Diffuser, centrifugal compression type power system and bladeless fan

The invention discloses a diffuser. The diffuser comprises a lower-portion component and an upper-portion component. The upper-portion component is fixed to the lower-portion component, and the upper-portion component and the lower-portion component are formed respectively. The lower-portion component comprises a lower-portion inner wall and a lower-portion outer wall, the upper-portion component comprises an upper-portion inner wall and an upper-portion outer wall, the upper-portion inner wall and the lower-portion inner wall are connected to form an inner air guide surface, the upper-portion outer wall and the lower-portion outer wall are connected to form an outer air guide surface, and the inner air guide surface and the outer air guide surface oppositely define an air guide channel used for diffusing airflow. The upper-portion component further comprises an upper air guide fin connected with the upper-portion inner wall and the upper-portion outer wall, the lower-portion component further comprises a lower air guide fin connected with the lower-portion inner wall and the lower-portion outer wall, and the upper air guide fin and the lower air guide fin are connected to form an air guide fin connected with the inner air guide surface and the outer air guide surface. In this way, breakage, caused by contraction deformation, of the air guide fin is reduced. The diffuser is simple in structure and convenient to assemble and disassemble. The invention further discloses a centrifugal compression type power system and a bladeless fan.