CN220337022U - Cavitation-free constant flow water feeding pump set - Google Patents
Cavitation-free constant flow water feeding pump set Download PDFInfo
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Abstract
The utility model provides a no cavitation constant flow feed pump package, includes main drain pump, feed pump, connects the pipeline between main drain pump water sucking mouth and feed pump export, and its special character is: still include control unit, electric junction manometer and electric valve, electric junction manometer is installed on the connecting tube, electric valve installs in the feed pump export, control unit respectively with electric junction manometer and electric valve are connected, change electric valve's aperture and then adjust through control unit the flow size of pump package. The beneficial effects are that: the pressure value of the connecting pipeline is always kept between 0 and 0.001MPa, constant-current positive-pressure drainage of the pump set is realized, and the MD pump motor does not overflow at high water level; at low water level, the flow is basically unchanged, so cavitation is not generated, the pump set operates stably, the service life is long, the efficiency of the water pump can be improved, the drainage speed is accelerated, the service cycle of the water pump is prolonged, and the daily maintenance amount of the water pump is reduced.
Description
Technical Field
The utility model relates to a cavitation-free constant flow water feeding pump set which is quick to start, efficient and energy-saving and is free of vacuumizing.
Background
The water supply and drainage system of the water pump is widely applied, is closely related to industrial and agricultural production and people life, is an electromechanical product which covers the social aspect in a large scale, the total installed amount of the water pump in the whole country is over ten millions, and the wear-resistant multistage water pump used in the coal mine only has hundreds of thousands, and has very large power consumption although the total amount is not high, and the power consumption of the water pump in one year accounts for 20% of the power consumption in the whole country.
The efficiency of the water pump is generally low, and mainly has two reasons, namely, the water pump is used for supplying water under negative pressure (in a vacuumizing mode) and has serious cavitation problem; secondly, even if water is supplied by positive pressure (a water feeding pump is arranged at the front end of a main drainage pump), the problem of flow attenuation in a water supply project exists, and cavitation can be reproduced once the flow attenuation is serious.
The H-Q curves of all water pumps are curves of the corresponding relation between the flow and the lift of the water pump, namely, when the water pump operates, the flow, the lift, the power and the efficiency values of the water pump are in dynamic change, and generally, the necessary cavitation allowance of the water pump is unchanged. The necessary cavitation allowance of the water pump is a natural phenomenon, the design and processing precision of the hydraulic model of the water pump cannot be changed, and the numerical value of the necessary cavitation allowance is continuously increased along with the aging of the water pump. That is, once the flow rate, head, motor speed of the water pump is determined, its necessary cavitation margin is determined. Therefore, the necessary cavitation allowance of the water pump exists objectively, and the water pump cannot overcome. Clearly, cavitation of the water pump is a detrimental occurrence.
In general, most water pumps are supplied by negative pressure, i.e. the water pump is installed on a bottom plate of a pump house near a water absorbing well, a vacuum pumping device is used for forming negative pressure in a pump body, then liquid enters the pump body under the action of atmospheric pressure, the water pump starts to run, the liquid is conveyed to a set place or height, a high water level is started, and a low water level is stopped. Although there are definite parameters on the water pump nameplate, in practice its flow, lift, power, efficiency values are dynamically changed. This can be demonstrated by the performance profile of the water pump. The efficiency of the design point of the water pump is highest; the flow of the large flow point is increased, the lift is reduced, the shaft power is increased, and the efficiency is reduced; the small flow point is that flow, lift, power and efficiency are all reduced. For convenience, drivers in pump rooms of enterprises often open all the front-end regulating valves of the water pump so that the water pump runs at a flow rate larger than that of a large-flow point. As a result, the necessary cavitation allowance of the water pump is continuously increased, namely the suction stroke is reduced, so that the cavitation phenomenon of the water pump is serious, the drainage speed is slowed down, and the pump efficiency is reduced too much.
The positive pressure water supply of the pump group is realized by additionally arranging the water feeding pump at the front end of the main drainage pump, so that the cavitation problem of the main drainage pump is theoretically eliminated. However, there is a problem that the flow rate decreases with the increase of the lift of the water feeding pump, and cavitation may occur.
Considering the actual drainage condition of the coal mine, the water feeding pump water conservancy model is in a structure form with large flow and low lift. The structure is characterized in that the flow is large at high water level (the lift of the water feeding pump is low at the moment), even the flow exceeds a design point a lot, and the motor of the main drainage pump has the possibility of overcurrent; at low water levels (when the head of the feed pump is raised), the main drain pump flow may not satisfy equation Q for some reason due to reduced flow 1 ＝(1+a)Q 0 Cavitation phenomenon occurs under the condition of (1), wherein: q (Q) 1 : flow rate of water feeding pump, Q 0 : flow rate of main drain pump, a: the coefficient, a, is 0.15-0.25.
Disclosure of Invention
The utility model aims to solve the problems in the prior art and provides a pump set of a cavitation-free constant flow water feeding pump.
The first technical solution of the utility model is:
the utility model provides a no cavitation constant flow feed pump package, includes main drain pump, feed pump, connects the pipeline between main drain pump water sucking mouth and feed pump export, and its special character is: still include control unit, electric junction manometer and electric valve, electric junction manometer is installed on the connecting tube, electric valve installs in the feed pump export, control unit respectively with electric junction manometer and electric valve are connected, change electric valve's aperture and then adjust through control unit the flow size of pump package.
Further, the electric valve is an electric valve with a inching function, so that the flow of the main drainage pump can be accurately regulated.
Further, the distance between the electric valve and the electric contact pressure gauge is more than or equal to 500mm, so that the influence of vortex on pressure is reduced.
The second technical solution of the utility model is:
the utility model provides a no cavitation constant flow feed pump package, includes main drain pump, feed pump, connects the pipeline between main drain pump water sucking mouth and feed pump export, and its special character is: the water feeding pump comprises a pump body, and is characterized by further comprising a control unit, a frequency converter and an electric contact pressure gauge, wherein the water feeding pump motor is a variable frequency motor, the electric contact pressure gauge is arranged on the connecting pipeline, the electric contact pressure gauge and the frequency converter are respectively connected with the control unit, the control unit is connected with the water feeding pump variable frequency motor through the frequency converter, and the control unit is used for receiving the pressure value of the connecting pipeline detected by the electric contact pressure gauge, changing the rotating speed of the variable frequency motor according to pressure change and then adjusting the flow of the pump unit.
The beneficial effects of the utility model are as follows:
1. the pressure value of the connecting pipeline is always kept between 0 and 0.001MPa by the cooperation of the control unit, the electric valve and the electric contact pressure gauge, so that constant-current positive-pressure drainage of the pump set is realized, the operation is stable, and the service life is long.
2. At high water level, the MD pump motor does not overflow; at low water levels, the flow is basically unchanged, so cavitation is not generated.
3. The water pump is always in a positive pressure constant flow water supply state, the flow is infinitely close to a constant value, the working condition point is fixed, and then the flow, the lift, the power and the efficiency value of the water pump are basically constant, so that the efficiency of the water pump is greatly improved, the water drainage speed is accelerated, the service cycle of the water pump is prolonged, and the daily maintenance quantity of the water pump is reduced.
Drawings
FIG. 1 is a schematic diagram of the pump unit of the cavitation-free constant flow water feeding pump of the embodiment 1 of the utility model;
FIG. 2 is a graph of MD pump performance for an attached vacuum;
FIG. 3 is a graph of MD pump performance for an added feed pump;
FIG. 4 is a graph of MD pump performance for example 1 of the present utility model;
fig. 5 is a schematic diagram of the pump unit of the cavitation-free constant flow water feeding pump of embodiment 2 of the present utility model.
Detailed Description
The utility model is described in detail below with reference to the attached drawings and examples:
example 1
As shown in fig. 1, the cavitation-free constant flow water feeding pump set comprises a main drainage pump 1, a water feeding pump 3, and a connecting pipeline 2 connected between a water suction port 101 of the main drainage pump and an outlet of the water feeding pump 3, wherein an electric joint pressure gauge 6 is arranged on the connecting pipeline 2, an electric valve 4 with a inching function is arranged at an outlet of the water feeding pump, the distance between the electric valve 4 and the electric joint pressure gauge 6 is more than or equal to 500mm, the electric joint pressure gauge 6 and the electric joint pressure gauge 4 are respectively connected with a control unit 5, and the control unit 5 is used for receiving a pressure value of the connecting pipeline 2 detected by the electric joint pressure gauge 6, changing the opening of the electric joint pressure gauge according to pressure change, and then adjusting the flow of the pump set.
The operation process of the cavitation-free constant flow water feeding pump set is as follows:
s1, setting a pressure interval value of a connecting pipeline through a control unit 5, wherein the pressure interval value is 0-0.001MPa;
s2, firstly starting a motor of the water feeding pump 3, then starting a motor of the main drainage pump 1, simultaneously switching on a power supply of the control unit 5 and the electric contact pressure gauge 6, and detecting the pressure value of the connecting pipeline 2 in real time through the electric contact pressure gauge 6;
s3, when the pressure value of the connecting pipeline is larger than 0.001MPa, the control unit 5 sends out a command to reduce the opening of the electric valve 4; when the pressure value is smaller than 0, the control unit gives an instruction to increase the opening of the electric valve 4; so that the pressure value in the connecting pipeline 3 is always kept between 0 and 0.001MPa, and the whole pump set runs at positive pressure and constant flow.
Further, the opening adjustment time of the electric valve 4 is less than or equal to 1s, so as to ensure the constant current effect and prevent cavitation.
Further, the design point flow Q of the water feeding pump 3 1 Is determined according to the following formula:
Q 1 ＝(1+a)Q 0 ，Q 0 and (3) designing the point flow for the main drainage pump, wherein a=0.1-0.25, and ensuring the flow increase value to be 10% -25% after the delay loss of the pipeline.
Illustrating:
about 6000m of a mine per day 3 The water of/h needs to be discharged, the horizontal height is 520m, and the model of the water pump is determined as follows: MD580-6 x 10 (hereinafter referred to as MD pump). The center of the water inlet pipe of the water pump is 900mm away from the bottom plate of the pump room, the vertical length of the water suction pipeline of the water pump is 8.5m, the water pump is started when the water level is 0.5m (high water level) away from the bottom plate of the pump room, and the water pump stops running when the water level is 8m (low water level) away from the bottom plate of the pump room.
The necessary cavitation margin for the pump can be found from the MD pump performance profile as:
flow q=450 m 3 The/h cavitation margin npsh=4.3m
Flow q=580 m 3 The/h cavitation margin npsh=5.3 m
Flow q=635 m 3 The/h cavitation margin npsh=5.7m
Under normal conditions, when an MD pump is used underground in a coal mine, the outlet valve of the water pump is fully opened, so that the lift of the working point of the water pump is lower than that of the design point, and the water pump is caused to operate at a large flow point. The necessary cavitation margin at this point is greater than 5.7m, even if calculated as 5.7m, the suction height H of the pump at standard atmospheric pressure:
H＝10.33-NPSH-h c -v 2 /2g-0.24
npsh=5.7m
h c ＝0.25m
v 2 /2g＝0.5
H＝3.64m。
And considering the factors such as the installation height of the water pump, the manufacturing error and the suction stroke reduction caused by the aging of the water pump, and the like, the MD pump is cavitation when the water level is 2.5m away from the bottom plate of the pump house. That is, the water pump is operated in cavitation at most of the height during the water discharge.
In the first installation mode, the MD pump is additionally provided with a vacuum pumping device, as shown in fig. 2, the average hourly flow q=490 m in one drainage period 3 And/h, draining water for 12.24 hours. The flow rate decays along with the water level falling, and the efficiency value deviates from the efficiency point of the design point seriously.
In the second mode, the MD pump is additionally provided with a water feeding pump, and after the water feeding pump is additionally arranged, the average hourly flow q=620 m in one drainage period 3 And/h, draining water for 9.68 hours. As can be seen from the pump performance curve, the pump set also decays as the water level decreases, as shown in fig. 3. Two situations may occur in this combination, one is that at high water levels, the feed pump flow exceeds the design point more, resulting in the MD pump operating at a high flow point. The large flow point at this moment is the large flow point of the pump group, this large flow point is bigger than the large flow point of the original MD pump, if the surplus of the main drainage pump motor is too small or old, it is possible to overcurrent; and when the water level is low, various adverse factors are superposed, such as: the water inlet is blocked and the water suction pipe is slightly blockedAir leakage, cavitation may occur.
In the third mode, the MD pump is additionally provided with a water feeding pump, an electric valve, an electric contact pressure gauge and a control unit.
Average hourly flow q=660 m for one drainage period 3 And water is discharged in 9.09 hours, so that the efficiency value is greatly improved. The flow rate of the water feeding pump does not change with the change of the lift, that is to say the flow rate of the pump is a constant value. The flow rate is basically unchanged no matter the water level is 1 meter or 9 meters. If the flow rate of the feed pump is constant, the flow rate of the MD pump is constant, i.e. the flow rate of the pump group is constant.
In general, the discharge height of the MD pump is unchanged, and the flow rate is theoretically unchanged (the flow rate of the water pump is attenuated because of cavitation), so that after the constant-flow water feeding pump is added, the flow rate, the lift, the efficiency and the shaft power of the pump set are basically unchanged. As shown in FIG. 4, the performance curves of the constant-current water feeding pump set are three, namely an H-Q curve, an efficiency curve and a power curve, and no cavitation allowance curve is needed.
Example 2
As shown in fig. 5, the cavitation-free constant flow water feeding pump set comprises a main drainage pump 1, a connecting pipeline 2, a water feeding pump 3, a control unit 5, an electric contact pressure gauge 6 and a frequency converter 7, wherein the water feeding pump motor 301 is a frequency conversion motor, the control unit 5 is connected with the water feeding pump frequency conversion motor 301 through the frequency converter 7, and the flow of the pump set is regulated by changing the rotating speed of the frequency conversion motor 301 through the frequency converter 7, so that the pressure of the connecting pipeline 2 is always between 0 and 0.001MPa, and the positive pressure constant flow operation of the whole pump set is realized.
The other steps are the same as in example 1.
The above is only a specific embodiment of the present utility model, and is not intended to limit the present utility model, but various modifications and variations can be made to the present utility model by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present utility model should be included in the protection scope of the present utility model.
Claims (4)
1. The utility model provides a no cavitation constant flow feed pump package, includes main drain pump, feed pump, connects the pipeline between main drain pump water sucking mouth and feed pump export, characterized by: still include control unit, electric junction manometer and electric valve, electric junction manometer is installed on the connecting tube, electric valve installs in the feed pump export, control unit respectively with electric junction manometer and electric valve are connected, change electric valve's aperture and then adjust through control unit the flow size of pump package.
2. The cavitation-free constant flow water feeding pump set according to claim 1, wherein: the electric valve is an electric valve with a inching function.
3. The cavitation-free constant flow water feeding pump set according to claim 1 or 2, characterized in that: the distance between the electric valve and the electric contact pressure gauge is more than or equal to 500mm.
4. The utility model provides a no cavitation constant flow feed pump package, includes main drain pump, feed pump, connects the pipeline between main drain pump water sucking mouth and feed pump export, characterized by: the water feeding pump comprises a pump body, and is characterized by further comprising a control unit, a frequency converter and an electric contact pressure gauge, wherein the water feeding pump motor is a variable frequency motor, the electric contact pressure gauge is arranged on the connecting pipeline, the electric contact pressure gauge and the frequency converter are respectively connected with the control unit, the control unit is connected with the water feeding pump variable frequency motor through the frequency converter, and the control unit is used for receiving the pressure value of the connecting pipeline detected by the electric contact pressure gauge, changing the rotating speed of the variable frequency motor according to pressure change and then adjusting the flow of the pump unit.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116428150A (en) * | 2023-03-18 | 2023-07-14 | 锦州重型水泵有限公司 | Cavitation-free constant-flow water feeding pump set and operation method |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116428150A (en) * | 2023-03-18 | 2023-07-14 | 锦州重型水泵有限公司 | Cavitation-free constant-flow water feeding pump set and operation method |
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