Abstract: Systems and methods are provided for mitigating recirculation of backflow fluid through a fan. The fan includes a housing having a channel that extends from an inlet to an outlet of the housing. A rotor assembly is positioned within the channel and is configured to direct a fluid flow from the inlet to the outlet. The rotor assembly includes a hub, a plurality of fan blades, and a shroud disposed about a circumference of the fan blades, where a radial gap extends between the shroud and the housing. The radial gap is configured to receive a portion of the fluid flow from the outlet as backflow fluid. The rotor assembly also includes an inlet flange that is configured receive the backflow fluid from the radial gap and to direct the backflow fluid in a direction away from the inlet prior to discharge of the backflow fluid from the radial gap.

Abstract: Systems and methods are provided for mitigating recirculation of backflow fluid through a fan. The fan includes a housing having a channel that extends from an inlet to an outlet of the housing. A rotor assembly is positioned within the channel and is configured to direct a fluid flow from the inlet to the outlet. The rotor assembly includes a hub, a plurality of fan blades, and a shroud disposed about a circumference of the fan blades, where a radial gap extends between the shroud and the housing. The radial gap is configured to receive a portion of the fluid flow from the outlet as backflow fluid. The rotor assembly also includes an inlet flange that is configured receive the backflow fluid from the radial gap and to direct the backflow fluid in a direction away from the inlet prior to discharge of the backflow fluid from the radial gap.

Abstract: A fan includes an impeller having blades of varying chord lengths. The fan includes a fan housing surrounding the impeller. The fan housing includes a protruding region, or throat, separated from each passing blade by a clearance, or throat gap, that varies according to the chord length. During rotation of the impeller, the impeller blades rotate about a rotational axis, passing the protruding region defining a minimum radial gap to the protruding region. Due to their different chord lengths, the impeller blades pass the throat region at different throat gaps. Shorter blades are likely to have lower amplitude static pressures and lower air velocities resulting at the blade tip, and are hence likely to generate a lower amplitude acoustic pulse at the protruding region. The variety of chord lengths modulate the amplitude of the pressure to spread acoustic sound across multiple frequencies thereby reducing peak amplitude of the acoustic sound.

Abstract: A fan includes an impeller having blades of varying chord lengths. The fan includes a fan housing surrounding the impeller. The fan housing includes a protruding region, or throat, separated from each passing blade by a clearance, or throat gap, that varies according to the chord length. During rotation of the impeller, the impeller blades rotate about a rotational axis, passing the protruding region defining a minimum radial gap to the protruding region. Due to their different chord lengths, the impeller blades pass the throat region at different throat gaps. Shorter blades are likely to have lower amplitude static pressures and lower air velocities resulting at the blade tip, and are hence likely to generate a lower amplitude acoustic pulse at the protruding region. The variety of chord lengths modulate the amplitude of the pressure to spread acoustic sound across multiple frequencies thereby reducing peak amplitude of the acoustic sound.