connects the trailing edge of the hub wall surface side and the rotation center of the centrifugal impeller are The centrifugal fluid machine according to claim 2, wherein the angle formed at the center of rotation is 3 to 20 °.
6. The centrifugal fluid machine according to any one of claims 1 to 5, further comprising a downstream stationary blade downstream of a trailing edge of the crossover blade.
7. The centrifugal fluid machine according to claim 6, wherein the downstream vane is arranged in the return flow passage.
8. The centrifugal fluid machine according to claim 6, wherein the downstream vane is located upstream of the trailing edge on the shroud wall surface of the crossover blade in the rotational direction of the centrifugal impeller.

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