EDF & Superchargers

[JSAMVTOL]

Join Date: Oct 2006
Posts: 43 Discussion - EDF-Physics & Superchargers

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I was curious about maintaining and/or boosting edf elec.motor/fan efficiency (lbs/ft thrust) by using a separate supercharger (smaller edf fan/duct) as the compressor.

Q: Would this in theory increase mass flow?
Based on basic edf thrust equation: mass flow x velocity = thrust

I realize fan inlet area / ambient temp. and density plays a factor, so

Q1. Decrease inlet air density with wator vapor. Less dense air.(water vapor when mixed in air pushes out nitrogen and other gases that are heavier, it replaces them as they move back into the free stream) Less air density means reduced drag on fan enabling more rpm at constant power?? am i close??

Q2. How do you get wator vapor from a smaller edf supercharger without weight penalties?

3. What if the inlet air was cooled (less or equal to exit air tem), had low density (due to wator vapor) and increase in charged air (increased mas flow from smaller edf supercharger of about 1.5psi).

Could this work?? or would the weight penalties from supercharging with intercooling mitigate any increase in edf efficiency.

Really curious

Thanks
JS

[Speed is Life]

You are a Honda/Mazda/Toyota/Subaru performance type guy right? :rolleyes:

Do a search, this has come up before dozens of times ;) ...............EDF's are not going to give you ANY useful boost for a car, period :( .

Water boost? Cool, if you are a KC-135 or a Thud.

-Mike

[AirX]

I remember reading a report on an early turbocharger being used on early deisel engine at high altitudes, they used water injection to raise the density of the air flow into the turbo. Many high altitude aircraft used water injection to raise density to raise power to useful levels.

To answer the questions that Jsamvtol asked to the best of my knowledge.

1. Yes but only slightly since horsepower is pressure applied to area like the sruface area of a piston or the surface area of the outlet of the EDF. Pressure will only raise under best case scenario for a 90mm to get 1 pound of pressure it will take 5.5hp at the shaft of the fan yeilding only 1000cfm flow, a 120mm will at the same shaft hp yeild .8 pounds pressure and only 1300cfm flowrate. Not much gained for adding performance to a gas engine compared to a proper turbocharger and it will only need the pressure from the burned fuel/air mixture to power it.

2.Decreasing air density will decrease power absorbed by the rotor and less thrust force produced. Water vapor will raise density, water is more dense than air.

3.Cooler air is more dense and more power will be absorbed in moving it.

Finaly no it wont make an apreciable increase in power from your gas engine.

Eric B.

BTW the only reason why it works as a power plant for our jets is the slight riase in pressure can be used to accelerate the efflux airflow to meaningful velocity for flight(a lot different from a turbine where you have a constant supply of thrust from burning fuel)

[JSAMVTOL]

was only referring to supercharger application with small edf for a larger sized edf on electric ducted fans.

reverse mounted,convergent duct, separate power supply, discharges at fan inlet lip..it would boost mass flow., one-way pressure valve / butterfly would guard against negative displacement by larger fan. :rolleyes:

could be used at lower speeds to push through stalls??? :o

[JetPlaneFlyer]

was only referring to supercharger application with small edf for a larger sized edf on electric ducted fans.

reverse mounted,convergent duct, separate power supply, discharges at fan inlet lip..it would boost mass flow., one-way pressure valve / butterfly would guard against negative displacement by larger fan. :rolleyes:

could be used at lower speeds to push through stalls??? :o

You lost me a bit there Jsamvtol. :rolleyes:
However if i get the general idea I think you have in mind a small EDF 'upstream' in series with a larger 'main' EDF unit? If so then this would not work very well at all... The small first stage fan would simply starve the second fan of air. I'd guess that overall flow through the system would be close to what would be achieved by the small fan alone and almost certainly less that what the larger fan was capable of delivering on it's own.

You would get better results from having the smaller fan mounted behind the larger fan, as you find in a multi stage axial compressor... However the gain over a single stage fan would probably still not be worth the added weight.

If you have something different in mind then can you draw a diagram?

Steve

[ronmeister]

Subaru performance type guy right?

-Mike
Oh hell yeah... I know I am :D

[JSAMVTOL]

I will post a sketch of what I have in mind.

I could see turbulent flow an issue, but I will post a pix of what I have in mind...