WO2017170640A1

WO2017170640A1 - Diffuser and multistage pump

Info

Publication number: WO2017170640A1
Application number: PCT/JP2017/012812
Authority: WO
Inventors: 和也平本; 真志大渕; 前田　毅
Original assignee: 株式会社荏原製作所
Priority date: 2016-03-29
Filing date: 2017-03-29
Publication date: 2017-10-05
Also published as: CN108700078B; BR112018069611A2; CN108700078A; TWI716571B; JP2017180193A; BR112018069611B1; TW201738462A; JP6712159B2

Abstract

This diffuser (250) is provided with: a case part (260, 270) for demarcating a cylindrical passage so that the diameter thereof is narrowed from a fluid inflow side toward an outflow side; and a plurality of diffuser blade parts (280) for helicoidally partitioning the cylindrical passage, the plurality of diffuser blade parts (280) being disposed in the cylindrical passage. In the plurality of diffuser blade parts (280), the angle formed by a circumferential direction and the blade surface tangential direction of the diffuser parts with respect to a revolving shaft at a discretionary meridian position of the case part (260, 270) is defined as a diffuser blade angle βw. This diffuser blade angle βw(°) changes by a change amount Δβw that satisfies the relationship Δβw < 2.4 × ΔXc with respect to the unit change amount ΔXc (mm) of the meridian position. Also, the diffuse blade angle βw is less than 90° in all areas.

Description

Diffuser and multistage pump device

The present invention relates to a diffuser and a multistage pump device.

Conventionally, multistage pumps are widely used to transfer fluids. The multi-stage pump is configured such that a plurality of impellers arranged along a drive shaft are accommodated in a diffuser that defines a fluid flow path. The diffuser guides and rectifies the fluid boosted by the impeller spirally, and transfers the fluid to the next stage impeller. In a multistage pump, a desired head can be obtained by changing the number of stages of the impeller and the diffuser.

Patent Document 1: Japanese Patent Laid-Open No. 6-323291

In the multistage pump device, the shape of the diffuser is designed so as to be the most energy efficient when operating at a predetermined rated discharge rate. For example, in general, the diffuser is designed such that the angle βw of the diffuser blade that defines the internal flow path is directed in the axial direction by removing the swirl velocity component of the outlet flow. However, in order to remove the swirl velocity component of the outlet flow while suppressing the separation of the flow in the diffuser, it is necessary to increase the axial length of the diffuser, and there is a problem that the total length of the pump is increased.

Also, in order to eliminate the swirl velocity component of the outlet flow with a diffuser having a short axial length, it is necessary to increase the angle βw of the diffuser blade, and the blade angle βw increases from the inlet to the outlet. In this case, separation tends to occur in the flow in the diffuser, and the efficiency of the diffuser decreases due to the secondary flow (flow disturbance) in the diffuser. Further, when the impeller and the diffuser are stacked in a plurality of stages, the separation generated in the preceding diffuser affects the impeller and the diffuser in the subsequent stages, resulting in a reduction in energy efficiency.

The present invention has been made in view of the above problems, and an object of the present invention is to propose a small-sized and highly energy-efficient diffuser and a multi-stage pump device in a multi-stage pump device in which a plurality of diffusers are stacked.

The diffuser of the present invention is used in a multistage pump, and is arranged concentrically with an impeller that rotates around a rotation axis, and guides a fluid that is attracted as the impeller rotates. This diffuser is arranged in a plurality of cases with a cylindrical flow path that defines a cylindrical flow path so that the diameter decreases from the fluid inflow side to the outflow side, and the cylindrical flow path is spirally formed. And a plurality of diffuser wing parts. For a plurality of diffuser blade portions, an angle formed by the circumferential direction with respect to the rotation axis and the blade surface tangential direction of the diffuser blade portion at an arbitrary meridional surface position of the case portion is defined as a diffuser blade angle βw. The diffuser blade angle βw (°) changes with a change amount Δβw that satisfies the relationship of Δβw <2.4 · ΔXc with respect to the unit change amount ΔXc (mm) of the meridian plane position. Further, the diffuser blade angle βw is smaller than 90 ° in all regions. Thus, the swirl velocity component remains in the outlet flow of the diffuser, the outlet flow of each diffuser can be stabilized regardless of the pump flow rate, and a small and highly efficient multi-stage pump device can be realized.

Further, it is preferable that the maximum outer diameter φDc of the flow path defined by the case portion and the meridional blade length Lc on the outer peripheral side of the diffuser blade portion satisfy the relationship of Lc / φDc <0.64.

Further, it is preferable that the maximum inner diameter φDh of the flow path defined by the case portion and the meridional blade length Lh on the inner peripheral side of the diffuser blade portion satisfy the relationship of Lh / φDh <0.63.

Further, in the diffuser blade portion, it is preferable that the meridian blade length Lh on the inner peripheral side is equal to or shorter than the meridian blade length Lc on the outer peripheral side.

In addition, the wall surface on the inner peripheral side at the outflow side end of the case portion has a maximum value θo of the angle formed with the rotation axis on the downstream side of the position where the inner diameter of the flow path is maximum, θo with respect to the specific speed Ns. It is preferable that the relationship> 1500 · Ns ^−0.6 is satisfied. Here, the specific speed Ns is defined as Ns = (Np · Qp ^1/2 ) where Np is the rotational speed (min ⁻¹ ) of the pump, Qp is the discharge amount (m ³ / min), and Hp is the total head (m). ) / Hp ^3/4 .

The multi-stage pump device of the present invention includes a plurality of stages of the above-described diffuser of the present invention and an impeller that is arranged concentrically with the diffuser and attracts fluid to the diffuser.

According to this multistage pump device, the same effect as the diffuser of the present invention can be obtained.

Moreover, the multistage pump device may further include a power source for rotating the impeller.

It is a longitudinal section showing the multi stage pump device of this embodiment typically. It is a schematic diagram which expands and shows the diffuser periphery of this embodiment. It is a schematic diagram which shows the inner case part and diffuser wing | blade part of a diffuser, omitting an outer case part. It is a figure which shows the efficiency curve of an impeller with respect to the discharge amount of a multistage pump. It is a figure which shows the efficiency curve of a diffuser with respect to the discharge amount of a multistage pump.

Hereinafter, a diffuser and a multistage pump device according to an embodiment of the present invention will be described with reference to the drawings. In the following embodiments, a deep well submersible motor pump including a submersible pump will be described as an example, but the present invention is not limited to such an example and can be applied to various multistage pump devices and diffusers.

FIG. 1 is a longitudinal sectional view schematically showing a multistage pump according to this embodiment. In the figure, bold arrows schematically show the flow of fluid. As shown in FIG. 1, the multistage pump device 10 includes a motor 100 as a power source and a pump unit 200 attached to the upper part of the motor 100.

The motor 100 is connected to an external power source (not shown) via an electric cable 102. The drive shaft 104 of the motor 100 is connected to the main shaft 230 of the pump unit 200 via the joint 106. In the present embodiment, the drive shaft 104 of the motor 100 and the main shaft 230 of the pump unit 200 extend in the axis (rotary shaft) Aw direction and are arranged concentrically. As long as the motor 100 can rotate the main shaft 230 of the pump unit 200, any motor 100 may be used. Since the motor 100 does not form the core of the present invention, the description of the detailed configuration is omitted.

The pump unit 200 includes a suction case 210, a discharge case 220, a main shaft 230, an impeller 240, and a diffuser 250.

The suction case 210 is provided on the upper part of the motor 100 and is arranged as the lowermost stage of the pump unit 200. The suction case 210 is fixed to the motor 100 by fastening a lower assembly portion 212 and the case 108 of the motor 100 with screws 214. The suction case 210 is formed in a substantially cylindrical shape, and a suction port 216 for sucking fluid is formed in the upper portion of the assembly portion 212. The assembly part 252 of the diffuser 250 is fastened to the assembly part 218 at the upper part of the suction case 210 with screws 253, and the diffuser 250 is fixed.

The discharge case 220 is provided on the upper part of the diffuser 250 and is disposed as the uppermost stage of the pump unit 200. The discharge case 220 is fixed to the diffuser 250 by fastening a lower assembly part 222 and an assembly part 254 of the diffuser 250 with screws 255. The discharge case 220 is formed in a substantially cylindrical shape, and the upper assembly portion 224 is attached to a discharge pipe (not shown). The discharge case 220 includes a check valve 226 that prevents the fluid from flowing backward.

The main shaft 230 is connected to the motor 100 through the joint 106 and is inserted through the suction case 210 and the diffuser 250. The main shaft 230 is supported by a bearing sleeve 268 of the diffuser 250. A plurality of impellers 240 are attached to the main shaft 230, and the plurality of impellers 240 rotate as the main shaft 230 rotates.

The impeller 240 has a cylindrical insertion portion for inserting the main shaft 230 and a plurality of blades attached to the outer peripheral surface of the insertion portion. The impeller 240 rotates integrally with the main shaft 230 and pumps fluid from the upstream (lower in the figure) to the downstream (upper in the figure) by a plurality of blades.

The diffuser 250 is made of metal or resin, and is arranged concentrically with the rotating shaft (main shaft 230) of the impeller 240. FIG. 2 is an enlarged schematic view showing the periphery of the diffuser of the present embodiment. Note that FIG. 2 shows a cross section along the axis Aw, but the diffuser blade 280 shows one diffuser blade 280 along the blade surface. Further, the diffuser blade portion 280 is not a cross section, but is shaded so as to facilitate understanding. Hereinafter, a cross section along the axis Aw is referred to as a “meridian plane”.

In this embodiment, the diffuser 250 accommodates the main shaft 230 and the impeller 240 and defines a fluid flow path. The diffuser 250 includes a liner ring 258 between the diffuser 250 and the impeller 240 in order to prevent backflow of fluid. The diffuser 250 has

assembly parts

252 and 254 at the top and bottom, and can be fixed to the suction case 210 and the discharge case 220. Further, the diffuser 250 is formed so that a plurality of stages can be stacked with a pair of the diffuser 250 and the impeller 240 as one stage (in the example of FIG. 1, two stages are stacked).

FIG. 3 is a schematic diagram showing the inner case portion of the diffuser and the diffuser wing portion with the outer case portion omitted. In FIG. 3, the blade surface of one diffuser blade portion 280 is shaded so as to correspond to FIG. 2. As shown in FIGS. 2 and 3, the diffuser 250 includes an inner case part 260 that defines the inner wall of the flow path, an outer case part 270 that defines the outer wall of the flow path, an inner case part 260, and an outer case part 270. And a plurality of diffuser wings 280 for connecting the two. The inner case portion 260, the outer case portion 270, and the diffuser blade portion 280 may be integrally formed by, for example, metal casting, or may be separately formed and connected.

The inner case portion 260 is provided with a bearing sleeve 268 into which the main shaft 230 is inserted (see FIG. 1). As shown in FIGS. 1 to 3, the inner case portion 260 is formed in a substantially cylindrical shape whose diameter decreases toward the upper side (downstream). The outer case part 270 includes a space having a shape corresponding to the outline of the inner case part 260 so that a flow path is defined between the outer case part 270 and the inner case part 260. That is, the outer case portion 270 is formed in a hollow shape, and is formed in a substantially cylindrical shape whose diameter decreases toward the top. The inner case portion 260 and the outer case portion 270 are arranged apart from each other, thereby defining a cylindrical flow path Fc through which a fluid attracted from the impeller 240 passes.

The inner case portion 260 and the outer case portion 270 are connected to each other by a plurality of (seven in this embodiment) diffuser blade portions 280 in a state of being separated from each other. The plurality of diffuser blade portions 280 are disposed in the cylindrical flow path Fc with an equal positional relationship in the circumferential direction with respect to the axis Aw, and are each formed in a plate shape having a smooth curved plate surface (blade surface). ing.

As shown in FIGS. 2 and 3, the diffuser blade portion 280 is configured to partition a cylindrical flow path Fc defined by the inner case portion 260 and the outer case portion 270 by the blade surface while rotating in the circumferential direction. Is arranged. The diffuser blade 280 has a plate surface substantially perpendicular to the axial direction of the main shaft 230 at the lower end (end on the inflow side of the flow path), and a plate surface at the upper end (end on the outflow side of the flow path). It is provided so as to be substantially parallel to the axial direction of the main shaft 230. Thereby, the diffuser wing | blade part 280 partitions so that the space demarcated by the inner side case part 260 and the outer side case part 270 may become a some spiral flow path.

In the present embodiment, the diffuser blade portion 280 is configured so that the blade angle βw changes with a small change amount Δβw. Here, the blade angle βw is an angle (°) formed by a tangent at the blade thickness center line Cd of the diffuser blade 280 along the fluid flow path and a circumferential tangent Rd around the axis Aw with respect to the tangent. . In the present embodiment, the thickness of the diffuser blade 280 is substantially constant, and the tangent of the blade thickness at the center line Cd is substantially the same as the tangent at the blade surface. However, the blade angle βw is not the center line Cd of the blade thickness, but the tangent to the blade surface on the upstream side (lower side in the figure) or the downstream side (upper side in the figure) of the diffuser blade part 280 and the axis Aw. It is good also as an angle (degree) which the tangent line Rd of the circumferential direction makes. The blade angle βw varies depending on the meridian position Xc (mm) of the inner case portion 260 and the outer case portion 270 (in the drawing, the blade angle βw (Xc1) with respect to the position Xc1 and the blade angle with respect to the position Xc2). βw (Xc2) reference). Specifically, the blade angle βw is small near the entrance of the diffuser 250 (downward in the figure) and large near the exit (upward in the figure). As a result, the fluid containing a large amount of the circumferential flow component attracted from the impeller 240 can be rectified and guided downstream (upward in the figure). In the diffuser blade portion 280 of the present embodiment, the variation Δβw of the blade angle βw with respect to the unit variation ΔXc of the meridian plane position Xc satisfies the relationship expressed by the following expression (1) in all regions. In other words, the blade angle βw has a derivative that is differentiated at the meridional surface position Xc less than 2.4 (° / mm) in all regions. Further, the diffuser blade angle βw is formed smaller than 90 ° in all regions. Thereby, a swirl velocity component intentionally remains in the fluid discharged from the outlet of the diffuser 250. In this way, by designing the diffuser blade portion 280 by determining the blade angle βw, it is possible to suppress the separation in the flow in the diffuser 250 even if the length of the meridian surface is reduced. Moreover, the flow of the fluid attracted to the diffuser 250 after the second stage can be stabilized. Thereby, energy efficiency can be improved especially in the diffuser 250 after the 2nd stage, and the energy efficiency of the multistage pump apparatus 10 can be improved.
Δβw <2.4 · ΔXc (1)

Generally, in the diffuser 250, the diffuser blade 280 is designed so that the swirl velocity component is not included as much as possible in the flow component of the fluid discharged from the outlet side. For this reason, the conventional diffuser 250 has a portion where the blade angle βw of the diffuser blade portion 280 is larger than 90 °, and the blade angle βw changes with a large change amount Δβw. However, if the blade angle βw has a portion larger than 90 ° or changes with a large change amount Δβw, the flow in the diffuser 250 is likely to be peeled off, and the energy efficiency may decrease particularly in the diffuser 250 after the second stage. I understood. For this reason, in this embodiment, the relationship of the formula (1) is satisfied in all regions, the diffuser blade angle βw is set to an angle smaller than 90 °, and the swirl velocity component is intentionally added to the fluid discharged from the outlet of the diffuser 250. It is designed to remain. Thereby, it is possible to suppress the separation in the flow in the diffuser 250 and to stabilize the flow of the fluid attracted to the second and subsequent diffusers 250, thereby improving the energy efficiency of the multistage pump device 10. Can do.

Further, in the diffuser 250, the maximum outer diameter φDc of the flow path Fc defined by the outer case portion 270 and the meridional blade length Lc on the outer peripheral side of the diffuser blade portion 280 satisfy the relationship of the following equation (2). . In the diffuser 250, the maximum inner diameter φDh of the flow path Fc defined by the inner case portion 260 and the meridional blade length Lh on the inner peripheral side of the diffuser blade portion 280 satisfy the relationship of the following equation (3). . Here, the meridional surface blade lengths Lc and Lh on the outer peripheral side and inner peripheral side of the diffuser blade portion 280 are the lengths of the regions where the diffuser blade portion 280 is provided on the meridian surfaces of the outer case portion 270 and the inner case portion 260. (See FIG. 2). Further, the meridional blade lengths Lc and Lh are such that the meridional blade length Lh on the inner circumferential side is equal to or shorter than the meridian blade length Lc on the outer circumferential side (the relationship of the following expression (4) is satisfied). ). By satisfying such a relationship, the diffuser 250 having a small length in the axis Aw direction can be obtained, and by showing the relationship of the expression (1), the multistage pump device 10 having a small size and high energy efficiency can be realized. .
Lc / φDc <0.64 (2)
Lh / φDh <0.63 (3)
Lh ≦ Lc (4)

The outer peripheral surface of the inner case portion 260 in the meridional section has a ratio of the maximum value θo of the angle formed with the axis Aw in the portion located on the discharge side from the position where the inner diameter of the flow path Fc is maximum (= φDh). The relationship of the following formula (5) is satisfied with respect to the speed Ns. Here, the specific speed Ns is expressed by the following equation (6), where Np is the rotational speed (min ⁻¹ ) of the pump (motor), Qp is the discharge amount (m ³ / min), and Hp is the total head (m). expressed. By satisfying such a relationship, the diffuser 250 having a small length in the axis Aw direction can be obtained, and by showing the relationship of the expression (1), the multistage pump device 10 having a small size and high energy efficiency can be realized. . In the present embodiment, the outer peripheral surface of the inner case portion 260 has the maximum angle (= θo) formed with the axis Aw at the outflow side end (upper end in the drawing) (see FIG. 2). ). However, the present invention is not limited to this example, and the outer surface of the inner case portion 260 may have a maximum angle with the axis Aw at a place that is not the outflow side end.
θo> 1500 · Ns ^−0.6 (5)
Ns = (Np · Qp ^1/2 ) / Hp ^3/4 (6)

FIG. 4 is a diagram showing the efficiency curve of the impeller with respect to the discharge amount of the multistage pump, and FIG. 5 is a diagram showing the efficiency curve of the diffuser with respect to the discharge amount of the multistage pump. Here, the thick solid line in FIG. 4 and FIG. 5 shows the first stage impeller 240 and the diffuser 250 in the multistage pump device 10 of the present embodiment that satisfies all the relationships of the above formulas (1) to (5). It is a graph. Moreover, the thick broken line in a figure is a graph which shows the 2nd stage | wheel impeller 240 and the diffuser 250 about the multistage pump apparatus 10 of this embodiment. The thin solid lines in the figure are graphs showing the first stage impeller and the diffuser in the multistage pump device of the comparative example that does not satisfy any of the relationships of the above formulas (1) to (5). Moreover, the thin broken line in a figure is a graph which shows the 2nd stage | wheel impeller and diffuser about the multistage pump apparatus of a comparative example. As shown in FIGS. 4 and 5, in the multistage pump device 10, the angle of the diffuser blade 280 is designed so as to be most efficient with a specific discharge amount as the rated Md. When the discharge amount departs from the rated Md, the fluid flow and the angle of the diffuser blade 280 are not matched and energy efficiency is lowered.

Generally, the diffuser 250 is designed so that the same object is stacked in a plurality of stages, and the energy efficiency of the diffuser 250 is designed to be most efficient for the one-stage diffuser 250. However, in this case, as shown in the comparative examples of FIGS. 4 and 5, high energy efficiency can be achieved for the first stage impeller and the diffuser (see the thin solid line in the figure). The energy efficiency of the impeller and diffuser is reduced (see the thin broken line in the figure). This is because the flow of fluid that has passed through the first stage impeller and the diffuser includes turbulence, and this turbulence affects the second stage and subsequent impellers and the diffuser. In particular, when the pump discharge amount is large, separation occurs in the flow in the diffuser, and the energy efficiency of the impeller and diffuser is significantly reduced. Further, the shorter the meridian surface of the diffuser, that is, the shorter the length of the diffuser in the axis Aw direction, the more easily the flow in the diffuser is disturbed, and the energy efficiency of the second and subsequent impellers and the diffuser decreases.

On the other hand, in the multistage pump device 10 of the present embodiment, the diffuser 250 is designed so as to satisfy the relationships of the above-described formulas (1) to (5). Thereby, as shown by the thick solid line and the broken line in FIGS. 4 and 5, the energy efficiency of the second stage impeller 240 and the diffuser 250 can be increased in the diffuser 250 having a small length in the axis Aw direction. This is based on intentionally leaving a swirl velocity component in the fluid discharged from the outlet of the diffuser 250. Thereby, the flow of the fluid attracted to the impeller 240 and the diffuser 250 after the second stage can be stabilized, and the energy efficiency can be improved as compared with the multistage pump device of the comparative example. In addition, the energy efficiency with respect to the discharge amount was similar to the relationship shown in FIGS. 4 and 5 even when the number of stages of the diffuser 250 and the impeller 240 was changed. Further, when the number of stages of the diffuser 250 and the impeller 240 is three or more, the efficiency curves of the third and subsequent impellers 240 and the diffuser 250 are the efficiency curves of the second stage shown in FIGS. It was the same as the thick broken line in the figure).

In the multistage pump device 10 of the present embodiment described above, the blade angle βw of the plurality of diffuser blade portions 280 is in all regions with respect to the unit variation ΔXc (mm) of the meridional surface position on the outer peripheral side or the inner peripheral side. In FIG. 5, the amount of change Δβw that satisfies the relationship of the expression (1) changes. Further, the blade angle βw of the diffuser blade portion 280 is formed to be smaller than 90 ° in all regions. As a result, the swirl velocity component remains in the outlet flow of the diffuser 250, the outlet flow of each diffuser 250 can be stabilized regardless of the pump flow rate, and the multistage pump device 10 having a small size and high energy efficiency can be realized.

Further, the maximum outer diameter φDc and the maximum inner diameter φDh of the flow path defined by the outer case portion 270 and the inner case portion 260 and the meridian blade lengths Lc, Lh on the outer peripheral side and inner peripheral side of the diffuser blade portion 280 are expressed by the formulas. The relationships shown in (2) to (4) were satisfied. Furthermore, the outer peripheral surface at the outflow side end of the inner case portion 260 is such that the angle θo formed with the axis Aw satisfies the relationship of the formula (5) with respect to the specific speed Ns. However, the diffuser blade portion 280 is not limited to such an example, and among the above relationships, the expressions (2) to (5) may satisfy at least one.

In the multistage pump device 10 described above, the motor 100 is installed below, and the pump unit 200 is installed above the motor 100. However, the motor 100 may be installed above the pump unit 200. Further, the pump unit 200 is not limited to the vertical placement as shown in FIG. Moreover, the multistage pump device 10 may be used in water or on land.

In the diffuser 250 described above, seven diffuser blade portions 280 are provided between the inner case portion 260 and the outer case portion 270. However, one to six, or more than eight diffuser blade portions 280 are provided. It may be.

Although the above-described diffuser 250 accommodates the impeller 240, a case for accommodating the impeller 240 may be provided separately from the diffuser 250.

In the multistage pump device 10 described above, the two-stage diffuser 250 and the impeller 240 are provided. However, the diffuser 250 and the impeller 240 may be provided with three or more stages.

Although the embodiments of the present invention have been described above, the above-described embodiments of the present invention are for facilitating understanding of the present invention and are not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and the present invention includes the equivalents thereof. In addition, any combination of the embodiment and the modified example is possible within a range where at least a part of the above-described problems can be solved or a range where at least a part of the effect can be achieved, and is described in the claims and the specification. Any combination or omission of each component is possible.

This application claims priority based on Japanese Patent Application No. 2016-066008 filed on Mar. 29, 2016. The entire disclosure including the specification, claims, drawings and abstract of Japanese Patent Application No. 2016-066008 is incorporated herein by reference in its entirety. The entire disclosure including the specification, claims, drawings, and abstract of JP-A-6-323291 is incorporated herein by reference in its entirety.

10 Multistage pump device, 100 motor, 102 electrical cable, 104 drive shaft, 106 joint, 108 case, 200 pump part, 210 suction case, 212 assembly part, 214 screw, 216 suction port, 218 assembly part, 220 discharge case , 222 assembly part, 224 assembly part, 226 check valve, 230 main shaft, 240 impeller, 250 diffuser, 252 assembly part, 253 screw, 254 assembly part, 255 screw, 258 liner ring, 260 inner case part 268 bearing sleeve, 270 outer case, 280 diffuser blade, Aw axis, βw diffuser blade angle, Rd circumferential tangent, Cd center line, Fc flow path, Xc meridian position, φDc maximum outer diameter, φDh maximum inner diameter , Ns specific speed, Dh maximum inner diameter .

Claims

A diffuser that is used in a multistage pump, is arranged concentrically with an impeller that rotates about a rotation axis, and guides a fluid that is attracted as the impeller rotates,
A case portion that defines a cylindrical flow path so that the diameter decreases from the fluid inflow side to the outflow side;
A plurality of diffuser blades arranged in a plurality of the cylindrical flow paths, and spirally dividing the cylindrical flow path;
With
The plurality of diffuser blades have a diffuser blade angle βw (°) that is an angle formed between a blade surface tangential direction of the diffuser blade and a circumferential direction with respect to the rotation axis at an arbitrary meridional surface position of the case portion. For the unit change ΔXc (mm) of the meridional surface position,
Δβw <2.4 · ΔXc
Changes with the amount of change Δβw that satisfies the relationship
The diffuser blade angle βw is less than 90 ° in all regions,
Diffuser.
The maximum outer diameter φDc of the flow path defined by the case part and the meridional wing length Lc on the outer peripheral side of the diffuser wing part are:
Lc / φDc <0.64
Satisfy the relationship
The diffuser according to claim 1.
The maximum inner diameter φDh of the flow path defined by the case portion and the meridional blade length Lh on the inner peripheral side of the diffuser blade portion are:
Lh / φDh <0.63
Satisfy the relationship
The diffuser according to claim 1 or 2.
The diffuser wing portion has an inner meridian wing length Lh that is equal to or less than an outer meridian wing length Lc.
The diffuser according to any one of claims 1 to 3.
The wall surface on the inner peripheral side at the outflow side end of the case portion has a maximum angle θo (°) with respect to the rotation axis on the downstream side of the position where the inner diameter of the flow path is maximized. A ratio expressed as Ns = (Np · Qp 1/2 ) / Hp 3/4 where Np is the speed (min −1 ), Qp is the discharge amount (m 3 / min), and Hp is the total head (m). For speed Ns
θo> 1500 · Ns −0.6
Satisfy the relationship
The diffuser according to any one of claims 1 to 4.
A diffuser according to any one of claims 1 to 5;
An impeller arranged concentrically with the diffuser and attracting fluid to the diffuser;
A multistage pump device comprising a plurality of stages.
A power source for rotating the impeller;
The multistage pump device according to claim 6.