Working principle of self-priming water pump

Working principle of self-priming pump

Centrifugal self-priming pumps can be divided into two types based on their working principle: internal mixing and external mixing.

Internal mixing type

Internal mixing type refers to gas-liquid mixing near the impeller inlet, and its principle is shown in the figure. Before starting the self-priming pump, a proper amount of liquid is poured into the pump body (to submerge the impeller), the reflux valve is opened, the pressure chamber is connected to the suction chamber, and after the impeller rotates, the liquid in the suction chamber and the impeller is transported to the pressure chamber through the impeller, and a negative pressure is formed at the impeller inlet. The pressure in the suction pipeline is higher than the pressure in the suction chamber, so the suction valve is opened, and the gas in the suction pipeline is sucked into the impeller, and the liquid in the pressure chamber is sucked into the impeller inlet through the reflux valve hole and the suction chamber for gas-liquid mixing. The impeller also transports the gas-liquid mixture to the pressure chamber. Since the volume of the gas-liquid separation chamber is large enough, the flow rate is reduced, and the gas and liquid are separated by the different specific gravity of liquid and gas. The gas is discharged through the pressure pipeline, and the liquid is sucked into the impeller through the reflux valve hole and mixed with the gas, and the cycle is repeated until the gas in the suction pipeline is completely discharged. At this time, the self-priming pump completes the self-priming process and reaches normal operation.

External mixing

External mixing refers to the mixing of gas and liquid at the outer edge of the impeller. Its working principle is shown in the figure. Before the self-priming pump is started, an appropriate amount of liquid is poured into the pump body. When the impeller rotates, the liquid in the suction chamber and the impeller is transported to the extrusion chamber through the impeller. Negative pressure is formed at the impeller inlet, and the suction valve is opened. The gas in the suction pipeline enters the impeller through the suction chamber and mixes with the liquid rotating at high speed with the impeller at the impeller outlet. Due to the action of the impeller, the gas-liquid mixture passes through the extrusion chamber to the gas-liquid separation chamber with a large enough volume. Due to the reduced flow rate, the liquid and gas are separated by different specific gravity. The gas is discharged through the extrusion pipeline, and the liquid returns to the outer edge of the impeller through the external flow channel. The cycle is repeated until the gas in the suction pipeline is completely discharged. At this time, the pump completes the self-priming process and reaches normal operation.

(1) To ensure that there is enough liquid in the pump body after the self-priming pump stops, a one-way valve is required at the pump body inlet, and the pump body inlet is higher than the impeller centerline to prevent the liquid in the pump body from being discharged into the suction pool due to siphon effect after the pump stops. (2) To effectively separate gas and liquid, a gas-liquid separation chamber with sufficient volume is required, and the outlet of the self-priming pump body should have a sufficient height from the impeller centerline. (3) The separated liquid is continuously returned to the impeller. For this purpose, there should be a reflux hole for the internal mixing self-priming pump and a large enough flow channel for the external mixing self-priming pump to return the separated liquid to the impeller.

Performance characteristics of self-priming pump

A centrifugal pump that can automatically pump water without filling the suction pipe with water is called a self-priming pump. There are many types of self-priming pump structures. Among them, the working principle of the external mixing self-priming pump is: fill the pump casing with water before starting the water pump (or there is water in the pump casing itself). After starting, the impeller rotates at high speed to make the water in the impeller groove flow to the volute. At this time, a vacuum is formed at the inlet, so that the water inlet check valve opens, and the air in the suction pipe enters the pump and reaches the outer edge through the impeller groove. On the other hand, the water discharged by the impeller into the air-water separation chamber flows back to the outer edge of the impeller through the left and right return holes. Under the action of pressure difference and gravity, the water flowing back from the left return hole is ejected into the impeller groove and is crushed by the impeller. After mixing with the air from the suction pipe, it is thrown to the volute and flows in the direction of rotation. Then it merges with the water flowing from the right return hole and flows along the volute. As the liquid continuously impacts the blades in the volute and is continuously crushed by the impeller, it is strongly stirred and mixed with the air to form a gas-water mixture, which continuously flows so that the gas and water cannot be separated. The mixture is peeled off by the partition tongue at the outlet of the volute and enters the separation chamber along the short pipe. In the separation chamber, the air is separated and discharged from the outlet pipe, while the water still flows to the outer edge of the impeller through the left and right return holes and mixes with the air in the suction pipe. This cycle is repeated, and the air in the suction pipe is gradually exhausted, so that the water enters the pump and the self-priming process is completed. Sewage pump self-priming pump oil pump diaphragm pump screw pump gear oil pump

The working principle of the internal mixing self-priming pump is the same as that of the external mixing self-priming pump. The only difference is that the return water does not flow to the outer edge of the impeller, but flows to the impeller inlet. When starting the internal mixing self-priming pump, the return valve at the bottom of the impeller must be opened to allow the liquid in the pump to flow back to the impeller inlet. Under the action of the high-speed rotation of the impeller, the water mixes with the air from the suction pipe to form an air-water mixture and is discharged to the separation chamber. Here, the air is discharged and the water returns to the impeller inlet from the return valve. This process is repeated until the air is exhausted and the water is sucked in. The self-priming height of the self-priming pump is related to factors such as the sealing gap in front of the impeller, the number of revolutions of the pump, and the liquid level height of the separation chamber. The smaller the seal gap in front of the impeller, the greater the self-priming height, which is generally taken as 0.3~0.5 mm; when the gap increases, in addition to the decrease in self-priming height, the pump head and efficiency are reduced. The self-priming height of the pump increases with the increase of the circumferential speed u2 of the impeller, but when it reaches the maximum self-priming height, the self-priming height no longer increases with the increase in the number of revolutions, and at this time it only shortens the self-priming time; when the number of revolutions decreases, the self-priming height decreases. Under the condition that other conditions remain unchanged, the self-priming height also increases with the increase of the water storage height (but it cannot exceed the optimal water storage height of the separation chamber). In order to better mix the air and water in the self-priming pump, the impeller blades must be fewer, so that the pitch of the blade grid is increased; and it is advisable to use a semi-open impeller (or an impeller with a wider impeller groove), which makes it easier for the return water to penetrate deeply into the impeller blade grid. Pipeline pump Water pump Chemical pump Magnetic pump Centrifugal pump Most self-priming pumps are equipped with internal combustion engines and installed on a movable trolley, which is suitable for field operations.

What is the working principle of a self-priming pump? For ordinary centrifugal pumps, if the suction liquid level is below the impeller, water should be pre-filled when starting, which is very inconvenient. In order to store water in the pump, a bottom valve needs to be installed at the inlet of the suction pipe. When the pump is working, the bottom valve causes a large hydraulic loss. The so-called self-priming pump does not need to be filled with water before starting (it still needs to be filled with water when starting for the first time after installation). After a short period of operation, the pump itself can suck up water and start normal operation. Self-priming pumps are divided into the following categories according to their working principles: 1. Gas-liquid mixing type (including internal mixing type and external mixing type); 2. Water ring wheel type; 3. Jet type (including liquid jet and gas jet). Working process of gas-liquid mixing self-priming pump: Due to the special structure of the pump body of the self-priming pump, there is a certain amount of water in the pump body after the water pump stops. After the pump is started again, due to the rotation of the impeller, the air and water in the suction pipeline are fully mixed and discharged to the gas-water separation chamber. The gas in the upper part of the gas-water separation chamber overflows, and the water in the lower part returns to the impeller and re-mixes with the remaining air in the suction pipeline until all the gas in the pump and the suction pipe is discharged, completing self-priming and pumping water normally. The water ring wheel self-priming pump combines the water ring wheel and the water pump impeller in a shell, and uses the water ring wheel to discharge the gas to achieve self-priming. When the pump works normally, the passage between the water ring wheel and the water pump impeller can be cut off by a valve, and the liquid in the water ring wheel can be discharged. The jet self-priming pump is composed of a centrifugal pump and a jet pump (or ejector). It relies on the ejector device to create a vacuum at the nozzle to achieve suction. Self-priming clean water pump; industrial self-priming pump; ZX self-priming pump 1. Overview of self-priming clean water pump products ZX self-priming centrifugal pump is the earliest energy-saving pump product developed after absorbing, digesting and improving relevant technical information at home and abroad. This pump is a self-priming centrifugal pump and has the advantages of self-priming ability that other pumps do not have. If corrosion-resistant mechanical seals and stainless steel materials are used, it can be used to pump some acid and alkali media in chemical and pharmaceutical factories.