JP3111548B2 - Vertical pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical shaft pump having a mixed flow impeller and the like, and more particularly to a vertical pump having a plurality of impellers disposed below a position corresponding to a minimum water level, and a pump casing below the impeller. This is suitable for a vertical axis pump of a preparatory standby operation type in which the suction pipe is connected to drain water while taking in air from the suction pipe at a low water level.

[0002]

2. Description of the Related Art Conventionally, as described in Japanese Patent Application Laid-Open No. 2-78791, an impeller is provided below a minimum water level, and an intake port is provided in a pump casing below the impeller. Connect the intake pipe, open the end of the intake pipe to the atmosphere, and when the water level drops, automatically inhale the air from the intake pipe, lowering the pumping capacity of the pump to a certain level There is known a method in which the pumping is automatically stopped by air-water separation, and a standby operation by idling operation (operation to continue idling until the water level reaches a predetermined water level).

[0003]

In the conventional vertical shaft pump described above, a vertical shaft pump or the like performing a preliminary standby operation performs a gas-liquid two-phase flow operation while suctioning air. There is a problem that dynamic imbalance due to stagnation or uneven distribution of air, or imbalance in load between the blades, increases the vibration value of the pump due to fluid force or the like, and depending on the conditions, it becomes impossible to continue operation. Was. This excitation force depends on the type of pump, Ns
Although it differs depending on the conditions, it becomes particularly large in a low flow rate region, and in the case of an axial flow pump, the value may be about several times the value in a normal operation at a rated point where air is not sucked. For this reason, there has been a problem that a conventional vertical shaft pump operating in gas-liquid two-phase flow cannot have the same reliability as a normal vertical shaft pump.

An object of the present invention is to provide a pump that performs such a gas-liquid two-phase flow operation so as to suppress the exciting force generated on the impeller during the gas-liquid two-phase flow operation.

It is another object of the present invention to reduce the vibration of the pump and to obtain a more reliable pre-standby vertical pump.

It is still another object of the present invention to suppress backflow occurring on the back surface of a pump impeller.

[0007]

A first feature of the present invention to achieve the above object is that a water level during operation of a pump is a minimum water level below which the air is sucked from a suction bell of a pump casing. Below the position corresponding to the level , the boss and the plurality of blades attached to this boss are
A pump case below the impeller.
The intake pipe is connected to the intake port, and the intake pipe is opened to the atmosphere at a level higher than the maximum water level of the pump suction tank. In the vertical pump, the blade
Boss from the central streamline at the blade exit side on the blade negative pressure surface
Or at the tip of the blade from the central streamline on the blade inlet side
And projecting in the normal direction of the blade negative pressure surface,
Is provided.

A second feature of the present invention is that a boss portion and the boss portion are provided.
Port under the impeller having a plurality of blades attached to the
An intake hole is provided in the pump casing, and an intake pipe is
Connect the other end of this intake pipe to the atmosphere,
When the water level in the tank is low,
In a vertical pump that performs gas-liquid two-phase flow operation, the impeller
Boss from the central streamline on the blade exit side on the blade negative pressure surface
Or at the tip of the blade from the central streamline on the blade inlet side
And projecting in the normal direction of the blade negative pressure surface,
Is provided.

[0009] The impeller is arranged in the circumferential direction of the boss.
Diagonal flow with multiple diagonal blades mounted at intervals
Open impeller with no impeller or shroud at the tip
The effect is great when applied to root wheels. Further, said backflow suppression
The length of the rib is the length of the blade where the rib is provided.
And the rib on the blade outlet side is the blade height.
At about 1/3 blade height position, the rib on the blade inlet side is
It is good to set each at the blade height position of about 2/3 of the root height
No.

[0010]

[0011]

[0012]

[0013]

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 4 shows an overall front view of a vertical stand-by type vertical shaft pump, and a pump casing 4 accommodating the impeller 1.
Is a casing liner 2 and a suction bell 3 provided thereunder.
have. The upper side of the pump casing is composed of a pumping pipe 5 and a discharge elbow 6. Discharge elbow 6
A discharge pipe 7 and a discharge valve 8 are provided on the discharge side.
An intake hole 9 is provided in a pump casing near the lower portion of the impeller 1, an intake pipe 10 is connected to the intake hole 9, and an intake amount adjusting valve 11 is provided in the intake pipe 10. The suction port 12 of the intake pipe 10 is installed at a position higher than the highest water level (HWL) in the water absorption tank. The position of the intake port 9 is at the conventional minimum water level (that is, the lowest water level below which the air is sucked from the suction bell 3) WL1. It is formed at a position where air is not sucked in but is sucked in from the intake hole 9 when the water level becomes lower than the water level WL1.

By configuring the flow control device in this manner, the pump is operated from a water level WL4 higher than WL1, and when the water level decreases and reaches WL1, air starts to be sucked into the pump casing through the intake hole 9. . Then, as the water level decreases, the intake air amount increases, and a certain water level WL
When it reaches 3, the pump becomes unable to pump water, and the impeller 1 becomes idle. Thereafter, when the water level rises again and reaches the water level WL2 where the impeller is located, the pump starts the draining operation again while sucking the air from the intake port, and when the inflow into the pump storage tank is larger than the drainage amount, The water level continues to rise, and when it reaches WL1, the intake from the intake port is automatically stopped, and the operation shifts to a normal pumping operation.

In FIG. 4, reference numeral 13 denotes an intake / exhaust air valve.

FIG. 5 schematically shows a flow pattern of a flow in a meridian (meridian) cross section of a pump (mixed flow pump) impeller 1. As shown in FIG. In the figure, the right half with respect to the main shaft 14 shows the flow state near the pump specification point, and the left half shows the flow state in the low flow rate region of the pump. In the flow near the specification point, the pumped water flows neatly along the meridian section of the blade 1b as shown by the arrow A. On the other hand, in the low flow rate region, the flow flows as shown by the arrow B in the left half of the figure, and flows into a region C (boss portion side) on the back surface exit side of the blade 1b and a region D (blade tip side) on the blade back surface entrance side. It is known that reflux occurs. The size of the backflow region, the position on the blade surface, and the like are slightly different depending on the specific speed Ns of the pump, the type of the pump, and the like, but any specific speed or type has a flow similar to that of FIG.

When the intake operation (gas-liquid two-phase flow operation) is performed in such a low flow rate region, the air is stagnated or unevenly distributed in the backflow regions C and D, thereby causing a dynamic imbalance or a blade. It has been found that the mutual load becomes unbalanced, and the fluid force generated by these causes the excitation force generated in the impeller to be remarkably increased as compared with a case in which the intake is not performed.

Hereinafter, specific experimental examples will be described. In the single-phase flow operation that does not take in air, the flow rate is reduced from the rated operation to a state where a reverse flow is generated as shown in the left half of FIG. 5 (around 60% flow rate at the rated time). It was found that when sucked, the exciting force generated in the impeller 1 became very large. It was also found that the excitation force generated on the blade can be reduced by reducing the size of the backflow in the backflow regions C and D in FIG.

FIG. 6 shows the gas-liquid two-phase flow characteristics of a certain pump.
Gas-liquid mixing ratio at the impeller inlet (void ratio α = Qa /
(Qa + Qw) Qa: air flow rate, Qw: liquid flow rate) are shown as parameters. In FIG. 6, the horizontal axis represents the discharge flow rate Q of the pump, and the vertical axis represents the total head Ha of the pump. Now, in FIG. 4, the operating point was at _one point a in WL1 (LWL), when starting the air from the air inlet water level drops, drops total head and ejected amounts both increase the intake air amount with a decrease in the water level And the characteristic curve of the pump becomes a → b → c →
The operating point moves as a ₁ → b ₁ → c ₁ → d ₁ . Water level drops to WL3, when the operating point reaches d _1, the pump is disabled and the pumping, the impeller 1 becomes idle operation. In the preceding standby type operation pump, a backflow occurs, and it is necessary to operate safely and stably even in a region where the excitation force is large. Hereinafter, embodiments of the present invention capable of performing stable operation with low vibration even in gas-liquid two-phase flow operation will be described with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. In the drawing, reference numeral 1 denotes an open-type mixed flow impeller having no shroud at the tip of the blade, 1a denotes a boss portion of the mixed flow impeller 1, and 1b denotes a plurality of bosses mounted at equal intervals in a circumferential direction of the boss portion 1a. As shown in FIG. 2, the mixed flow blades 1c and 1d are backflow suppressing ribs formed on the suction surface of each blade 1b in a direction normal to the suction surface. The rib 1c is a central streamline on the blade exit side (streamline at the center in the blade height direction).
It is located closer to the boss 1a than f, and has a shape along the streamline during rated operation. The rib 1d is located on the blade tip side (casing liner 2 side) with respect to the central streamline f on the blade inlet side, and has a shape along the streamline at the time of rated operation. These backflow suppressing ribs 1c,
The length of 1d is preferably substantially equal to the length of the backflow areas C and D shown in FIG. In general, the length of the backflow region is about half the length of the blade, and therefore, the length of the rib is preferably about half the length of the blade where the rib is provided. The mounting positions h ₁ and h ₂ of the ribs 1 c and 1 d in the blade height direction are such that the rib 1 c on the blade outlet side is located on the boss side when the blade height of the portion where the rib is provided is h. At 1/8 to 3 / 8.h, preferably about 1 / 3.h, the rib 1d on the blade inlet side is 5/8 from the boss side.
It is good to provide at the height position of about 7 / 8.h, preferably about 2 / 3.h, respectively.

When there are no ribs, the flow pattern in the backflow region of the pump is the same as that of FIG. 5, but in this embodiment, since the backflow prevention ribs 1c and 1d are provided as described above, Exciting force to impeller 1 generated in the reverse flow region during the phase flow operation can be reduced, and the vibration value of the pump can be reduced.

That is, due to the above-mentioned structure, at the time of the low flow rate operation in which the air is drained while taking in air, as shown in FIG. By providing the prevention ribs 1c and 1d, the backflow is divided, and the size of the backflow region can be reduced. In particular, during the intake operation, bubbles (air) tend to stay or be unevenly distributed in the reverse flow region. However, the presence of the ribs makes it easier for bubbles to be swept away. It becomes difficult to move, and as a result, the dynamic imbalance and the imbalance of the load between the blades can be reduced, and the fluid force due to these imbalances can be reduced. Therefore, according to the present embodiment, the size of the backflow region generated on the back surface of the blade can be reduced even in the preceding standby operation in which the intake is performed in the low flow rate region, and the dynamic imbalance due to the stagnation or uneven distribution of air, and the blade The fluid force generated by the imbalance between the loads can be reduced, the vibration force acting on the impeller can be suppressed to a small value, and the vibration value of the pump can be reduced.

In the above-described embodiment, an example in which one rib is provided in each of the backflow regions A and B has been described. However, as shown in FIG. Is provided, the radial movement of the bubbles staying in the backflow region can be suppressed smaller, and the vibration can be further reduced. Further, in the above-described embodiment, the example in which the ribs are provided in both the backflow regions A and B has been described.
A rib may be provided only in one of the backflow regions A and B, and depending on the specific speed Ns of the pump, a large vibration reduction effect may be obtained by merely providing the rib in the one region. Generally, when ribs are provided in the backflow region A, a remarkable vibration reduction effect can be obtained without providing ribs in the backflow region B.

The present invention can be applied to a pump that performs gas-liquid two-phase flow operation, such as a vertical stand-by type vertical pump, and has a remarkable effect. However, it can be applied to a normal pump that performs single-phase flow operation. Also, the backflow reduction effect by the rib can be obtained. Further, the present invention can be applied not only to the vertical shaft pump, but also to a horizontal shaft pump, etc., and the type of the pump impeller is not limited to the mixed flow type, but is also applicable to an axial flow type or a centrifugal type. The present invention can be applied not only to the open type impeller, but also to a closed type impeller having a shroud (side plate) at the tip of the blade.

[0027]

According to the present invention, when the water level is low, the intake pipe is
Vertical pump that performs gas-liquid two-phase flow operation while sucking air
The backflow region of the blade suction surface, where backflow occurs in the low flow rate region,
That is, the central flow on the blade exit side at the blade negative pressure surface of the impeller
Boss side from line, or blade tip from central streamline on blade inlet side
At the end position, project in the normal direction of the blade suction surface and follow the streamline.
The backflow prevention rib is shaped like
Flow can be suppressed, which results in
Discharge of stagnant air bubbles (air) can be promoted.
As a result, in the low flow rate region, air stagnation or
There is a dynamic imbalance due to the presence
Or the fluid force due to the imbalance of the load between the blades
Pump blades during gas-liquid two-phase flow operation
Reduce the vibration value of the pump by reducing the excitation force on the car
be able to. Therefore, according to the present invention, the pump blade
Reduces the vibration force generated on the root wheel and reduces vibration
There is an effect that a high vertical pump can be obtained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a main part showing one embodiment of a vertical shaft pump of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a longitudinal sectional view of a main part for explaining the operation of the embodiment of FIG. 1;

FIG. 4 is a front view of the vertical shaft pump.

FIG. 5 is an explanatory diagram showing a flow pattern of an impeller negative pressure surface in a backflow region of the pump.

FIG. 6 is a diagram showing a gas-liquid two-phase flow characteristic of a pump and a change in an operating point in a preceding standby operation.

FIG. 7 is a longitudinal sectional view of a main part showing a modification of FIG. 1;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Impeller, 1a ... Boss part, 1b ... Blade, 1c, 1d ...
Backflow prevention rib, 2 ... casing liner, 3 ... suction bell,
4 pump casing, 5 pumping pipe, 6 discharge elbow, 7 discharge pipe, 8 discharge valve, 9 intake hole, 10 intake pipe, 11 intake amount adjustment valve, 12 intake port, 13 ... Intake / exhaust air valve, 14: spindle, f: central streamline, A, B: streamline, C,
D: Backflow area.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-78791 (JP, A) JP-A-52-41902 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F04D 13/00 F04D 29/00-29/66

Claims (12)

(57) [Claims] A boss portion is provided below a position corresponding to a minimum water level at which water is sucked from a suction bell of a pump casing when the water level during operation of the pump is lower than the water level.
And an impeller having a plurality of blades attached to the boss portion, and suction air is supplied to a pump casing below the impeller.
A vertical shaft pump having a configuration in which a hole is provided and an intake pipe is connected to the intake port, and the intake pipe is opened to the atmosphere at a level higher than the highest water level of the pump suction tank, and drains while suctioning from the intake pipe at a low water level. central streamline of the blade exit side of definitive the blade suction surface of the impeller
More boss side, or blade tip from central streamline on blade inlet side
And protrudes in the direction normal to the blade suction surface,
A vertical shaft pump further provided with a backflow suppression rib having a shape along a streamline . 2. The backflow suppressing rib according to claim 1,
A vertical shaft pump provided at least on the boss side of the central streamline on the blade outlet side. 3. The backflow suppressing rib according to claim 1,
A vertical shaft pump provided at least on the blade tip side (casing liner side) with respect to the central streamline on the blade inlet side. 4. The backflow suppressing rib according to claim 1,
A vertical shaft pump provided both on the boss side from the central streamline on the blade outlet side and on the blade tip side from the central streamline on the blade inlet side. 5. The blade according to claim 1, wherein
The car is a vertical shaft pump that is a mixed flow impeller . 6. The diagonal flow impeller according to claim 5, wherein
Blades installed at equal intervals in the circumferential direction
Equipped with a vertical pump. 7. The blade according to claim 1, wherein
Cars are open-type wings without a shroud at the tip of the wing.
Vertical shaft pump that is the base wheel. 8. A boss and a plurality of bosses attached to the boss.
Inlet on pump casing below impeller with impeller
The intake pipe is connected to this intake hole, and other
Open the end to the atmosphere when the water level in the suction tank is low.
Stands for gas-liquid two-phase flow operation while sucking air from the intake pipe.
In the shaft pump, a central streamline on a blade outlet side of a blade negative pressure surface of the impeller
More boss side, or blade tip from central streamline on blade inlet side
And protrudes in the direction normal to the blade suction surface,
In addition, a backflow prevention rib shaped along the streamline is provided.
And vertical shaft pump. 9. The backflow suppressing rib according to claim 8, wherein
A vertical shaft pump provided at least on the boss side of the central streamline on the blade outlet side . 10. The backflow suppressing rib according to claim 8, wherein
Is at least the blade tip side from the central streamline on the blade inlet side
A vertical pump provided on the (casing liner side). 11. The backflow suppressing rib according to claim 8, wherein
Is the boss side from the central streamline on the blade outlet side, and the blade inlet
Shaft pons provided on both sides of the blade tip from the central streamline on the side
H. 12. The backflow suppressing rib according to claim 11,
Is about the blade length of the part where the rib is provided.
And the rib at the blade outlet side is about 1 of the blade height.
At the blade height position of / 3, the rib on the blade inlet side is the blade height.
About 2/3 of the blade height
A vertical shaft pump characterized by the above-mentioned.