Working principal of a single stage centrifugal pump
A. The working principle of the single-stage pump is as follows: Before the single-stage centrifugal pump is started, the pump casing is filled with the liquid to be transported; after starting, after the start, the impeller is driven by the shaft to rotate at a high speed, and the liquid between the blades must also rotate. Under the action of centrifugal force, the liquid is thrown from the center of the impeller to the outer edge and obtains energy, leaving the outer edge of the impeller at high speed into the volute casing. In the volute, the liquid decelerates due to the gradual expansion of the flow path, and part of the kinetic energy is converted into static pressure energy, and finally flows into the discharge pipe at a relatively high pressure and is sent to a place where it is needed. When the liquid flows from the center of the impeller to the outer edge, a certain vacuum is formed at the center of the impeller. Since the pressure above the liquid level of the tank is greater than the pressure at the inlet of the pump, the liquid is continuously pressed into the impeller. It can be seen that as long as the impeller rotates continuously, the liquid will be continuously sucked in and discharged.
B. Main components of the centrifugal pump The main components of the centrifugal pump are the impeller, the pump casing and the shaft seal.
1 Centrifugal pump impeller The centrifugal pump impeller is used to transfer the mechanical energy of the prime mover directly to the liquid to increase the static pressure and kinetic energy of the liquid to increase the static pressure energy. The impeller generally has 6 to 12 back bend blades. The impeller has three types: open type, semi-closed type and closed type. The open impeller has no cover on both sides of the blade, which is simple to manufacture and convenient to clean. It is suitable for conveying materials containing a large amount of suspended matter, and the efficiency is low, and the liquid pressure is not high; the semi-closed impeller has no cover on the suction side. Plate with cover plate on the other side, suitable for conveying materials that are easy to precipitate or contain particles, and low efficiency, such as various sewage pumps, but now Zhonglian can produce sewage pumps for open impellers; closed impeller The impeller has front and rear cover plates on both sides of the blade, which is highly efficient and is suitable for conveying cleaning liquid without impurities. The general horizontal single-stage centrifugal pump impeller is mostly of this type. The impeller has two suction and double suction modes.
2 Centrifugal pump casing The function is to close the impeller in a certain space so that the liquid can be sucked in and out by the action of the impeller. The pump casing is often made into a volute shape, so it is also called a volute. Since the cross-sectional area of the flow passage is gradually enlarged, the high-speed liquid drawn from the periphery of the impeller gradually reduces the flow velocity, so that part of the kinetic energy is effectively converted into static pressure energy. The pump casing not only collects the liquid that is pumped out by the impeller, but is also an energy conversion device. 3 Centrifugal pump shaft seal device The function is to prevent the liquid in the pump casing from leaking out along the shaft or the outside air leaking into the pump casing. Commonly used shaft sealing devices for centrifugal pumps are filled with packing and mechanical seals. The filler is generally impregnated with oil or graphite coated asbestos rope. The mechanical seal mainly achieves the purpose of sealing by the relative movement between the moving ring mounted on the shaft and the stationary ring fixed on the pump casing. Similar products developed according to single-stage centrifugal pumps are: vertical circulating booster pumps