JP5233465B2 - Multistage mixed flow pump - Google Patents

Description

  The present invention relates to a multistage mixed flow pump having a plurality of mixed flow impellers and a cylindrical guide blade disposed on the downstream side of each mixed flow impeller, and is particularly suitable when the specific speed is medium. The present invention relates to a multistage mixed flow pump.

The medium / high specific speed pump has a lower total lift and a higher flow rate than the low specific speed pump. Therefore, it is inlet diameter relatively close value diameter D ₂ out with D ₁ of the impeller, a meridian plane shape is mixed flow type. Further, in order to efficiently recover the pressure by the guide vanes, a bowl casing structure is frequently used so that a flow that is oblique to the shaft can be converted to a flow that is turned in the axial direction at the inlet.

  In such a conventional bowl type mixed flow pump, a complicated three-dimensional blade shape is used in order to make the flow inside the pump smooth and highly efficient. And in order to implement | achieve this complicated three-dimensional blade | wing, the guide blade | wing and the bowl type casing are manufactured as an integral casting product. When a cast product is used, it takes a lot of time and cost to manufacture and cast a wooden mold, which is a bottleneck in the pump manufacturing process.

  In order to improve the problems caused by adopting the cast product, in Patent Document 1, the guide blade is approximated by a part of a cone, and a steel plate is pressed against a conical jig to perform press forming. The inner and outer walls of the casing are formed into a cylindrical shape or a conical shape that can be easily roll-formed, and the entire ball-shaped casing is made into a can.

Japanese Patent No. 3126662 Nihon Kogyo Publishing "Turbo Pump New Revised Edition" (particularly, page 32, see Fig. 3.11)

  In the pump described in Patent Document 1, the inner casing is formed of an upstream cone portion, an intermediate cylindrical portion, and a downstream cone portion in the guide vane casing, and is equivalent to a cast guide vane casing. As a result, the inner casing manufacturing process becomes complicated at the guide vane casing outlet end.

  By the way, in a multi-stage pump in which impellers are provided in multiple stages to increase the discharge pressure of the pump, it is possible to improve the pump efficiency by guiding the flow exiting the upstream guide vane to the downstream impeller with little loss. is important. Therefore, on the downstream side of the ball casing part or the ball casing part forming the guide vanes, the outer diameter of the casing is reduced to guide the desired flow to the downstream impeller.

  That is, in the multistage mixed-flow pump, in order to reduce the inner and outer walls of the outlet end of the guide vane casing, a contracted pipe or the like is disposed on the downstream side of the guide vane casing. When a contraction tube or the like for reducing the inner and outer walls is disposed downstream of the cylindrical guide vane casing, the guide disposed in the guide vane casing is required unless the axial length of the contraction tube or the like is sufficiently long. Only the blades cannot turn all the rotational speed components at the impeller exit in the axial direction. And as described in the said nonpatent literature 1, the secondary flow which is the same direction as the rotation direction of an impeller on the outer wall side and the opposite direction on the inner wall side is formed. As a result, a large swirl velocity component remains in the flow, particularly on the outlet outer wall side of the guide vane casing.

  Furthermore, the swirling flow remaining on the outlet outer wall side of the guide vane casing is forcibly moved to the inner diameter side by a contracted tube or the like, and at that time, from the action of the free vortex flow expressed by the following (Equation 1), Increase turning speed.

C _u4 ∝1 / r (Formula 1)
When a swirl velocity component (here, C _u4 = C _u1 ) is added to the flow, the total head H generated by the impeller represented by the following (Equation 2) decreases. Here, U ₂ is the peripheral speed of the impeller outlet, C _u1 is the peripheral component of the absolute speed flowing into the impeller, C _u2 is the peripheral component C _u2 of the absolute speed flowing out of the impeller, and η is the pump hydraulic efficiency. , G is the gravitational acceleration.

H = η × U ₂ × (C _u2 −C _u1 ) / g (Formula 2)
This swirl speed component not only reduces the work of the next stage impeller, but also the flow in the contracted flow or tapered flow path is pressed against the outer wall side by centrifugal force, and loss due to separation of the flow from the inner wall of the tapered tube is lost. To increase. In addition, the mainstream of the next stage impeller has a great adverse effect that the mainstream drifts.

  The present invention has been made in view of the above-mentioned problems of the prior art, and the object of the present invention is to achieve the desired performance without sacrificing the manufacturability of guide vanes used in a single-stage mixed flow pump even in a multi-stage mixed flow pump. It is to satisfy the requirements of high specific speed and high efficiency.

A feature of the present invention that achieves the above object is that a plurality of mixed flow impellers are attached to a single rotating shaft, and at least a first mixed flow impeller is provided between the first mixed flow impeller and the second mixed flow impeller. In the multi-stage mixed flow pump in which the guide flow path means for guiding the exiting flow to the two-stage mixed flow impeller is formed, the guide flow path means is arranged in the cylindrical casing and the casing at intervals in the circumferential direction. A first guide channel means having a plurality of guide vanes, a contraction tube that forms a contraction channel whose cross-sectional area becomes narrower as it goes downstream, and a circumferential interval in the contraction tube A plurality of radially formed rectifying plates, and a plurality of guide vanes in which the direction of the outlet portion is parallel to the axis, and the plurality of rectifying plates guiding the Ri Ah in parallel to the axis plate, smooth current plate flow from the guide vane 2 Danhasuryu impeller It lies in the fact.

And in this aspect, the the guide vane and the rectifying plate is arranged adjacent to the axial direction and guide vanes and rectifier plates have good that are arranged with a gap in the axial direction. Leading and trailing edges of the integer Nagareban may be substantially perpendicular to the rotation axis inclined with respect to the rotational axis, the leading and trailing edges both outer diameter side inner diameter side It may be located on the guide vane side in the axial direction. It is desirable that the first guide channel means and the second guide channel means are manufactured integrally, and both have a can-making structure.

  According to the present invention, in the multistage mixed flow pump, the contracted flow path to the next stage impeller is formed downstream of the guide vanes arranged on the downstream side of the impeller, Since the flow straightening plate parallel to the shaft is arranged, the swirling speed component remaining at the guide vane outlet can be removed, and without sacrificing the manufacturability of the guide vane used in the single-stage mixed flow pump, the desired high specific speed and Satisfy high efficiency requirements.

  Hereinafter, several embodiments of the multistage mixed flow pump according to the present invention will be described with reference to the drawings. 1 to 3 are views of an embodiment of the multistage mixed flow pump 30. FIG. 1 is a meridional sectional view of the main part of the multistage mixed flow pump 30. FIG. 2 is a flow of the multistage mixed flow pump 30 shown in FIG. FIG. 3 is an AA line development view of the multi-stage mixed flow pump 30 shown in FIG. 1 and shows the relationship between the guide vanes 5 and the rectifying plate portion 7.

  FIG. 1 is a diagram showing a first two-stage portion of a multistage mixed flow pump 30, in which two sets of impellers 2 a and 2 b are attached to the rotary shaft 1 by an impeller nut 12. The impeller 2 a is accommodated in the casing liner 3. A cylindrical casing 4 formed in a substantially cylindrical shape is disposed between the two sets of impellers 2a and 2b. A plurality of guide vanes 5 are arranged in the cylindrical casing 4 at intervals in the circumferential direction. The cylindrical casing 4 is supported by a bearing 13. Note that guide vanes are also arranged on the downstream side of the second stage impeller 2b, but are not shown in the figure.

  Downstream of the first stage guide vane 5 is disposed a contraction pipe 6 composed of an inner tapered pipe 6a and an outer tapered pipe 6b that smoothly guides the flow from the guide vane 5 to the second stage impeller 2b. Yes. In the flow path formed between the two taper tubes 6a and 6b, a plurality of rectifying plates 7 that are parallel to the rotating shaft 1 and formed radially are disposed. The current plate 7 is integrally formed with the tapered tubes 6a and 6b by welding or the like. The front edge portion and the rear edge portion of the current plate 7 are formed perpendicular to the rotating shaft 1. The number of rectifying plates 7 is an integral multiple of the number of guide vanes 5 or a number that is a fraction of an integral number, here twice the number.

  The operation of this embodiment configured as described above will be described below. In the multi-stage mixed flow pump 30 shown in the present embodiment, the flow formed by the impeller 2a tilting in the circumferential direction at the impeller exit flows into the guide vane 5 with a swirl speed component. The guide blade 5 is configured so that the turning speed component generated in the impeller 2a is removed by setting the direction of the exit portion to a direction parallel to the axis.

  However, if the swirl velocity component of the flow generated by the impeller 2a is too large, or if the number of blades of the guide vane 5 cannot be increased in consideration of efficiency reduction due to wall friction or collision loss, the flow has a swirl component. While remaining, it flows into the second stage impeller 2b side. In this embodiment, even when the flow cannot be diverted in the axial direction, the rectifying plate 7 that rectifies the flow in the axial direction is provided on the downstream side of the guide vane 5, so the swirl speed component is removed, The flow may be axially redirected.

  The two adjacent guide blades 5 and 5 and the outer wall 4a and the inner wall 4b constituting the cylindrical casing 4 form a pseudo rectangular channel. According to the present embodiment, since the rectifying plate 7 and the guide vane 5 are spaced apart from each other in the axial direction, the rotation direction of the rotary shaft 1 as viewed from the suction side, which occurs in the pseudo rectangular channel, It has the effect of suppressing the development of secondary flow in the same direction.

  The flow in the meridian plane of the mixed flow pump 30 will be described using the meridional cross-sectional view of the multistage mixed flow pump 30 shown in FIG. As described above, the rectifying plate 7 suppresses the turning speed in the tapered flow-reducing tube 6 formed inward as it goes downstream. Thereby, the malfunction that the turning speed component of the flow which flows out from the guide blade 5 part reduces the work amount of the next stage impeller can be prevented.

  By the way, if the flow has a swirl velocity component in the guide vane 5 part, the magnitude of the swirl speed component is increased as a free vortex flow in the contracted tube 6 part as shown in the above formula 1. At the same time, the flow B1 in the contracted flow path is pressed against the outer tapered tube 6a side. When the flow as a whole is pressed against the outer tapered tube 6a side, separation of the flow is formed in the vicinity of the inner tapered tube 6b in the intermediate portion in the axial direction.

  According to this embodiment, since the swirl velocity component in the flow flowing out from the guide vane 5 part is reduced, it is possible to suppress the flow B2 of the contracted pipe 6 part from being displaced to the outer tapered pipe 6a side. It is possible to avoid an even greater adverse effect such as an increase in loss in the pipe 6 and the mainstream drifting at the center of the next stage impeller 2b.

  As described above, according to the present invention, the swirl speed remaining at the guide blade outlet is obtained by arranging the rectifying plates parallel to the plurality of axes in the contracted flow path to the next stage impeller installed downstream of the guide blade. Since the component can be removed by the current plate, the adverse effect caused by the swirling flow from the guide vanes combined with the tapered flow path can be alleviated. In addition, since a cylindrical casing is used instead of the bowl-type casing, when the can pump is used, the casing can be manufactured by roll bending, and the number of linear welds is increased, thereby improving the productivity of the casing. .

  Furthermore, even if cylindrical guide vanes are used, the axial length does not increase when formed in a multistage pump. The reason for this is as follows. When the guide blade portion is formed only by the cylindrical casing, a step is generated between the casing inner wall portion and the shaft portion. In this case, this level difference causes a large fluid loss. In order to avoid the loss that occurs at the stepped portion, a taper portion may be disposed in the casing downstream portion. However, if it is attempted to reduce the loss using only the taper tube, the taper angle must be set to a relatively small angle in order to prevent separation of the flow from the wall surface. As a result, the axial length of the tapered tube is increased. On the other hand, in this embodiment, since the rectifying plate is attached to the tapered tube portion, the axial length can be shortened while taking the swirl component of the flow. Thereby, the high efficiency requirement equivalent to that in the single stage can be satisfied.

  It should be noted that the degree of rectification of the outlet flow of the guide vane 5 is greatly influenced by the circumferential relative positional relationship between the guide vane 5 and the rectifying plate 7. That is, it is necessary to appropriately arrange the rectifying plate 7 in the circumferential direction with respect to the guide blade 5. As shown in FIG. 3, the main flow B <b> 3 is displaced toward the pressure surface 5 a side of the guide vane 5 in the guide vane 5 due to the swirl velocity component of the flow flowing out from the outlet of the impeller 2 a.

  If the length of the guide vane 5 is not sufficient, the main flow B3 is not turned in the axial direction (vertical direction in FIG. 3) but is displaced toward the pressure surface 5a side of the guide vane 5 and flows out while leaving the swirl speed component. Therefore, the position of the rectifying plate 7 is arranged on the pressure surface side with respect to the guide blade 5 from the central portion between the pitches of the guide blade 5. That is, it is approaching the pressure surface 5a of the guide vane 5 in the circumferential direction.

  Another embodiment of the multi-stage mixed flow pump according to the present invention will be described with reference to FIGS. FIG. 4 is a partial meridional cross-sectional view of the first stage and the second stage of the multistage mixed flow pump 30, and FIG. 5 is a view for explaining the flow of the multistage mixed flow pump 30. FIG. 5 shows a state where the flow rate is reduced to near the deadline.

  The present embodiment is different from the above-described embodiment in that the front edge 8a and the rear edge 8b of the current plate 8 are formed so as to be inclined to the upstream side from the line perpendicular to the rotary shaft 1 as going to the outer diameter side. is there. That is, the front edge 8a of the rectifying plate 8 is close to the rear edge of the guide blade 5 on the outer tapered tube 6a side, and is away from the rear edge of the guide blade 5 on the inner tapered tube 6b side. As for the rear edge 8b of the rectifying plate 8, the outer tapered tube 6a side is further away from the center portion of the next stage impeller 2b than the inner tapered tube 6b side. Others are the same as in the above embodiment, and the description is omitted.

  In the multistage mixed flow pump 30 of this embodiment configured as described above, it is not possible to turn all of the swirl speed component of the flow flowing out from the impeller 2a in the axial direction by the guide vane 5, and the swirl speed component remains. However, the flow is turned in the axial direction without the swirling speed component remaining in the rectifying plate 8. And the effect which suppresses with respect to the secondary flow formed in the flow path of 5 parts of guide blades by the effect | action similar to the said Example is produced.

  Since the rectifying plate 8 suppresses the swirling flow in the contracted pipe 6, it is possible to prevent the work amount of the next stage impeller 2 b from being reduced by the swirling speed component of the flow flowing out from the guide blade 5 part. Not only that, the centrifugal force of the swirl velocity component of the flow that presses the flow in the contracted tube 6 portion toward the outer tapered tube 6a becomes smaller, so that separation of the flow that may occur in the vicinity of the wall surface of the inner tapered tube 6b occurs. Can be suppressed. Thereby, the loss in the contracted pipe 6 can be reduced, and the further serious adverse effect that the main stream is displaced and flows into the center part of the next stage impeller 2b can be avoided.

  In the low flow rate region, as shown in FIG. 5, the relative proportion of the centrifugal force acting on the flow in the impeller 2a increases, and the outlet flow is biased outward. At the same time, a backflow D is generated on the inner wall 4b side of the guide vane 5 part, and the flow in the guide vane 5 part is also biased toward the outer wall 4a side. On the other hand, a reverse flow F is generated at the inlet of the next stage impeller 2b, and the flow E greatly meanders in the contracted pipe 6.

  In this embodiment, since the rectifying plate 8 is inclined to the outer tapered tube 6a side, the rectifying plate 8 immediately rectifies the flow exiting the guide vane 5 portion displaced to the outer tapered tube 6a side. Therefore, the rectifying action on the meandering flow E is increased.

  In addition, when the backflow F arises in the entrance of the next stage impeller 2b, the strong swirl speed component of the same direction as the rotation direction of the impeller 2b will generate | occur | produce by the backflow F. If the backflow F interferes with the upstream rectifying plate 8, the risk of erosion increases due to the collision of the flow. In addition, the swirl velocity component of the flow recovers pressure, and the total lift increases. However, in this embodiment, since the current plate 8 is inclined upstream with respect to the next stage impeller 2b, interference with the backflow F can be avoided.

  As described above, according to the present invention, since the plurality of rectifying plates parallel to the shaft are arranged in the contracted flow path provided downstream of the guide vanes, the swirl speed component remaining at the guide vane portion outlet is converted to the rectifying plate. Can be removed. And it can suppress that the centrifugal force resulting from a swirl flow makes a flow peel from an inner side taper wall surface. In addition, when operating at a low flow rate from the low flow rate range to the cutoff point, the flow that flows backward from the next stage impeller is less likely to interfere with the rectifying plate, and the reverse flow at the inlet of the next stage impeller may erode the rectifying plate. Sex is reduced. Furthermore, it is possible to suppress an increase in the deadline lift resulting from the suppression of the swirl velocity component of the reverse flow at the inlet of the impeller, and to prevent high pressure from acting on the discharge pipe. Therefore, the pressure resistance of the discharge pipe can be lowered.

  As a result, according to the present invention, even when the mixed flow pump is formed in multiple stages, the same high efficiency requirement as that of the single stage pump can be satisfied without sacrificing the manufacturability of the guide vanes. In each of the above embodiments, the first stage and the second stage of the multi-stage mixed flow pump have been described. However, in each of the second and subsequent stages, the above-described operation and effect can be achieved by using the current plate according to the present invention. Can be obtained. Further, when it is difficult to attach such guide vanes to all stages, it is preferable to provide them adjacent to at least the first stage guide vanes.

The meridian plane sectional view which shows the principal part of one Example of the multistage mixed flow pump which concerns on this invention. The figure explaining the flow around the baffle plate in the multistage mixed flow pump shown in FIG. FIG. 2 is a diagram of guide vanes and a rectifying plate portion provided in the multistage mixed flow pump shown in FIG. The meridian plane sectional view which shows the principal part of the other Example of the multistage mixed flow pump which concerns on this invention. The figure explaining the flow around the baffle plate in the multistage mixed flow pump shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Rotary shaft, 2 ... Impeller, 2a ... First stage impeller, 2b ... Second stage impeller, 3 ... Casing liner, 4 ... Cylindrical casing, 5 ... Guide blade, 5a ... Guide blade pressure surface, 6 ... Shrink Flow tube, 7, 8 ... Rectifying plate, 12 ... Impeller nut, 13 ... Bearing, B1 ... Flow in guide vane part, D ... Back flow in guide vane part, E ... Flow in guide vane part in low flow rate region, F ... Blade Backflow at the car entrance.

Claims (5)

A plurality of mixed-flow impellers are attached to a single rotating shaft, and at least the flow from the first-stage mixed flow impeller is converted into a two-stage mixed flow impeller between the first-stage mixed flow impeller and the two-stage mixed flow impeller. In the multistage mixed flow pump in which the guide channel means for guiding is formed,
The guide channel means has a first guide channel means having a cylindrical casing and a plurality of guide vanes arranged in the casing at intervals in the circumferential direction, and has a cross-sectional area as it goes downstream. A second guide channel means having a contraction tube forming a narrowed contraction channel and a plurality of radially formed rectifying plates disposed in the contraction tube at intervals in the circumferential direction; a plurality of said guide vanes is a direction orientation parallel to the axis of the outlet portion, a plurality of said straightening vanes Ri Ah in parallel to the axis plate, the 2 Danhasuryu vanes the flow from the guide vane A multi-stage mixed flow pump characterized in that the current plate smoothly guides to a car . Multistage mixed flow pump according to claim 1 wherein the guide vanes and said current plate is disposed adjacent to the axial direction, and the rectifying plate and the guide vanes, wherein the kite is arranged with a gap in the axial direction . The multistage mixed-flow pump according to claim 2, wherein a front edge portion and a rear edge portion of the current plate are substantially perpendicular to the rotation axis . The front edge portion and the rear edge portion of the current plate are inclined with respect to the rotation shaft, and both the front edge portion and the rear edge portion are positioned on the guide blade side in the axial direction from the inner diameter side to the outer diameter side. The multistage mixed flow pump according to claim 2 , wherein the multistage mixed flow pump is provided. 5. The multistage according to claim 1, wherein the first guide channel means and the second guide channel means are each integrally manufactured, and both have a can-making structure. Mixed flow pump.

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