What are the three types of the centrifugal fan?
There are three kinds of centrifugal fans: forward curved blade centrifugal fan, backward inclined blade centrifugal fan and radial blade centrifugal fan. Next, we will introduce these three fans in detail. 1. Forward curved blade centrifugal fan the running speed of forward curved blade centrifugal fan is relatively low, which is usually suitable for the working conditions of large air volume and low static pressure. The typical flow range is 30% – 80% wocms (full open flow), and the highest static pressure efficiency is 60% – 68%, which usually occurs slightly to the right of the maximum static pressure.
The power curve tends to increase, which is a “easy overload” fan. The advantages of forward curved blade fan are low cost, low speed, thinner shaft and smaller bearing can be selected, and has a wide operation range. The disadvantage is that the shape of performance curve may be parallel to the resistance curve of pipe network, and the reduction of system static pressure may lead to motor overload. In addition, the structural strength of the blade is low and can not run at a higher speed. 2. The speed vector of backward inclined blade centrifugal fan is about twice that of forward curved fan. Generally, the reasonable range of applied flow is 40% – 85% wocms, and the highest static pressure efficiency is about 80%. For a given working condition, generally speaking, larger fans have higher efficiency. The fluctuation of backward inclined blade fan is greater than that of forward curved blade fan. The advantage of backward inclined blade fan is high efficiency and no overload in power curve. Its power curve usually reaches the maximum value in the middle of the common range, so it is generally not overloaded. The blade and impeller have high structural strength and can be used in high static pressure system. The disadvantage of backward inclined blade fan is that due to the high running speed of impeller, it needs coarser shaft and larger bearing, and has high requirements for balance. In addition, the fluctuation of static pressure is easy to cause the change of working condition. The improvement of backward inclined blade fan is to replace constant section blades with wing section blades. This improvement not only improves the static pressure efficiency of the fan to about 86%, but also reduces the noise of the fan accordingly. The advantages of backward inclined airfoil blade fan are paid attention to by more and more fan users, especially the end manufacturers of air conditioner. It is widely used in some places requiring high efficiency and low noise. 3. Radial blade centrifugal fan radial blade fan is a fan between forward curved and backward inclined blades. It has good strength and wear resistance, and the blade outlet angle is 90 °. Except for some occasions requiring wear resistance and corrosion resistance, other occasions are not commonly used.