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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.
--
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