Proportional Air Inlet Control

Discussion in 'OnBoard Electronics & Controls' started by steve123, Dec 28, 2014.

  1. steve123
    Joined: Dec 2014
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    Location: China

    steve123 Junior Member

    Hi,
    I have a customer requesting "Engine Air Inlet Fans proportionately conrolled by engine rpm".
    Anyone help on this please ?
     
  2. Poida
    Joined: Apr 2006
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    Location: Australia

    Poida Senior Member

    That is how the fans were operating in the "old Days."

    That fan ran off the crank shaft, the faster the engine the faster the fan went.

    Then someone decided it was better to have fans running in relation to heat.

    It would be interesting to know the application, ie what sort of engine is going where.
     
  3. steve123
    Joined: Dec 2014
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    Location: China

    steve123 Junior Member

    Hi,
    Engines as yet undecided but its for fast ferry catermeran and a requirement in basic spec.
     
  4. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    The easiest solution is a mechanical linkage to the engine. For example, a belt driven fan.
     
  5. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    You can kiss off some HP to do this, but the way to go is a thermostatically controlled fan(s). It's fool proof, the belt can't break, the fan can be a whole light lighter, the fan can be placed in a more convenient location, etc. Frankly lots of reasons to use the temperature control, electric fan, compared to a mechanical setup. Most automotive applications now employ the lighter and more reliable electric cooling fans, for the same reasons. Lastly, there's no sound reason to have the fan governed by engine RPM, in spite what a client might insist on. There's an efficient speed the fan needs to run at, so the setup should insure this. Tell the client he's incorrect and it's time to step into the 21st century, in this regard.
     
  6. steve123
    Joined: Dec 2014
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    steve123 Junior Member

    PAR,
    Thankyou..you have just supported what i told my colleagues.
     
  7. whitepointer23

    whitepointer23 Previous Member

    I run a Horton fan on the cummins m11 in my truck, they have an air operated clutch and thermoswitch or ecu driver to engage at the correct temp. brilliant fan but when it cuts in you feel it suck the power . probably no advantage in a constant rev situation like a ferry I guess.
     
  8. CDK
    Joined: Aug 2007
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    Location: Adriatic sea

    CDK retired engineer

    If the client wants fan speed proportional to rpm that's what he should get; the customer is always right!

    China produces millions of proportionally controlled fans for computer applications. You need something more powerful, based on the same principle. A $25 Arduino microcontroller and some Mosfet output bricks is the hardware you need. The software is freeware on the internet, all you need is someone who puts 2 and 2 together.
    The controller reads an rpm signal, looks up the corresponding fan speed in a table and outputs a PWM signal to the fans.
     
  9. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    The customer is rarely right and this is the very reason they've come to a professional. It's important to remind clients of this simple fact. I talk clients out of stuff they "think" they want all the time. Reasonable and logical debate about the "issue" in question is usually all it takes and most of the time the client appreciates the frank conversation, especially if you're clever enough to tie it with some cost savings, which is simply an old marketing technique.
     

  10. AndySGray
    Joined: Jun 2014
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    Location: Cayman

    AndySGray Senior Member

    Strictly speaking both methods are proportionaly linked to engine RPM.

    Measuring temperature has an advantage that it also compensates for ambient conditions, variations in fuel quality and, importantly, engine load among others. BUT there is a significant latency or delay.

    It has found favour in automotive applications as the vehicle speed is actually doing the same job as a fan - if you're travelling at 50, the aerodynamic forces are sucking air through the radiator at speeds greater than that, so the fan is redundant and can be turned off. You really only need the fan in slow traffic in summer.

    Remember the previous solution with the viscous coupled fans - they turned at about engine speed when idle but slipped as rev's increased, this would not have been good in marine applications.

    The engine rev's method has much less delay but doesn't compensate for load or that you may be trying to 'warm up' the engine(s) first thing on a cold morning, though if engine power is dramatically ramped up the fan will react much faster.

    :idea:
    That said most marine cooling is not related to air flow anyway...
    So perhaps the customer was thinking more about the air charge for combustion ?
    :idea:

    Much more efficient to be pulling cool external air from the outside of the vessel than have the engine suck warm air from the engine room...
    THAT is directly linked to rpm. (with some compensation for Turbo boost pressure with increasing revs)

    CDK's solution is inexpensive and smart - additional sensors can be added (fuel flow and ambient temp.) and it could even adjust itself to tune to operating conditions of the vessel much as a fuel injection ECU does on a car.

    :cool:
     
    1 person likes this.
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