|
|
An old Smokey Yunick NASCAR trick. :-)
Charlie
(If there's a lesson from the past decade, it might be that
over-reaction to mistaken of falsified problems can be very
counterproductive....)
On 08/18/2011 02:18 PM, Bobby J. Hughes wrote:
That would be considered extended
range
tanks. J
From: Rotary motors in
aircraft [mailto:flyrotary@lancaironline.net] On
Behalf Of Mark Steitle
Sent:
Thursday, August 18, 2011
12:14 PM
To:
Rotary motors in aircraft
Subject:
[FlyRotary] Re: Dennis
Haverlah Fuel System...or any others, for that
matter.
Kelly,
You can use a -16, but
you'll still be limited by the inlet/outlet size
of the Andair valve. I'm using -8 supply with a -6
return. These
were upsized from original -6/-4 called for in the
plans.
Mark
On Thu, Aug
18, 2011 at 12:37 PM, Kelly Troyer <keltro@att.net>
wrote:
Sounds like fuel line to the EFI pump
(external pump) needs to be about AN-8 or
even
AN-10
instead of the typical AN-6 used by
most............
Kelly
Troyer
"DYKE
DELTA
JD2"
(Eventually)
"13B
ROTARY"_ Engine
"RWS"_RD1C/EC2/EM2
"MISTRAL"_Backplate/Oil Manifold
"TURBONETICS"_TO4E50
Turbo
From: Al Wick <alwick@juno.com>
Sent: Thursday, August
18,
2011 12:15 PM
Subject:
[FlyRotary] Re: Dennis
Haverlah Fuel System...or any others,
for that matter.
< Mark's
problem can best be described as an
"Air
<Lock"
in the pressure line
I'd
describe it as not having "wet fuel
inlet". When you turn that fuel
valve "on" the first time, if inlet
gets wet, you've nailed an
important design characteristic.
You can
simulate this with clear hose and
water. Seal off one end of hose. No
air leaks
allowed. Then pour water in other
end. If water makes it to closed
end, you've
got a good design. It's that simple.
You'll
notice that small diam hose doesn't
behave the same. What happens when I
add
filter to the hose? What if I put a
loop in the line? You are asking the
air at
capped end to displace. The air has
to be able to move toward open end
of tube.
Play with it, pretty interesting.
If your
plumbing is already done, you can
tape clear hose to plumbing and do
the test
with water.
All you
are doing is converting theory to
facts. Important concept.
-----
Original Message -----
Sent: Wednesday,
August 17,
2011 12:40 PM
Subject:
[FlyRotary] Dennis Haverlah Fuel
System...or any others, for that
matter.
Al ,
Mark , Ernest and All,
Perhaps a name change for the
problem is in
order.............Instead of
an
actual
"Fuel Vapor Lock" Mark's problem can
best be described as an
"Air
Lock"
in the pressure line (Or Air
Entrapment Lock)..........Ernest's
problem
of
injectors that leak down fuel (into
the manifold or the engine with
potential
flooding
or the fire hazard of dripping fuel
in the cowl) has the same solution
(bypass
orifice) either external or internal
to the regulator.......Both problems
no
matter what you call them can be
cured with the same
solution.............
Al as for the leaky injectors it
would be great if these things did
not
wear
over
time but they do eventually become
unable to hold pressure and will
exhibit
leak-down at some
rate........Unfortunately the Rotary
engine is much
more
prone to flooding and hard starting
if this fuel ends up in the Rotor
chamber..........If
the
primary injectors are left in their
stock positions and are
leaky
this is a direct route to the
Rotor............The secondary
injectors may
or may
not be a problem depending position
and/or manifold design...........
The
bottom line is both potential
problems can be averted with a
simple
bypass
orifice.............As for an actual
"Fuel Vapor Lock" as you say
this is
a
different problem and can be
addressed by careful attention to
fuel pump
positioning
(external or in-tank) ,supply tube
(or hose) size, low restriction
filters
to pump inlet, heat shielding if
appropriate,
etc................IMHO
Kelly
Troyer
"DYKE
DELTA
JD2" (Eventually)
"13B
ROTARY"_
Engine
"RWS"_RD1C/EC2/EM2
"MISTRAL"_Backplate/Oil Manifold
"TURBONETICS"_TO4E50
Turbo
Sent:
Wednesday, August 17,
2011 1:46 PM
Subject:
[FlyRotary] Re: Dennis
Haverlah Fuel System...or any
others, for that matter.
You wrote,"You also test
it without the
bleed line?"
Yes, the test
led to the search for a
solution. You can see the
"bypass
circuit" on Egg's fuel system
schematic at http://www.eggenfellneraircraft.com/Manual-Updates/EarlyManualFuel.html.
This
is what I incorporated into
my fuel system, and it solved
the problem. Its been quite a
few years now, but I may still
have some of the posts on the
Eggenfellner list that
occurred in
search for this as the final
solution.
You wrote,"FWIW,
everything you
describe is not vapor
lock, has nothing to
do with
vapor lock."
As I said,
I'm not sure if my condition
fits the definition of "vapor
lock", but
that's what someone labeled
it, and it stuck. The problem
is that EFI
pumps don't draw or push air
very well. So, if the flowing
fuel is
replaced by air due to an
empty tank, the pump keeps
running, but essentially stops
pumping fuel. With a 40#
spring in the downstream
circuit, it is
virtually impossible for the
pump to pass the air even
though the
selector valve has been
swiched to the full tank. I
would agree that the
fuel injectors should be able
to pass the air, provided the
prop is still
turning. (This was not the
case with my ground test.) The
bypass circuit
ensures that flow will be
restored as soon as the
bubble passes
through the pump and the fuel
pump regains its prime.
<I
would
think that a
well-designed fuel
system with the
pumps located as low
as
possible
Instead
of speculations, you can
actually measure how
good it is. A pump,
clear fuel lines,
and water instead of
fuel. Pinch fuel line
with pliers to increase
pressure
drop. Watch bubbles
come out of solution.
Hear the rattle from
pump due
to it's inability to
flow air.
If you
also put a pressure gage
on pump inlet, you can
see how fine fuel filter
increases risk. You can
see how small diameter
tubing increases risk,
heat,
head pressure, etc etc.
<the
result
of a forced landing
Egg had
one
forced landing. It was
caused by vapor lock.
Absolutely NOTHING to do
with the
lack of bleed line. A
day later, Jan made it
to the crash site. Pump
would not
flow fuel until he
cracked the line loose.
This is simply because
the inlet to
pumps was not wet. He
did not understand this.
He just reacted to
symptoms.
Nothing to do with vapor
lock. Remember, this was
crash site. Who knows
what
attitude plane was at.
As I described, if you
screwed up your plumbing
from
tank to pump, then pump
is not self priming.
<tested
this
system on the ground
and it works as
advertized
You also
test
it without the bleed
line?
FWIW,
everything you describe
is not vapor lock, has
nothing to do with vapor
lock.
-----
Original Message
-----
Sent:
Wednesday, August
17,
2011 9:19 AM
Subject:
[FlyRotary] Re:
Dennis Haverlah
Fuel System...or
any others, for
that matter.
I would
think
that a
well-designed fuel
system with the
pumps located as
low as
possible, in
a cool area, and a
return
system should not
be
troubled with
vapor
locking. Although
I guess it could
happen in Death
Valley
in August if the
a/c is left out in
the
sun for 8 hours,
and running auto
gas. So far, I
haven't had any
problem
here in Texas
(temps 105*
today).
My purpose
for installing the
bypass circuit was
more critical to
safe flight. (The
solution was the
result of a forced
landing, or
two, in an
Eggenfellner
Subaru
installation.)
During ground
runs, using a
5-gallon
can, I found that
the efi fuel pumps
could not restore
pressure once the
tank
had been allowed
to run dry. When
this occurred, the
EFI
pump would suck a
big slug of air
into the inlet
side of the pump,
loose
pressure, and
being unable to
build psi equal to
the pressure
regulator
setting, it would
stop pumping fuel
(vapor lock). The
only way to
restore
operation was to
crack open the
system downstream
of the pump until
the slug of
air could be
passed on through
the fuel
pump. Not sure
this meets
your definiton of
"vapor lock", but
I think it does,
but for a
different reason
than fuel vapor
pressure.
I have
tested
this system on the
ground and it
works as
advertized. If
the tank runs
dry, switched to a
full tank, the efi
pump will restore
pressure to the
system
within a few
seconds. I urge
all builders to
run this test on
their fuel
system to
determine whether
or not their pumps
are able to
restore pressure
after running a
tank dry. Or,
just don't ever
run a tank dry.
On Wed,
Aug
17, 2011 at 10:22
AM, Ernest
Christley <echristley@att.net>
wrote:
Al Wick
wrote:
I'm
really
concerned for
some of these
fuel designs.
The fuel bleed
has nothing to
do with
vapor lock.
Virtually no
effect at all.
I don't
know
why others are
doing it, but for
me, the bleed has
nothing at all to
do with
vapor lock. Some
conversations have
been mixed
together, so I can
see how
that could be the
impression. The
point of the
pressure bleed is
to bleed
off the pressure
after shutdown.
I have a strong,
positive head
pressure going
into my pumps.
They, and
the regulator, are
about 8" directly
below the tank.
Excess fuel
goes back to the
opposite side of
the tank from the
pickup, and a
single line
goes forward to
feed the
injectors. The
fuel lines are
arranged such that
heat soaking the
lines to the point
of boiling the gas
will push liquid
fuel
down hill and
behind the
firewall,
isolating the
gaseous gas with
its heat at
the top of the
line. Turning the
pumps on will
pressurize the
line to 55psi,
returning most of
the gaseous fuel
back to a liquid
state. The ECM is
programmed for a
longer clearing
pulse on hot
start.
The point of the
bleed is to allow
fuel to move back
to the tank. I
had
the issue of a the
pressurized lines
being perfectly
sealed. The
pressurized fuel
was finding the
path of least
resistance out,
which just
happened to be out
the injector and
into the intake
manifold where it
sat as a
little puddle.
Heat soaking the
lines would not
push liquid fuel
downhill
and back behind
the firewall. It
would push more
fuel into the
manifold.
A puddle of gas
sitting in a
composite
manifold, just
above a hot
exhaust
stack is just bad
mojo. A poorly
sealed regulator
allows the
pressure to
bleed off in about
5 seconds (give or
take), isolating
the hot fuel in
front of
the firewall, and
keeping the rest
cool and out of
the intake
manifold.
Got nuthin' to do
with vapor lock.
--
Homepage: http://www.flyrotary.com/
Archive and UnSub:
http://mail.lancaironline.net:81/lists/flyrotary/List.html
|
|