Fuel Tank Routing with multiple tanks
12-28-2016, 12:39 PM
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Fuel Tank Routing with multiple tanks
I figure i would touch base with you guys on multiple tank fuel line routing and get some feed back, be it positive, negative or just thoughts on what you would change or improve on the two different setups below. Listed below are, 4 tank single turbine and second, 6 tanks multi turbine.
12-28-2016, 04:43 PM
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That makes sense, funny part about it is that was taken out of the jet central manual on my cheetah, but good point, thank you. the trap I'm using on both systems is the intairco types can you recommend a quality in line filter that will not cause flow issues and yet be serviceable.
Last edited by YOADRIAN; 12-28-2016 at 04:49 PM.
12-28-2016, 08:15 PM
#4
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That makes sense, funny part about it is that was taken out of the jet central manual on my cheetah, but good point, thank you. the trap I'm using on both systems is the intairco types can you recommend a quality in line filter that will not cause flow issues and yet be serviceable.
12-29-2016, 10:45 AM
#5
On the twin turbine set up assuming all the tanks are the same size (or at least tanks 2 and 3 are) I would run 2 and 3 in parallel then on to tank 1, this should cause less "drag" than all three tanks in series. Even if tank 2 or 3 empty slightly unevenly by the time tank 1 is fully depleted it should have easily emptied them both.
I to concur with the earlier comment and would also place the filter after the pump between the tap and upstream of both valves.
I to concur with the earlier comment and would also place the filter after the pump between the tap and upstream of both valves.
Last edited by Mark Vandervelden; 12-29-2016 at 10:49 AM.
12-30-2016, 06:37 AM
#7
One thing I have learned with multi-tank setups is that you have to be very careful about series-connected tanks. The issue comes up on filling more than it does in normal operation, and it has to do with flow resistance in the vent lines when they are filled with fluid. The flow rates on filling are probably 5-10x what we see in operation feeding a turbine so this is when the problem is going to show up. Same could be true for draining too...
As the tanks fill, they "vent" to the next tank in series, which fills, and then "vents" to the next series tank if there is one - or to the taxi tank. With the high flow rates on fuel fill there can be a really large pressure in the tanks closest to the pump and it can cause cracking of hard tanks.
There are two simple ways to address this. First, I would recommend 3/16" lines on all lines in a series setup to minimize flow impedance, and second, I'd consider a variable speed pump to adjust the flow rate after the "closest" tank fills ... at which point you have fluid in the vent lines instead of air.
I saw this for the first time in a Yellow F-15 which has large flat main tanks. I added a wet belly tank in series and once the soft main tanks filled they were inflating like balloons before I stopped the pump. I then did some work with pressure gauges at various points in the fuel system and it was dramatic how much pressure could be built up in the "early" tanks (closest to the pump) when they filled and started flowing liquid thru their vents to the subsequent tanks.
Also keep in mind that the taxi tank is, in effect, the next tank in series so with two mains in series, you'd actually have three in series once you were overflowing into the taxi tank.
Dave
As the tanks fill, they "vent" to the next tank in series, which fills, and then "vents" to the next series tank if there is one - or to the taxi tank. With the high flow rates on fuel fill there can be a really large pressure in the tanks closest to the pump and it can cause cracking of hard tanks.
There are two simple ways to address this. First, I would recommend 3/16" lines on all lines in a series setup to minimize flow impedance, and second, I'd consider a variable speed pump to adjust the flow rate after the "closest" tank fills ... at which point you have fluid in the vent lines instead of air.
I saw this for the first time in a Yellow F-15 which has large flat main tanks. I added a wet belly tank in series and once the soft main tanks filled they were inflating like balloons before I stopped the pump. I then did some work with pressure gauges at various points in the fuel system and it was dramatic how much pressure could be built up in the "early" tanks (closest to the pump) when they filled and started flowing liquid thru their vents to the subsequent tanks.
Also keep in mind that the taxi tank is, in effect, the next tank in series so with two mains in series, you'd actually have three in series once you were overflowing into the taxi tank.
Dave
12-30-2016, 09:56 PM
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The first picture shows the exact tanks that where pulled out and all lines that where used are 3/16 ID and the aircraft was set up with two separate vents from the rear tanks one for each side. All the tanks run along the center of fuse, so any lateral balance issues would be negligible and for the cg concerns the kit was designed with the tank placement at there locations. The line length for each section is the distance from tank to tank. The filling pump has been tuned down not to cause issues while filling. I will check out that pwn speed controller but it would be nice to see how you set that up. The additional setups are listed a/b/c to get some feed back on these setups not including the original posted above. I take it no issues with the 4 tank 1 engine set up?
