JPH04314997A - Advance standby pump - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is installed in a water absorption tank,
The present invention also relates to a water pump having an impeller positioned below the water level in the water tank, and particularly to a pump that enables water pumping operation even when the water level of the water tank is low, for example, performs advance standby operation.

0002

[Prior Art] Conventionally, as described in Japanese Unexamined Patent Publication No. 2-78791, an impeller is positioned below the water level of a water absorption tank, a through hole leading to the outside is provided near the inlet of the impeller, and the water level When the water level drops, air is inhaled through this through hole to reduce the pump's pumping capacity, thereby controlling the flow rate, and when a certain water level is reached, the air and water are separated and the system shifts to idle operation. There is a known method of performing standby operation with this configuration alone, but if you actually perform advance standby operation with only this configuration, the vibration value of the pump will increase during gas-liquid two-phase operation with intake air, and depending on the conditions, the operation may be interrupted. The vibration level may reach such a level that it becomes impossible to continue. Therefore, with this conventional technology alone, the advance standby operation pump cannot be used.
It was not possible to provide the same level of reliability as a pump under normal operation.

0003

[Problems to be Solved by the Invention] In the above-described conventional technology, it is not possible to suppress fluctuations in the gas-liquid two-phase pump characteristics due to fluctuations in the intake air amount during intake operation, and as a result, the operating point changes greatly over time. , which causes so-called self-excited vibration, increasing the vibration of the pump.

SUMMARY OF THE INVENTION An object of the present invention is to provide a pre-standby operation pump that reduces vibration of the pump by suppressing fluctuations in the amount of intake air during the gas-liquid two-phase operation. Our goal is to provide the following.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a device for suppressing intake air amount fluctuations in an intake line including an intake hole or in the vicinity of the intake hole.

Second, as a device for suppressing fluctuations in the amount of intake air, a multi-stage or single-stage orifice is provided in the intake line or near the intake hole.

Thirdly, as a device for suppressing fluctuations in the amount of intake air, one or more perforated plates are provided near the intake line or the intake hole.

Fourthly, as a device for suppressing fluctuations in the amount of intake air, a restriction is provided at one or more locations in the intake line or near the intake hole.

Fifth, as a device for suppressing fluctuations in the amount of intake air, an impeller is provided in the intake line to suppress fluctuations in the differential pressure between the pressure inside the pump's suction pipe and the atmosphere.

Sixth, as a device for suppressing fluctuations in the amount of intake air, a device for rectifying the flow near the intake hole and suppressing pressure fluctuations near the intake hole is provided.

Seventh, as a device for rectifying the flow near the intake hole, an even number of relative positions within the same cross section of the suction pipe upstream of the intake hole are connected by pipes.

Eighthly, as a device for rectifying the flow near the intake hole, a restriction is provided in the suction pipe upstream of the intake hole.

Ninth, the intake air amount fluctuation suppressing device is disposed at the connection portion between the intake pipe and the suction pipe in the intake line.

[0014]

[Operation] Among the vertical shaft pumps that perform advance standby operation, the flow rate is controlled by intake air, and the pump is operated in gas-liquid two-phase at a low water level, especially the pump that controls the flow rate by naturally sucking air. The amount of intake air fluctuates due to nearby pressure fluctuations, and the operating point constantly changes, causing self-excited vibrations. Therefore, in the present invention, a device for suppressing fluctuations in the amount of intake air is provided in the intake line or near the intake hole of such a preliminary standby operation type pump. Due to this,
It is possible to suppress fluctuations in the intake air amount of the pump and reduce the vibration value generated in the pump as a result of self-excited vibration.

[0015]

[Embodiments] Hereinafter, embodiments of the present invention will be explained with reference to the drawings.

In FIG. 1, a suction bell 3 of the pump casing is connected to the lower side of the casing liner 2 of the pump casing 4 housing the impeller 1, and a pumping pipe 5, which is a part of the pump casing, is connected to the upper side. and a discharge elbow 6 are connected to form a vertical shaft pump. A discharge pipe 7 and a discharge valve 8 are provided on the discharge side of the discharge elbow 6. Further, an intake hole 9 is provided near the bottom of the impeller 1, an intake pipe 10 is provided continuously with the intake hole 9, an intake air amount adjustment valve 11 is provided in the intake pipe 10, and The port 12 is installed at a position higher than the highest water level (HWL) in the water absorption tank, and these constitute a flow rate control device. The intake hole 9 is installed at a conventional lowest water level, that is, at a lowest water level WL1 at which air is sucked in from the suction bell 3 below this water level, and no air is taken in from the intake hole 9.

Now, if this pump is operated at a water level WL4 higher than WL1, and when the water level reaches WL1 as the water level decreases, the pump starts to intake air from the intake hole 9. As the water level decreases, the intake air amount increases. At a certain water level WL3, the pump becomes unable to pump water, and the impeller 1 becomes idling. After this,
When the water level rises again and the water level reaches WL2, the pump goes into intake operation again. If the amount of inflow is larger than the amount of pumped water, the water level continues to rise and stops intake when it reaches WL1. , transition to normal pumping operation.

FIG. 2 shows a first embodiment.

In the advance standby operation pump described in FIG. 1, during intake operation, air is introduced into the pump through the intake pipe 10 by the differential pressure between the static pressure P within the pump and the atmospheric pressure P0. At this time, if the static pressure inside the pump fluctuates, the amount of air taken in will fluctuate. Generally, when a pump sucks air, it is known that the performance of the pump can be determined by the mixing ratio of air and water (void ratio) as shown in Figure 3. According to this, the amount of intake air Variation in means that the operating point changes over time around a certain operating point. This will be explained using FIG. 4. Assume that a certain pump is operated at a point where the void rate is b%■. At this time, as the pressure P inside the pump shown in Fig. 2 fluctuates, the intake air amount increases and the void ratio rises to a%, and the operating point shifts to point ■ from the relationship with the pump system head curve. and transition. In addition, the intake air volume decreases due to the same reason,
When the void ratio decreases to c%, the operating point shifts to point ■.

The two-phase flow characteristics of the pump shown in FIG. 3 depend on the type of pump, Ns, intake method, etc., but the higher the sensitivity to changes in air amount, the greater the change in the operating point described above. .

[0021] Such a change in the operating point increases the load fluctuation of the pump during operation, which in turn increases the excitation force.
The vibration value of the pump increases.

In such a pump, if an intake air amount fluctuation suppressing device 14 is provided in the intake line (or in the vicinity of the intake hole) as shown in FIG. 2, vibrations due to fluctuations in the operating point can be suppressed. Can be done.

FIG. 5 shows a first embodiment, in which an intake hole 9 is provided in the upper part of the bell mouth 3.
is open to the atmosphere through an intake pipe 10. When the current water level is reached, P<P0 and air flows into the pump. The inflow amount at this time is determined by the differential pressure ΔP between P and P0 and the intake pipe loss, but if P changes due to changes in the water level or other factors, the intake air amount changes. In this embodiment, in order to suppress fluctuations in the amount of intake air due to fluctuations in P, a multi-stage or single-stage orifice is provided near the intake hole. As a result, the static pressure P inside the pump and
Fluctuations in the differential pressure ΔP with respect to the atmospheric pressure P0 are suppressed, stable intake is performed, and fluctuations in the pump operating point can also be suppressed.

[0024] In this case, the same effect can be expected if the device provides a localized loss as shown in claims 3 and 4.

FIG. 6 shows a second embodiment, in which static pressure P in the suction pipe of the pump and atmospheric pressure P0 are applied to the suction line.
An impeller 16 is provided which is driven by a pressure difference between the two. The impeller 16 is driven by the air sucked into the pump due to the differential pressure between P and P0, but due to the inertial effect of the impeller 16, P
Even if the value of changes, the fluctuation in the amount of intake air is suppressed and the intake air is stabilized.

FIG. 7 shows a third embodiment, in which a device for rectifying the flow is provided on the upstream section A-A of the intake hole 9. In the cross section A-A on the upstream side of the intake hole 9, if the pipes 17 and 18 are connected to each other at positions facing each other, if an imbalance in the static pressure within the cross section occurs due to non-uniform flow, for example, P1 >P2, a flow from ■ to ■ occurs through the pipe 18. Further, when P3>P4, a flow from ■ to ■ is generated through the pipe 17, and the flow is rectified in the entire cross section, and the flow is stabilized. This stabilizes the flow near the intake hole 9, resulting in stable intake air.

FIG. 8 shows a fourth embodiment, in which a throttle valve 19 is provided upstream of the intake hole 9 to rectify the flow near the intake hole 9 and stabilize the intake air. .

[0028]

[Effects of the Invention] According to the present invention, it is possible to stabilize the intake air of the pump during intake operation, stabilize the operation of the pre-standby operation pump in the two-phase flow operation state, and further reduce vibration. It becomes possible.

[Brief explanation of drawings]

FIG. 1 is an overall side view of a pre-standby operation pump.

FIG. 2 is a sectional view showing an embodiment of the present invention.

FIG. 3 is an explanatory diagram of driving characteristics.

FIG. 4 is an explanatory diagram of driving characteristics.

FIG. 5 is a sectional view showing an embodiment of the present invention.

FIG. 6 is a sectional view showing a second embodiment of the present invention.

FIG. 7 is a sectional view showing a third embodiment of the present invention.

FIG. 8 is a sectional view showing a fourth embodiment of the present invention.

[Explanation of symbols]

3...Suction bell, 9...Intake hole, 10...Intake pipe, 15...Multi-stage or single-stage orifice.

Claims (1)

[Claims] 1. A vertical shaft advance standby operation pump characterized in that a device for suppressing fluctuations in intake air amount is provided in an intake line including an intake hole or near the intake hole.