What Are The Unique Design Features Of Mixed Flow Pumps?

Nov 09, 2025

Mixed flow pump is a fluid machinery between centrifugal pump and axial flow pump, which combines the advantages of both and has been widely used in many industrial and hydraulic engineering fields. The unique design features of mixed flow pumps enable them to exhibit high-quality performance under specific working conditions. The following will elaborate on the unique design features of mixed flow pumps.

 

1, Impeller design

 

Blade shape and angle

 

The blade shape of a mixed flow pump is unique and usually twisted. This shape allows the blades to have different blade placement angles at different radii. At the inlet of the impeller, the blade placement angle is small to reduce the impact loss of the inlet water flow and improve the suction performance of the water pump. As the radius increases, the blade placement angle gradually increases, which can enable the water flow to obtain appropriate energy enhancement in the impeller. For example, in some large mixed flow pumps, the blade inlet placement angle may be between 10-20 degrees, while at the outlet it may reach 30-40 degrees.

The twisted design of the blades also makes the flow of water in the impeller more uniform, reducing the occurrence of eddies and shedding phenomena. This helps to improve the hydraulic efficiency of the water pump and reduce energy loss.

 

Number and distribution of leaves

 

The number of blades in a mixed flow pump is generally between 3-6. The number of blades will affect the performance of the water pump. A smaller number of blades can reduce the disc friction loss of the impeller, but it may increase the unevenness of the water flow; A larger number of blades can improve the head and efficiency of the water pump, but it can also increase the difficulty and cost of manufacturing the impeller.

 

 

The distribution of blades on the impeller is also carefully designed. Usually, a symmetrical distribution is used to ensure the dynamic balance of the impeller during rotation. This symmetrical distribution helps to reduce vibration and noise during pump operation, and improve the stability of pump operation.

 

2, Pump body structure

 

Spiral shell shape

 

The shape of the volute of a mixed flow pump is different from that of a centrifugal pump and an axial flow pump. Its volute is usually spiral shaped, but the helix angle is between that of a centrifugal pump and an axial flow pump. This snail shell shape can better adapt to the velocity and direction changes of the water flow at the outlet of the mixed flow pump impeller, gradually transforming the high-speed water flow at the impeller outlet into pressure energy.

The inner wall of the snail shell is designed to be smooth to reduce friction loss between the water flow and the snail shell wall. At the same time, the outlet width of the snail shell gradually increases to adapt to the diffusion of water flow and further improve the efficiency of the water pump.

 

Inlet and outlet design

 

The inlet of a mixed flow pump is usually rectangular or circular, and its design should ensure that the water flow can smoothly enter the impeller. The shape and size of the inlet channel need to be optimized to reduce the resistance of the inlet water flow and improve the suction performance of the water pump.

The design of the outlet should take into account the direction of water flow discharge and pressure requirements. The outlet is generally rectangular or tapered, with a certain angle between its direction and the rotation direction and axial direction of the impeller, to adapt to different pipeline connections and engineering requirements.

 

3, Guide vane design

 

Shape and quantity of guide vanes

 

The guide vanes of mixed flow pumps are usually twisted annular structures. The shape and quantity of guide vanes have a significant impact on the performance of the water pump. The number of guide vanes is generally between 4-8, and their shape design should ensure that they can effectively guide the water flow at the impeller outlet, making it flow along the axial direction and further increasing the pressure of the water flow.

 

 

The distance between the inlet edge of the guide vane and the outlet edge of the impeller should be appropriate to avoid water flow impact and detachment. At the same time, the outlet edge of the guide vane should gradually shrink to reduce the outlet velocity of the water flow and improve the efficiency of the water pump.

 

Function of guide vanes

 

The guide vanes play an important role in mixed flow pumps. It can not only guide the water flow, but also recover the kinetic energy of the impeller outlet water flow and convert it into pressure energy. In addition, guide vanes can also play a role in balancing axial forces, reducing axial thrust during pump operation, and improving the stability of pump operation.

 

4, Sealing and Bearing Design

 

sealing design

 

The sealing design of mixed flow pumps should ensure that no leakage occurs during operation. For mixed water pumps, mechanical seals or packing seals are usually used. Mechanical seals have the advantages of good sealing performance and long service life, but the cost is relatively high; Packing sealing has a simple structure and low cost, but its sealing performance is relatively poor.

In some special working conditions, such as mixed flow pumps transporting corrosive or high-temperature media, special sealing materials and structures are required. For example, for mixed flow pumps that transport corrosive media, corrosion-resistant sealing materials such as fluororubber can be used; For mixed flow pumps with high-temperature media, cooling mechanical seals can be used to prevent seal failure due to high temperatures.

 

bearing design

 

The bearings of a mixed flow pump must bear the weight of the impeller and pump shaft, as well as the axial and radial forces during operation. Therefore, the design of bearings should have sufficient load-bearing capacity and reliability. Usually, rolling bearings or sliding bearings are used.

Rolling bearings have the advantages of low friction coefficient and flexible starting, but they require regular lubrication and replacement; Sliding bearings have the advantages of strong load-bearing capacity and smooth operation, but require high lubrication and cooling. In the design of mixed flow pumps, appropriate bearing types should be selected based on specific operating conditions and requirements, and reasonable lubrication and cooling designs should be carried out.

 

5, Material selection

 

Impeller material

 

The material selection of mixed flow pump impeller should be determined based on the properties of the conveying medium and working conditions. For mixed flow pumps that transport clean water or mildly corrosive media, materials such as cast iron, cast steel, or stainless steel are usually used. Cast iron impellers have the advantages of low cost and good casting performance, but their corrosion resistance is poor; The strength and toughness of cast steel impellers are good, suitable for working conditions with high pressure; Stainless steel impellers have good corrosion resistance and wear resistance, and are suitable for conveying media with strong corrosiveness or containing solid particles.

For some special working conditions, such as transportation of high temperature, high pressure or highly corrosive media, special alloy materials such as nickel based alloys, titanium alloys, etc. can also be used.

 

Pump body and guide vane materials

 

The materials of the pump body and guide vanes should also be selected according to the properties of the medium and working conditions. For general mixed water pumps, cast iron or cast steel can be used to manufacture the pump body and guide vanes; For mixed flow pumps that transport corrosive media, materials such as stainless steel, fiberglass, or plastic can be used. Fiberglass reinforced plastic has the advantages of light weight and good corrosion resistance, and is suitable for some small and lightweight mixed flow pumps; Plastic has good corrosion resistance and insulation properties, making it suitable for some special working conditions.

 

6, Operating characteristics

 

Flow head curve

 

The flow head curve of a mixed flow pump shows a hump shape. When the flow rate is low, the head is high. As the flow rate increases, the head gradually decreases. When the flow rate reaches a certain value, the head begins to rise again. This flow head curve enables mixed flow pumps to maintain a certain level of efficiency under different operating conditions.

 

 

Compared with centrifugal pumps, mixed flow pumps have higher head at low flow rates and are more suitable for working conditions that require larger head; Compared with axial flow pumps, mixed flow pumps have a slower head drop at high flow rates and better stability.

 

Efficiency characteristics

 

The efficiency curve of a mixed flow pump is relatively flat and can maintain high efficiency over a large flow range. This enables mixed flow pumps to have good adaptability under conditions with large flow changes. For example, in farmland irrigation systems, due to different irrigation demands in different seasons and plots, the flow rate will vary greatly. Mixed flow pumps can maintain high operating efficiency and save energy in this situation.

The unique design features of mixed flow pumps make them widely applicable in fields such as water conservancy, agriculture, and industry. With the continuous development of technology, the design and manufacturing technology of mixed flow pumps will continue to innovate and improve, providing more efficient and reliable fluid conveying equipment for the development of various industries.