The fan rotor generally includes a large number of forward curved blades (around 35) with inner-to-outer diameter ratio of approximately 0.75. The rotor generally includes a series of partition disks and end-plates. A variety of tone noise de-phasing features may be used in the impeller design, including non-uniform blade spacing. The main parameters of the commonly used double circular arc type blades are shown in Fig. 3. Variation and optimization of impeller design and housing for air-conditioning applications has been examined by many developers over decades and is relatively mature, while its use as a propulsor or flow control device in aircraft applications has received much less attention.