JP2009074416A - Vertical shaft pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vertical shaft pump capable of surely sucking air from a suction port with preventing swirl flow at the suction port, solving a problem that suction performance drops and that foreign matter is caught, and stably performing pumping operation. <P>SOLUTION: This pump is provided with a rotary shaft 20 arranged in a vertical direction and rotating around a shaft, an impeller 21 rotated by rotation of the rotary shaft 20 and sucking water and make the same flow upward, a suction pipe 5 arranged at an upstream side of the impeller 21 and forming a channel in which water flows toward the impeller 21, the suction port 6 provided on the suction pipe 5 at an upstream side position of the impeller 21, and a suction pipe 40 communicating to the suction port 6 at one end and opening to atmosphere at another end. The suction pipe 5 has a section shape in which distance to a channel wall surface from a center of a figure of the channel section is not constant at a position provided with the suction port 6. The suction port 6 is provided at a position separated from the center of the figure further than a position where distance to the channel wall surface from the center of the figure is the minimum. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a vertical pump installed in a suction water tank, and more particularly to a vertical pump that can perform a pumping operation even when the water level in the suction water tank is lowered and is suitable for a preceding standby operation.

  The pump station is provided at a predetermined sewage collection point in order to prevent sewage overflow in heavy rain. In other words, a vertical pump for drainage is installed in a suction tank equipped with an inlet and an outlet for sewage, and when the water storage level of the suction tank exceeds a predetermined height, the pump is operated to drain into a river, etc. Like to do.

  In such a pump station, an operation method called a prior standby operation has been conventionally employed. This is because if there is rainfall and a large amount of rainwater is expected to flow into the sewer, the pump must be started (empty operation) before the inflow begins, and a delay will occur in response to the sudden inflow of rainwater, sewage, etc. Without draining. Even if the water storage level drops once due to the operation of the pump, the pump is similarly idled to prepare for the next inflow.

FIG. 8 is a diagram illustrating an example of a vertical pump that performs this type of operation. As shown in FIG. 8, the vertical shaft pump 113 includes an impeller 112 at the tip of a rotary shaft 117 arranged in the vertical direction, and the impeller 112 sucks air together with water, so that the lowest water level LWL of the suction water tank 111 is obtained. Even in the following, it is possible to continue operation. In the vertical shaft pump 113, on the upstream side of the suction pipe 114 from the impeller 112, the h ≒ ^v 2 / 2g inlet 115 that passes through the position lower LLWL from the water level LWL provided, the mounting of the impeller 112 to the intake port 115 An intake pipe 116 having the other end 116a that opens above the position is attached. Here, v is the flow velocity of the water flowing through the suction pipe 114, and g is the gravitational acceleration. Thus, below the minimum water level LWL, the amount of drainage is gradually reduced by the air flowing in through the air intake 115, thereby avoiding a sudden pumping stop due to a drop in the water level, and from the installation position of the impeller 112. Even when the water level rises from the lower water level, the start of rapid pumping is avoided by reducing the amount of drainage by the air flowing in through the air inlet 115 until the water level reaches the lowest water level LWL. In such a vertical shaft pump, it is possible to prevent vibration due to the suction vortex being drawn from the suction pipe 114 when the water level is lowered.

  In this way, for example, for rainwater drainage in large cities, the pump is started in advance according to rainfall information etc. regardless of the suction water level, and when the water level rises from the low water level, the total amount is increased while gradually increasing the water amount from the idle operation When the water level drops from the high water level to the operation, the operation can be smoothly shifted from the full operation to the idling operation while gradually reducing the water amount. However, if the water level is below the minimum water level LWL and an attempt is made to intake air through the intake pipe 116, a positive pressure is generated at the intake port 115 due to the swirling flow below the impeller 112, and the water level is below LWL. Insufficient inspiration was sometimes performed.

In order to prevent the above-described swirling flow from occurring, as described in Japanese Patent Laid-Open No. 2006-189016 (Patent Document 1), the rotating shaft of the impeller is extended upstream, and the vicinity of the lower end of the rotating shaft is A vertical shaft pump is proposed in which a bearing box having a bearing to be supported is provided, and the bearing box is supported by a bearing box support plate which is a plurality of plate-like members projecting radially inward from the inner wall of the suction pipe. Yes. In this vertical shaft pump, the bearing box support plate is arranged on the upstream side of the impeller, thereby preventing the swirling flow from occurring in this portion and generating the positive pressure due to the swirling flow at the intake port portion. Is to ensure stable intake from the intake port.
JP 2006-189016 A

  In the vertical shaft pump described in Japanese Patent Application Laid-Open No. 2006-189016 described above, a bearing box support plate is provided which is a plurality of plate-like members protruding radially inward from the inner wall of the suction pipe. There is a problem that the plate crosses the suction flow path and becomes a resistance to the flow of water, the suction performance is lowered, and consequently the pump performance is lowered. In addition, there is a problem that a foreign matter mixed in water is caught on the bearing box support plate.

  The present invention has been made in view of the above-described circumstances, and prevents the swirling flow at the intake port so that intake can be reliably performed from the intake port, as well as the problem that the suction performance is deteriorated and foreign matter is caught. It is an object of the present invention to provide a vertical shaft pump that can perform pumping operation stably.

In order to achieve the above-described object, one aspect of the present invention includes a rotating shaft that is arranged in a vertical direction and rotates around an axis, an impeller that rotates by rotating the rotating shaft, sucks water, and flows upward. A suction pipe disposed on the upstream side of the impeller and forming a flow path for flowing the water toward the impeller, an intake port provided in the suction pipe at a position on the upstream side of the impeller, and one end thereof An intake pipe that communicates with the intake port and has the other end opened to the atmosphere, and the suction pipe has a constant distance from the centroid of the cross section of the flow path to the flow path wall surface at the position where the intake port is provided. The intake port is provided at a position farther from the centroid than a position where the distance from the centroid to the flow path wall surface is minimum.
According to the present invention, since the distance r from the centroid (O) of the channel cross section to the channel wall surface is not uniform, when considering the velocity gradient from the centroid (O) to the channel wall surface, At the position (r _min ) where the distance from the centroid (O) to the channel wall surface is minimum, the velocity gradient on the channel wall surface becomes zero. The velocity gradient is a negative value at a position farther from the centroid (O) than the position (r _min ) where the distance from the centroid (O) of the channel cross section to the channel wall surface is minimum, Separation occurs in the flow on the wall surface, and a reverse flow occurs. Accordingly, the pressure becomes a negative pressure state, and intake from the intake port becomes possible.

According to a preferred aspect of the present invention, the intake port is located downstream in the rotational direction of the impeller from a position where the distance from the centroid to the flow path wall surface is minimum. .
According to the present invention, in the vicinity of the wall surface downstream (downstream in the rotational direction of the impeller) from the position (r _min ) where the distance from the centroid (O) of the flow channel cross section to the flow channel wall surface is minimum, The slope is negative. Therefore, on the downstream side of the position (r _min ) where the distance from the centroid (O) of the flow path cross section to the flow path wall surface is minimum, the flow on the wall surface is separated and a reverse flow is generated. Accordingly, the pressure becomes a negative pressure state, and intake from the intake port becomes possible.

According to a preferred aspect of the present invention, the cross-sectional shape is a polygon.
According to a preferred aspect of the present invention, the air inlet is located near the vertex between the vertex of the polygon and a midpoint of one side of the polygon.
According to a preferred aspect of the present invention, the polygon is a quadrangle.
According to a preferred aspect of the present invention, the cross-sectional shape is an ellipse.
According to a preferred aspect of the present invention, the intake port is located in the vicinity of an intersection of the elliptical long axis and the ellipse.

According to a preferred aspect of the present invention, the suction pipe transitions from a circular cross section to a polygon cross section from the upper side toward the lower side.
According to a preferred aspect of the present invention, the suction pipe transitions from a circular cross section to a square cross section from the upper side toward the lower side.
According to a preferred aspect of the present invention, the suction pipe transitions from a circular cross section to an elliptic cross section from the upper side toward the lower side.
According to the present invention, by changing the cross-sectional shape of the suction pipe from a circular cross section to a desired shape such as a polygonal cross section, a square cross section, an elliptical cross section, etc., the cross section of the intake pipe at the position where the air inlet is provided The shape can be optimized.

  According to the present invention, there is no swirling flow in the vicinity of the intake port of the suction pipe, and a negative pressure can be ensured, so that intake from the intake port can be reliably performed. In addition, the suction flow path of the suction pipe has no rib-like member protruding from the flow path wall surface that resists the flow of water, so that good suction performance can be maintained and foreign matter is not caught. Therefore, if the water level is lowered, intake is performed more reliably, and stable operation can be performed even if the water level is lowered, that is, the vertical shaft pump is suitable for the preceding standby operation.

Hereinafter, an embodiment of a vertical shaft pump according to the present invention will be described with reference to FIGS.
FIG. 1 is a longitudinal sectional view showing a main part of a vertical shaft pump according to the present invention. The vertical shaft pump of the present invention is a vertical shaft pump suitable for the preceding standby operation. The pre-standby operation is an operation for starting the pump in advance before the inflow starts and discharging the water without a delay with respect to the rapid inflow of the rain water when inflow of a large amount of rain water is expected.

  As shown in FIG. 1, the vertical shaft pump 1 of the present invention is fixed via a mounting flange 50 on a floor plate 101 that covers a suction water tank 100 that primarily stores rainwater and the like. The vertical shaft pump 1 includes a pump casing 2 that hangs down in the suction water tank 100, and an impeller 21 that is fixed to a rotary shaft 20 disposed in the pump casing 2.

  The pump casing 2 is configured by connecting an L-shaped pumped-pipe casing (casing body) 3, a liner casing 4, and a suction pipe 5 that are arranged in the vertical direction from above through a flange. The lower end of the suction pipe 5 is a suction port 5s that is widened and opened. A drain pipe connected to a river or the like is connected to the upper end of the pump pipe casing 3 (not shown). An impeller 21 is accommodated in the liner casing 4.

In the present embodiment, the impeller 21 is formed of an open type impeller, but may be a closed type impeller. The impeller 21 is a mixed flow impeller, but may be an axial flow impeller. A liner ring 22 is provided on the outer peripheral side of the impeller 21 with a slight gap from the outer peripheral edge of the impeller 21 (the tip of the open blade). In addition, a guide vane 23 is provided above the impeller 21 so as to convert the fluid velocity energy into pressure.
The rotary shaft 20 that supports the impeller 21 includes a first radial bearing 25 in the middle stage of the pumping pipe casing (casing body) 3 and a second radial bearing 27 that is supported by the inner cylinder 26 inside the guide vane 23. Is supported by

  The pumped-pipe casing (casing main body) 3 is configured to include a vertical tube body portion parallel to the rotation shaft 20 and a bent tube portion bent in the horizontal direction above, and the rotation shaft 20 passes through the bent tube portion. is doing. The rotating shaft 20 is connected to an electric motor (not shown) as a driving device that rotationally drives the rotating shaft 20. The electric motor may not be directly connected to the rotating shaft 20 but may be connected to the rotating shaft 20 via a gear train, for example, so that the rotation speed can be adjusted. A seal 28 is disposed in a penetrating portion through which the rotary shaft 20 penetrates the pumped-pipe casing (casing body) 3 to prevent leakage of water through the penetrating portion. In addition, a bearing housing 30 that holds a bearing 29 is provided in the bent pipe portion of the pumping pipe casing 3, and the rotating shaft 20 is moved by the bearing 29 above the penetrating portion where the rotating shaft 20 passes through the pumping pipe casing 3. I support it. Thereby, the vibration of the rotating shaft 20 caused by the driving device is prevented.

The suction pipe 5 is provided with an intake port 6 penetrating at a position LLWL below the tip of the impeller 21 and lower than the lowest water level LWL by h≈v ² / 2g. Is connected to an intake pipe 40.

  As shown in FIG. 1, the end 41 of the intake pipe 40 opened to the atmosphere is directed downward by a U-shaped pipe so that foreign matter such as dust does not enter. In FIG. 1, the end 41 is located above the floor board 101, but may be located in the suction water tank 100 below the floor board 101. As will be described later, when the water level becomes the lowest water level LWL and air is sucked into the suction pipe 5 through the intake pipe 40, the end 41 may be exposed to the atmosphere. Although the number of intake pipes 40 may be one, a plurality of, for example, four intake pipes 40 is preferable because air sucked from the intake pipe 40 easily flows to the intake pipe 5 evenly.

  Here, the relationship between the structure of the vertical pump 1 in the height direction and the water level will be described. The water level HWL is the highest water level of the suction water tank 100. The water level will not rise any further. Below that is the lowest water level LWL. This is a value peculiar to the pump. If the water level falls below this level, some problem occurs and the pump cannot continue to operate. Typically, the water level below which the suction pipe 5 starts to suck air in a vortex shape, and vibrations and noise are generated and the operation cannot be continued. However, the minimum water level LWL may be determined under conditions other than the spiral air suction.

  Below the lowest water level LWL is the suction start water level SLWL of the impeller 21. This water level corresponds to the water level at the tip of the impeller 21. This is because when the water level rises from a low water level and the impeller 21 comes into contact with water, the water-air stirring is started and water is discharged soon. That is, the impeller 21 is installed below the lowest water level LWL. Usually, the lowest operating water level LLWL of the vertical pump 1 is at a position lower than the suction start water level SLWL. Below the minimum operating water level LLWL, there is a water level A1 at the lower end (opening) of the suction pipe 5.

Here, the intake port 6 is arranged at the height of the lowest operating water level LLWL. The lowest operating water level LLWL is a position lower than the lowest water level LWL by h≈v ² / 2g. Here, v is the flow velocity of water at that position, and g is the acceleration of gravity. That is, since the pressure is lowered by the amount of velocity head according to Bernoulli's theorem due to the flow of water, the pressure is zero (atmospheric pressure) at the position where the head becomes equal to the velocity head at the lowest water level LWL. This position is defined as the minimum operating water level LLWL. If it does in this way, when a water level will become below the lowest water level LWL, it will become a negative pressure in the position of the lowest operating water level LLWL. Accordingly, the intake port 6 positioned at the lowest operating water level LLWL has a negative pressure, and the intake port 6 communicates with the atmosphere through the intake pipe 40, so that air is introduced from the end 41 of the intake pipe 40 into the intake pipe 5. Is sucked.

  When the water level drops to the lowest operating water level LLWL, the air from the end 41 of the intake pipe 40 to the intake port 6 through the intake pipe 40 is released to the atmosphere, and the space in the intake pipe 5 is broken in vacuum. Water falls. That is, when the water level drops to the height at which the intake port 6 is formed, the vertical shaft pump 1 does not pump water.

  Next, the operation of the vertical shaft pump 1 will be described with reference to FIG. First, the vertical pump 1 is started in a state where the water level is lower than the water level A1 at the lower end (opening) of the suction pipe 5. For example, when there is rainfall information indicating that heavy rain has fallen upstream of the river, it is predicted that the water level will suddenly rise after a certain time. In such a case, the vertical pump 1 for the preceding standby operation is started in a state where the water level is lower than A1. This is the start of the preceding standby operation.

  The water level in the suction water tank 100 rises due to the inflow of rainwater, and exceeds the lower end water level A1 of the suction bell. Even if the water level exceeds the water level A1 or exceeds the minimum operating water level LLWL, water is not yet sucked up. The impeller 21 is idling. When the water level further rises and reaches the suction start water level SLWL, the impeller 21 starts to suck water. At this time, since the air is also sucked into the suction pipe 5 from the suction port 6 through the suction pipe 40, the operation is not the operation of discharging the total water amount of the vertical shaft pump 1. That is, the vertical shaft pump 1 is performing a water / air mixing operation. When the water level further rises, the amount of intake air gradually decreases and the amount of water increases instead. Eventually, when the water level rises to the lowest water level LWL, the intake air amount becomes zero and the total water amount of the vertical shaft pump 1 is discharged. That is, the steady operation is started.

  Furthermore, the water level rises to a water level between the lowest water level LWL and the highest water level HWL, and the vertical shaft pump 1 continues the steady operation. Thereafter, the water level is lowered due to the drainage of the vertical shaft pump 1 and when the water level falls below the minimum water level LWL, the air starts to be sucked into the suction pipe 5 through the intake pipe 6 through the intake pipe 40. That is, the air / water mixing operation is started again. As the water level falls, the amount of intake air increases and the amount of water decreases instead. When the water level further decreases and reaches the minimum operating water level LLWL, the suction of water is finished, and the impeller 21 enters an idling state in which it is operated in the air. That is, the vertical shaft pump 1 is in an air lock state in which no water is sucked.

  In this way, the impeller 21 continues to be in an idling state in the air. When the rain continues, the operation is continued as it is, the water level rises again, and the vertical pump 1 starts to suck water when it reaches the suction start water level SLWL as described above. In this way, the vertical shaft pump 1 for the preliminary standby operation can continue operation between the idle operation and the operation of the total water amount regardless of the water level of the suction water tank 100. The transition between the idling operation and the total water amount operation is smoothly performed because the vertical shaft pump 1 sucks air from the intake port 6 together.

  Next, the structure of the suction pipe 5 and the intake port 6 formed in the suction pipe 5 will be described with reference to FIGS. 2 and 3 are views showing the suction pipe 5, FIG. 2 is a longitudinal sectional view of the suction pipe 5, and FIG. 3 is a view taken in the direction of arrow III in FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 2, and FIG. 5 is a cross-sectional view taken along line V-V in FIG.

As shown in FIGS. 2 to 5, the suction pipe 5 has a circular cross section at the top, transitions from a circular cross section to a square cross section from the top toward the middle, and a constant quadrilateral cross section from the middle to the bottom. The rectangular cross section gradually increases in the shape of a truncated pyramid from the bottom to the bottom. That is, as shown in FIGS. 2 to 5, the suction pipe 5 has a circular cross section having a diameter r from the point A to the point B at the upper end, and changes from a circular cross section to a square cross section from the point B to the point C. The point C has a rectangular cross section with a long side length L ₁ and a short side length L ₂ , and the same dimension (long side length L ₁ , short side length) from the C point to the D point. L ₂ ) having a rectangular cross section, the length of the long side and the short side gradually increases from point D to point E, and the length of the long side L ₃ and the length of the short side at point E the length of L ₃ is in a square cross-section equal.

4 which is a cross-sectional view taken along the line IV-IV in FIG. 2 shows a state where the suction pipe 5 is changed from a circular cross section to a square cross section.
In FIG. 5, which is a cross-sectional view taken along the line VV of FIG. 2, a state of a rectangular cross section having a long side length L ₁ and a short side length L ₂ is shown. As shown in FIG. 5, the intake pipe 5 is formed with four intake ports 6 at a height position close to the point E. The suction pipe 5 constitutes a square bell mouth having a rectangular cross section with a constant area from the point C to the point D and a square cross section with an area gradually increasing from the point D to the point E.

Next, the relationship between the square bell mouth and the intake port 6 will be further described. FIG. 5 shows a cross section at the position where the air inlet 6 is provided. As shown in FIG. 5, the inner peripheral surface 5a of the suction pipe 5 constitutes a flow channel wall surface, and the inner side of the inner peripheral surface 5a constitutes a rectangular flow channel cross section. If the distance from the centroid (O) of the channel cross section to the channel wall surface is r, this distance r is not constant and is different from r ₁ , r ₂ , r ₃ , r ₄ . That is, the distance r ₁ from the centroid (O) of the flow path cross section to the flow path wall surface on the short side L ₂ side is the minimum distance r _min , from the centroid (O) of the flow path cross section to the apex of the rectangle of the distance _{r 4} is the largest distance _{r max.} The intake port 6 is provided at a position (r ₃ ) farther from the centroid (O) than a position where the distance from the centroid (O) of the flow path cross section to the flow path wall surface is minimum (r _min ). It has been. The intake port 6 is located upstream of the flow in the square bell mouth from the position where the distance from the centroid (O) of the rectangular channel cross section to the channel wall surface is the maximum distance (r _max ).

  In the case of a circular bell mouth, the distance r from the centroid (O) of the channel cross section to the channel wall surface is constant. Therefore, there is no flow slip on the bell mouth wall surface, so the velocity component becomes zero. In the case of a circular bell mouth, since the distance r is uniform from the centroid (O) of the channel cross section, the velocity gradient is always positive and the pressure distribution is positive. Therefore, in the case of a circular bell mouth, it may be difficult to inhale from the intake port.

四角形の流路断面の頂点（角部）に近づくにつれ（流路断面の図心（Ｏ）からの距離ｒが大きくなるにつれ）、流路壁面上における速度勾配は次式のように負の値を示す。

すなわち、流路断面の図心（Ｏ）から流路壁面までの距離が最小となる位置（ｒ_ｍｉｎ）から下流側（羽根車の回転方向の下流側）の壁面付近では、上記式（２）で示されるように、速度勾配は負の値になる。このことから、流路断面の図心（Ｏ）から流路壁面までの距離が最小となる位置（ｒ_ｍｉｎ）より下流側では、壁面表面の流れは剥離が発生し、逆流Ｆ_２が生じる。したがって、圧力が負圧状態となり、吸気口６からの吸気が可能となる。
なお、四角形に沿った流れでは角部で渦が発生し、負圧状態が発生し難い。発生しても非常に弱い負圧状態である。したがって四角形の頂点に吸気口６を設けることは適当でない。 FIG. 6 is a schematic enlarged view in which the portion VI in FIG. 5 is enlarged. In FIG. 6, y represents a direction and u represents a velocity. In Guideline point flow rate smaller discharge amount, the swirl flow F ₁ is generated in the vicinity of the center portion of the suction tube 5, the centrifugal force acts, the pressure increases. In the square bell mouth, since the distance r from the centroid (O) of the channel cross section to the channel wall surface is not uniform, when considering the velocity gradient from the centroid (O) to the channel wall surface, At a position (r _min ) (point P in FIG. 6) at which the distance from the centroid (O) to the channel wall surface is minimum, the velocity gradient on the channel wall surface is as follows.

As the apex (corner) of the rectangular channel cross section is approached (as the distance r from the centroid (O) of the channel cross section increases), the velocity gradient on the channel wall surface becomes a negative value as shown in the following equation: Indicates.

That is, in the vicinity of the wall surface on the downstream side (downstream in the rotational direction of the impeller) from the position (r _min ) where the distance from the centroid (O) of the flow channel cross section to the flow channel wall surface is minimum, the above formula (2) As shown, the velocity gradient has a negative value. Therefore, on the downstream side of the position (r _min ) where the distance from the centroid (O) of the flow path cross section to the flow path wall surface is minimum, the flow on the wall surface is separated, and a backflow F ₂ is generated. Accordingly, the pressure becomes a negative pressure state, and intake from the intake port 6 becomes possible.
In the flow along the quadrangle, vortices are generated at the corners, and a negative pressure state is unlikely to occur. Even if it occurs, it is a very weak negative pressure state. Therefore, it is not appropriate to provide the intake port 6 at the apex of the square.

FIG. 7A to FIG. 7H are schematic cross-sectional views showing modifications of the cross-section of the suction pipe and correspond to FIG. The suction pipes shown in FIGS. 7 (a) to 7 (h) have various channel cross-sectional shapes, but in any case, the inner peripheral surface 5a of the suction pipe 5 constitutes the channel wall surface. The inside of the inner peripheral surface 5a forms a cross section of the flow path, and has a cross-sectional shape in which the distance r from the centroid (O) of the cross section of the flow path to the flow path wall surface is not constant. The intake port 6 is located farther from the centroid (O) than the position (r _min ) at which the distance from the centroid (O) of the cross section of the flow path to the flow path wall surface is minimum. Therefore, the suction pipes shown in FIGS. 7A to 7H also have the same effects as the suction pipes shown in FIGS. 7A to 7H is the same as the suction pipe shown in FIGS. 5 and 6 in that the suction pipe transitions from a circular cross section to an ellipse or a polygonal cross section.

The suction pipe 5 shown in FIG. 7A has an elliptical channel cross section, and the intake port 6 is provided at a position close to the intersection point _Pv between the ellipse and the major axis of the ellipse. The intake port 6 is located farther from the centroid (O) than the position (r _min ) at which the distance from the centroid (O) of the channel cross section to the channel wall surface is minimum, and this minimum position ( r _min ) on the downstream side of the flow (downstream in the rotational direction of the impeller). The flow along the ellipse has a curvature. Therefore, centrifugal force acts, and at the apex of the ellipse, the centrifugal force becomes maximum and the pressure rises. Therefore, it is not appropriate to provide the inlet 6 at the top of the ellipse.
Suction pipe 5 shown in FIG. 7 (b) has a hexagonal flow cross-section, the inlet 6 is provided in a position close to the hexagonal apex P _t at each side of the hexagon.
Suction pipe 5 shown in FIG. 7 (c) has an octagonal channel cross section, the inlet 6 is provided at a position close to the vertex P _t at each side of the octagon.
Suction pipe 5 shown in FIG. 7 (d) has a trapezoidal flow path section, the intake port 6 is provided at a position close to the vertex P _t at each side of the trapezoid.
Suction pipe 5 shown in FIG. 7 (e) has a flow cross-section of triangular intake port 6 is provided at a position close to the vertex P _t at each side of the triangle.

The suction pipes 5 shown in FIGS. 7B, 7C, 7D, and 7E will be described. Each suction pipe 5 has a polygonal channel cross section, and each intake port. 6 is provided at a position close to the vertex between the midpoint and the vertex of one side of the polygon. The intake port 6 is located farther from the centroid (O) than the position (r _min ) at which the distance from the centroid (O) of the channel cross section to the channel wall surface is minimum, and this minimum position ( r _min ) on the downstream side of the flow (downstream in the rotational direction of the impeller). In the flow along the polygon, vortices are generated at the corners, and a negative pressure state is unlikely to occur. Even if it occurs, it is a very weak negative pressure state. Therefore, it is not appropriate to provide an inlet at the apex of the polygon.

The suction pipe 5 shown in FIGS. 7 (f), 7 (g) and 7 (h) is different from the intake pipe shown in FIGS. 7 (a) to 7 (e) in the concept of an ellipse or a polygon. Although not included, the distance r from the centroid (O) of the channel cross section to the channel wall surface is not constant.
The suction pipe 5 shown in FIG. 7 (f) has a channel cross section in which the upper half is a semi-elliptical shape and the lower half is a square shape, and one intake port 6 is an intersection P of the semi-elliptical major axis and the semi-elliptical shape. _v is provided in a position close to the other two inlet 6 is provided at a position close to the vertex P _t of the rectangle.
The suction pipe 5 shown in FIG. 7 (g) has a human-shaped channel cross section having four mountain-shaped protrusions, and the intake port 6 has an apex P _t of each human-shaped protrusion. It is provided in the position close to.
Suction pipe 5 shown in FIG. 7 (h), each vertex has a substantially triangular shape of the flow channel cross section with a circular arc-shaped rounded, the air inlet 6 in proximity to the arcuate vertex P _t position Is provided.

In the suction pipe 5 shown in FIGS. 7 (f), 7 (g), and 7 (h), the intake port 6 has the smallest distance from the centroid (O) of the flow path cross section to the flow path wall surface. It is located farther from the centroid (O) than the position (r _min ), and is located downstream of the flow (downstream in the rotational direction of the impeller) from the minimum position (r _min ).

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications may be made within the scope of the technical idea described in the claims and the specification and drawings. Is possible.

FIG. 1 is a longitudinal sectional view showing a main part of a vertical shaft pump according to the present invention. FIG. 2 is a longitudinal sectional view of the suction pipe. 3 is a view taken in the direction of arrow III in FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 5 is a cross-sectional view taken along the line V-V in FIG. FIG. 6 is a schematic enlarged view in which the portion VI in FIG. 5 is enlarged. FIG. 7A to FIG. 7H are schematic cross-sectional views showing modifications of the cross-section of the suction pipe and correspond to FIG. FIG. 8 is a diagram illustrating an example of a conventional vertical shaft pump.

Explanation of symbols

1 Vertical shaft pump 2 Pump casing 3 Pumped-pipe casing (casing body)
4 Liner casing 5 Suction pipe 5a Suction port 6 Suction port 20 Rotating shaft 21 Impeller 22 Liner ring 23 Guide vane 25, 27 Radial bearing 26 Inner cylinder 28 Seal 29 Bearing 30 Bearing housing 40 Intake pipe 41 End 50 Installation housing 100 Suction water tank 101 Floor plate 111 Suction water tank 112 Impeller 113 Vertical shaft pump 114 Suction pipe 115 Air inlet 116 Air pipe 116a Other end 117 Rotating shaft

Claims (10)

A rotation axis arranged in a vertical direction and rotating around an axis;
An impeller that rotates by rotation of the rotating shaft, sucks water and flows it upward,
A suction pipe that is arranged on the upstream side of the impeller and forms a flow path for flowing the water toward the impeller;
An intake port provided in the suction pipe at a position upstream of the impeller;
An intake pipe having one end communicating with the intake port and the other end opened to the atmosphere;
The suction pipe has a cross-sectional shape in which the distance from the centroid of the flow path cross section to the flow path wall surface is not constant at the position where the intake port is provided;
The vertical shaft pump, wherein the intake port is provided at a position farther from the centroid than a position where the distance from the centroid to the flow path wall surface is minimum.   2. The vertical shaft pump according to claim 1, wherein the intake port is located on a downstream side in a rotation direction of the impeller from a position where a distance from the centroid to the flow path wall surface is minimized.   The vertical shaft pump according to claim 1 or 2, wherein the cross-sectional shape is a polygon.   The vertical shaft pump according to claim 3, wherein the intake port is located between the vertex of the polygon and a midpoint of one side of the polygon.   The vertical shaft pump according to claim 3 or 4, wherein the polygon is a quadrangle.   The vertical shaft pump according to claim 1 or 2, wherein the cross-sectional shape is elliptical.   The vertical shaft pump according to claim 6, wherein the intake port is located in the vicinity of an intersection of the elliptical long axis and the ellipse.   2. The vertical shaft pump according to claim 1, wherein the suction pipe transitions from a circular cross section to a polygonal cross section from the upper side toward the lower side.   The vertical pump according to claim 1, wherein the suction pipe transitions from a circular cross section to a quadrangular cross section from the upper side toward the lower side.   2. The vertical shaft pump according to claim 1, wherein the suction pipe transitions from a circular cross section to an elliptic cross section from the upper side toward the lower side.

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