fuel tank protection research at nasa grc clarence t. chang nasa glenn research center cleveland,...
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Fuel Tank Protection Research at NASA GRC
Clarence T. ChangNASA Glenn Research Center
Cleveland, Ohio 44135USA
INTERNATIONAL AIRCRAFT SYSTEMS FIRE PROTECTION WORKING GROUP MEETING
November 1-2, 2005Atlantic City, New Jersey
USA
Adaptive OBIGGS
Inert gas
Inert gasgeneration
Ullageignitionmodel
Ullageflammability
sensors
O2 sensor
Correctiveresponses Ignitable
fuel tankullage
mixture
Detonationtransition
Ignitionsources
Fuel tankconstraints
The Problem
CTC 9-15-2005
Outside air
No ignition
Ullage detonation
Tank over-pressure
Limitedignition
MostlyFATALMay be
survivable
SurvivableDamage
NoProblem
AlwaysFATAL
The OutcomesThe Inputs
Fuel
Fuel Modification Reduces Ignition Overpressure
0
25
50
75
100
125
150
175
200
-10 0 10 20 30 40 50 60
Temperature/ oC
Vap
or P
ress
ure/
mm
Hg
iso-Octane (2,2,4-trimethyl Pentane)2,2,3-trimethyl Pentane2,2,3,3-tetramethyl Butanen-Octanen-Heptane
Isomeric forms of Octane
MIE = 1.5 mJ
MIE = 0.25 mJ
n-Octane
iso-Octane
MTBE
Linear Species (n-Octane) Form Reactive Ethylene While Branched Species (iso-Octane, MTBE) Form Reaction Quenching Isobutylene
Vapor Pressure Increases With Branching
Ignition Energy Increases with Branching
Energy Density Increases with Branching
Vapor Phase iso-Octane Concentration is 3 Times That of n-Octane at 40oC, MIE is a Factor of 6 Higher
Substitution of Branched for Linear Alkanes Reduces Pressure Impulse Thus Reducing Structural Failure
Branched Alkanes Increase Ignition Delay That Decreases Reaction Rates and Leads to Flame Extinction
Combustion Pressure Impulse
0
1000
2000
3000
4000
5000
6000
7000
0 500 1000 1500 2000 2500 3000 3500 4000
Time (ms)
dP/d
T (A
tm/s)
Linear AlkanesBranched Alkanes
Ignition Sensitization: Minimum Ignition Energy Dependent on Spark Duration!
n-Octane MIE vs. Spark Duration
10-1
100
101
102
103
100 101 102 103 104
Spark Duration, μs
Sp
ark
En
erg
y ,
mJ
n-Octane, 35.9 ºC, Φ =2
n-Octane, 18.3 ºC, Φ =1
n-Octane, 17 ºC, Φ =0.95
n-Octane, 19.8 ºC, Φ =1.06
n-Octane, 19.8 ºC (no spark)
Fuel tank Protection -Deflagration-to-Detonation Transition
1. Ignition in compartment A results in constant-volume combustion2. Constant volume combustion results in over-pressure in A maximum 8x3. Pressurized gas jets into compartment B at sonic speed.4. Jet poses 4-10 order of magnitude stronger ignition energy than the MIE5. Jet ignites ullage gas in B, transition from deflagration to detonation wave.
Some deflagration over-pressure may be survivable.Detonation is not survivable.
AC B
Ullage gas
Liquid fuel at bottom
UnspecifiedIgnition Source
DeflagrationDetonation
Improved Inert-Gas Recovery from Combustion Derived Inerting
Φ = 0.70 Dry Combustion Products and Air at 150 ºF and 180 ºF at 40 psig
80
82
84
86
88
90
92
94
96
98
100
0 10 20 30 40 50 60 70 80 90 100
Inert-Gas Recovery Fraction, %
Iner
t-G
as P
uri
ty, %
CDI, Φ = 0.70,
N2+CO2
CDI, Φ = 0.70,
N2 only
ASM, N2 only
180 ºF150 ºF
1/3 More N2 Recovery or ¼ less Bleed Air Needed
In-Tank Real-Time Multi-Species Fiber Optic Flammability Sensor
• Real-Time: 5 second update interval for feedback control, and critical time-dependent process monitoring
• Multi-Species Analysis: N2, O2, CO2, H2O, CO, CH4, other HC’s, H2, H2S, NO, SO2,…
• Precise: currently has 1% precision in 5 seconds for N2; future versions will require < 1 second for same precision
• Rugged and Reliable: system has no moving parts to go out of alignment or consumables to wear out
• Intrinsically-Safe: No electrical penetration into measurement volume
• Cost-Effective: Monitor multiple locations simultaneously with multiple fiber sensors and one base unit
0
0.05
0.10
0.15
0.20
0.25
30 60 90 120 150 180 210 240 270 3000
0.2
0.4
0.6
0.8
H2O
CO2
O2
N2
Time (seconds)
O2
, C
O2
, H
2O
[M
ole
Fra
ctio
n]
N2
[M
ole
Fra
ctio
n]
Real-Time FiberOptic Gas Analyzer
Gas Inlet
Gas Outlet
Respiration Gas Monitoring Example
Low-VolumeGas SamplingChamber(or Fuel Tank Ullage)
Advantages
Fiber OpticSensor Probe
Contact Information at NASA Glenn Research Center
CDI-OBIGGS & Ignition MitigationClarence Chang, Ph.D.
Deflagration-to-Detonation Transition ScienceNan-Suey Liu, Dr.-Ing.
In-Tank Real-Time Flammability SensorQuang-Viet Nguyen, Ph.D.
Fuel & Ignition ScienceMarty Rabinowitz, Ph.D.