The differences between axial-flow pumps, mixed-flow pumps and centrifugal pumps
Axial-flow pumps, mixed-flow pumps and centrifugal pumps differ in terms of their working principles, structural features and performance characteristics.
1 Working principle
Axial flow pump: The axial flow pump generates axial thrust on water through the rotating impeller, causing the water to be transported along the axis. Its working principle is similar to that of an aircraft's propeller. The direction in which the liquid exits the impeller is parallel to the axis, that is, it flows along the axis direction.
Mixed-flow pump: The mixed-flow pump combines the characteristics of a centrifugal pump and an axial-flow pump. It utilizes the centrifugal force generated by the rotation of the impeller and the axial thrust to jointly convey the liquid. The direction in which the liquid exits the impeller is inclined relative to the axis.
Centrifugal pump: The centrifugal pump relies on the centrifugal force generated by the high-speed rotation of the impeller to throw water towards the edge of the pump casing, thereby creating a low-pressure area to draw in water and a high-pressure area to discharge water. The direction in which the liquid flows out of the impeller is perpendicular to the axis, that is, it flows out along the radial direction. The direction in which the liquid flows out of the impeller is inclined relative to the axis.
Structural Characteristics
Axial-flow pump: The impeller is usually submerged in water and can be installed in various ways such as vertical, horizontal, inclined, and cross-flow. The impeller blades are either fixed or adjustable to adapt to different working conditions.
Mixed-flow pump: The impeller structure is between that of a centrifugal pump and an axial-flow pump, having both the volute of a centrifugal pump and the guide vanes of an axial-flow pump. Its head is higher than that of an axial-flow pump but lower than that of a centrifugal pump, and its flow rate is between the two.
Centrifugal pump: The impeller is located inside the pump casing and is connected to the motor through a coupling. The pump casing is mostly in the form of a volute, used to collect and guide the water flow. Single-suction or double-suction impellers, multi-stage impellers, etc. can be configured as needed.
Performance characteristics
Axial flow pump: It has a large flow rate and a low head (generally no more than 10 meters). It is suitable for applications with low head and large flow, such as irrigation and drainage. Before starting, the discharge valve should be opened to reduce the starting power, and the motor is less likely to be burned out.
Mixed-flow pump: It combines the high head of a centrifugal pump and the large flow of an axial-flow pump, making it suitable for applications with significant variations in head. Generally, the mixed-flow pump operates within a range of 10 to 20 meters, and its flow rate and head relationship lies between that of a centrifugal pump and an axial-flow pump. Its main feature is an efficient combination of flow rate and head. When starting the mixed-flow pump, it is recommended to choose an open gate start.
Centrifugal pump: High head, relatively small flow rate. Suitable for applications with high head and small flow. The head of a single-stage centrifugal pump can reach over 20 meters. Examples include water supply systems and pressurization. Before starting, it is necessary to fill the pump with water to create the required vacuum. During operation, it is recommended to start by closing the valve. This way, the power consumption is lower and the motor is less likely to be damaged.
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Application scenario
Axial flow pump: Widely used in fields such as agricultural irrigation, urban drainage, and shipyard drainage. It is particularly suitable for situations with significant water level fluctuations.
Mixed-flow pump: Suitable for irrigation and drainage in hilly areas, forced circulation in industrial processes, and marine aquaculture, etc. Its wide adaptability has enabled it to be applied in various scenarios.
Centrifugal pump: It is almost ubiquitous, from household water supply to industrial production, and even in urban water supply and drainage systems, it is widely used. In general, axial flow pumps are suitable for large-scale irrigation and drainage due to their large flow rate and low head; mixed flow pumps are suitable for variable working conditions due to their comprehensive performance; centrifugal pumps, with their high head and wide adaptability, have become one of the most common types of pumps. When choosing, it should be decided based on the specific application requirements which type of pump to use.
