What are the differences between forward-inclined and backward-inclined centrifugal fans and how to select properly?


Centrifugal fans are widely used for ventilation in factories, mines, tunnels, ships and buildings. They are machinery that relies on input mechanical energy to increase gas pressure and deliver gas. It is a driven fluid machine. Centrifugal fans are divided into forward-inclined and backward-inclined centrifugal fans. But what is the difference between the two types of fans? 

The forward-inclined and the backward-inclined centrifugal fans differ in the exit blade angles. When the angle is greater than 90 degrees, it is called a forward-inclined centrifugal fan. When it is less than 90 degrees, it is called a backward-inclined centrifugal fan. When the size and speed of the centrifugal fan are the same, the larger the exit angle, the higher the pressure generated, so forward-inclined centrifugal fans have a greater total pressure than backward-inclined centrifugal fans. However, forward-inclined centrifugal fans have a larger dynamic pressure to total pressure ratio. As the airflow speed is higher, and the system loss is greater when converted to static pressure, so the efficiency is not as high as backward-inclined centrifugal fans.


The most common in China is the forward-inclined centrifugal fans of multiple blades. They are of lower price as the impeller can be mass-produced by riveting. It should be noted that when it is not suitable for such impellers, do not use this type of fan. Usually, the fan selection is recommended by the manufacturer and the distributer. INFINAIR will help customers select the most suitable and cost-effective fan with its specialized model selection software. However, there are still many people who are not quite sure how to distinguish the quality of centrifugal fans. So how do we usually distinguish them?

In telling the quality of centrifugal fans, it is necessary to check whether the real fan performance meets the air pressure and air volume specified in the catalog. Only when the air pressure and air volume live up to what is required by the actual system, can centrifugal fans be considered standard. Also, the noise of the centrifugal fan needs to be checked. Noise is also a form of environmental pollution, which not only affects work and life, but also brings nuisances to other people around, and even consumes more energy. If the efficiency is high, the power consumption is low. So it is important to ensure the high efficiency of fan running. What is more, the higher the vibration value of bearings of centrifugal fans, the more easily bearings are damaged. The lower the vibration value, the longer the bearing life. Therefore, the vibration value of the centrifugal fan should also be paid attention to when doing the model selection.