Centrifugal fan is not a positive displacement equipment. Compared with positive displacement fan, centrifugal fan has certain advantages and disadvantages: centrifugal fan has higher efficiency, while positive displacement fan has lower capital cost and can achieve higher compression ratio. [4] [5] [6] [7] [8] in residential, industrial and commercial applications, centrifugal fans are usually compared with axial fans. Axial flow fans usually operate at high volume, low static pressure and high efficiency. [9] Therefore, axial fans are usually used for high-capacity air flow, such as warehouse exhaust or room circulation, while centrifugal fans are used to move air in pipeline applications, such as houses or typical office environments.