I've read from many sources that Dyson Air Multipliers are more efficient and quieter than normal fans. Now, with the proof of concept, is it possible to use its principles as a propulsion system for, say, a quieter helicopter?
Unlike John Rennie, I think that the problem is not in the efficiency of this system but in the fact, that it will not generate considerable lift. So even if marketing materials are completely true and Dyson Air Multiplier is more energy efficient than conventional fans this efficiency only applies to moving air (which is its intended use) but not to the lifting force.
The principle behind Air Multiplyer (see this video) is creating the flow around the surface of the duct which induces considerably greater flow through the duct. However the resulting flow would be nearly potential and the net force on the duct would be quite small.
Somewhat similar effect does occur in helicopters: Vortex ring state, where under certain conditions increasing the air flow through the rotor does not produce additional lift. In helicopters this is harmful and could even cause the crash, but the Air Multiplier effectively creates similar 'vortex' around the duct for the purpose of moving air.
This is really a comment, but it got a bit too long for the comment box.
The term efficiency has a very specific meaning in Physics. In the case of a fan we can measure the power the fan consumes simply by measuring what current it draws from the main. We can in principle measure the power the fan produces by measuring the velocity of the air stream produced. The efficiency would then be the ratio of the power produced to the power consumed.
I can't find figures for the efficiency of the Dyson fan, but I would be very surprised if it was anything like as high as a conventional fan. The Dyson fan sucks air in at the base, pushes it along internal tubes to the ring where the air is expelled, under pressure, though orifices in the ring. All of this consumes energy and decreases the efficiency. By contrast a conventional bladed fan has none of these energy losses.
NB you may have seen claims that the Dyson fan moves 15 times as much air as it pumps through the ring. This is not a comment on the efficiency but rather it's the fan equivalent of a gear ratio.
So the bottom line is that I have seen no evidence that the Dyson fan is more efficient than a bladed fan, and therefore better for use in airplanes or helicopters, and would guess the reverse is true.
I honestly thought about it myself before. I think it is to do with the fans power-to-weight ratio.
I couldn't find the fans technical specifications, but adoring to Amazons shipping weight (6.4 lb = 2.9 kg) of a 10 inch (25 cm) Dyson fan, we can estimate it weighs around 2 kg.
This is an awful lot for such a small device! Traditional propellers this size can weigh around 200g (For example the ones used in model aircraft. Of course they are optimised for low mass, yet the difference still seems large.
NB: I know this is a physics forum, and in this post I used mass and weight interchangeably, but I can't think a mass verb like "weigh"
It seems like the dyson fan uses a regular fan to pull air into its base creating its air multiplying effect. If that's the case a single fan and motor could drive multiple dyson structures at once, which could result in an overall lower net weight. Not sure how well these things would perform outdoors in air turbulence, but they might make for nifty indoor propulsion for a quad if they produced sufficient airflow.