How to improve the self-priming ability and time of self-priming pump
The self-priming pump needs to meet the requirements of self-priming performance, which depends on two aspects:
The exhaust capacity of the impeller itself;
The conditions to provide sufficient exhaust for the impeller are determined by the structure of the pump body and make the two best combinations
The formula of impeller displacement: G= B *U2*K;
G is the displacement (m³);
B is the width of the blade exit (m);
U2 is the maximum circumferential speed of the impeller outlet (m/s);
K is the coefficient.
It can be concluded from the above formula that it increases with the increase of the width of the impeller blade outlet and the maximum circumferential speed of the impeller outlet.
The conditions to provide sufficient exhaust for the impeller must meet the following three requirements:
1 Sufficient liquid is needed for gas-liquid mixing, that is, a sufficiently large liquid storage chamber is required;
2 Make the separated liquid participate in the gas-liquid mixing again in an appropriate amount, that is, a suitable return hole is required;
3 To speed up the gas-liquid separation, a gas-liquid separation acceleration device is required.
From the above analysis, it can be seen that the main factors affecting the self-priming performance are: the width of the impeller blade outlet, the maximum circumferential speed of the impeller outlet, the liquid storage chamber, the return hole and the gas-liquid separation acceleration device.
Increase the self-priming time of the self-priming pump
1. The discharge valve must be opened to start
The gas in the suction pipe of the self-priming pump must be pumped away after the self-priming pump is started. Therefore, the valve must be opened to start the gas so that the gas can be discharged from the discharge port.
2. There must be enough liquid in the self-priming pump cavity
If there is no liquid in the cavity of the self-priming centrifugal pump, no gas-liquid foam mixture can be formed, and no gas can be pumped. Too little self-priming pump cavity can also not play a role in pumping air. Figure 1 shows the liquid circulation in the cavity of the self-priming centrifugal pump during the pumping process.
Experiments on a self-priming centrifugal pump show that its pumping capacity is closely related to the amount of liquid in the pump. When the liquid in the self-priming pump is less than 1.5L, the vacuum degree is very small, and the working state of the pump is unstable, air will leak into the pump, the circulation will be interrupted, and continuous air extraction will not be possible; when the amount of germanium in the pump is greater than 2.OL , The backwater blocks the lower tongue, and the air will not leak into the pump. At this time, continuous pumping begins. The vacuum degree increases with the increase of the liquid storage in the pump. When the liquid volume in the high suction range self-priming pump reaches 3.5L, the vacuum degree can reach 9m; when the liquid storage volume is greater than 3.5L, the vacuum degree increases slowly with the increase in liquid storage volume, as shown in Figure 2. . From this point of view. The storage volume of 3.5L is the most appropriate.
In order to ensure the speed and reliability of pumping, a sufficient amount of liquid should be filled into the pump cavity before starting.
The self-priming vacuum degree of the self-priming pump at different speeds is shown in Figure 3. It can be seen from the figure that the speed n has a great influence on the degree of self-priming vacuum, and the influence of the speed does not weaken until it is close to the ultimate vacuum degree. When the pump is self-priming, the prime mover speed should be adjusted to a high speed in order to shorten the self-priming time.
Measures to improve self-priming performance
(1) Increase the maximum circumferential speed of the impeller outlet and the width of the impeller blade outlet. The maximum circumferential speed of the impeller outlet can be achieved by increasing the impeller directly to increase the speed of the impeller. But too large to ensure that increasing the maximum circumferential speed of the impeller outlet and the width of the impeller blade outlet will change the basic performance parameters of the pump such as flow and head. Therefore, the maximum circumferential speed of the impeller outlet and the width of the impeller blade outlet should be appropriately increased on the premise that the flow and head of the pump meet the requirements of use.
(2) The relationship between water storage capacity and self-priming performance: When the water storage capacity increases, the self-priming height of the pump increases significantly, but when the water output is too large, the gas discharge process will be slowed down, that is, the self-priming time will be increased. Therefore, when the self-priming height requirements are high but the self-priming time requirements are not too strict, the water storage capacity of the pump can be increased, that is, the volume of the liquid storage chamber, but when the self-priming time requirements are strict, the liquid storage should be reasonably determined The size of the room.
(3) The relationship between the area of the recirculation hole and the self-priming time and height: within the critical recirculation hole area, when the area of the recirculation hole increases, the self-priming time decreases and the self-priming height decreases accordingly. Therefore, when the self-priming time requirement is strict and the self-priming height requirement is not high, the area of the recirculation hole can be appropriately increased, otherwise, the area of the recirculation hole should be appropriately reduced.
(4) The gas-liquid separation acceleration device can be installed to accelerate the gas-liquid separation, that is, the self-priming time can be shortened. The simplest gas-liquid separation acceleration device is to add a baffle in the gas-liquid separation chamber. As shown in Figure 1. The addition of baffles in the gas-liquid separation chamber has almost no effect on the self-priming height. Therefore, as long as the structure permits, a baffle should be installed in the gas-liquid separation chamber to accelerate the gas-liquid separation and shorten the self-priming time.
Improve self-priming ability of self-priming pump
(1) Install a suction bottom valve at the end of the suction pipe of the self-priming sewage pump. The suction bottom valve is actually a check valve. It ensures that the water flow can only enter the suction pipe from the pool and cannot flow back. Therefore, if the suction pipe is filled with water, although the pump axis is higher than the working water level of the pool, it is due to the suction bottom valve. The water in the suction pipe will not flow into the pool, and the suction pipe can be filled with water all the time, ensuring that the pump can start automatically and quickly. The reliability of this suction method is affected by the quality of the suction bottom valve. For example, if it is not tightly closed or leaks, the water in the suction pipe will slowly flow into the pool. After a long time, there will be no water in the suction pipe, which causes the pump to start. Artificial irrigation.
(2) The self-priming sewage pump reduces the bends, drop height and horizontal distance of the inlet pipe.
(3) The self-priming sewage pump is equipped with a suction tank before the pump. This method requires a suction tank to be installed on the suction pipe of the water pump. Before the first operation of the pump, the tank should be filled with water manually. After the first operation is stopped, because the height of the water inlet pipe of the suction tank is higher than the height of the water surface in the pipe, The water level in the pool is lower than that in the tank, and the water in the tank will not flow back into the pool. Therefore, a certain amount of water can be stored in the suction tank, and because of the height of the outlet pipe of the suction tank (ie the suction pipe of the water pump) It is lower than the height of the water surface in the pipe, so it can ensure that the suction pipe of the water pump is filled with water. When the water pump is running again, the water in the water tank is pumped away by the water pump, and negative pressure appears in the tank. The water in the pool is supplemented by atmospheric pressure. In the suction tank, through the suction tank in the pool.
(4) The self-priming sewage pump is equipped with a vacuum pump on the suction pipe of the water pump. Before the water pump is started, the vacuum pump is started first, so that the suction pipe of the water pump is filled with water first to ensure that the pump starts automatically and quickly. This type of water absorption requires a complete automatic control system to ensure normal operation.
