Flight-Testing of the FAA Onboard Inert Gas Generation System on ...

APPENDIX D—CALCULATION OF BLEED AIR CONSUMPTION
Given bleed airflow Q &
Bleed,
NEA flow QNEA , and Permeate (OEA) flow Q for a given ASM,
intuitively <strong>the</strong> following equation applies:
&
&
Perm
or,
Q&
= Q&
+
Bleed
Perm
NEA
Q&
= Q&
− Q&
Also, a mole balance <strong>of</strong> oxygen for <strong>the</strong> same ASM yields <strong>the</strong> following equation.
Bleed
NEA
Q&
Perm
Moles <strong>of</strong> O2 in Air = Moles <strong>of</strong> O2 in NEA + Moles <strong>of</strong> O2 in Permeate
& = &
] ⋅ Q&
( 0.
21)
QBleed
[ O 2 ] NEA ⋅ QNEA
+ [ O 2
Where: [ O 2 ] NEA = NEA Oxygen Concentration
O ] = OEA Oxygen Concentration
[ 2
Perm
Combining equations 1 and 2 and solving for QBleed gives: &
Perm
Perm
0.
21)
Q&
= [ O ] ⋅ Q&
+ [ O ] ⋅ ( Q&
− Q&
( Bleed
2 NEA NEA
2 Perm Bleed NEA
& = &
&
] ⋅Q&
( 0.
21)
QBleed
[ O2
] NEA ⋅QNEA
+ [ O2
] Perm ⋅QBleed
− [ O2
& − &
&
] ⋅Q&
( 0.
21)
QBleed
[ O2]
Perm⋅
QBleed
= [ O2]
NEA⋅
QNEA
− [ O2
Q& Bleed ⋅(
0.
21−
[ O ] Perm)
= Q&
NEA ⋅([
O2
] NEA − [ O2
]
Perm
2 Perm
)
Perm
NEA
)
NEA
(D-1)
(D-2)
([ O2]
NEA −[
O2]
Perm)
QBleed
= QNEA⋅
( 0.
21−[
O ] )
& & (D-3)
2 Perm
This equation allows for <strong>the</strong> calculation <strong>of</strong> <strong>the</strong> bleed air consumed by an ASM based inerting
system given <strong>the</strong> NEA flow and purity as well as <strong>the</strong> oxygen concentration <strong>of</strong> <strong>the</strong> permeate.
D-1/D-2