Tank Inerting
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In civilian aviation, tank inerting is normally about pumping nitrogen into the center wing tank to reduce the possibility of a spark in the tank from causing an ‘explosion’ in an empty fuel tank.
But in the F16 its about fuel tank pressurization, something completely different to civilian aviation terms.
Any comments on it?
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good luck Brother other than the nitrogen mixed into my Guinness I cannot comment further
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F-16 use a 13lbs halon tank to inert its fuel tanks. The bottle is located on the left wheel well and it is only filled with Halon during combat.
Type “F-16 halon tank inerting” in Google and you will find some reading material.From F-16.net
http://www.f-16.net/forum/viewtopic.php?p=18711 -
Thanks for the quick reply.
So ‘tank inerting’ is the same thing, they reduce the possibility of tank ‘explosions’.But in BMS -1 it’s made to sound as though the tank inerting switch is related to fuel tank pressurization. That’s where I was confused.
Anyway, it’s a N/I item in BMS, but nice to know… -
The pressure in the tanks change when tank inerting, but it is not the way tanks are inert. You can find more info on the -1 manual available online. You should be able to find it in Google.
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the pilot uses the inert switch to depressurize the tanks for air-air refueling.
The external tanks feed with pressure. internal tanks have fuel pumps and/or gravity feed. -
the pilot uses the inert switch to depressurize the tanks for air-air refueling.
The external tanks feed with pressure. internal tanks have fuel pumps and/or gravity feed.That is also incorrect, the tank have a lower pressure when the IFR door is open. Also, all tank use pressure among other things to feed fuel.
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External tanks are the only tanks that require tank pressure to feed.
I herd the internal tank will feed without the boost pumps or pressurize with loss of performance.So if the inert switch is off, the tanks are pressurized with (bleed?) air pressure?
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External tanks are the only tanks that require tank pressure to feed.
I herd the internal tank will feed without the boost pumps or pressurize with loss of performance.So if the inert switch is off, the tanks are pressurized with (bleed?) air pressure?
Yes, external tanks are the only ones that require air pressure to transfer, but internal tanks also use pressure to transfer fuel. Internal tanks don’t need it as external tanks but use pressure non the less. With tank inerting on, tanks are still pressurize at a lower pressure, same with if the in flight refueling (IFR) door open. At any case, the tanks are pressurize by the by the Environmental Control System (ECS)
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sure, under normal condition the tanks are under pressure. However, if the tank is ruptured by a bullet and does not explode, because of inert gases, the internal tanks will still feed without pressure. from what I heard.
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Yes, they will transfer what ever does not leak out, they are not self sealing.
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I always thought the inert tank switch removed the oxygen by using a bottle of inert gas to pressurize the tanks. This doesn’t seem to be the case.
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Not so much as remove as displace some and mix with. It’s a two part process that changes the pressure schedule on the internal tanks (F-1, A-1, CFT, and L R wing internal, but not F-2) and meters Halon to those same tanks. The combat schedule is a lower pressure schedule. The other part is the discharge of Halon (20-30s) about 50% of the charge and and a slow trickle over the next several minutes. The agent is vented overboard just as the fuel tank headspace is of air/vapor.
One positive of the reduced internal tank pressure facilitates feed from externals. One downside is fuel boils off more readily at lower pressures.
The fuel system is a combination of electrical pump, fluid pressures, and gravity. Fuel still flows in the absence of some of these mechanisms but at a reduced rate or in reduced flight regimes. You can test this by during the ENG FEED knob to off which disables all electric pumps and opening the AAR door (air source OFF too for giggles) and the engine will still run. That’s not gravity only since the FFP is hydraulically powered but that’s only the pumps from the reserve tanks to the engine. The other internal tanks should still continue to feed the reserves.
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Ok, there is a init process. After init process are the tank pressurize with air or Halon?
I don’t know what would cause the fuel to heat up and boil off while in the tanks. The fuel is pre-heated before it goes to the engine. <shrug>I’m not sure the FFP is a pump or act like pump when it;s fuel inlet is not pressurized. It seem to be the Jesus bolt of the system.
The internal tank are linked with feed and vent lines. I can’t see pressure pushing fuel thru the feed lines with a vent line. No pumps, that leaves gravity. However, I’ve seen the unabridged fuel system schematic and it’s not your daddy’s Evinrude fuel system. It is unbelievable how many bits and pieces it. has.</shrug>
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Ok, there is a init process. After init process are the tank pressurize with air or Halon?
Tanks are pressures with air, halon is added to the mix if the Tank inerting switch is move to on.
I don’t know what would cause the fuel to heat up and boil off while in the tanks. The fuel is pre-heated before it goes to the engine.
Is not heat that cause fuel to boil but lack of pressure, like water boiling at room temperature if pressure is low enough
I’m not sure the FFP is a pump or act like pump when it;s fuel inlet is not pressurized. It seem to be the Jesus bolt of the system.
FFP takes fuel from reservoirs and helps maintain balance and a positive feed to the engine. If it fails they are bypass tubing.
The internal tank are linked with feed and vent lines. I can’t see pressure pushing fuel thru the feed lines with a vent line. No pumps, that leaves gravity. However, I’ve seen the unabridged fuel system schematic and it’s not your daddy’s Evinrude fuel system. It is unbelievable how many bits and pieces it. has.
Not sure if I understand.
Some info
As fuel is taken from
the reservoirs, it is replaced through a siphon, vent, bleed air
pressurization system; by the other tanks in the system; right
wing to F1 to F2 to forward reservoir; and left wing to A1 to
aft reservoir, respectively. A power transfer system is also
included to scavenge the tanks to minimize unusable fuel and
as a redundancy to the siphoning system. -
It’s a combination of temperature and pressure that determines boiling point. The higher you the colder it gets. Pressure and temperature go down when climbing to higher altitude. I didn’t know that was a problem.
thats what I figured on the FFP. there are pumps after the FFP, on the engine;s fuel injection system. one engine type has a bleed air turbine powered fuel pump for the after burner.
As fuel is taken from
the reservoirs, it is replaced through a siphon, vent, bleed air
pressurization system; by the other tanks in the system; right
wing to F1 to F2 to forward reservoir; and left wing to A1 to
aft reservoir, respectively. A power transfer system is also
included to scavenge the tanks to minimize unusable fuel and
as a redundancy to the siphoning system.I assume the power transfer system is a pump that continue to pump fuel into the next tank and when the tank is full their is a return line. And also pump provides more fuel flow when demanded than with the siphoning system can alone.
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Guys, you can’t burn a liquid. It won’t happen. What burns is the vapor or “gas” that comes from that liquid. If you were to make a spark within a filled fuel container - not drop it in, since the fumes would definately ignite - you should see no reaction. Again, as long as you didn’t find an air pocket. It’s when you make the fuel mix with the air that you produce that explosion that takes you down. And yes, now is when I expect someone to have multiple examples to prove me wrong.
To the colder argument making less pressure, yes. If you cool a compressed gas it will decrease in pressure. And if you heat it up it will increase in pressure. If you vent that gas you reduce both the pressure and the temperature of the gas that comes out. For those of us who don’t fully understand boiling point vs. pressure on a liquid, the lower the pressure of a closed system the lower the boiling point of that liquid in that system. As an example, water normally boils at 100C/212F at sea level. This would be at the roughly assumed normal pressure at sea level of 101.32 kPa / 14.7 psi. If you were to keep the water at the same temperature but reduced the pressure it would begin to boil at some point. If you want a painful demonstration ask someone about the bends.
Why should anyone care about the pressure in the system or the boiling point? Hiccups in power are not pleasant, and no fuel to the engine - either due to the tanks being empty or not - means the engine stops working. How long can you fly a brick? Keep in mind, you only have that backup generator for ~ 7 mins.
Sorry for going long winded again.
-Babite -
Must of been a problem for SR-71 devs.
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you can boil a liquid simply by reducing the pressure upon it, applying no external heat. the molecular motion within the fluid itself will cause the reaction. fuels and chemicals often more easily than water. i think that point is being missed.
Must of been a problem for SR-71 devs.
it was.
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you can boil a liquid simply by reducing the pressure upon it, applying no external heat. the molecular motion within the fluid itself will cause the reaction. fuels and chemicals often more easily than water. i think that point is being missed.
We use a vacuum chamber to remove air from epoxies in the composite lab. The epoxies boiled but it was air bubbles that increased in volume and floated to the surface. I would say the epoxy was not turning into a gas.
many liquids will vaporize at ambient temps and pressures. Higher temps and less pressure can change the rate.
I’m kind of curious about how much fuel loss is due to venting to maintain correct tank pressure. Tank pressure to high and something breaks.
If you want a painful demonstration ask someone about the bends
The Bends has nothing to do with vaporizing anything or changing liquid to a gas. Bends has to do with nitrogen saturation in the bones or joint. The body can retain more nitrogen under pressure. During a rapid change in pressure the nitrogen bubbles increase in size and cause problems, iirc.
