Working Principle Of Centrifugal Pump, Working Principle Of Single-stage Centrifugal Pump

Jun 06, 2020

Single-stage centrifugal pump refers to a centrifugal pump with an impeller, which is widely used in the delivery of liquid under large and medium flow and low pressure. At present, single-stage centrifugal pumps have reached serialization, the flow rate can be in the range of 6.3-2020m3/h, the head can be in the range of 8-125m, and due to the different materials and structures of single-stage centrifugal pumps, they can transport different medium.

    Centrifugal pumps are widely used in industrial and agricultural production and life due to many advantages such as high efficiency and simple structure.

Send clean water, mud, acid, alkali, salt solution and liquid organic matter and other materials.

    1. Working principle of centrifugal pump

    Before introducing the working principle of the centrifugal pump, first make a simple experiment. Use a washbasin filled with water, stir the water in the washbasin with your hands for circular motion. As the speed of hand stirring increases, the speed of the water in the washbasin for circular motion becomes faster and faster. The water in the middle of the washbasin It rushed to the edge of the washbasin so that it would overflow from its side. Why does water overflow around the washbasin? This is due to the centrifugal force generated during the circular motion of water. Centrifugal force is generated when any object moves in a circular motion. The centrifugal pump uses the centrifugal force generated by the liquid during the rotation to transport the liquid.

The main working part of the centrifugal pump is the impeller 4, which has 6 to 8 blades bent backwards to push the liquid for rotational movement. The impeller is fastened to the pump shaft 8 in the pump housing 5. The suction port of the pump is in the center of the pump casing and is connected to the suction tube 3. The discharge port of the pump is connected to the discharge pipe 7 in the tangential direction of the pump casing; a bottom valve 2 is installed at the beginning of the suction pipe to stop the liquid in the pump from flowing back to the storage tank when stopping. The role of the bottom screen 1 of the bottom valve is to prevent debris from entering the pipeline. A regulating valve 6 is installed on the discharge pipe to regulate the flow of liquid, and a check valve should also be installed to prevent the liquid from flowing back and causing an accident during shutdown. When the motor drives the impeller to rotate through the pump shaft, the liquid is sucked into the pump from the center of the pump casing through the suction pipe, and then discharged through the discharge pipe tangent to the pump casing, and then enters the discharge pipe to the destination.

    Before the centrifugal pump is started, the pump should be filled first to make the conveyed liquid fill the suction line and pump casing. After starting, the high-speed rotating impeller drives the liquid between the blades to rotate together. Under the broom of centrifugal force, the liquid moves outward from the impeller along the flow path between the blades, is thrown out from the end of the blade, and enters the spiral pump casing. At this time, the flow rate is relatively high, which can reach 15 ~ 25m/s, increased kinetic energy; at the same time, due to the fluid's own strength, the static pressure energy of the liquid has also been improved. After the liquid enters the pump casing, the area of the flow channel in the volute-shaped pump casing gradually expands, and the flow velocity of the liquid gradually decreases, converting part of the kinetic energy into static pressure energy. To the pump outlet, the filial pressure energy of the liquid is further increased. After that, it is discharged from the discharge pipe. At the same time, the liquid from the center of the impeller is thrown out, forming a low-pressure area, resulting in a pressure difference between the atmospheric pressure on the liquid surface in the reservoir and the partial vacuum at the center of the impeller. Under the effect of this pressure difference, the liquid will continuously i- enter the impeller along the suction line to supplement the discharged liquid. The impeller keeps spinning, fluid! Just continually fan and discharge.

  In summary, the working principle of the centrifugal pump is that the impeller filled with liquid rotates at high speed in the pump casing, so that the liquid is subjected to centrifugal force, and the force is converted into kinetic energy and static pressure energy to be transferred to the liquid, thereby attracting the liquid and discharge.

   If the suction tube or pump casing is not filled with liquid before starting, or if air is leaked during operation, the density of air is much smaller than the density of liquid, and the resulting centrifugal force is small. The vacuum formed at the suction port Low, not enough to suck liquid into the pump. At this time, although the impeller rotates, it cannot deliver liquid. This phenomenon is called "air binding". In order to eliminate the "air binding" phenomenon, the pump is usually filled before the pump is started, and the suction pipe and the pump casing are filled with liquid under the action of the bottom valve; for large flow pumps, in order to reduce resistance loss, the bottom valve is often not installed , The pump is used to suck the gas without starting the pump, and then start; if the installation position of the centrifugal pump is lower than the liquid level of the liquid storage tank, and the pipeline outlet is open to the atmosphere, the person and the outlet valve of the pump can be opened to automatically fill liquid.

   It should be noted that during the installation and use of the centrifugal pump, the population of the entire suction pipe inlet to the centrifugal pump should be kept rising or horizontal, and there must be no falling stage, otherwise, the suction pipe will form a hump, and the pump When the centrifugal pump is running, the air bag will enter the impeller, and the air will also form an air bond.