A bladeless fan, also known as an Air multiplier fan, is a fan that blows air from a ring or oval opening with no external blades.^[1] Despite the name, these fans do have blades, mounted on a propeller hidden in the base.

How it works

1. The base contains a conventional bladed fan that sucks in a small amount of air from the perforations around the base, and blows it upwards into the channel in the top ring.
2. This channel distributes this airflow around the ring, pushing it out through a thin slot around its inside circumference. This results in a relatively low flow rate, high-speed ring of air stream being exhausted in the desired direction.
3. This circular air stream interacts with ambient air (in the center of the ring, and around the outside of the ring), causing it to be pulled in the direction of the stream (via a phenomenon called entrainment).

   The initial air stream slows down, in exchange for producing a new total flow with a much higher flow rate than the original (Dyson claims it's ~16x higher^[2]).

The buffeting of a conventional fan comes from their lower number of larger blades, which push air inconsistently across the air stream's cross section. This design mitigates this by collecting the full airflow of the small fan, "averaging out" any buffeting that would have otherwise happened.^{[citation needed]}

History

The concept was created by Toshiba in 1981 and was later popularized by industrial designer James Dyson, who used the technique in a consumer fan introduced in 2009, calling it the Air Multiplier.^[3][4] It was included in Time's 50 Best Inventions of 2009 list.^[5] The principle has been in use for a long time as an ejector or injector.^[6]