How to choose centrifugal fan impeller

When we choose to buy a centrifugal fan, the choice of the model of the centrifugal fan is very important, and the choice of the impeller is more important, so how do we choose the impeller of the centrifugal fan?

In a centrifugal fan, adding the number of blades of the impeller can increase the theoretical pressure of the impeller, because it can reduce the influence of relative vortex (that is, adding K value). However, the increase in the number of blades will increase the conflict loss of the impeller channel, which will reduce the practical pressure of the fan and increase the energy consumption.

Therefore, for each impeller, there is an unfixed number of blades. The detailed determination of the number of blades sometimes depends on the experience of the planner. According to the current situation in my country, Table 2 recommends the selection scale of the number of blades.

Centrifugal fan planning requirements: the operating point that meets the required flow and pressure should be near the power point; the power value should be as large as possible, and the power curve should be flat; the stable operating range of the pressure curve should be wide; the fan has a simple structure and good manufacturability; materials It is convenient to select and accessories; it has sufficient strength and rigidity, safe and reliable operation; stable operation, low noise; good adjustment performance, strong operation adaptability; fan size as small as possible, light weight; convenient operation and maintenance, easy disassembly and transportation Row.

There are often contradictions between aerodynamic performance and structure (strength, craftsmanship). Generally, the main contradiction must be grasped and handled in coordination. This requires planners to choose a reasonable plan to deal with the main contradictions.

Depending on the purpose of the fan, the requirements are different. For example, fans used in public buildings are generally used for ventilation. Generally, the most important requirement is low noise. Multi-blade centrifugal fans have this feature; and those that require large flow Centrifugal fans are generally of double suction type; for some high-pressure centrifugal fans, the specific speed is low, and the relative share of leakage loss is generally larger.