Axial flow pumps are significant parts in different modern applications, especially in situations requiring high stream rates with moderately low head. 

Impeller

The impeller is the core of an axial flow pump, liable for moving energy to the liquid and making the siphoning activity.The impeller design of an axial flow pump is very different from that of a centrifugal pump, and it presents a propeller-like structure. This impeller usually has 3 to 6 blades arranged around a central hub, which is quite similar to the propeller on an airplane or ship.

The blades on the impeller are carefully cast, mainly to improve the flow and efficiency of the liquid. As the fluid rotates, it obtains kinetic energy from the impeller and flows along the axial direction. The design of the impeller blades affects the performance of the pump, including flow, pressure and efficiency.

In modern impeller designs, advanced elements are often incorporated, such as indexed blades or variable blade points. These innovations make the pump more flexible in operation, allowing operators to adjust the pump performance according to the changing needs of the system.

Guide Vanes

The main function of the guide vane is to guide the flow of fluid in the pump and improve the overall efficiency. The guide vanes are set in front and behind the impeller to make the fluid flow smoother, reduce turbulence, and enhance the performance of the pump.

At the front end of the impeller, the role of the inlet guide vane is to pre-rotate the incoming fluid so that it forms a good alignment with the impeller blades, effectively transfer energy, improve the efficiency of the pump and reduce the risk of cavitation.

After the fluid passes through the impeller, part of its rotational energy will be recovered by the outlet guide vane located downstream. The role of the outlet guide vane is to convert this part of the rotational energy into pressure energy, thereby further improving the total head and overall efficiency of the pump.

Diffusers and Elbows

Axial flow pumps rely heavily on diffusers and elbows to control the flow of fluid as it leaves the pump. Most of the time, the diffuser is a slowly expanding passage that slows down the high-velocity fluid that leaves the impeller and turns kinetic energy into pressure energy. The pump's overall performance and efficiency can only be improved through this conversion procedure.

In order to alter the flow direction of the fluid, typically from axial to radial, elbows are frequently incorporated into the design of the pump. In order to reduce the amount of energy lost through friction and turbulence, these parts need to be carefully designed. In some designs, elbows and the diffuser function can be combined to create a single component that both changes the direction of the flow and recovers pressure.

Pump Shaft

The pump shaft is a crucial component that connects the drive system's rotational power to the impeller. It must be constructed to withstand the weight of the impeller and other rotating parts, as well as the torsional and bending stresses generated by pump operation.

Axial flow pumps feature straight-line components and a longer shaft than other pumps. The stiffness and precise alignment of the shaft ensures stable operation and reduces vibration.

To cope with the harsh operating environment and corrosion protection in industrial applications, axial flow pump shafts are often made of high-strength materials such as stainless steel. In addition, key parts of the shaft may be sleeved or coated to reduce wear and ensure long-term use.

Bearings

Bearings are very important because they support the pump shaft and allow it to rotate freely while keeping its alignment. In order to deal with the various loads encountered during operation, axial flow pumps typically employ both thrust bearings and radial bearings.

The shaft is supported by radial bearings, which are specially designed to resist forces perpendicular to the direction of shaft rotation. The specific type of bearing used, such as sleeve, ball or roller, will be determined by the design and actual application of the pump.

When an axial flow pump is in operation, strong axial forces are generated, which is when thrust bearings are needed. These forces will cause the impeller and shaft to move in the direction of fluid flow, and the thrust bearing, which may be a ball bearing, roller bearing or hydrodynamic bearing, will prevent this movement and ensure that the rotating parts maintain the correct axial position.

Suction Pipe

Fluid flows into the axial flow pump through the suction pipe, or inlet pipe, which has the key function of ensuring that the fluid enters the impeller evenly and smoothly.

The suction pipe needs to be precisely sized to ensure the right flow rate and minimize friction losses. As the fluid approaches the impeller, the pipe often adopts a design such as a bellmouth or gradual widening to reduce turbulence and optimize fluid flow.

The suction pipe is equipped with a vortex preventer or baffle to prevent the formation of vortices, which may bring in air and thus reduce the performance of the pump in some applications, especially when the pump faces a positive suction pressure head.

Pump Casing

The primary pressure boundary is provided by the pump casing, also known as the housing, which covers all of the internal components of the axial flow pump. It must be constructed to minimize energy losses caused by friction and turbulence while still being able to withstand the internal pressures created by pump operation.

The housing of an axial flow pump is usually cylindrical and aligned with the pump shaft. This housing design can be split horizontally or vertically to facilitate assembly and maintenance of internal parts.

For easy maintenance and corrosion prevention, the housing is often equipped with replaceable wear rings or bushings. In high-performance applications, the housing may also integrate cooling channels or jackets to control temperature.

Drive

The rotational power required to run the axial flow pump comes from the drive system. Even though it isn't actually a part of the pump, the drive is an important part of the pumping system as a whole.

Axial flow pumps mostly use electric motors as the main drive source because of their high reliability, high efficiency and simple control. In large installations, the electric motor may be connected to the pump through a gearbox to achieve the required speed.

Other drive methods such as diesel engines, gas turbines or hydraulic motors may be selected for certain specific applications depending on factors such as power supply, site environment and operational requirements.

Axial Flow Pump Manufacturer

Tianjin Kairun welcomes your consultation. You can contact us at catherine@kairunpump.com.

References

1. Gülich, J. F. (2014). Centrifugal Pumps. Springer.

2. Karassik, I. J., Messina, J. P., Cooper, P., & Heald, C. C. (2008). Pump Handbook. McGraw-Hill Education.

3. Nelik, L., & Brennan, J. (2005). Progressing Cavity Pumps, Downhole Pumps, and Mudmotors. Gulf Publishing Company.

4. Tuzson, J. (2000). Centrifugal Pump Design. John Wiley & Sons.

5. Volk, M. (2013). Pump Characteristics and Applications. CRC Press.

6. American National Standards Institute. (2010). ANSI/HI 2.1-2.2 Rotodynamic (Vertical) Pumps for Nomenclature and Definitions.