There is no logical reason why this would not work, I know you're thinking you can't get free power, but the power isn't free, all it would do is the same thing a real supercharger, or for that matter a turbocharger, does, which is push the air density up so you can burn more fuel in a given space.
The problem is that it's hard to increase air density, and these cheap little electric fans don't really do much of that at all, as soon as they get back pressure they can't overcome it. You can stop the fan blade with one finger, while we're looking at pounds per square inch of overpressure to accomplish anything useful.
It still seems like you -could- build a working electric supercharger, by finding or designing an electric fan that builds real pressure (even 6 or 8 psi over atmospheric would accomplish something), but you're up against another physics problem: a real supercharger takes power right off the engine to run the fan. An electric would take power off the battery, which is generated by an alternator hooked up to the engine. This means you get losses twice instead of just once. And the alternator doesn't really take much power at all, it's more of a trickle charger, keeping the battery full. Maybe add a more powerful alternator, and a second battery... but the reason you were putting an electric in was because it was cheap and easy, this system is probably more expensive and harder to do than a regular supercharger.
opcorn:
