Centrifugal Pumps, Mixed-flow Pumps, Axial-flow Pumps

Centrifugal pumps, mixed-flow pumps, and axial-flow pumps are the three most common types of general-purpose pumps used in industrial, agricultural, water conservancy, and other fields. Their core differences lie in the fluid flow pattern, the matching relationship between head and flow rate, and structural design, which further determine their distinct application scenarios.

I. Core Differences

The most essential difference among the three is the direction of fluid flow inside the pump, as well as the derived head, flow rate, and efficiency characteristics. A brief summary is as follows:

Centrifugal pumps: high head, medium flow rate

Mixed-flow pumps: medium head, large flow rate

Axial-flow pumps: low head, ultra-large flow rate

Specifically:

Centrifugal pumps: Fluid flows perpendicular to the pump shaft (radial flow). They feature a wide head range, typically 10–200 m and above, with head varying significantly with flow rate. The flow rate ranges from a few m³/h to thousands of m³/h. The high-efficiency zone is relatively narrow, and efficiency drops noticeably when deviating from the design condition.

Mixed-flow pumps: Fluid flows diagonally, between radial and axial directions. Head is moderate, generally 10–50 m, with gentle head variation. Flow rate is usually 1–2 times higher than that of centrifugal pumps of the same specification. The high-efficiency zone is wider, suitable for a broad range of working conditions.

Axial-flow pumps: Fluid flows parallel to the pump shaft (axial flow). Head is low, only 1–20 m, with little head variation with flow rate. Flow rate can reach thousands to tens of thousands of m³/h, much higher than centrifugal and mixed-flow pumps. The high-efficiency zone is concentrated, ideal for large-flow, stable working conditions.

II. Structural Features

1. Centrifugal Pumps

Core components: impeller and volute. The impeller is mostly closed with curved blades. Fluid is drawn into the center of the impeller and thrown radially into the volute by centrifugal force, achieving pressurization and delivery.

They feature a compact structure and moderate size, and can be single-suction or double-suction (such as the double-suction split-case pumps mentioned earlier). They are easy to install and maintain, and compatible with various media (clean water, wastewater, corrosive liquids, etc.).

2. Mixed-flow Pumps

They combine structural features of centrifugal and axial-flow pumps. The impeller blades are twisted; fluid entering the impeller has both radial and axial flow, hence the name “mixed-flow”.

Pump casings are mostly vertical or horizontal. The impeller diameter is larger than centrifugal pumps but smaller than axial-flow pumps, with a structure between the two. They combine the pressurization capability of centrifugal pumps and the large-flow advantage of axial-flow pumps.

3. Axial-flow Pumps

Impeller blades are helical, similar to a propeller. Fluid flows parallel to the pump shaft and is pushed forward by the thrust of the blades.

Pump casings are usually vertical (horizontal versions are also available). They have a large impeller diameter, high rotational speed, and a relatively simple structure but require large installation space. Some models have adjustable blades to adapt to different flow requirements.

III. Application Scenarios

1. Centrifugal Pumps

Mainly suitable for scenarios requiring pressurization and moderate flow, the most widely used across almost all industries:

Industry: industrial circulating water, boiler feed water, chemical medium delivery, plant water supply pressurization

Municipal: urban water supply, secondary water supply pressurization, treated wastewater discharge

Agriculture: small farmland irrigation (high-head plots), orchard irrigation

Others: emergency water supply, small fire pressurization, ship water supply

2. Mixed-flow Pumps

Suitable for medium head, large flow, balancing pressurization and flow, mostly used in water conservancy and agriculture:

Agriculture: large-area farmland irrigation, farmland drainage (medium-head plots)

Water conservancy: river drainage, small and medium reservoir water diversion, urban waterlogging drainage (no high-head requirement)

Industry: large plant circulating water (large flow, medium head), cooling tower water supply

3. Axial-flow Pumps

Mainly suitable for low head, ultra-large flow, mostly used in large-scale water conservancy, agricultural irrigation, and municipal drainage:

Agriculture: large-area farmland irrigation, large irrigation area water conveyance

Water conservancy: large reservoir water diversion, river flood discharge, large urban waterlogging projects

Industry: circulating water systems of large power plants and chemical plants (large flow, low head)

Others: port and dock drainage, seawater desalination pretreatment