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Old Oct 08, 2012, 11:45 AM
UncleMatt is offline
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Originally Posted by Odysis View Post
EDFs do compress air. How much by? Let's find out.

Something like an SM89-45, with a 4771mm2 fan area, putting out 4.5kg thrust with a 100% FSA exhaust.

4.5kg is 44.1N, 4771mm2 is 4771e-6m2. Simply, the pressure change is
dP=9243 Pascals.

For those not into SI units, that's 2.7inches, or 1.3psi, or around 1/10th of an atmosphere.
So, it's got a pressure ratio of 1.1. Not enough for the job at hand, but nothing to be sneezed at, no?

Three inline would obviously give around 1.33 ratio, but huge amounts of power.
I love a man who knows his math! That was a very helpful rundown on EDFs and compression. I have seen other threads where a guy placed 2 EDFs so their impellers would emulate a multi-stage axial compressor, but the goal was additional air velocity, not pressure increase. I wonder if that would produce the 1.3 pressure ratio I am after here. But it will probably take an axial setup designed to compress more to get there without using too much power or adding too much weight.

If more ideas are out there, let them flow! Also, it may be off topic here, but if anyone knows of a scale roots type air pump that might work for this, let me know.
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Last edited by UncleMatt; Oct 08, 2012 at 11:50 AM.
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