|
I'm really concerned for your life risk. This is a
very high risk fuel design. Puts your fuel pressure at pump inlet very very
close to the vapor pressure of fuel. This suddenly makes the design sensitive to
a whole bunch of environmental factors.
Ask this question: Millions of automobiles. When
they designed automotive fuel systems, why did every single engineer return fuel
to tank instead of pump inlet? So much more expensive to send to tank.
You can bench test your design and prove how close
it is to failure. Just need to measure fuel pressure at pump inlet, measure pump
temp. Use hair dryer to force pump to higher temp. Put all the numbers in
spreadsheet, then calculate distance between vapor pressure and your readings.
Adjust for worst case, which would be high altitude airport, hot day sitting on
tarmac for 1 hour, heat soaked engine compartment, car fuel containing ethanol.
Marginal designs can fly for years without failure.
This is the nature of failure. Use care, I'm concerned.
-al wick
----- Original Message -----
Sent: Sunday, June 06, 2010 6:47 AM
Subject: [FlyRotary] Re: high/low
pressure pumps question
Hope this helps...
On 6/6/2010 2:21 AM, Todd Bartrim
wrote:
>
> Hi Charlie;
> Hmmmnn, I gotta say a picture (or
drawing) is worth a thousand words.
> Todd (sent on my new-fangled
google phone with a really damn small
> keyboard)
>
>>
On 2010-06-05 8:46 PM, "Charlie England" <ceengland@bellsouth.net
>>
<mailto:ceengland@bellsouth.net>>
wrote:
>>
>> Hi Todd,
>>
>> My thought is
to set up the fuel path thus: fuel source through a T
>> into
injection pumps, through filters, through combining T, through
>>
the regulator(in cockpit), through firewall to engine. The
>>
regulator's bypass port (in the cockpit) would be plumbed just like
>> yours, except no heat exchanger since the bypass fuel would never
see
>> the heat of the engine compartment. The bypass would still T
into the
>> supply to the injection pumps, like your system.
Obviously, a
>> manifold pressure line would be required through the
firewall into
>> the cockpit to the pressure
regulator.
>>
>> My original plan (different injection that
didn't require a return
>> line) was similar to your selector setup:
main tanks feeding stock
>> van's selector, with the 3rd port on it
being fed by a 2nd vans
>> selector to select either of the 2 aux
tanks. No transfer pump would
>> have been required, & no
crossover valve. Failure of the primary
>> valve could have been a
'show stopper', but the newer valves seem to
>> be rock solid
reliable. Going to this system using the gear type
>> pumps
requiring a return line forced re-thinking. Using your idea to
>>
return the bypassed fuel at the pump inlet effectively eliminates the
>> 'return' issue, & tempts me to return to the original fuel
selector
>> layout, with the addition of a Facet boost pump. The
fact that the
>> optical sensors will work looking into the side of
a fuel line (the
>> T), instead of needing them in the tank &
that they still give almost
>> a full minute's warning, is very
encouraging. I'll start looking for
>> a convenient place to mount
them.
>>
>> I hope that Tracy will chime in on how he
plumbed the regulator on
>> his -8.
>>
>> Many
thanks for the extra details.
>>
>>
Charlie
>>
>>
>>
>> On 6/5/2010 12:32 PM,
Todd Bartrim wrote:
>>
>>
>
>> > Hi
Charlie
>> > Not sure I
understand correctly what you mean? Can
you
>> sketch it out quickly?
I'...
>>
>> > *From*: Charlie
England <ceengland@bellsouth.net
>>
<mailto:ceengland@bellsouth.net>
>>
<mailto:Charlie%20England%20%3cceengland@bellsout.
>>
<mailto:Charlie%2520England%2520%253cceengland@bellsout.>..
>>
>>
> *Subject*: [FlyRotary] Re: high/low pressure pumps
question
>> > *Date*: Sat, 05 Jun 2010
08:38:09 -0...
>>
>>
>>
>> --
>>
Homepage: http://www.flyrotary.com/
>>
Archive and UnSub: http://mail.lancaironline.net:81/lists...
>>
--
Homepage: http://www.flyrotary.com/
Archive and
UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html
|