Engine Nacelle Halon Replacement, FAA, WJ Hughes Technical Center

1
Engine Nacelle Halon Replacement,FAA, WJ Hughes
Technical Center

• Point of Contact Doug Ingerson
• Department of Transportation
• Federal Aviation Administration
• WJ Hughes Technical Center
• Fire Safety Branch, AAR-440
• Bldg 205
• Atlantic City Int'l Airport, NJ 08405 USA
• tel [phone]
• fax [phone] or 609-646-5229
• email Douglas.A.Ingerson_at_faa.gov
• web page http//www.fire.tc.faa.gov/

2
Major Topics for Review

• Overview of Work, October 02 March 03
• Finalizing Environmental Test Parameters
• Quantifying Halon Replacement
• Evaluating Pool Fire Behavior
• Finding Certification Distribution
• Near Term Plans
• Complete Certification Distribution Work
• Complete Pool Fire Evaluation
• Evaluate Varied Agent Discharge Impact on
  Reignition Time Delay
• Equivalence Testing

3
FINALIZING ENVIRONMENTAL TEST PARAMETERSExtinguis
hing agent storage temperature

• Referring to the storage temperature of the
  extinguishing agent during fire testing
• Agent storage temperature has been 100F
• Desire expressed for an additional storage
  temperature of 65F
• FINAL DECISION
• Fire testing will be completed at an agent
  storage temperature of 100F
• Basis for decision
• Flammability behavior
• Based on a system of fuel, air, and extinguishing
  agent within a fixed volume having consistent
  ignition energy (similar to ASTM E-695)
• Increasing pressure requires increasing agent
  concentration to remain nonflammable
• Increasing temperature requires increasing agent
  concentration to remain nonflammable
• Given this behavior for comparable combustion
  behavior
• The peak concentration value for a higher
  temperature will provide adequate protection at
  lower temperature
• The challenge is for the extinguishing agent to
  DISTRIBUTE and attain the peak value found at the
  higher temperature while being stored at a lower
  temperature
• This can be demonstrated by non-fire,
  distribution test alone

4
FINALIZING ENVIRONMENTAL TEST PARAMETERSExtinguis
hing agent storage temperature

5
FINALIZING ENVIRONMENTAL TEST PARAMETERSExtinguis
hing agent storage temperature

6
FINALIZING ENVIRONMENTAL TEST PARAMETERSExtinguis
hing agent storage temperature

• Basis for decision (continued)
• Uncertainty due to gas analysis technology
• NIST demonstrates possible difficulty with higher
  boiling point agent (CF3I) at low storage
  environmental temperatures
• Varying liquid/vapor fractions of extinguishing
  agent observed during discharge
• Room temperature agent fixture ventilation
• Cold temperature agent/room temperature fixture
  ventilation
• Cold temperature agent fixture ventilation
• NIST utilized relatively unobtrusive technology
  for gas analysis
• No sample transport sample analyzed in test
  environment during discharge events
• Minimal impact on the agent distribution during
  its measurement
• FAA Tech Center utilizing Statham-derivative
  technology
• Gas sample is transported to sensor sample is
  heated by transport path
• Sensor assembly is a heated environment sample
  is heated prior to measurement
• Uncertainty at FAA Tech Center
• Gas analysis error - sample transport and
  measurement will heat and change liquid agent to
  vapor
• The gas analysis error may not permit accurate
  description of the transport phenomena in the
  test fixture

7
FINALIZING ENVIRONMENTAL TEST PARAMETERSLower
air mass flow rate

• Lower air mass flow in the test fixture at the
  FAA Tech Center is too large
• Lower air mass flow has been 1.0 lbm/s
• Desire to see 0.2 0.4 lbm/s which match flows
  found in fielded nacelles
• FINAL DECISION
• Lower air mass flow rate will be 1.0 lbm/s
• Basis for decision
• Work at FAA Technical Center founded on testing
  completed at 1.0 lbm/s
• Changing to lower mass flow will invalidate
  database for agent dispersion and fire testing
• The test fixture at the FAA Technical center is
  capable of 0.7 lbm/s minimum
• Decreasing ventilation rate typically decreases
  agent quantity required to meet certification
• Lower mass flows move fire protection design
  towards non-ventilated compartments

8
Quantifying a Halon replacementInitial step
Basis/Process

• Reignition time delay is the duration between the
  extinguishment of the fire and its subsequent
  reignition
• Environmental constraints
• Test fixture set up for one macroscopic test
  scenario
• Macroscopic test scenario one ventilation
  configuration one fire scenario
• Agent discharged within 1 second
• Agent storage temperature of 100F
• A small collection of individually unique tests
  are performed
• Intended to map the behavior of the replacement
  candidate
• A quantity can be estimated as a possible
  equivalent to the performance of Halon 1301

9
Quantifying a Halon replacementInitial step -
Illustration

10
Quantifying a Halon replacementFinal step - Basis

• Process requires repeating 5 tests to determine
  if a quantity is halon equivalent
• An unsuccessful quantity can be determined in as
  few as 2 tests
• This process is based on the statistical behavior
  of past test results
• Based on 7 test sequences each sequence
  contained 5 replicate tests
• Test sequences were varied conditions providing
  reignition delay results
• Evaluated the trend of the reignition time delay
  over the 5 tests
• Evaluation determined whether the sequence of 4
  tests would continue to a fifth
• This process was successful for 6 of the 7 test
  sequences

11
Quantifying a Halon replacementFinal step -
Process

• Process
• The average reignition time delay and sample
  standard deviation for halon are known
• Run tests 1 through 4 with the replacement
  candidate at repeated test condition
• Beginning with test 2
• Calculate the running average of the reignition
  time delay for the replacement candidate
• Determine if the running average falls within /-
  1 sample standard deviation (halon) of the halon
  average reignition time delay
• If yes, continue otherwise change mass and start
  again

12
Quantifying a Halon replacementFinal step -
Process

• Process (continued)
• Run test 5 and perform the FINAL evaluation
• The running average of the reignition time delay
  (RTD) for the replacement candidate must be equal
  to or greater than that of halon
• The sample standard deviation for the replacement
  candidate must be less than or equal to that of
  halon

13
Evaluating Pool Fire BehaviorBackground

• Purpose
• Observe combustion behavior
• Dependent upon a recirculation zone
• Recirculation zone forms behind flame stabilizing
  baffle over the pool of fuel
• Determine threat for use in equivalence procedure
• Work description
• Looked at impact on fire behavior
• Varying upstream baffle height
• Hot surface behaviors tube arrays
• 2 tube diameters
• 2 tube lengths
• 2 positions above fuel surface
• 2 positions downstream from flame stabilizing
  baffle
• 2 exposed fuel surface areas
• Continually operating electrodes
• Characterize fire growth
• Performed tests without discharging agent

14
Evaluating Pool Fire BehaviorUpstream baffle
height

• Reviewed literature for experience
• Work by Hirst, Farendon, et al.
• Indicated 1 baffle height worst case
  demonstrated by
• Blow-off velocity
• Agent concentration
• Ran tests to observe fire behavior related to
  baffle height
• Used baffle heights of 0.50, 1.50, 2
• Exposed fuel surface area of 10.8x10.8
• Fuel depth of 0.50
• Tube array used to monitor heating ability of
  fire
• 4 straight tubes in a rhombus stack, 24 long x
  0.50OD
• Supported 2.25 above fuel surface and 4.25
  downstream from baffle
• Observations as baffle height increased
• Tube array temperature increased
• Temperatures 16 30 downstream decreased
• Hottest tube array temperature NOT comparable to
  profiles observed in hot surface ignition in the
  spray fire scenario

15
Evaluating Pool Fire BehaviorUpstream baffle
height - Illustration

16
Evaluating Pool Fire BehaviorHot surface/tube
array - Descriptions

• Purpose
• Further observation of the fire behavior
• Determine the surface area of the pool for the
  final threat in the equivalence process
• Determine worst case tube array for evaluation
  against agent discharge
• Altered tube array characteristics
• 0.25 0.50 diameters
• 5 10 tube lengths
• Tube array supported 0.25 and 1 above fuel
  surface
• Located 2, 4, 8, 12, 16 downstream from
  flame stabilizing baffle
• 10.8x10.8 10.8x20.5 exposed fuel surface
  areas
• Tube array consisted of 3 tubes stacked in an
  inverted triangular wedge
• Thermocouple imbedded in tube array at the middle
  of the tube length
• Fuel depth of 0.50
• Ran multiple tests evaluating the various
  conditions described

17
Evaluating Pool Fire BehaviorHot surface/tube
array - Illustration

AIRFLOW
18
Evaluating Pool Fire BehaviorHot surface/tube
array Observations

• Tube array temperatures attaining 1250 1325F
• Temperatures consistently hotter when
• Tube diameter was 0.25
• Tube array was downstream 4 or less from baffle
• Tube array was supported 1 above fuel surface
• Larger fuel surface area produced greatest
  thermal output
• Larger fuel surface had no apparent impact on
  heating the tube array

19
Evaluating Pool Fire BehaviorHot surface/tube
array Tube array temperatures

20
Evaluating Pool Fire BehaviorContinually
operating electrodes - Descriptions

• Purpose
• Further observation of the fire behavior
• Determine worst case electrode configuration for
  evaluation against agent discharge
• Conditions for analysis
• Electrode gap of 0.13
• Position gap 1.25, 0.25, 0.016, 0 above
  fuel surface
• Electrode gap placed 0.5, 2, 5, 10, 17
  downstream from flame stabilizing baffle
• Electrode gap placed on fore/aft center line of
  the pool
• 10.8x20.5 exposed fuel surface area
• Fuel depth of 0.50
• No tube array
• Marked fuel pan to determine flame propagation
  behavior
• Ran multiple tests evaluating the various
  conditions described

21
SLIDE 21
SLIDE 21
22
SLIDE 22
23
Evaluating Pool Fire BehaviorContinually
operating electrodes - Observations

• Pool did not ignite unless electrode gap was in
  contact with fuel surface
• Flames propagated across the surface of the pool
  faster opposing the bulk air flow in the test
  section
• Shortest duration to full pan involvement
  occurred with mobile electrode gap located 17
  downstream from the flame stabilizing baffle

24
Evaluating Pool Fire BehaviorContinually
operating electrodes - Observations

25
Evaluating Pool Fire BehaviorContinually
operating electrodes - Observations

26
Evaluating Pool Fire BehaviorConclusions

• Varied baffle heights
• No reason suggested by data that 1 tall baffle
  is not worst case
• Further evaluation required
• Tube array
• Tubes apparently not hot enough for hot surface
  ignition based on spray fire results
• Worst case tube configuration
• Exposed fuel surface of 10.8 x 20.5 length
• Three 0.25OD x 10 long tubes
• Tube array located 4 downstream from baffle and
  supported 1 above fuel
• Electrodes
• Fastest pan fire developed when electrodes were
  positioned at the aft end of the pool
• Recirculation zone is clearly present
• Worst case electrode configuration
• Location of 17 downstream from baffle
• Electrode gap touched fuel at surface

27
Evaluating Pool Fire BehaviorConclusions
(continued)

• General comments
• Tube array apparently not hot enough for hot
  surface ignition in any configuration attempted
• The hottest tube array was located above the fuel
  in a region where the electrodes could NOT ignite
  the pool
• Final determination to be made with worst cases
  tested individually combined against the
  discharge of a fire extinguishing agent

28
Agent Distribution SearchBackground

• Former Halon quantities producing certification
  at a storage temperature of 65F
• 5.2 lbf Halon 1301 _at_ ventilation of 2.2 lbm/s
  100F
• 3.2 lbf Halon 1301 _at_ ventilation of 1.0 lbm/s
  280F
• These quantities produced excessive concentration
  profiles since fire testing was occurring at at
  an agent storage temperature of 100F
• Work occurring to find agent quantities that will
  produce certification at a storage temperature of
  100F
• 5.2 lbf Halon 1301 will be in the 3.5 4.0 lbf
  range
• No estimate for reduction from 3.2 lbf Halon 1301

29
Agent Distribution SearchPreliminary results
3.90 lbf Halon 1301 _at_ ventilation of 2.2 lbm/s
100F

30
Near Term Plans

• Complete certification distribution work
• Finalize work at ventilation rate of 2.2 lbm/s _at_
  100F
• Accomplish work for the condition of 1.0 lbm/s _at_
  280F
• Complete pool fire evaluation
• Run new quantities of halon against the pool fire
• Determine which worst case to use in the
  equivalence procedure
• Evaluate the impact of varied agent storage
  pressure on reignition time delay
• Store the same amount of agent in the same volume
  at the same temperature
• Alter storage pressure
• Observe impact on the reignition time delay
• Incorporate experience into the equivalence
  procedure
• Equivalence testing