The main reasons for self-suction of self-suction pump:
1. Determination of the reservoir volume and the height of the reservoir
Liquid storage volume means that the volume of the liquid portion of the pump can be stored after the pump is stopped, which is the volume of the pump body below the lowest point of the pump inlet. This volume is mainly a part of the separation chamber of the extruding chamber and the gas liquid. The volume of liquid storage should not be less than half of the design flow. For example, the design flow of the pump, the reservoir volume is not less than, the storage volume is too small [that is, too little liquid stored in the pump]. This makes the time of self-suction increases, and can't even self-suction; In addition to having sufficient reservoir volume, there must be a certain reservoir height, which is the height of the pump suction minimum to the center of the impeller. Usually, it is approximately equal to the impeller radius.
2. The determination of the volume of the gas-liquid separation chamber and the outlet height of the pump body
The separation of gas liquid is the part of the pump body that is outside the chamber. The larger the volume, the better the separation effect of gas and liquid, the faster the separation, however, when the volume of the gas-liquid separation chamber is large enough to a certain extent, the regrowth effect is not significant. The reverse side causes the pump body to be bulky, so the gas-liquid separation chamber has an optimal volume value. According to the existing experience, its value is equal to or slightly larger than the volume of liquid storage. The height of the pump outlet to the center line of the impeller can be determined according to the volume of the reservoir and the volume of the separation chamber of the gas liquid.
3. The determination of the flow velocity of the chamber
The flow rate of the liquid in the centrifugal pump is lower than the normal centrifugal pump, which is about 80 to 90% of the liquid velocity in the centrifugal pump.
4. The determination of the clearance between the tongue and the impeller
For centrifugal self-suction pumps, the gap between the tongue and the impeller has great influence on the performance of the self-priming, the smaller the gap between the tongue and the impeller, the shorter the time of self-suction. If the design is a double cochlear chamber, the gap between the tongue and the impeller can be determined according to the general centrifugal pump. The lower tongue is located on the cochlea base circle.
5. Turning of the back cover of impeller
For the external mixed centrifugal self-suction pump, when the outer circle velocity of impeller is smaller than that, the self-suction effect can be improved by adopting the method of turning the back cover plate of the turning impeller. The reason is the mixing of liquids and gases in the process of self-suction. The cutting amount cannot be too large, otherwise it will significantly reduce the lift and efficiency of the pump. At that time, the diameter of the posterior cover plate of impeller was cut; At that time, it was added to the upper tongue, so as to avoid the circulation of the bubble liquid in the back cover plate, which affected the effect of self-suction.
6. The area of reflux hole
The area of backflow hole has a great influence on the self-suction performance of internal mixed centrifugal pump. If the area is large, the flow of the reflux hole is much higher than that of the impeller, so the time of self-suction is short, but the maximum vacuum degree is decreased. If the area of backflow hole is small, then the time of self-suction is long and the maximum vacuum height is high. In this paper, the time of self-suction and the height of self-suction should be considered when determining the area of backflow hole.