1. Raccoon

    Raccoon Member

    Don't you just love that sound? :) And yes, skephu is correct!
     
  2. Graham2001

    Graham2001 Active Member

    Actually it's heat transfer.
     
  3. Trailblazer

    Trailblazer Moderator Staff Member

    As Mick said, the angle hides the gap. But it also foreshortens the view, so to makes the trails look denser and more impressive, as in this image which is often used by chemtrail theorists:

    [​IMG]

    http://www.airliners.net/photo/Emirates/Boeing-777-21H/0718260/
     
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  4. SamBST

    SamBST New Member

    Hmmm... it is a complicated business this thing going on in the fan. Although you correctly point it has to create a low pressure zone in front of the fan (or the air wouldn't get into the engine :)) the design of the intake expands the air before reaching the fan, increasing its pressure. Why? Because the fan works better with slow, high pressure air for subsonic flight. The purpose of the intake (or inlet) is to try to recover the free stream pressure as much as possible, inside the intake.
     
  5. skephu

    skephu Senior Member

    Expanding the air will reduce its pressure, not increase it.
     
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  6. SamBST

    SamBST New Member

    That's why I said it is a complicated business. The shape of the intake makes the fast moving air increase its volume before reaching the fan. As the fast moving air increases its volume, it slows down and increases its static pressure.
     
  7. Mick West

    Mick West Administrator Staff Member

    I think here it's more the fan sucking in the air that reduces the pressure. The shape of the intake in front of the fan is not going to make the air expand - quite the opposite from most cross-sections I've looked at, which show a slight narrowing.

    And when the plane is moving, things will be different again, the engine will be scooping up air at 500mph - which is very different to sucking in air when the plane is not moving at all.
     
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  8. SamBST

    SamBST New Member

    Actually, for subsonic flight, all intakes have a divergent shape: http://soliton.ae.gatech.edu/people/jseitzma/classes/ae4451/subsonic_inlet_sizing2.pdf
     
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  9. Jazzy

    Jazzy Closed Account

    And you can see the internal pressure map showing increasing pressure within the divergence - during normal cruise.
    At takeoff, with increased engine power, this lowers the pressure (and thus the local temperature) sufficiently to induce condensation - if the air is sufficiently humid.
    Happy New Year. :)
     
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  10. SamBST

    SamBST New Member

    A complicated thing is aerodynamics!
     
  11. skephu

    skephu Senior Member

    Here's a shorter version of the long video about HBTFs:

     
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  12. Ray Von Geezer

    Ray Von Geezer Senior Member

    In an interesting development, Max Bliss seems to be taking on Dane Wiginton and Russ Tanner's HBTF claims.

    MaxHBTF.

    https://www.facebook.com/photo.php?...0428768655396.417477.685100395&type=3&theatre

    Ray Von
     
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  13. Trailblazer

    Trailblazer Moderator Staff Member

    And meanwhile Russ has posted exactly this:

    upload_2016-5-26_15-49-40.

    Can we shut Russ and Max in a room with a camera?
     
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  14. Ray Von Geezer

    Ray Von Geezer Senior Member

    Leeds/Bradford is usually sopping wet, but I don't think it's from the jets.

    Putting aside that he's clearly clueless about how combustion produces water, doesn't he realise he basically just "debunked" chemtrails? Similar to Ian Simpson / Look-up.org previously.

    Ray Von
     
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  15. TEEJ

    TEEJ Senior Member

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  16. Trailblazer

    Trailblazer Moderator Staff Member

    Yes, I had just started a thread saying exactly that.
     
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  17. MikeG

    MikeG Senior Member

    Untitled.

    This comment just floored me. Does he take into account, I don't know, altitude, relative humidity, temperature? Common sense? Wow.
     
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  18. David Fraser

    David Fraser Senior Member

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  19. derwoodii

    derwoodii Senior Member

    and clouds, he seems to forgetful about the fluffy white clouds in the sky
     
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  20. Mick West

    Mick West Administrator Staff Member

    And this continues to be an issue with them nearly a year later:
    https://www.facebook.com/mrmaxbliss/posts/10155021271245396
    With some spirited discussion in the comments:
    https://www.facebook.com/mrmaxbliss...0155023653710396&comment_tracking={"tn":"R4"}
     
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  21. Dan Page

    Dan Page Active Member

    Ok, I'm confused, Max is just like Dane, trying to convince everyone there is contrails up there? Has he seen Dane's website? Certainly Dane is spreading lies and disinformation which is what we the rational and non-chemtrail believers are saying. And isn't Dane the "God" of chemtrails and geoengineering? Seems like a case of the pot calling the kettle black. :confused:
     
  22. Trailblazer

    Trailblazer Moderator Staff Member

    I'm confused by that part too. Dane features the "High-bypass turbofans cannot create contrails" idea right on the front page of his website.

    Although, in the past, Dane has gone on record as how to tell the difference between contrails and chemtrails. Consistency isn't a big thing with the chemtrail theory!
     
  23. Mick West

    Mick West Administrator Staff Member

    There's a segment of the chemtrail conspiracy community that think Dane is a "shill" because he think's global warming from CO2 emissions is real.
     
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  24. WeedWhacker

    WeedWhacker Senior Member

    High Bypass Turbo Fan engines indeed can create contrails. This is just basic science.
     
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  25. dlandelle

    dlandelle Member

    I would not like to appear as a member of the "chemtrail conspiracy community" because it sounds ridiculous.
    But if Turbofan produces MORE thrust, with LESS water.
    More efficient, it requires EVEN LESS combustion for same equivalent thrust, so EVEN LESS CO2 and H2O.
    How can this produce MORE condensation with LESS water ?

    I hear the thermal argument, but an argument does not produce water...
     
  26. Mick West

    Mick West Administrator Staff Member

    The exhaust gasses are the same, just a bit cooler. The AMOUNT of exhaust gasses is irrelevant, that just affects the size of the contrail. It's the cooler temperature that makes contrails more frequent.
     
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  27. JFDee

    JFDee Senior Member

    A turbofan does not create less water in relation to the amount of fuel it uses. It burns (converts) the fuel more completely so it may even create a little more vapor than a legacy jet engine - always in relation to the fuel intake.

    The thermal argument is central. The required time for the vapor to cool is shorter so saturation can happen earlier. Thus condensation is more likely to happen before the vapor is 'diluted' with outside air too thinly.
     
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  28. Ray Von Geezer

    Ray Von Geezer Senior Member

    In perfect combustion of a hydrocarbon all that would be produced is CO2 and H2O, the more efficient the combustion process of an engine the closer it gets to complete combustion and the more water (and CO2) it will produce.

    Secondly I think there's a habit, and not just amongst the "chemtrail" crowd, to mistakenly equate "efficiency" only with an engine doing the same amount of work for less fuel burned, probably because most of us are conditioned to think in terms like MPG.

    For applications like a plane, train or truck an engine that can do more work for the same amount of fuel is more desirable than one that can do the same work for less fuel. Both engines are "more efficient" than their predecessor, but the former would bring efficiencies beyond fuel consumption (like being able to carry a 50t load instead of 40t, or 450 passengers instead of 350).

    Basically, more efficient combustion means more water, and "more efficient" doesn't necessarily mean less fuel burned (or water generated).

    Ray Von
     
  29. MikeC

    MikeC Senior Member

    the amount of water produced is directly proportional to the amount of fuel burned

    The high bypass fans use less fuel per unit of thrust - but they produce a LOT more thrust, so use more fuel in total.

    Hence they produce more water.
     
    • Agree Agree x 1
  30. GregMc

    GregMc Senior Member

    Also it might be useful to remember that the thousands of tons of water in a horizon spanning contrail mostly came from the atmosphere itself , not the plane, and the idea that the stuff in a contrail was something carried onboard the plane is a misconception that even debunkers seem to fall into.
    From Knollenberg's papers on ice budget , for a persistent contrail more than 99% of the water making up the trail was already in the sky and didn't come from the plane.

    So the difference in the amount of water created in exhaust between high or low bypass engines is a discrepancy or quibble over less than 1% of the total water in the trail. What's more important as Mick explains earlier is the greater likelihood of the trail being triggered in the first place by the high bypass engine
     
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  31. Bruce Blackfin

    Bruce Blackfin New Member

    Really nice video. I always like these kind of thermodynamics and heat transfer problems. Thanks!
     
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