【Daily Discussion】Utilities - Water Supply and Drainage - 20200722

The impeller of an axial flow pump is equipped with 2 to 7 blades and rotates inside a cylindrical pump casing. Fixed guide vanes are installed on the pump casing at the upper part of the impeller, to eliminate the rotational motion of the liquid, convert it into axial motion, and transform the kinetic energy of the rotational motion into pressure energy. Axial flow pumps are usually single-stage, with a few being two-stage. The flow rate range is quite wide, ranging from 1.8 to 3.6 million cubic meters per hour ； The head is generally below 20 meters. Axial flow pumps are generally vertical, with the impeller submerged under water; there are also horizontal or inclined axial flow pumps. When the impeller of a small axial flow pump is installed above the water surface, a vacuum pump is required to remove air and assist with starting the pump by drawing in water. The blades of axial flow pumps come in two types: fixed and adjustable. The operating conditions of large axial flow pumps (mainly referring to flow rate) often require significant changes during operation, and adjusting the installation angle of the blades allows the pump to operate within its high-efficiency range under different conditions. The blade installation angle of small pumps is generally fixed. Axial flow pumps are the type of dynamic pump with the highest specific speed, ranging from 500 to 1600. The flow-head and flow-shaft power characteristic curves of the pump are steep in the low-flow range; therefore, operation in this unstable low-flow region should be avoided. The shaft power of an axial flow pump is highest at zero flow rate; therefore, the valve on the discharge pipeline must be opened before starting the pump in order to reduce the starting power. Axial flow pumps are mainly suitable for applications requiring low head and high flow rates, such as irrigation, drainage, dock drainage, water level regulation in canal locks, or as large-scale circulation pumps in power plants. Axial flow pumps with high head (made two-stage if necessary) can be used for waterjet propulsion in shallow-water vessels.

Axial flow pumps are generally vertical, with the impeller submerged under water; there are also horizontal or inclined axial flow pumps. When the impeller of a small axial flow pump is installed above the water surface, a vacuum pump is required to remove air and assist with starting the pump by drawing in water. The blades of axial flow pumps come in two types: fixed and adjustable. The operating conditions of large axial flow pumps (mainly referring to flow rate) often require significant changes during operation, and adjusting the installation angle of the blades allows the pump to operate within its high-efficiency range under different conditions. The blade installation angle of small pumps is generally fixed. Axial flow pumps are the type of dynamic pump with the highest specific speed, ranging from 500 to 1600. The flow-head and flow-shaft power characteristic curves of the pump are steep in the low-flow range; therefore, operation in this unstable low-flow region should be avoided. The shaft power of an axial flow pump is highest at zero flow rate; therefore, the valve on the discharge pipeline must be opened before starting the pump in order to reduce the starting power. Axial flow pumps are mainly suitable for applications requiring low head and high flow rates, such as irrigation, drainage, dock drainage, water level regulation in canal locks, or as large-scale circulation pumps in power plants. Axial flow pumps with high head (made two-stage if necessary) can be used for waterjet propulsion in shallow-water vessels.

Axial flow pumps are characterized by their simple structure, high flow rate, and low head. In most axial flow pumps, the installation angle of the blades can be changed, which allows the operational parameters to be adjusted; as a result, they have a wide operating range and high efficiency.

Axial flow pumps are characterized by their simple structure, high flow rate, and low head. In most axial flow pumps, the installation angle of the blades can be changed, which allows the operational parameters to vary; as a result, they have a wide operating range and high efficiency