Zhonghu Pump Industry’s working condition adjustment of water pumps
Zhonghu Pump Industry’s working condition adjustment of water pumpsThe operating point of the water pump device is the intersection point of the water pump characteristic curve and the water pump pipeline system characteristic curve. Any of these two curves
If one of the meaning changes, the operating point will shift.
The main methods for changing the position of the water pump characteristic curve include variable speed adjustment (speed regulating operation), variable diameter adjustment (wheel changing operation), variable speed adjustment
Angle adjustment (changing the installation angle of the blades of the axial flow pump), section adjustment (increasing or decreasing the number of impeller stages of the multi-stage pump) and the combination of water pumps
Connection and series work, etc. The main factor affecting the position of the characteristic curve of the water pump piping system is the change in static head (water level change).
The main factor affecting the shape of the characteristic curve of the water pump pipeline system is the change in the resistance loss of the pipeline system (valve adjustment). above
Changes in various factors will cause changes in the operating point. In actual projects, in order to meet changes in water volume or water pressure, it is possible to adopt
Use some measures to change the working condition point of the water pump
,Automatic adjustment
The static head of the water pump is increased. Therefore, the position of the characteristic curve of the water pump pipeline system will move, and the change of the working condition point will occur.
As shown in Figure 1-16. When the water level of the water pump suction pool (or the water level of the river) or the water level of the high-level pool changes, the water level will also change.
The position of the characteristic curve of the pump piping system moves, as shown in Figure 1-16.
It can be seen from the figure that the operating point of the water pump changes with changes in water level or changes in pressure in the water supply pipeline system.
Move left and right along the water pump characteristic curve to continuously establish new equilibrium operating points. That is, the operating point moves within a certain range.
, this kind of water pump operating point automatically changes with changes in pipeline conditions, which is called automatic adjustment. The water pump automatically adjusts the water pump's
The scope of use is expanded, but it also causes a certain waste of energy.
, valve adjustment (throttle adjustment)
Adjusting the opening degree of the water pump water control valve can change the pipeline impedance S, making the position of the water pump pipeline system characteristic curve
The location has moved. Therefore, in actual operation, it can be artificially adjusted by adjusting the opening of the control valve at the water pump outlet.
Adjust the water pump operating point to meet operation needs
As shown in Figure 1-17, the operating point when the valve opening reaches the maximum is point A, which is called the limit operating point. With control
When the control valve is closed, the impedance S gradually increases, the pipeline characteristic curve gradually increases, and the water pump operating point gradually moves to the left at points B and C.
Wait
When the valve is closed, the impedance S is infinite and the flow rate Q=0. Therefore, by changing the opening degree of the control valve
The size of the pump can change the operating point of the water pump from the no-load operating point to the extreme operating point to control the flow and maintain the supply.
The purified water pressure in the water pipeline system basically remains unchanged.
Economically, the valve adjustment is to increase the valve resistance (impedance S increases) and consume more of the water pump than the energy AH.
method to maintain a certain water supply. For example, when the water pump works at point C, the lift provided by the water pump is greater than the minimum lift required by the pipeline.
The extra AH lift is used to overcome the local resistance loss caused by the wide door closing hours, which is the artificial wave.
fee. The power it consumes is AN=YQHkW). Since valve adjustment causes a certain amount of energy waste, therefore, in the pump station
102n
In the design and operation, under normal circumstances, it is not suitable to use valves to adjust the flow. However, since the Q-N curve of the centrifugal pump is rising
If the valve is used to adjust the flow rate, the shaft power of the water pump will also be reduced, and there will be no overload hazard to the prime mover, and the valve adjustment
It is convenient and flexible, so wide door adjustment is still a common method in small pumping stations.
3. Speed adjustment
The parameters of the water pump given in the water pump sample are all parameters at the rated speed. If the water pump speed changes, then
The parameters of the water pump must change. The change rules between the water pump speed, flow rate, head and power are consistent with the law of proportion (details
See introduction to Chapter 3). Figure 1-18 shows the change of the operating point of the water pump device with the rotation speed. It can be seen from the figure that if
By changing the speed of the water pump and raising or lowering the pump characteristic curve, the operating point of the water pump device can be adjusted. Is there any variable speed adjustment method?
There is a throttling loss, but a speed-adjustable prime mover must be used, such as a diesel engine, a DC motor, and a variable frequency speed-adjustable AC motor.
The performance of the water pump changes with the change of the impeller outer diameter. When the cutting amount is not very large, the water pump impeller outer diameter is related to the flow rate.
The changing rules of quantity, lift and power are consistent with the cutting laws (see the introduction in Chapter 3 for details). The different
Changes in the pump characteristic curve and operating point at outer diameter. It can be seen from the figure that cutting the outer diameter of the impeller can improve the characteristics of the water pump.
The curve moves downward, and its pattern is similar to that when changing the rotation speed.
In addition to the above adjustment methods, parallel connection of water pumps and series connection of water pumps can also change the position of the water pump characteristic curve, so that the working conditions
point changes, the specific content of this part will be introduced in detail in the next section. In addition, axial flow pumps can be changed by changing the impeller
The installation angle changes the characteristic curve of the water pump, thereby adjusting the pump operating point.