[Diy_efi] LP injection

[A6intruder]

What's the freezing temp of LP?  An early post on the LP injection mentioned
injectors freezing and everyone talked about where the water comes from.  Is
it possible an injector of liquid LP would have the LP freeze in it?

When I was in college our aero lab loved to run a "ram jet" in the wind
tunnel.  They could only run 3-4 minutes because the LP in the two LARGE
tanks froze solid on the top surface of the liquid (it must have been a top
draw).  Point is LP can freeze solid too.  'As an injector sprays the liquid
LP all the heat drawn into the the LP spray could cause the liquid in the
injector to freeze?

???

Daniel R. Nicoson
Equipment Exchange Company
Phone:  (814) 774-0888
Fax:      (814) 774-0880

-----Original Message-----
From: diy_efi-admin at diy-efi.org [mailto:diy_efi-admin at diy-efi.org]On Behalf
Of Bill Washington
Sent: Tuesday, November 19, 2002 7:00 PM
To: diy_efi at diy-efi.org
Subject: [Diy_efi] Re: Diy_efi digest, Vol 1 #363 - 9 msgs

Gents,
    I have not tried it, but am only relating what was said by some fuel
injection professionals during a presentation at our car club.
I suspect that since injectors are designed to work at ambient temp and
upwards, the variety of materials used in the injectors are such that
the differential rates of thermal expansion/contraction are designed for
that temperature range, not for the -20 to -40Deg Celcius that would be
experienced in injecting LPG, when there may be mechanical seizure due
to differential contraction.
    1. Remember that these are precision devices, therefore the
tolerances are very close, so only a very small differential contraction
in the wrong direction would be necessary to seize up the injector.
    2. In injecting LPG it MUST be injected as a liquid to achieve any
consistency in metering with existing injectors which are all designed
to meter liquids.
To inject it as a gas I suspect that the injector would have to be a
radically different design.With a liquid a slight change in feed
pressure will affect only the flow rate, whereas with a gas a slight
change in pressure affects density and flow rate, the pressure becomes
much more critical in trying to achieve a known metered volume of fuel!

Message: 7
Date: Sun, 17 Nov 2002 21:58:52 -0500
To: diy_efi at diy-efi.org
From: sy2th <sy2th at direcway.com>
Subject: Re: [Diy_efi] LPG injection
Reply-To: diy_efi at diy-efi.org

Well, maybe I need correcting also, but that makes absolutely NO sense to
me.  "Freeze" meaning ices up?  Where does the water come from?  It would
have to be in the gas for that to happen, and lots of it.  Nitrous comes
out of the nozzle every bit as cold as propane, never heard of any
'freezing' problems.  The LPG systems I've seen draw vapor from the top of
the cylinder, not liquid from the bottom as nitrous systems do, so what
gets cold is mainly the tank & the delivery line.  Remove the nozzle from a
propane torch & open it, aimed @ your hand - not real cold at all, but the
tank chills.  Now, invert the tank, so's liquid comes out - - bit of a
different situation, no?  Somehow, I don't think so, Al.....

Barry - Sy#26  -  (but, hey, I'm no expert.....)
Bangor, MI

At 10:19 AM 11/18/02 +1100, you wrote:

>>Glynne,
>>         I stand to be corrected, but from what I understand there is one
>> major hurdle which has dogged the concept of LPG injection. And that is
>> the "Latent Heat of Vaporisation" of the LPG. The reason is that liquid
>> fuels are injected as microfine droplets, but still a liquid however when
>> you try to inject LPG it submilates, IE it turns directly from a liquid
>> to a gas. To do this it absorbs heat from the surounding structure(metal,
>> air, etc) - large amounts of heat - much more localised cooling than the
>> waste heat into the area from the combustion chambers - and tends to
>> freeze the injector - literally freeze it solid (either open or closed!)
>> - thus end of control, BIG problems! This problem may have been solved,
>> but to my knowledge has not yet been. This is obviously a much more
>> fundamental issue to resolve before considering an ECU!
>>Regards
>>Bill W
>
>



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