JP4707969B2 - Multistage fluid machinery - Google Patents

Description

  The present invention relates to a multistage fluid machine. In particular, the present invention is suitably applied to a multistage pump, a multistage compressor, and the like for high pressure water supply in a power plant, a water treatment plant, and the like.

  This type of multi-stage fluid machine is disclosed in, for example, Patent Document 1.

  A conventional multistage fluid machine will be described with reference to FIGS. 6 (A) and 6 (B). In the plurality of impellers 2 fixed to the rotating shaft 1, the outlet 2 b is positioned outside the inlet 2 a in the radial direction of the rotating shaft 1 (indicated by an arrow A). The stage casing 3 and the diffuser 4 form a flow path from the outlet 2 b of the impeller 2 to the inlet 2 a of the next stage impeller 2, that is, a diffuser flow path 6 and a return flow path 7. The diffuser 4 extends in the radial direction A of the rotary shaft 1 from the diffuser flow path 6 toward the inlet 2b of the next stage impeller 2 from the diffuser flow path 6 in the diffuser flow path 6 near the outlet 2b of the impeller 2. A return guide vane 9 disposed in the return flow path 7 is provided. The fluid such as water exiting the outlet 2b of the impeller 2 recovers static pressure by the diffuser blade 8 in the diffuser flow path 6, and then is rectified by the return guide blade 9 and passes through the return flow path 7 to the next impeller 2 Into the inlet 2a. As shown in FIG. 6B, the return guide vanes 9 are arranged radially with respect to the axis L of the rotating shaft 1.

In the multistage fluid machine of FIG. 6, the return guide vane 9 is designed so that the swirl component of the fluid at the trailing edge 9a becomes zero at the highest efficiency point, for example. Further, the position in the radial direction A of the rear edge 9a of the return guide vane (the length of the return guide vane 9 in the radial direction A) is the innermost end in the radial direction A of the front edge 5a of the blade 5 of the impeller 2. It is set so as to substantially match 5b. By setting the length of the return guide vane 9 in this way, it is possible to suppress the backflow from the next stage impeller 2 in the partial flow rate region, and to obtain a good total head-flow rate characteristic. Specifically, referring to the total head-flow rate characteristic H ₀ in FIG. 8, the total head H increases as the flow rate Q decreases in the partial amount region where the flow rate is lower than the maximum efficiency point (flow rate Q _he ). ing. In FIG. 8, η ₀ and SP ₀ indicate the efficiency-flow rate characteristic and the shaft power-flow rate characteristic of the multistage fluid machine of FIG. 6, respectively.

  However, since the position in the radial direction A of the rear edge 9a of the return guide vane 9 substantially coincides with the innermost end portion 5b in the radial direction A of the front edge 5a of the vane 5 of the impeller 2 as described above, During operation at the maximum efficiency point, in the region α outside the radial direction A from the trailing edge 9a of the return guide vane 9, the swirl component remains even after passing through the return guide vane 9, and the next stage impeller 2 A fluid flows into the inlet 2b. The remaining swirl component may cause a reduction in the maximum efficiency depending on the shape of the blade 5 of the impeller 2.

In order to improve the maximum efficiency, as shown in FIGS. 7A and 7B, the length of the return guide vane 9 in the radial direction A is reduced, and the rear edge 9 a of the return guide vane 9 is attached to the impeller 2. What is necessary is just to arrange | position to the radial direction A outer side of the rotating shaft 1 rather than the front edge 5a of the blade | wing 5. FIG. Referring to the efficiency-flow rate characteristic η ₁ in FIG. 8, the maximum efficiency η _1h of the multistage fluid machine in FIG. 7 is higher than the maximum efficiency _η0h of the multistage fluid machine in FIG.

However, if the length of the return guide vane 9 in the radial direction A is set short as shown in FIG. 7, the effect of suppressing the backflow from the impeller 2 at the next stage in the partial flow rate region cannot be obtained, and a good total head− The flow characteristics cannot be obtained. Specifically, referring to the total lift-flow rate characteristic H ₁ in FIG. 8, since there is a region where the total lift H ₁ decreases as the flow rate Q decreases, the total lift-flow rate characteristic H ₁ in the partial amount region. Indicates a mountain-like characteristic (mountain characteristic), and the total lifting height is also lower than in the case of FIG. In FIG. 8, SP ₁ indicates the shaft power-flow rate characteristic of the multistage fluid machine of FIG.

  As described above, when the length of the return guide blade 9 in the radial direction A is long (FIG. 6), the maximum efficiency cannot be sufficiently improved. Conversely, if the length of the return guide blade 9 in the radial direction A is short (FIG. 7), the total head-flow rate characteristic in the partial flow rate region is not good.

Patent 3,299,638

  It is an object of the present invention to provide a multistage fluid machine that has the highest efficiency and that can obtain a good total head-flow rate characteristic in a partial flow rate region.

  In this specification, with respect to the blade, the “front edge” refers to the upstream side in the fluid flow direction or the edge on the inlet side to the blade, and the “rear edge” refers to the downstream side in the fluid flow direction or the outlet from the blade. The side edge.

The present invention includes a plurality of impellers that are fixed to a rotating shaft and whose outlets are positioned radially outside the rotating shaft with respect to the inlet, and the inlets of the impellers in the next stage from the outlets of the impellers A plurality of diffuser blades positioned at an outlet of the impeller in a multi-stage fluid machine including a return flow path extending in a radial direction of the rotation shaft toward the rotation path and a plurality of return guide blades disposed in the return flow path And a diffuser comprising the plurality of return guide vanes, and a plurality of rectifying plates that extend through the axis of the rotating shaft and that are provided on a bush that is inserted through the rotating shaft and is fixed to the diffuser. The trailing edges of the plurality of return guide vanes are positioned radially outward of the rotating shaft with respect to the leading edges of the impeller blades, and the rectifying plates are arranged in front of every other return guide vane. The edge is the return guide Extending along the trailing edge of the root, and to provide a multistage fluid machine, characterized in that provided from the trailing edge of the return guide vanes in the return flow path so as to extend toward the rotating shaft.

  First, the trailing edge of the return guide vane is positioned on the outer side in the radial direction of the rotating shaft with respect to the leading edge of the vane of the impeller. In other words, the return guide vane has a short length in the radial direction of the rotating shaft. Therefore, in the flow rate range including the highest efficiency, the swirl component due to the preceding stage impeller is extremely small at the entrance of each impeller. Therefore, the efficiency in the flow rate region including the highest efficiency is improved.

  Next, since the rectifying plate extending from the rear edge of the return guide vane toward the rotating shaft is provided, the backflow from the next stage impeller in the partial flow rate region is rectified. In other words, the influence of the swirling component at the inlet of the next stage impeller on the behavior of the fluid on the outlet side of the preceding stage impeller can be reduced. Therefore, although the radial length of the rotating shaft of the return guide vane is short as described above, good total head-flow rate characteristics can be obtained in the partial flow rate region. Specifically, the peak-like characteristic (mountain shape characteristic) of the total head-flow rate curve resulting from the reduction of the total head with a decrease in the flow rate can be improved, and the reduction of the total lifting height can be prevented. .

  The rectifying plate is provided in a part of the return guide vane. In other words, the number of rectifying plates is smaller than the number of return guide vanes. Therefore, the influence of providing the rectifying plate is minimized in the flow rate region other than the partial flow rate region, and the maximum efficiency is achieved by shortening the radial length of the rotating shaft of the return guide vane as described above. Efficiency in the flow area is improved. The rectifying plate is preferably provided regularly, that is, for each of one or a plurality of return guide vanes.

  Further, the current plate extends from the rear edge of the return guide vane toward the rotation shaft, and is located on the radially inner side of the rotation shaft with respect to the return guide vane. Therefore, by providing the current plate, the dimension of the multistage fluid machine in the axial direction of the rotating shaft does not increase.

  As described above, according to the multistage fluid machine of the present invention, it is possible to obtain a good total head-flow rate characteristic in the partial flow rate range while achieving high efficiency in the flow rate range including the maximum efficiency, and The multistage fluid machine does not increase in size in the axial direction.

To increase the effect of rectifying the backflow from the next stage of the impeller in the partial throughput area by the rectifying plate, the front edge of the rectifier plate is Ru extends along the trailing edge of the return guide vanes.

Rectifying plate is not complicated shape such as a three-dimensional curved surface, Ru mere flat der is constant thickness. Also, the rectifying plate that is disposed radially relative to the axis of the rotary shaft. Therefore, manufacture is easy.

  The plurality of rectifying plates are fixed to a diffuser including a plurality of diffuser blades located at an outlet of the impeller and the plurality of return guide blades.

A plurality of rectifying plates bush rotating shaft is inserted, and fixing the bushing to the diffuser. Providing such a bush makes it easier to manufacture or assemble a multistage fluid machine.

In the multistage fluid machine of the present invention, the trailing edge of the return guide vane is located on the radially outer side of the rotating shaft with respect to the leading edge of the impeller blade, and a rectifying plate provided on a part of the plurality of return guide vanes is provided. In addition, the flow straightening plate extends from the trailing edge of the return guide vane toward the rotating shaft, improving the efficiency in the flow rate range including the highest efficiency point without increasing the size of the multistage fluid machine in the axial direction of the rotating shaft. In addition, good total head-flow rate characteristics can be obtained in the partial flow rate region. The current plate is not a complicated shape such as a three-dimensional curved surface, but a simple flat plate with a constant thickness. The rectifying plates are arranged radially with respect to the axis of the rotating shaft. Therefore, manufacture is easy. A plurality of rectifying plates are provided on the bush through which the rotating shaft is inserted, and the bush is fixed to the diffuser. Providing such a bush makes it easier to manufacture or assemble a multistage fluid machine.

  Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

(Implementation form)
1 and 2 show a multistage pump according to an embodiment of the present invention.

  Referring to FIG. 1, a casing 11 of this multistage pump includes a plurality of stage casings 12 that are respectively overlapped in a ring shape, a suction side casing 13 and a suction side of one end (right end in the figure) of these stage casings 12. A side ring 14 and a discharge side casing 15 and a discharge side ring 16 at the other end (the left end in the figure) of the stage casing 12 are provided. The suction side casing 13 and the discharge side casing 15 fasten the plurality of stage casings 12 in the direction of the axis L of the rotating shaft 19 (indicated by the arrow B) by the stay bolts 17, whereby the casing 11 is held integrally. A plurality of impellers 20 fixed to the rotating shaft 19 are accommodated in one stage casing 12, respectively. Further, a ring-shaped diffuser 21 is provided for each stage casing 12. The rotary shaft 19 extends through the casing 11 in the horizontal direction in the drawing. The rotating shaft 19 is sealed at both ends by shaft sealing devices 23A and 23B housed in packing boxes 22A and 22B fixed to the suction side and discharge side rings 14 and 16, respectively. Further, both ends of the rotating shaft 19 are rotatably supported by bearings 25A and 25B attached to brackets 24A and 24B fixed to the packing boxes 22A and 22B. In the drawing of the rotary shaft 19 protruding from the bracket 25A, the right end is mechanically connected to a motor (not shown). In order to balance the pressure in the direction of the axis L acting on the rotary shaft 19, a balance disk 26 and a balance sheet 27 are provided.

When the rotary shaft 19 is rotationally driven by the prime mover, the fluid such as water sucked from the suction port 13 a provided in the suction side casing 13 is pressurized by the impeller 20 of each stage rotating together with the rotary shaft 19. Thereafter, the ink is discharged from a discharge port 15 a formed in the discharge side casing 15.

  2 (A) and 2 (B), the plurality of impellers 20 fixed to the rotating shaft 19 are arranged such that the outlet 20b is outside the radial direction of the rotating shaft 19 (indicated by the arrow A) than the inlet 20a. Is located. The stage casing 12 and the diffuser 21 form a flow path from the outlet 20 b of the impeller 20 to the inlet 20 a of the next stage impeller 20, that is, a diffuser flow path 31 and a return flow path 32. The diffuser 21 is provided with a plurality of diffuser blades 34 and a plurality of return guide blades 35. Unlike the blades 36 of the impeller 20, the diffuser blades 34 and the return guide blades 35 are fixed blades or stationary blades that are stationary even during rotation of the rotary shaft 19. The diffuser blade 34 is disposed in the diffuser flow path 31 near the outlet 20 b of the impeller 20.

  The return guide vane 35 is disposed in the return channel 32 extending in the radial direction A of the rotary shaft 19 from the diffuser channel 31 toward the inlet 20a of the next stage impeller 20. As shown in FIG. 2B, the return guide vanes 35 are airfoil when viewed from the direction of the axis L of the rotary shaft 19 and are arranged radially with respect to the axis L. In the present embodiment, the number of return guide blades 35 is 18. Referring to FIG. 2A, the front edge 35a and the rear edge 35b of the return guide vane 35 in the Meridian section are straight lines extending in the direction B of the axis L and parallel to each other. Further, the rear edge 35b of the guide vane 35 is located on the outer side in the radial direction A of the rotary shaft 19 from the end 36b on the outermost side of the rotary shaft 19 in the radial direction A of the front edge 36a of the vane 36 of the impeller 20. Yes.

  A rectifying plate 37 is provided for a part of the plurality of return guide blades 35. As shown in FIG. 2 (B), in the present embodiment, every other rectifying plate 37 is provided for 18 return guide vanes 35 arranged radially, and the number of rectifying plates 37 is nine. is there. In other words, the rectifying plate 37 is provided sparser than the return guide vane 35.

  Referring to FIGS. 2A and 2B, the rectifying plate 37 has a flat plate shape with a constant thickness, and is arranged radially with respect to the axis L of the rotating shaft 19. The rectifying plate 37 extends in the radial direction A from the rear edge 35 b of the corresponding return guide vane 35 toward the rotary shaft 19. In other words, the current plate 37 is provided on the inner side in the radial direction A than the return guide vane 35.

  Further, like the diffuser blade 34 and the return guide blade 35, the rectifying plate 37 is a fixed blade or a stationary blade and is fixed to the diffuser 21. Specifically, referring to FIGS. 3 and 4 together, a rectifying plate 37 is provided on a bush 38 through which the rotary shaft 19 is inserted, and a flange 38 a provided at one end of the bush 38 is connected to the diffuser 21. It is fixed with bolts. It is not necessary to fix the individual rectifying plates 37 to the diffuser 21 separately, and the bush 38 only has to be fixed to the diffuser 21, so that the multistage pump can be easily manufactured or assembled.

As shown in FIG. 2A, the front edge 37 a of the rectifying plate 37 extends in the axial direction B of the rotating shaft 19 and extends along the rear edge 36 c of the blade 36 of the impeller 20 in the Meridian section. The front edge 37a of the rectifying plate 37 and the rear edge 35b of the return guide vane 35 are in contact with each other, and the return guide vane 35 and the corresponding rectifying plate 37 constitute almost one fluid element. On the other hand, the trailing edge 37 b of the rectifying plate 37 extends in the radial direction A of the rotating shaft 19. Any part of the rectifying plate 37 is disposed closer to the impeller 20 than the return guide vane 35. In other words, the rectifying plate 37 does not protrude beyond the return guide vane 35 to the impeller 20 side of the next stage.

Next, the operation of the above configuration will be described. First, as described above, the rear edge 35b of the return guide vane 35 is located on the outer side in the radial direction A of the rotary shaft 19 with respect to the front edge 36a of the vane 36 of the impeller 20. In other words, the return guide vane 35 has a short length in the radial direction A of the rotating shaft 19. Therefore, in the flow rate region including the highest efficiency point, the swirl component due to the preceding impeller 20 becomes extremely small at the inlet of each impeller 20, and the efficiency in this flow rate region is improved. In FIG. 8, H ₂ , η ₂ , and SP ₂ indicate the total head-flow rate characteristic, the efficiency-flow rate characteristic, and the shaft power-flow rate characteristic of the multistage pump of this embodiment, respectively. When the efficiency-flow rate characteristics η ₀ and η ₂ are compared between the present embodiment and the case where the return guide vane is long (see FIGS. 6A and 6B), the highest efficiency point (flow rate Q in the present embodiment) The efficiency η _2h at _he ) is higher than the efficiency η _0h when the length of the return guide vane is long.

Next, since the rectifying plate 37 extending from the rear edge 35b of the return guide vane 35 toward the rotating shaft 19 is provided, the backflow from the next stage impeller 20 in the partial flow rate region is rectified. In other words, the influence of the swirling component at the inlet 20a of the next stage impeller 20 on the behavior of the fluid on the outlet 20b side of the previous stage impeller 20 can be reduced. Therefore, although the length in the radial direction A of the rotating shaft 19 of the return guide vane 35 is short as described above, a good total head-flow rate characteristic can be obtained in the partial flow rate region. Referring to FIG. 8, when the length of the return guide vane is simply shortened (FIGS. 7A and 7B), the total head-flow rate characteristic H ₁ shows a mountain-like characteristic (mountain characteristic). total head of the present embodiment - flow characteristics H ₂ may be improved chevron characteristics, reduction of deadlines total head is also sufficiently suppressed.

  Further, not all the return guide vanes 35 are provided with the rectifying plates 37, but the rectifying plates 37 are provided only for a part of the return guide vanes 35. Therefore, the influence of the efficiency reduction in the flow rate region including the highest efficiency point due to the provision of the flow regulating plate 37 is minimized, and the length of the return guide vane 35 in the radial direction A of the rotating shaft 19 is reduced as described above. By shortening, the efficiency in the flow rate region including the highest efficiency point is improved.

  Further, the rectifying plate 37 is provided on the inner side in the radial direction A of the return guide vane 35 and does not protrude beyond the return guide vane 35 toward the next stage impeller 20. Therefore, an increase in the dimension of the multistage pump in the axial direction B of the rotating shaft 19 due to the provision of the rectifying plate 37 can be suppressed.

( Reference example )
In the reference example of the present invention shown in FIGS. 5A and 5B, nine rectifying plates 37 are directly fixed to the diffuser 21 separately. Since other structures and functions of the reference example is the same as the implementation form, the same elements will not be described are denoted by the same reference numerals.

  Although the present invention has been described by taking a multistage pump as an example, the multistage fluid machine of the present invention can also be applied to a multistage centrifugal compressor. Moreover, you may provide a baffle plate in the return guide blade | wing of every several sheets.

Sectional view showing a multi-stage pump according to the implementation embodiments of the present invention. (A) is a principal part enlarged view of FIG. 1, (B) is a figure which shows the return guide blade and the baffle plate seen from the axial direction of the rotating shaft. The front view of the bush for baffle plate fixation. FIG. 4 is a partial cross-sectional view taken along line IV-IV in FIG. 3. (A) is a principal part expanded sectional view of the multistage pump which concerns on the reference example of this invention, (B) is a figure which shows the return guide blade and the baffle plate seen from the axial direction of the rotating shaft. An example of the conventional multistage pump is shown, (A) is a principal part expanded sectional view, (B) is a figure which shows the return guide blade and the baffle plate seen from the axial direction of the rotating shaft. The other example of the conventional multistage pump is shown, (A) is a principal part expanded sectional view, (B) is a figure which shows the return guide blade and the baffle plate seen from the axial direction of the rotating shaft. Flow and total head in a multi pump according to implementation form of a conventional multistage fluid machine and the present invention, the diagram showing the relationship between the shaft power, and efficiency.

Explanation of symbols

11 Casing 12 Stage casing 13 Suction side casing 13a Suction port 14 Suction side ring 15 Discharge side casing 15a Discharge port 16 Discharge side ring 17 Stay bolt 19 Rotating shaft 20 Impeller 20a Inlet 20b Outlet 21 Diffuser 22A, 22B Packing box 23A, 23B Shaft seal device 24A, 24B Bracket 25A, 25B Bearing 26 Balance disk 27 Balance sheet 31 Diffuser flow path 32 Return flow path 34 Diffuser blade 35 Return guide blade 35a Front edge 35b Rear edge 36 Impeller blade 36a Front edge 36b End 36c Rear edge 37 Current plate 37a Front edge 37b Rear edge 38 Bush 38a Flange

Claims (1)

A plurality of impellers fixed to the rotating shaft and having outlets positioned radially outside the rotating shaft with respect to the inlet; and from the outlet of the impeller toward the inlet of the next stage of the impeller In a multistage fluid machine including a return flow path extending in the radial direction of the rotation shaft and a plurality of return guide vanes arranged in the return flow path,
A diffuser comprising a plurality of diffuser blades located at the exit of the impeller and the plurality of return guide vanes;
A plurality of rectifying plates extending radially with respect to the axis of the rotating shaft, provided on a bush that is inserted through the rotating shaft and fixed to the diffuser;
The rear edges of the plurality of return guide vanes are located on the radially outer side of the rotating shaft with respect to the front edges of the vanes of the impeller,
The rectifying plate has a leading edge extending along the trailing edge of the return guide blade with respect to every other return guide blade, and the rotation shaft extends from the rear edge of the return guide blade in the return flow path. A multi-stage fluid machine, wherein the multi-stage fluid machine is provided so as to extend toward the center .

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