Volumetric flow rate for jet fuel
Volumetric flow rate for jet fuel
(OP)
We are a group of C-130 flight engineers trying to determine the amount of fuel that can be transferred in a manner not covered in the operations manual.
We need to determine a GPM or GPH for fuel flow into a tank.
The pipe length is 3 feet, the tube is .5 ID 6061 AL, Fluid density is .03 lbs/gal (JP5), Kinematic viscosity is 8.5mm/2/s, pressure is 40 psi from pump and line is open to tank with no back pressure.
I have tried some online calculators but lack the true engineering back ground to be confident in the result. Any help would be greatly appreciated.
TIA, Rob130
We need to determine a GPM or GPH for fuel flow into a tank.
The pipe length is 3 feet, the tube is .5 ID 6061 AL, Fluid density is .03 lbs/gal (JP5), Kinematic viscosity is 8.5mm/2/s, pressure is 40 psi from pump and line is open to tank with no back pressure.
I have tried some online calculators but lack the true engineering back ground to be confident in the result. Any help would be greatly appreciated.
TIA, Rob130





RE: Volumetric flow rate for jet fuel
Your density data is wrong. JP5 would have a density of around 6.7 lb/USgal (SG=0.8).
If the ID is 0.5 inches then you will get a flow of around 28 USGPM. If the ID is 0.5 feet then the flow would be 6000 USGPM.
Both of these calculations assume that the piping on the suction side of the pipe is not a restriction, and the pump would continue to supply 40 psi at the calculated flows.
regards
Katmar
RE: Volumetric flow rate for jet fuel
BTW, density for jet 5 is .788-.845 kg/L or nominally 6.75 #/gal.
DB
RE: Volumetric flow rate for jet fuel
DB
RE: Volumetric flow rate for jet fuel
BTW, I see I made a typo in the last paragraph. It should of course read
"Both of these calculations assume that the piping on the suction side of the pump is not a restriction, and the pump would continue to supply 40 psi at the calculated flows."
katmar
RE: Volumetric flow rate for jet fuel
I made another mistake, the tube is .5 in but the fitting the fuel passes thru into the tank is .375 in.
The pump is centrifugal pump with a rated output of 40 psi no flow and 27,400 gph at 12 psi.
Assume the only demand on the pump is the .5 tube and fuel passing trhu the .375 in fitting, fuel being pumped into the airspace above the fuel in an unpressurized tank.
RE: Volumetric flow rate for jet fuel
Anyway, I'm guessing the two points you gave us are the extremes on the pump's curve, i.e., shut off and runout? For a pump capable of that performance to discharge into this small a opening, my guess is that you'll be operating way way way closer to the 40 psi and no flow end than to the other, in which case you probably won't move enough product thru the pump to keep it from overheating. It sounds like you're working on a real worst case scenario kind of effort here. My gut reaction is that it'll break something before it can do you any good.
Like I said though, I'm electrical and the real pipe and pump guys may have some tricks of the trade I don't know about.
DB
RE: Volumetric flow rate for jet fuel
We are trying to determine a volumetric flow thru a .375 in. open line into a fuel tank.
It is one of those trivia questions/C-130 urban lengends dealing with the question of how much fuel you can transfer, inflight, using the 40psi out put of a fuel pump, thru an open valve designed to bleed residual pressure from the crossfeed fuel manifold and into the #2 fuel tank thru a .375 in. ID bulkhead fitting.
The vavle is designed to be open only while the primer valve switch is depressed, and closes when the valve switch is released. The valve orifice is 1 inch and is not the restriction. If, while the switch is depressed you open the circuit to the valve, it will remain in the open position and any fuel in the manifold will flow into the #2 tank.
I would like to be able to inform our instructors and students as to the rate, in pph/ppm, they could expect to see in this scenario.
Thanks again, Rob130
RE: Volumetric flow rate for jet fuel
To simplify it a little, if you had 40 psi behind a 0.5" hole in a bulkhead, you'd move about 31 gpm. Change the hole to 0.375 and flow drops to the 16-17 gpm ballpark. I don't think we're too far off for the purpose of proving or busting an "urban legend." I wouldn't try to fly my numbers over any mountains though.
So, what's the story that's going around? What kind of rates have supposedly been seen?
DB
RE: Volumetric flow rate for jet fuel
RE: Volumetric flow rate for jet fuel
I agree with blackwed - if I was flying in that plane I would much rather know that someone had measured the actual flow than rely on my own calcs!
RE: Volumetric flow rate for jet fuel
How much flow you get though the cross feed primer valve would depend on how much excess flow you have in the pump(s). But using that valve could cause some problems. Take a situation where number one pump was weak, but still meets tests, and could barely feed its engine, then you open number one cross feed valve and primer valve. This would cause number one engine to be starved of fuel and can do damage to engine.
The primer valve was designed to bleed the cross feed manifold after draining and pressure tests. What you are planning to do is not approved; otherwise it would be in the manuals. If something should go wrong there would be a lot of questions asked, especially if the instructors are teaching unapproved practices to students.
RE: Volumetric flow rate for jet fuel
We do not teach, endorse or recommend this procedure. As you say, if it is not in the Operators Manual we do not teach it as a procedure or "technique".
This information will be used to discourage engineers from performing a common though unapproved procedure. After extened ground operation with the APU running (fuel supplied by #2 tank) you can get an unbalanced fuel load.
Engineers will hit the prime and pull CB to put fuel back in #2 to balance fuel. So what happens when they forget about it during ground ops? The open prime valve will continue to fill the tank at a rate faster than burn off, the topping valves are not in play and the excess flow into the tank can fill the tanks 3% airspace and cause the tank to vent on the ground.
AVIAT "But using that valve could cause some problems. Take a situation where number one pump was weak, but still meets tests, and could barely feed its engine, then you open number one cross feed valve and primer valve. This would cause number one engine to be starved of fuel and can do damage to engine."
Very true, but the engine fuel low pressure warning light would illuminate and the pumps are designed to gravity feed so the engineer would see this (hopefully). The real problem would be if the pump failed, air would be drawn into the crossfeed manifold with the prime valve open, the engine pumps would suck air and not fuel! Good/Bad Scale - Bad.
I want to try and keep people from outsmarting themselves when they think they know how something works but really don't!
RE: Volumetric flow rate for jet fuel
You could do it on more that one airplane and average them. Density changes with temperature. If you have a wide range of temperatures you may want to compensate for that.
RE: Volumetric flow rate for jet fuel