# Presentation: 665196

## 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:			609-485-4945
- fax:		609-485-7074 or 609-646-5229
- email:		Douglas.A.Ingerson@faa.gov
- web page:	_http://www.fire.tc.faa.gov/_

##  Major Topics for Review 

*** ***

*** ******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**

## FINALIZING ENVIRONMENTAL TEST PARAMETERSExtinguishing agent storage temperature

- FINALIZING ENVIRONMENTAL TEST PARAMETERSExtinguishing agent storage temperature

- Referring to the storage temperature of the extinguishing agent during fire testing
- Agent storage temperature has been 100°F
- Desire expressed for an additional storage temperature of –65°F
- FINAL DECISION :
- _Fire testing will be completed at an agent storage temperature of 100°F_
- 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

## FINALIZING ENVIRONMENTAL TEST PARAMETERSExtinguishing agent storage temperature

- FINALIZING ENVIRONMENTAL TEST PARAMETERSExtinguishing agent storage temperature

## FINALIZING ENVIRONMENTAL TEST PARAMETERSExtinguishing agent storage temperature

- FINALIZING ENVIRONMENTAL TEST PARAMETERSExtinguishing agent storage temperature

## FINALIZING ENVIRONMENTAL TEST PARAMETERSExtinguishing agent storage temperature

- FINALIZING ENVIRONMENTAL TEST PARAMETERSExtinguishing 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

## FINALIZING ENVIRONMENTAL TEST PARAMETERSLower air mass flow rate

- 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

## Quantifying a Halon replacementInitial step – Basis/Process

- 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 100°F
- 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

## Quantifying a Halon replacementInitial step - Illustration

- Quantifying a Halon replacementInitial step - Illustration

## Quantifying a Halon replacementFinal step - Basis

- 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

## Quantifying a Halon replacementFinal step - Process

- 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

## Quantifying a Halon replacementFinal step - Process

- Quantifying a Halon replacementFinal step - Process

- Process (continued)
- Run test #5 and perform the FINAL evaluation
- The running average of the _r_eignition _t_ime _d_elay (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

## Evaluating Pool Fire BehaviorBackground

- 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

## Evaluating Pool Fire BehaviorUpstream baffle height

- 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 10.8”x10.8”
- Fuel depth of 0.50”
- Tube array used to monitor heating ability of fire
- 4 straight tubes in a rhombus stack, 24” long x 0.50”OD
- 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

## Evaluating Pool Fire BehaviorUpstream baffle height - Illustration

- Evaluating Pool Fire BehaviorUpstream baffle height - Illustration

## Evaluating Pool Fire BehaviorHot surface/tube array - Descriptions

- 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
- 10.8”x10.8” & 10.8”x20.5” 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

## Evaluating Pool Fire BehaviorHot surface/tube array - Illustration

- Evaluating Pool Fire BehaviorHot surface/tube array - Illustration

- AIRFLOW

## Evaluating Pool Fire BehaviorHot surface/tube array – Observations

- Evaluating Pool Fire BehaviorHot surface/tube array – Observations

- Tube array temperatures attaining 1250 – 1325°F
- 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

## Evaluating Pool Fire BehaviorHot surface/tube array – Tube array temperatures

- Evaluating Pool Fire BehaviorHot surface/tube array – Tube array temperatures

## Evaluating Pool Fire BehaviorContinually operating electrodes - Descriptions

- 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
- 10.8”x20.5” 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

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## Evaluating Pool Fire BehaviorContinually operating electrodes - Observations

- 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

## Evaluating Pool Fire BehaviorContinually operating electrodes - Observations

- Evaluating Pool Fire BehaviorContinually operating electrodes - Observations

## Evaluating Pool Fire BehaviorContinually operating electrodes - Observations

- Evaluating Pool Fire BehaviorContinually operating electrodes - Observations

## Evaluating Pool Fire BehaviorConclusions

- 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 0.25”OD 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

## Evaluating Pool Fire BehaviorConclusions (continued)

- 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

## Agent Distribution SearchBackground

- Agent Distribution SearchBackground

- Former Halon quantities producing certification at a storage temperature of –65°F
- 5.2 lbf Halon 1301 @ ventilation of 2.2 lbm/s & 100°F
- 3.2 lbf Halon 1301 @ ventilation of 1.0 lbm/s & 280°F
- These quantities produced excessive concentration profiles since fire testing was occurring at at an agent storage temperature of 100°F
- Work occurring to find agent quantities that will produce certification at a storage temperature of 100°F
- 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

## Agent Distribution SearchPreliminary results

- Agent Distribution SearchPreliminary results

**3.90 lbf Halon 1301**
**@ ventilation of **
**2.2 lbm/s & 100°F**

## Near Term Plans  

- Near Term Plans

-  Complete certification distribution work
- Finalize work at ventilation rate of 2.2 lbm/s @ 100°F
- Accomplish work for the condition of 1.0 lbm/s @ 280°F
- 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