All Electric Jet Drive Discussion

Discussion in 'Jet Drives' started by anthonydimare, Aug 7, 2015.

  1. anthonydimare
    Joined: Aug 2015
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    anthonydimare Junior Member

    I'm looking to discuss what would need to go into designing a commercial all electric jet drive craft. I'm new to propulsion, and curious to see what the community hear thinks. I've run the basic physics behind a system like this and it seems feasible.

    Things I think would be great to hear opinions on:
    - Brush-less Electric Motor design & sourcing. Doesn't have to be marine specific. Aerospace an automotive seem to be ahead.
    - Impeller optimization strategies. Potentially adjustable pitch? Composites? 3D printed metal for optimized structure design?
    - High performance, lightweight materials, what else besides aluminum & stainless would be applicable?
    - Direct drive to cut efficiency losses in a gearbox. What are the weight implications?
    - Innovative trust vectoring systems ideas.
    - Adjustable nozzles to make micro adjustments in trust.

    Other projects like this? I know there's Torqueedo (http://www.torqeedo.com/en/products) But I'm interested in a system a little more beefy. Any unique home builds out there?

    I'd be curious to see who else is super interested in a system like this. (I've been obsessed a little obsessed lately :D ).
     
  2. Waverunner Eagl
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    Waverunner Eagl Junior Member

    Epic boats has an electric v-drive boat. You could take a look at what they've done as a jumping off point.

    -I'd start with an AC motor
    -here's a pretty cool pump design to look at - http://www.intellijetmarine.com/IntelliJET Development History.htm
    - Why are you limiting fiberglass from the get-go?
    -To know if a direct drive is applicable you'll have to look at the power curve of the motor, and compare that to the impeller you want to run
     
  3. CDK
    Joined: Aug 2007
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    CDK retired engineer

    Unless you are talking about scale models, it is a pretty dumb idea.
    Jet drives are used mainly because they are simple, cheap and need little maintenance. The penalty is a disappointing efficiency compared to props, no big deal as long as there is plenty engine power and fuel is relatively inexpensive.

    To be successful an electric drive must be power efficient from beginning to end. No sane designer would tie a high performance electric motor to a wasteful impeller pump.

    Energy storage costs and weight are prohibitive for any project above hull speed.
     
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  4. NavalSArtichoke
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    NavalSArtichoke Senior Member

    Yep, all you need is a tank full of volts and amps, and yer ready to go!

    I would keep the volts and amps in separate tanks, though, until you're ready to use them.
     
  5. anthonydimare
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    anthonydimare Junior Member

    Awesome start, exactly the kind of conversation I want to be having. Why are you sold on an AC induction drive? Generally the propulsion system would be optimized to run at a single "operating speed" which means a DC brush-less could be optimized for that particular RPM, torque loading, and permanent magnetic needs. Only downside is the need for permanent magnets. But the brush-less would be more efficient. Then again, the AC would allow you to upload new control software as efficiency gains are found. I'm still torn.

    That's an awesome pump. Exactly the kind of control ideas I had in mind to make the system more efficient.

    Fiberglass is a no go, 1 - sustainability just isn't there. 2 - fiberglass doesn't scale well. There's no real economies of scale when it comes to composites. Aluminum is abundant, cheap, and recyclable.

    Time will tell for the drive. You're right, need more information.
     
  6. HammyMan
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    HammyMan New Member

    I'd be siding with CDK to a point. There are a number of diesel/gas/electric hybrids that I have been involved with that are Hamilton Jet driven. I have not seen an electric motor yet that I could stand behind and say yes this would work as a stand alone with a jet. Elon Musk might have something up his sleeve though, look at what they are doing with Tesla.
    The commercial aspect is a little more worriesome, as the performance needs are higher demand on the power package. Providing you can get consistent performance out of an electric motor the jet will be a fine package, especially at over 25 knots where the jets today outstrip props in terms of efficiency.
     
  7. NavalSArtichoke
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    NavalSArtichoke Senior Member

    You're still putting the cart before the horse.

    Nowhere have you stated how you intend to power the electric motor. If you are planning on using batteries, these tend to be heavy and bulky, and the high current draw will limit their range.

    The only thing left is a verrry long extension cord.
     
  8. anthonydimare
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    anthonydimare Junior Member

    Curious if you think there isn't a motor developed? Or do you think it's not possible? My intuition was the same for higher speeds.
     
  9. anthonydimare
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    anthonydimare Junior Member

    And NavalSArtichoke from a power standpoint let's assume there's a big enough battery, and that it's not a design constraint. I'm more curious about "what would it take" to make an all electric jet system.
     
  10. HammyMan
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    HammyMan New Member

    Anything is possible theoretically and I do not know of a capable electric motor and battery combo today that could be a commercial success. Corvus battery came close, but no cigar
     
  11. gonzo
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    gonzo Senior Member

    If you are designing an electric drive, a battery or any other energy storage device is you principal constraint. Electing to bypass that makes the rest of the discussion irrelevant.
     
  12. Tiny Turnip
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    Tiny Turnip Senior Member

  13. Frank41
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    Location: Lake Conroe

    Frank41 Junior Member

    Marrying a BLDC motor to a Jet Drive has huge possibilities.
    The motor starts with maximum torque at zero RPM, producing unrivaled hole shot acceleration.
    It also maintains nearly constant torque throughout its power band, efficiently providing good torque at normal operating speed.
    Then, it can rev up to twice its operating RPM. The big question I have at this point in my reviews is how much Hp the pump absorbs at that speed (the RPM at which the motor can no longer overcome the torque required by the pump to maintain that speed). My goal is to have a system that can cruise at 45 to 50 knots and have a top speed of approximately 75 knots. My boat weight will be in the range of 4,000 to 7,000 pounds. Hence, I merely need to find a pump-motor combination that will produce the desired results within my limited budget.
    Now, we all know this is going require lots of stored electrical energy. A few years ago I priced out a battery bank to accomplish this at approximately $50,000. This and the lagging technology slowed my design pace a bit. If I remember correctly those batteries would keep me powered up for 4 hours and take 20 hours to recharge on a 50 KW dock power plug, so I implemented an onboard 35 KW generator.
    The necessary technology is here now and I am resurecting my project.
    I am looking to this forum to help find appropriate pump curves and motor power curves to help arrive at a good design.
     
  14. anthonydimare
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    anthonydimare Junior Member

    That's all correct Frank41. Would love to follow your progress throughout your build. Are you willing to share any details on size, the motor you sourced (and resulting power curve)? Is this a retrofit or are you going completely custom?
    Curious on the capacity of the power-bank your sourced then? I'm sure there are better options available now, at much better prices.

    Please post if you find the forum for pump curves / optimization, I'd love to jump in that as well.

    Best of luck!
     

  15. Frank41
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    Frank41 Junior Member

    The installation is for a planned new build of a welded aluminum trailerable sport-work-fishing boat to sleep 2 comfortably + 1 or 2 not so comfortably.
    LOA = 26' to 30'. Beam = 8.5' or 10'. Yet to be verified, the size of the anticipated motor(s) would be 125 to 250 KW. Running for 4 hours would require a battery capacity of approximately 1,000 KWH.
    Since I'm not all that familiar with Naval Architecture I am going to need some help with determining the power required to achieve the desired operating and top speeds of 50 and 70 mph, respectively.
    I have picked jet drive to minimize draft and maximize speed. I am leaning toward a Hamilton Jet drive for its extreme low speed handling (it can turn on a dime) and its crash stopping ability. I don't see the Intelijet having either of those capabilities.
     
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