An axial fan is a compressor. It is simply a compressor with a high volume, low pressure rise characteristic.
Low pressure being the clinker!
Low is all relative. A pressure ratio of 1.1 to 1.25 is not unreasonable for a single stage centrifugal compressor. Note that they do not have an axial fan there, they have a radial blower that they have modified by adding a diffuser to the outlet. They have basically made a crude centrifugal compressor by sacrificing flow rate for pressure rise.
Yeah, 10-15 kW is a lot, but I don't think they are claiming that.
It's fairly conservative even for a low displacement engine.
Calculations, then. Suppose a 1.6 litre four stroke engine is running at 4000 rpm. It will displace 0.8 litres of air per revolution, which gives 3200 litres per minute, or 113 cfm. Suppose we wish to compress that air by 4 psi. It starts out at atmospheric (15 psi) and finishes at 19 psi. Using this
handy-dandy calculator, we can work out the power requirement. Plugging in the numbers gives 2.2 theoretical HP, or 1.6 kW. If we round that up to 2 kW to allow for imperfect efficiency we are still far below 10-15 kW.
They are running a 12 V motor at 36 V for short enough periods to avoid burning out the windings.
What is the extra voltage going to achieve? Even if the can spin that impeller twice as fast it wont be moving any more air once it runs over it's fan curve. All it will produce is NVH.
Fan affinity laws. Volume flow increases with the speed and the pressure rise with the square of the speed. That's why airplane propellers turn
really really fast. There are limits when parts of the machine reach sonic velocities, but there is no chance our blower is going to do that.
If they get a 4 psi pressure rise above atmospheric, that is a pressure ratio of about 1.25.
That setup wont achieve 1 psi no matter how fast or hard you spin the impeller.
Skepticism is good, but I'm not inclined to say it's impossible.
That's a bit much for a plain old fan of course, but they have modified their fan to change its characteristics.
How? A fan is never going to become an efficient high volume compressor.
It doesn't need a very high volume. 113 cfm is quite low. You can get more pressure if you can accept a reduction in volume.
OK, enough speculation. I'll have to do some calculations and see how far away from reality this thing might be.
I know the result. Accurate calculation will only help to debunk this nonsense.
I'm not sure where to look, but I need to see fan curves for heater blowers used in automotive applications.