Pump casing

Abstract

To provide a pump casing improved in a pump efficiency and suction performance by reducing pressure loss of fluid and securing the uniformity of a flow rate of an inflow into an impeller.SOLUTION: A pump casing 3 has a fluid flow passage 4. The fluid flow passage 4 has a first flow passage space FS1 and a second flow passage space FS2. The first flow passage space FS1 has a shape that its cross sectional area becomes smaller. The second flow passage space FS2 has a shape that its cross sectional area becomes larger.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a pump casing. [Background technology]

[0002] A pump is a fluid machine for transporting liquid (e.g., water). The pump includes an impeller and a pump casing that houses the impeller. The pump is configured to pressurize the liquid sucked into the pump casing by rotation of the impeller and to discharge the pressurized liquid from a discharge port of the pump casing.

[0003] Generally, a pump casing has a tongue that redirects the flow of liquid sucked into it and creates a swirling flow (see, for example, Patent Documents 1 and 2). When the liquid inside the pump casing collides with the tongue, a pressure loss occurs in the liquid. As a result, the flow velocity of the liquid in a local area of ​​the flow path decreases, the flow of the liquid becomes gentle, and the flow direction of the liquid is redirected. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2010-121541 A [Patent Document 2] Patent Publication No. 2021-195887 [Patent Document 3] Japanese Patent Application Publication No. 3-290096 Summary of the Invention [Problem to be solved by the invention]

[0005] However, if pressure loss occurs due to the collision of the liquid with the tongue, the uniformity of the liquid flow rate may decrease, the liquid flow may be bent suddenly, the liquid may separate from the pump casing wall, or vortexes may occur in the liquid flow path. Furthermore, cavitation may occur due to a lack of liquid flow or a local pressure drop due to the liquid pressure loss. Thus, if pressure loss occurs due to the collision of the liquid with the tongue, various problems may occur, and the pump efficiency and suction performance may decrease.

[0006] Therefore, an object of the present invention is to provide a pump casing that can improve pump efficiency and suction performance by reducing the pressure loss of the liquid and ensuring uniformity of the inflow flow rate into the impeller. [Means for solving the problem]

[0007] In one embodiment, a pump casing that houses an impeller is provided. The pump casing has a liquid flow path formed therein, and when an angular range of a winding angle in the liquid flow path is divided into a first angular range and a second angular range, the liquid flow path has a first flow path space corresponding to the first angular range and a second flow path space corresponding to the second angular range and connected to the first flow path space, the first flow path space has a shape in which a cross-sectional area of ​​the first flow path space decreases from a start end of the first flow path space toward the second flow path space, and the second flow path space has a shape in which a cross-sectional area of ​​the second flow path space increases from a boundary with the first flow path space toward a terminal end of the second flow path space.

[0008] In one embodiment, the first flow path space has a first outer curved contour having a smaller radius of curvature from a start of the first flow path space toward the second flow path space, and the second flow path space has a second outer curved contour having a larger radius of curvature from a boundary with the first flow path space toward an end of the second flow path space. In one embodiment, the first flow path space has a first inner curved contour having a smaller radius of curvature from a start of the first flow path space toward the second flow path space, and the second flow path space has a second inner curved contour having a larger radius of curvature from a boundary with the first flow path space toward an end of the second flow path space. In one embodiment, the first flow path space has a first cross-sectional height that decreases from a start of the first flow path space toward the second flow path space, and the second flow path space has a second cross-sectional height that increases from a boundary with the first flow path space toward a terminal end of the second flow path space.

[0009] In one embodiment, each of the first flow path space and the second flow path space has a cross-sectional area that changes depending on the winding angle, and a slope of a curve showing the change in cross-sectional area of ​​the second flow path space is greater than a slope of a curve showing the change in cross-sectional area of ​​the first flow path space. In one embodiment, a cross-sectional area of ​​the first flow path space at the reference angle of the winding angle is larger than an area of ​​an inlet diameter of the liquid flow path. Effect of the Invention

[0010] The liquid flow path having the first flow path space and the second flow path space has a shape that forms a gentle swirling flow of the liquid and smoothly changes the flow direction of the liquid. Therefore, the pump casing can omit the tongue. As a result, the pump casing can reduce the pressure loss of the liquid and improve the pump efficiency. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a perspective view showing an embodiment of a double suction pump. [Diagram 2] FIG. 2 is a vertical sectional view of the double suction pump shown in FIG. [Diagram 3] FIG. 2 is a top view of a double suction pump with the upper casing removed. [Figure 4] FIG. 4 is a cross-sectional view taken along line AA in FIG. [Diagram 5]FIG. 2 is a diagram showing a part of the internal structure of a pump casing according to the embodiment. [Figure 6] FIG. 4 is a diagram showing a part of the internal structure of a pump casing according to a comparative example. [Figure 7] FIG. 2 is a perspective view showing an entire liquid flow path. [Figure 8] FIG. 8(a) is a diagram showing the winding angle in the liquid flow path, FIG. 8(b) is a graph showing the relationship between the winding angle and the cross-sectional area of ​​the liquid flow path, and FIG. 8(c) is a graph showing the relationship between the winding angle and the flow velocity of the liquid flowing through the liquid flow path. [Figure 9] FIG. 9(a) shows the results of an analysis of the magnitude of pressure loss and flow lines that occur in the liquid flow path for each cross-sectional area of ​​the liquid flow path corresponding to the winding angle, FIG. 9(b) shows the magnitude of the flow velocity of the liquid flowing into the impeller, and FIG. 9(c) shows the cavitation region that occurs in the impeller. [Figure 10] 10(a) to 10(g) are diagrams showing the cross-sectional shapes of the liquid flow paths corresponding to the winding angles. [Figure 11] FIG. 11(a) shows the results of an analysis of the magnitude of pressure loss and flow lines that occur in the liquid flow path for each cross-sectional area of ​​the liquid flow path corresponding to the winding angle, FIG. 11(b) shows the magnitude of the flow velocity of the liquid flowing into the impeller, and FIG. 11(c) shows the cavitation region that occurs in the impeller. [Figure 12] FIG. 2 is a diagram showing the cross-sectional profile (outer curved profile, inner curved profile) and cross-sectional height of a liquid flow path. [Figure 13] FIG. 13(a) is a diagram showing the relationship between the winding angle and the cross-sectional height of the liquid flow path, FIG. 13(b) is a diagram showing the relationship between the winding angle and the outer curved contour, and FIG. 13(c) is a diagram showing the relationship between the winding angle and the inner curved contour. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings described below, the same or corresponding components are denoted by the same reference numerals, and duplicated descriptions will be omitted. In the multiple embodiments described below, the configuration of one embodiment that is not particularly described is the same as the other embodiments, so duplicated descriptions will be omitted.

[0013] Fig. 1 is a perspective view showing one embodiment of a double suction pump. Fig. 2 is a vertical cross-sectional view of the double suction pump shown in Fig. 1. Fig. 3 is a top view of the double suction pump with an upper casing removed. Fig. 4 is a cross-sectional view taken along line AA in Fig. 3.

[0014] The double suction pump P1 includes a rotating shaft 1, a double suction impeller 2 fixed to the rotating shaft 1, and a pump casing 3 that houses the impeller 2. The pump casing 3 has a spiral shape and has a liquid flow path 4 formed therein.

[0015] The pump casing 3 includes an upper casing 3a and a lower casing 3b that are divided vertically by a horizontal plane passing through the central axis CL of the rotating shaft 1, which serves as the rotation center of the impeller 2. The rotating shaft 1 is supported by shaft supports 40, 40 formed on the upper casing 3a and the lower casing 3b. The gap between the rotating shaft 1 and the shaft supports 40, 40 is sealed by shaft seals 11, 11.

[0016] The pump casing 3 has a suction port 6 that draws in liquid and a discharge port 7 that discharges the liquid pressurized by the impeller 2. The suction port 6 and the discharge port 7 are formed in the lower casing 3b. The suction port 6 and the discharge port 7 open in opposite directions to each other in a direction perpendicular to the rotating shaft 1.

[0017] As shown in Figures 2 to 4, the liquid flow path 4 has an upper spiral flow path 4a, 4a and a lower spiral flow path 4b, 4b arranged on either side of the impeller 2, and an elliptical flow path 4d, 4d connected to the lower spiral flow path 4b, 4b.

[0018] The pump casing 3 has an upper discharge passage 5a and a lower discharge passage 5b arranged in the center thereof. The upper discharge passage 5a is arranged between the upper spiral passages 4a, 4a, and the lower discharge passage 5b is arranged between the lower spiral passages 4b, 4b. The impeller 2 is arranged inside the upper discharge passage 5a and the lower discharge passage 5b.

[0019] A drive unit (not shown) is connected to the end of the rotating shaft 1. When the drive unit is driven, the impeller 2 rotates together with the rotating shaft 1, and liquid is sucked into the pump casing 3 through the suction port 6.

[0020] The liquid sucked into the pump casing 3 through the suction port 6 passes through the elliptical passages 4d, 4d (see FIG. 4) and flows into the lower spiral passages 4b, 4b (see FIG. 2 and FIG. 3). The liquid then flows into the upper spiral passages 4a, 4a. The liquid that has flowed into the upper spiral passages 4a, 4a passes through the upper spiral passages 4a, 4a and flows into the impeller 2 (see the arrow in FIG. 2).

[0021] The liquid is pressurized by the action of the rotating impeller 2 and centrifugal force, and is discharged into the upper discharge flow passage 5a and the lower discharge flow passage 5b on the radially outer side of the impeller 2. The liquid then flows through the upper discharge flow passage 5a and the lower discharge flow passage 5b, and is discharged from the discharge port 7.

[0022] As shown in FIG. 1, the pump casing 3 has an upper flange 8 formed on the joint surface of the upper casing 3a with the lower casing 3b, and a lower flange 9 formed on the joint surface of the lower casing 3b with the upper casing 3a.

[0023] Each of the upper flange 8 and the lower flange 9 has bolt holes (not shown) into which a plurality of bolts 10 serving as fasteners are inserted. The upper casing 3a and the lower casing 3b are fastened to each other by inserting each bolt 10 into the bolt hole and tightening it.

[0024] The upper casing 3a has a suction casing portion 20, 20 that forms the upper spiral passage 4a, 4a, and a discharge casing portion 21 that forms the upper discharge passage 5a. The discharge casing portion 21 is disposed between the suction casing portions 20, 20.

[0025] Fig. 5 is a diagram showing a part of the internal structure of the pump casing according to this embodiment. Fig. 6 is a diagram showing a part of the internal structure of the pump casing according to a comparative example. As is clear from the comparison between Fig. 5 and Fig. 6, in the comparative example, the pump casing has a tongue portion for guiding the flow of liquid to the impeller, while in this embodiment, the pump casing 3 does not have a tongue portion.

[0026] Forming a tongue portion causes a pressure loss of the liquid due to collision of the liquid with the tongue portion. If a pressure loss of the liquid occurs, there is a risk of a decrease in pump efficiency. The pump casing 3 according to this embodiment has a liquid flow path 4 having a characteristic shape instead of forming a tongue portion. Therefore, the pump casing 3 can reduce the pressure loss of the liquid and improve the pump efficiency. The shape of the liquid flow path 4 will be described below with reference to the drawings.

[0027] Fig. 7 is a perspective view showing the entire liquid flow path. As shown in Fig. 7, the liquid flow path 4 has a spiral shape extending from the liquid inlet 4c to the impeller 2. The liquid that passes through the liquid inlet 4c branches into an outer stream 4X and an inner stream 4Y and flows to the impeller 2. The joining point P of the outer stream 4X and the inner stream 4Y corresponds to the position where the tongue portion is located in the comparative example. The outer stream 4X and the inner stream 4Y join at the joining point P, and the joined liquid flows into the impeller 2.

[0028] FIG. 8(a) is a diagram showing the winding angle in the liquid flow path, FIG. 8(b) is a graph showing the relationship between the winding angle and the cross-sectional area of ​​the liquid flow path, and FIG. 8(c) is a graph showing the relationship between the winding angle and the flow velocity of the liquid flowing through the liquid flow path.

[0029] In FIG. 8(b), the horizontal axis represents the winding angle, and the vertical axis represents the ratio value (cross-sectional area ratio value) obtained by dividing the cross-sectional area of ​​the liquid flow path 4 by the area of ​​the liquid inlet 4c of the liquid flow path 4. The cross-sectional area ratio value is a dimensionless quantity. In FIG. 8(c), the horizontal axis represents the winding angle, and the vertical axis represents the ratio value (flow velocity ratio value) obtained by dividing the flow velocity of the liquid flowing in the outer flow 4X by the flow velocity of the liquid at the liquid inlet 4c. The flow velocity ratio value is a dimensionless quantity.

[0030] FIG. 9(a) shows the results of an analysis of the magnitude of pressure loss and flow lines that occur in the liquid flow path for each cross-sectional area of ​​the liquid flow path corresponding to the winding angle, FIG. 9(b) shows the magnitude of the flow velocity of the liquid flowing into the impeller, and FIG. 9(c) shows the cavitation region that occurs in the impeller.

[0031] 10(a) to 10(g) are diagrams showing the size of the cross-sectional shape of the liquid flow path corresponding to the winding angle.

[0032] 8(a), the rotation angle of the liquid flow path 4 about the central axis CL of the rotating shaft 1 is defined as the winding angle. In this winding angle, if the angle on a vertical line extending downward and perpendicular to the central axis CL is determined as the reference angle (0 degrees), the winding angle increases in the counterclockwise direction.

[0033] In FIG. 8(a), the winding angle is shown in an angle range from 0 degrees to 270 degrees. When the angle range of the winding angle is divided into a first angle range and a second angle range, the liquid flow path 4 has a first flow path space FS1 corresponding to the first angle range and a second flow path space FS2 corresponding to the second angle range. The second flow path space FS2 is connected to the first flow path space FS1. In the embodiment shown in FIG. 8(a), the first angle range is a range from 0 degrees to 225 degrees, and the second angle range is a range from 225 degrees to 270 degrees.

[0034] As shown in FIGS. 8(b), 9(a), and 10(a) through 10(f), the first flow path space FS1 has a shape in which the cross-sectional area of the first flow path space FS1 gradually decreases from the start end of the first flow path space FS1 (i.e., winding angle 0 degrees) toward the second flow path space FS2. More specifically, the cross-sectional area AR2 at a winding angle of 45 degrees is smaller than the cross-sectional area AR1 at a winding angle of 0 degrees (AR2 < AR1). The cross-sectional area AR3 at a winding angle of 90 degrees is smaller than the cross-sectional area AR2 at a winding angle of 45 degrees (AR3 < AR2).

[0035] Similarly, the cross-sectional area AR4 at a winding angle of 135 degrees is smaller than the cross-sectional area AR3 at a winding angle of 90 degrees (AR4 < AR3). The cross-sectional area AR5 at a winding angle of 180 degrees is smaller than the cross-sectional area AR4 at a winding angle of 135 degrees (AR5 < AR4). The cross-sectional area AR6 at a winding angle of 225 degrees is smaller than the cross-sectional area AR5 at a winding angle of 180 degrees (AR6 < AR5).

[0036] Thus, the first flow path space FS1 has a shape in which its cross-sectional area gradually decreases from the cross-sectional area AR1 to the cross-sectional area AR6. On the other hand, the second flow path space FS2 has a shape in which the cross-sectional area of the second flow path space FS2 increases from the boundary with the first flow path space FS1 (i.e., winding angle 225 degrees) toward the end of the second flow path space FS2 (i.e., winding angle 270 degrees).

[0037] More specifically, as shown in FIGS. 9(a), 10(f), and 10(g), the cross-sectional area AR7 at a winding angle of 270 degrees is larger than the cross-sectional area AR6 at a winding angle of 225 degrees (AR7 > AR6). Thus, the second flow path space FS2 has a shape in which its cross-sectional area gradually increases from the cross-sectional area AR6 to the cross-sectional area AR7.

[0038] In this embodiment, each of the first flow path space FS1 and the second flow path space FS2 has a cross-sectional area that changes according to the winding angle. The cross-sectional area of ​​the first flow path space FS1 gradually decreases as the winding angle increases. The cross-sectional area of ​​the boundary between the first flow path space FS1 and the second flow path space FS2 is the smallest. The cross-sectional area of ​​the second flow path space FS2 gradually increases as the winding angle increases.

[0039] 8(b), the slope SL2 of the curve showing the change in the cross-sectional area of ​​the second flow path space FS2 is larger than the slope SL1 of the curve showing the change in the cross-sectional area of ​​the first flow path space FS1. In other words, the numerical value (absolute value) showing the slope SL2 is larger than the numerical value (absolute value) showing the slope SL1. The slope SL2 is preferably within a range of 1 to 1.5 times the slope SL1.

[0040] If the slope SL2 exceeds 1.5 times the slope SL1, the rate of change of the cross-sectional area of ​​the second flow passage space FS2 increases, the flow resistance of the liquid increases, and separation of the liquid flow may occur, resulting in increased pressure loss. The increased pressure loss may result in reduced pump performance. In addition, the risk of cavitation occurring due to a localized pressure drop in the flow passage increases, leading to reduced suction performance.

[0041] The flow velocity of the liquid flowing through the liquid flow path 4 depends on the cross-sectional area of ​​the liquid flow path 4. Here, the flow velocity of the liquid is calculated as the value of the velocity component in the direction perpendicular to the cross section of the flow path. If the cross-sectional area is large, the flow velocity of the liquid is small, and conversely, if the cross-sectional area is small, the flow velocity of the liquid is large. As shown in FIG. 8(c), the flow velocity of the liquid flowing through the liquid flow path 4 (more specifically, the flow velocity of the liquid flowing in the outer flow 4X) gradually increases and then becomes gentle (see FIG. 8(c)). In the graph shown in FIG. 8(c), the flow velocity distribution of the liquid flowing through the liquid flow path 4 is generally uniform compared to the velocity distribution in the comparative example.

[0042] According to this embodiment, the liquid flow path 4 having the first flow path space FS1 and the second flow path space FS2 can form a gentle liquid flow, and the liquid flow direction is smoothly changed without providing a tongue. By changing the liquid flow direction smoothly, the occurrence of pressure loss in the liquid flowing through the liquid flow path 4 can be suppressed to the greatest extent possible, and the liquid that increases the uniformity of the flow rate is caused to flow into the impeller 2 (see FIG. 9(b)).

[0043] Furthermore, such an inflow of liquid can minimize the area where pressure loss occurs in the impeller 2, and suppress the occurrence of cavitation (see FIG. 9(c)). By suppressing the occurrence of cavitation, the suction performance of the pump P1 can be improved.

[0044] In this way, the pump casing 3 can omit the tongue portion (see FIG. 6) by forming the liquid flow path 4. As a result, the pump casing 3 can reduce the pressure loss of the liquid and improve the pump efficiency of the pump P1.

[0045] Furthermore, the pump casing 3 without a tongue portion can achieve the following effects. The pump casing 3 is generally manufactured by casting. Since the tongue portion has a thin-walled shape, in the process of pouring metal into a mold, the metal is not sufficiently poured into the tongue portion, which may cause defects due to poor molding. However, in this embodiment, the pump casing 3 does not have a tongue portion, so defects due to poor molding do not occur.

[0046] 8(b), in the comparative example, the cross-sectional area ratio value at a winding angle of 0 degrees is approximately 1, while in this embodiment, the cross-sectional area ratio value at a winding angle of 0 degrees is approximately 1.5. In other words, the cross-sectional area of ​​the first flow path space FS1 at the reference angle of the winding angle is larger than the cross-sectional area of ​​the liquid inlet 4c of the liquid flow path 4 (i.e., the area of ​​the inlet aperture of the liquid flow path 4). On the other hand, in the comparative example, the cross-sectional area of ​​the flow path space at the reference angle of the winding angle is approximately the same as the area of ​​the inlet aperture of the liquid flow path 4.

[0047] Thus, at a winding angle of 0 degrees, the cross-sectional area ratio value of this embodiment is larger than the cross-sectional area ratio value of the comparative example. Also, the cross-sectional area ratio value at a winding angle of 0 degrees is determined so that the flow velocity of the liquid flowing in the outer flow 4X from a winding angle of 0 degrees is slightly smaller than the inflow flow velocity into the impeller 2.

[0048] In one embodiment, the cross-sectional area ratio value at a winding angle of 0 degrees may be 1.2 to 1.6. The cross-sectional area ratio value at a winding angle of 45 degrees is approximately 0.7, and in a comparative example, the cross-sectional area ratio value at a winding angle of 45 degrees is approximately 0.6.

[0049] In this embodiment, the cross-sectional area ratio value at a winding angle of 0 degrees is larger than the cross-sectional area ratio value in the comparative example. As shown in Fig. 8(a), the distance in the flow direction from a winding angle of 0 degrees to a winding angle of 45 degrees is longer than the distance in other angle ranges. With this configuration, the flowing liquid can be gradually decelerated and the flow direction can be changed in the angle range from a winding angle of 0 degrees to a winding angle of 45 degrees.

[0050] Thus, even if the flow velocity of the liquid flow path from a winding angle of 0 degrees to a winding angle of 45 degrees is smaller than that of the comparative example, no significant pressure loss occurs. Furthermore, in this embodiment, since a tongue portion is not provided, collision between the flow and the tongue portion does not occur. As shown in FIG. 8(c), the flow velocity of the liquid flowing in the outer flow 4X at a winding angle of 45 degrees or more becomes almost uniform, and a more uniform flow velocity distribution can be obtained than in the comparative example. Since the velocity gradient in the flow direction is smaller than in the comparative example, as a result, the pressure loss occurring throughout the entire liquid flow path 4 can be made relatively small.

[0051] Fig. 11(a) is a diagram showing the results of an analysis of the magnitude of pressure loss and flow lines occurring in the liquid flow path for each cross-sectional area of ​​the liquid flow path corresponding to the winding angle, Fig. 11(b) is a diagram showing the magnitude of the flow velocity of the liquid flowing into the impeller, and Fig. 11(c) is a diagram showing the cavitation region occurring in the impeller. Figs. 11(a) to 11(c) show the analysis results of a pump in a comparative example.

[0052] As is clear from a comparison of Figures 9(a) to 9(c) and Figures 11(a) to 11(c), in the comparative example, the pressure loss occurring in the liquid flow path is relatively large, and the flow velocity of the liquid flowing into the impeller is also relatively large. Therefore, in the comparative example, the cavitation region occurring in the impeller is also relatively large.

[0053] Thus, according to this embodiment, the liquid flow path 4 has a characteristic shape (i.e., the cross-sectional area of ​​the liquid flow path 4 gradually decreases in the flow direction of the outer flow 4X, and gradually increases midway through the liquid flow path 4). Therefore, the flow speed of the liquid flowing through the liquid flow path 4 can be controlled. By controlling the flow speed in this way, the flow direction of the liquid can be smoothly redirected.

[0054] Fig. 12 is a diagram showing the cross-sectional contour (outer curved contour, inner curved contour) and cross-sectional height of a liquid flow path. Fig. 13(a) is a diagram showing the relationship between the winding angle and the cross-sectional height of a liquid flow path, Fig. 13(b) is a diagram showing the relationship between the winding angle and the outer curved contour, and Fig. 13(c) is a diagram showing the relationship between the winding angle and the inner curved contour.

[0055] 13(a), the horizontal axis indicates the winding angle, and the vertical axis indicates the ratio (cross-sectional height ratio) obtained by dividing the cross-sectional height by the diameter of the liquid inlet 4c of the liquid flow path 4. The cross-sectional height indicates the length in the height direction at the cross section of the liquid flow path 4. The cross-sectional height ratio is a dimensionless quantity.

[0056] In Fig. 13(b), the horizontal axis indicates the winding angle, and the vertical axis indicates the ratio value (outer curved contour ratio value) obtained by dividing the outer curved contour by the diameter of the liquid inlet 4c. The outer curved contour indicates the curvature radius (or curvature) of the outer cross-sectional contour in the cross section of the liquid flow path 4. The outer curved contour ratio value is a dimensionless quantity.

[0057] In Fig. 13(c), the horizontal axis indicates the winding angle, and the vertical axis indicates the ratio value (inner curved contour ratio value) obtained by dividing the inner curved contour by the diameter of the liquid inlet 4c. The inner curved contour indicates the curvature radius (or curvature) of the inner cross-sectional contour in the cross section of the liquid flow path 4. The inner curved contour ratio value is a dimensionless quantity.

[0058] As shown in Fig. 12, the liquid flow path 4 has a cross-sectional height Sh. The cross-sectional height of the first flow path space FS1 is defined as a first cross-sectional height, and the cross-sectional height of the second flow path space FS2 is defined as a second cross-sectional height. In this case, as shown in Fig. 13(a), the first flow path space FS1 has a first cross-sectional height that decreases from the start end of the first flow path space FS1 (i.e., a winding angle of 0 degrees) toward the second flow path space FS2. The second flow path space FS2 has a second cross-sectional height that increases from the boundary with the first flow path space FS1 toward the end end of the second flow path space FS2.

[0059] 12, the liquid flow path 4 has an outer curved contour R1 disposed at a position away from the rotation axis 1 and an inner curved contour R2 disposed on the side of the rotation axis 1. The outer curved contour R1 has a first outer curved contour in the first flow path space FS1 and a second outer curved contour in the second flow path space FS2. Similarly, the inner curved contour R2 has a first inner curved contour in the first flow path space FS1 and a second inner curved contour in the second flow path space FS2.

[0060] As shown in Fig. 13(b), the first outer curved contour of the first flow path space FS1 has a shape in which the radius of curvature decreases (i.e., the curvature increases) from the start of the first flow path space FS1 toward the second flow path space FS2. More specifically, the radius of curvature of the first outer curved contour is almost constant from a winding angle of 0 to 135 degrees, and gradually decreases from a winding angle of 135 to 225 degrees (see Fig. 13(b)).

[0061] As shown in FIG. 13(b), the second outer curved contour of the second flow path space FS2 has a shape in which the radius of curvature gradually increases (i.e., the curvature decreases) from the boundary with the first flow path space FS1 toward the end of the second flow path space FS2.

[0062] 13(c), the first inner curved contour of the first flow path space FS1 has a shape in which the radius of curvature decreases (i.e., the curvature increases) from the start of the first flow path space FS1 (i.e., the winding angle is 0 degrees) toward the second flow path space FS2. The second inner curved contour of the second flow path space FS2 has a shape in which the radius of curvature gradually increases (i.e., the curvature decreases) from the boundary with the first flow path space FS1 toward the end of the second flow path space FS2.

[0063] 13(a) and 13(c), the cross-sectional height of the liquid flow path and the radius of curvature of the inner curved contour hardly change depending on the winding angle, and the radius of curvature of the outer curved contour of the liquid flow path gradually decreases depending on the winding angle. In this way, the pump casing as the comparative example has a liquid flow path that changes two-dimensionally.

[0064] On the other hand, in this embodiment, the curve showing the change in the radius of curvature of the outer curved contour R1, the curve showing the change in the radius of curvature of the inner curved contour R2, and the curve showing the change in the cross-sectional height Sh all draw curves similar to the curve showing the change in the cross-sectional area of ​​the liquid flow path 4. Thus, in this embodiment, the pump casing 3 has a liquid flow path 4 that changes three-dimensionally depending on the winding angle.

[0065] The above-described embodiments have been described for the purpose of enabling a person having ordinary skill in the art to practice the present invention. Various modifications of the above-described embodiments are naturally possible for a person skilled in the art, and the technical idea of ​​the present invention can be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is to be interpreted in the broadest scope according to the technical idea defined by the claims. [Explanation of symbols]

[0066] 1 Rotation axis 2 Impeller 3 Pump casing 3a Upper casing 3b Lower casing 4 Liquid flow path 4a Upper vortex channel 4b Lower vortex channel 4c liquid inlet 4d elliptical channel 5a Upper discharge passage 5b Lower discharge passage 6 Intake port 7 Outlet 8 Upper flange 9 Lower flange 10 Volts 11 Shaft seal 20 Suction casing section 21 Discharge casing part P1 double suction pump CL center axis 4X Outer Flow 4Y Inner flow P confluence FS1 First passage space FS2 Second flow space AR1~AR7 cross-sectional area SL1 Tilt SL2 Tilt Sh Section height R1 Outer curved contour R2 Inner curved contour

Claims

1. A pump casing that houses an impeller, The pump casing has a liquid flow path formed therein, When the angle range of the winding angle in the liquid flow path is divided into a first angle range and a second angle range, the liquid flow path is a first flow path space corresponding to the first angle range; a second flow passage space corresponding to the second angle range and connected to the first flow passage space, the first flow path space has a shape in which a cross-sectional area of ​​the first flow path space decreases from a start end of the first flow path space toward the second flow path space, The second flow path space has a shape such that a cross-sectional area of ​​the second flow path space increases from a boundary with the first flow path space toward a terminal end of the second flow path space.

2. The first flow space has a first outer curved contour having a radius of curvature that decreases from a start of the first flow space toward the second flow space, The pump casing according to claim 1 , wherein the second flow space has a second outer curved contour having a radius of curvature that increases from a boundary with the first flow space toward an end of the second flow space.

3. The first flow space has a first inner curved contour having a radius of curvature that decreases from a start of the first flow space toward the second flow space, The pump casing according to claim 1 , wherein the second flow passage space has a second inner curved contour having a radius of curvature that increases from a boundary with the first flow passage space toward an end of the second flow passage space.

4. The first flow path space has a first cross-sectional height that decreases from a start end of the first flow path space toward the second flow path space, The pump casing according to claim 1 , wherein the second flow passage space has a second cross-sectional height that increases from a boundary with the first flow passage space toward a terminal end of the second flow passage space.

5. Each of the first flow path space and the second flow path space has a cross-sectional area that changes according to the winding angle, The pump casing according to claim 1 , wherein a slope of a curve representing the change in the cross-sectional area of ​​the second flow passage space is greater than a slope of a curve representing the change in the cross-sectional area of ​​the first flow passage space.

6. The pump casing according to claim 1 , wherein a cross-sectional area of ​​the first flow passage space at the reference angle of the winding angle is larger than an area of ​​an inlet diameter of the liquid flow passage.

Images