What is an axial flow pump?

　　What is an axial flow pump

　　Axial flow pump is a kind of rotary power pump, also known as propeller pump, strictly speaking, it does not belong to the centrifugal pump, axial flow pump is equipped with an axial impeller, relying on the impeller rotation of the fluid generated by the lift and work, as the name suggests, in this kind of pump, the fluid and the pump shaft parallel pumping.

　　Axial pump impellers are usually equipped with two to seven vanes, which rotate in a circular casing, and the pump casing downstream of the impeller is generally provided with a fixed guide vane for eliminating the rotational motion of the fluid to axial movement, axial pumps are usually single-stage, and two-stage for special applications (e.g., for water-jet propulsion of shallow-water vessels), and axial pumps are usually vertical (with impellers immersed in the fluid), as well as horizontal and inclined The impeller blades of axial flow pumps are usually vertical (impeller submerged in the liquid), as well as horizontal and inclined.

　　Axial pump impeller blades can be divided into fixed, semi-adjustable and fully adjustable, small axial pump impeller blade installation angle is usually fixed, large axial pump operating conditions (mainly refers to the flow rate) in the operation often need to make a large change in the installation angle of the blade (usually adjustable) can make the pump in different operating conditions to maintain the operation in the high-efficiency zone.

　　Mixed-flow pumps partly by centrifugal force, partly by propeller action, the impeller blades are subject to a certain degree of “distortion”, however, in fact, radial flow pumps (centrifugal pumps), mixed-flow pumps and axial pumps and there is no accurate demarcation line, in general, axial pumps and mixed-flow pumps are mainly suitable for high-flow, low-head pumps applications, and Centrifugal pumps are most suitable for high head conditions. Axial flow pumps have poor suction capacity and must be submerged to start.

　　Principle of operation of axial flow pumps

　　Axial pump conveying liquid is not relying on the centrifugal force of the impeller on the liquid, but the use of rotating impeller blade thrust so that the liquid being conveyed along the direction of the pump shaft flow, when the pump shaft is driven by the motor rotation, due to the blade and the pump axis axis has a certain helix angle, so the liquid produces a thrust (or called lift), the liquid out of the discharge pipe along the discharge.

　　This is similar to the rationale for the operation of electric fans, near the fan blades in front of the air is pushed to the front of the blades, so that the air flow, when the liquid is launched, the original position will form a local vacuum, the outside of the liquid in the role of atmospheric pressure, along the inlet pipe will be sucked into the impeller, as long as the impeller continues to rotate, the pump will be able to continuously suck and discharge of liquid.

　　Application of axial flow pump

　　Axial flow pumps are mainly suitable for large flow rate and low head, widely used in different industries all over the world:

　　1)For fishery, agriculture, municipal and commercial sewage treatment.

　　2) Irrigation and flooding of farmland, drainage of cities and shipyards.

　　3)Used as circulating water pumps in large power plants.

　　4)Used in chemical industry for circulating liquid in evaporator.

　　5) Other, such as paper, fertilizer industry applications.

　　Since the starting power of axial flow pumps is much greater than the working point power, axial flow pumps will not start with the outlet valve closed, which will overload the motor, and usually take the open valve to start to minimize the required starting power and current

　　Advantages of axial flow pumps

　　Large flow, simple structure, light weight, small external dimensions, its shape is tubular, so it covers a small area.

　　1)It does not need to be filled with water, and it is simple to operate before starting.

　　2)Ideal pump for high flow and low head applications.

　　3)For axial flow pumps, the effect of fluid rotation is small and pump efficiency is relatively high.

　　4)Compared to many conventional pumps, the pump form factor is relatively small, making it easy to use and handle.

　　For regulated axial flow pumps, when the working conditions change, as long as the vane angle is changed, it can still be maintained at a higher efficiency.

　　Disadvantages of axial flow pumps

　　1)Problems of suction range, poor suction capacity, must be submerged to start.

　　2)Unable to handle liquids with high viscosity.

　　3)Low head, not suitable for high head applications.