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Need opinions for electric aircraft project

#1
Hello, I am currently working on a capstone project for my bachelor's degree where I have been added to a team of aerospace engineering students tasked with designing a lightweight VTOL aircraft. The parameters of the project imply that fully electric or fuel powered helicopters will not be able to meet the demands, so a hybrid system in an unorthodox aircraft is essentially required.
Now that I've introduced the project, the thing I would like expertise on is a concept I saw on the Alpha Electro, made by Pipistrel LLC. This aircraft uses the propeller as a wind turbine when descending to charge the batteries.
I have very little experience with power generation in general but have been told that turbines are very tricky to work with and control, becoming dangerous and destabilized if not handled properly.
What kind of systems would need to be in place to control RPM without destroying the propeller or placing extra wear and tear on parts?
Thank you in advance
 

leaded50

Legendary member
#2
wind turbines biggest problem is the bearings, if its "direct drive", or through gearbox.(eg. heat)
A propeller on a plane do rotate at given prm by motor power, and if should rotate without the power, just by windforces , i believe it will rotate slower...at least does by a electric RC plane. Adjustable pitch on prop to control RPM vs speed isnt unusual on prop planes..

Im not any aviation expert though, neither on wind turbines. This is my thoughts about what learned, or heard persons in such businesses says.
Why dont rather think about solarcells to charge in flight? It will be more easy to incorporate in a plane.
 
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JasonK

Elite member
#3
How big is your project - physical size target?

I doubt your going to get regenerative breaking working well without variable pitch. Nor do I expect that you would recover enough power to be of note by doing regenerative breaking of of the prop like that (at least at typical RC scale - the reference said up to 13% with all of their engineering skill behind it).

You also mentioned VTOL, which typically means a powered landing vs a regenerative breaking landing (which is what the Alpha Electro appears to be doing to recover that power).

To me, it sounds like that they are looking for something like this (based on your limited details, this is my first though on how to meet the apparent requirements):
Fuel powered motor -> generator -> batteries -> Electric motors for thrust (both lift and forward)
given that forward flight can use significantly less power then hovering, you can take off/land on power from the batteries. In cruse, the fuel powered motor can supply more power needed, so it will be recharging the batteries during flight.

IIRC, if your running a motor just as a generator you can tune/run it at a much higher efficiency then if it needs to have a wide operating envelope.
 

CappyAmeric

Active member
#4
Maybe a perpetual motion machine?

Seriously, it depends on what is supposed to be achieved.

The energy extracted and stored from a descent with a free spinning turbine would be minuscule compared to the energy expended to ascend. VTOL makes the formula even less viable.