Small Hybrid Electric Aircraft

Discussion in 'Electric Propulsion' started by litespeed, Aug 14, 2019.

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  1. Aug 19, 2019 #41

    RonL

    RonL

    RonL

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    I would say a conventional power system, single or twin or some other configuration for takeoff and climb to speed. Somewhat minimal battery storage (for weight consideration) and two power recovery tubes that have counter-rotation airflow for torque equalization.
    Conditioning the velocity of airflow inside the tube will move the vast majority of mass and temperature into a high friction driving flow that is moving at an accelerated spin speed, far above the speed of entrance air.
    (vortex tubes have air spin at over 1,000,000 rpm in a 1" pipe, from a 1/4" tube @ 100 psi) of course, a much larger design would reduce spin speed by many times. My older refrigeration manual described the power of friction inside the tiny 3/4" tube, to be equal to 1/2 horsepower (this resulted in heat transferred to the tube shell)

    I believe an image of basic structure and operation in one's mind, must precede any evaluation and analysis of numbers and size.

    Edit to add content (always forget to say the important things)
    That friction driving flow will power a generating stator and possibly assist in a mechanical form of drive assist to the electric discharge fan, which should be producing a slight positive thrust.

    The power to the rear fan will determine if this is just an energy recovery system or a possible additional power source to aid in flight.
     
    Last edited: Aug 19, 2019
  2. Aug 19, 2019 #42

    Sockmonkey

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    While pondering the stirling and it's variants like the manson engine for hybrid purposes, I came across this thing.
    [​IMG]
    The principal is simple. One piston pumps air into the tube which is then heated by an external source, and the expanding air is vented into the second cylinder turn the crank. You get the clean constant burn and flex-fuel capability without anything fiddly or complex.
    Seems pretty nifty.
    Now what if we replaced those pistons with a pair of positive-displacement rotor pumps? Then you get vibration-free smooth power delivery that would be really good for spinning a generator.
     
  3. Aug 19, 2019 #43

    emir_82

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    But you "already bought" that other stuff. So you have to think the exchange of a fraction of the battery pack for the hybrid system in therms of price and weight.
    For the sailplane I need "only" 5kwh in total. In that case it doesn't worth it.
     
  4. Aug 19, 2019 #44

    pictsidhe

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    So you are going to fly a plane at X mph through the air, slow some of that air down to extract work from it?
     
  5. Aug 19, 2019 #45

    RonL

    RonL

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    No, the fan at the rear will actually pull a suction at the front.
     
  6. Aug 19, 2019 #46

    pictsidhe

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    so your device will produce thrust and power?
     
  7. Aug 19, 2019 #47

    Sockmonkey

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    A NACA cowling should work for reduced cooling drag/thrust production just as well for an electric motor as it does for a radial.
     
  8. Aug 19, 2019 #48

    RonL

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    Yes, to the extent that temperature can be raised or lowered, when in the passage through the tube and how much.
     
  9. Aug 19, 2019 #49

    litespeed

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    So I can do some rough calculations and mud map a system, I ask the following.

    What is the airframe?
    What is the power for takeoff and cruise?
    Min power for level flight?
    How long do you want as power flight time?
    What weight can it carry as engine systems and fuel in total (ie as any power system, either gas powered or electric)
    And anything else you have as requirements?

    Does it have available space to place the hybrid and batteries?
    Where would you place the motive engine- ie in a pylon or nose?

    Then we can work out if a system can be designed that is suitable.


    The same invitation is open to anyone and any design type but slippery is better.
    Cheers
     
    emir_82 likes this.
  10. Aug 19, 2019 #50

    pictsidhe

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    So the energy does come from cooling air?
     
  11. Aug 19, 2019 #51

    RonL

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    Yes, but at the expense of expending energy to attain the speed of say 150 or 200 mph.
     
  12. Aug 19, 2019 #52

    litespeed

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    Sockmonkey,

    Interesting as far as stirling engines go, but they all have very poor performance for anything but oddities and desktop ornaments.

    They just can't make enough grunt to be useful as they are external combustion engines.

    Much better to use a two stroke which is a very simple engine with very few moving parts and bags of power for size and weight.
     
  13. Aug 19, 2019 #53

    Hot Wings

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    I agree - not that it really matters.
    2 strokes have a bad reputation with regard to efficiency, but if tuned to one RPM or operated in 4 stroke mode, they can do very well with regard to BSFC and still retain their good power to weight ratio.
     
  14. Aug 19, 2019 #54

    pictsidhe

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    Huh?
    What goes in to the device, and what comes out?
     
  15. Aug 19, 2019 #55

    litespeed

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    A well designed stroker is ok fuel wise and in the hybrid situation its super light weight and power more than overcome a bit more fuel use.
    Sure once we scale things up, then a four stroke engine tends to come out on top.

    However a injected two stroke is entirely different and can be very economical when done well.
     
  16. Aug 19, 2019 #56

    Sockmonkey

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    The killer for stirlings is the power to weight ratio and the fact that best efficiency means the cylinders need to be hotter than a normal IC engine would run, requiring expensive alloys.
    The lack of throttle response isn't an issue for hybrids and/or electrical power generation.
    The manson versions have a better power to weight ratio and cooler cylinders because they heat the air charge outside the cylinder and dump it once it's been used to push the piston instead of trying to cool it back down in time fort the next stroke.
    http://manson-ericsson-hae.blogspot.com/p/ma.html
    It's not all that different from a conventional ICE in that it takes in cold air, heats it so it expands and does work, then expels it.
     
  17. Aug 19, 2019 #57

    litespeed

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    For this design exercise I will stick to know and common technology that can be easily replicated or purchased.

    I do not want to have too many new technologies involved as this leads to lots of unknowns and pushes up the risk profile for operation in the air.

    So - be using common off the shelf stuff were possible.

    In this case that means two stroke, rotary or unlikely but possible a four stroke.
     
  18. Aug 20, 2019 #58

    pictsidhe

    pictsidhe

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    What is the airframe, litespeed?
     
  19. Aug 20, 2019 #59

    litespeed

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    Thats what I am waiting for, a proposed airframe to do a study on.



     
  20. Aug 20, 2019 #60

    pictsidhe

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    If it's just a study, why not just pick one?
     

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