Centrifugal impeller

means an impeller with a number of blades extending between a back plate and shroud in which airflow enters axially through one or two inlets and exits radially at the impeller periphery. The airflow exits either into open space, or into a housing with a fan flow angle greater than or equal to 70 degrees. Impellers can be classified as single inline or double inlet. Blades can be tilted backward or forward with respect to the direction of impeller rotation. Impellers with backward-tilted blades can be airfoil-shaped (AF), backward-curved single-thickness (BC), backward-incline single-thickness flat (BI), or radial-tipped (RT). Impellers with forward titled blades are known as forward-curved impellers (FC).