J. Lee 11-17-04

Simulation Methods for Fire Suppression Process inside Engine Core and APU Compartments

Boeing Commercial Airplanes GroupSeattle, Washington, 98124-2207, USA

Jaesoo Lee

The Fourth Triennial International Aircraft Fire and Cabin Safety Research Conference

Lisbon Conference Center, PortugalNovember 15-18, 2004

J. Lee 11-17-04

• FAA Tech Center: D. Ingerson: Nacelle Fire Simulator Test Data

• Boeing: C. Roseburg: Thermodynamic Properties of Agents A. Nazir: Hflowx Modification D. Lackas, J. Petkus: Certification Test Data M. Dunn: Engine Cooling Airflow Data D. Dummeyer: APU FireX Test Data M. Grueneis, R. Moody, B. Hsiao: Mesh Generation

Acknowledgment

J. Lee 11-17-04

• Introduction / Background

• Engine Fire Suppression Process

• Simulation Methods: FireX System Agent Concentration Distribution

• Example Applications: FAA Nacelle Fire Simulator APU Compartment Engine Core Compartment

• Conclusions

• Future Activities

Outline

Engine Fire / Overheat Detection and Fire Extinguishing

Engine Fire SwitchfireX agent

fireX agent

Thermal Sensors

Aural / Visual

Warnings

J. Lee, 11-17-04

J. Lee 11-17-04

Environmental and Physical Properties (Halon 1301 and Alternate FireX Agents)

Chemical Formula CF3Br CF3CHF2 CF3I CH2CBrCF3

Ozone Depletion Potential 16 0 0.0002 0.0037

Molecular Weight 148.9 120.0 196.9 174.9

Global Warming Potential 5600 2800 5 400

Critical Temperature, ºF 152.6 151.3 251 -

Atmospheric Lifetime, years 65 33 0.0137 0.011

Liquid Density at 77 ºF, lb/ft3 96.01 74.3 131.4 102.9

Boiling Point, ºF -72 -55 -9 34

Heat of Vaporization, Btu/lb 35.5 70.7 48.1 -

Vapor Pressure at 77 ºF, psia 234.8 200.4 63.7 10.9

Halon HFC CF3I BTP 1301 -125Properties

J. Lee 11-17-04

Certification Requirement (Engines and APUs)

• If Halon 1301 (CF3Br) is used as the fire extinguishing agent, the minimum agent concentration is 6 % by volume for a minimum of 0.5 seconds for all 12 concentration probe locations, simultaneously (FAA AC 20-100).

Range of Concentration Histories

%V/V

Time

6.0

½ sec

min. conc. history

max. conc. history

12

3

4

5

6 7

8

11

9

12

10

Probe Locations inside APU Compartment

Injection Nozzle

J. Lee 11-17-04

Technology Status and Need

• No Analysis Tool to Simulate the Entire Fire Suppression Process for Engines and APUs.

• FireX System can be Over-Designed (Heavy, Excess Discharge of Agent to Environment) or Under-Designed.

• Installation of Injection Nozzles: Many Ground Tests to meet FAA Requirements. Time-Consuming and Costly.

• Need an Analytical Tool for Performance Design of FireX Systems: Engine Nacelles / APUs of Commercial, Military Airplanes, Helicopters. Reduces Cost of Design / Certification by ~50 Percent. Technology Ready for Halon Replacement.

J. Lee 11-17-04

Simulation of Fire Extinguishing Process

• Complex Geometries • Uncertainties in Airflow Sources

• Complicated Flow Physics: Two-Phase Agent Jet Flow Droplet Formation / Break-up Droplet Interaction with Solid Surfaces

• Two-Phase CFD Problems Coupled Transport Phenomena Long Analysis Cycle Time

Challenges:

StorageBottle

FireXAgent

Storage

Liquid- / Gas-Phase

FireX Agent / N2

Distribution

Pipe

InjectionNozzles

Compartment

Ventedair

InjectionNozzles

Compartment

air

Non-Pressurized

Engine Core

Air/Agent Mixture

Gas

J. Lee 11-17-04

Elements of the Simulation Process

FireX System Analysis

CFD MeshGeneration

Engine Core Compartment

Geometry

CFD Analysis for

Concentration Propagation

Initial Vented Airflow

Distribution

Post-Processingfor

Concentration Histories

J. Lee 11-17-04

Unsteady Analysis of Agent Injection Process

AgentStorageBottle

AgentStorageBottle

Distribution

Pipe

MultipleInjectionNozzles

Agent Mass, Bottle (P, T, Vol),Distribution Pipes,Nozzle Size

HflowxUnsteady BCs at

Injection Nozzles

ŵ (t)liquid ŵ (t)vapor P (t)mixture

T (t)mixture

J. Lee 11-17-04

FLOW SPLIT

• 9/32”ID ORIFICE

•55/8” TUBE NOZZLES

STORAGE BOTTLE

• Halon Mass = 5.2 lbm • Bottle Volume = 219 In3

• Charge Pressure = 720 psig • Test Temperature = 100 ºF

Agent Types:

• ICHEM = 1 (Halon 1301) = 2 (HFC-125) = 3 (CF3I)

Validation Analysis of Hflowx

J. Lee 11-17-04

Predicted Agent Discharge Characteristics

FireX System Conditions

Agent Mass: 22 lbmBottle Volume: 800 In3

Charge Press.: 825 psiaTest Temp.: 10 FPipe Diameter: 0.75 InPipe Length: 80 Ft

Two-Phase Vapor / Liquid Mixture Jet

Liquid-Phase Agents Vapor-Phase Agents

J. Lee 11-17-04

CFD Modeling of Agent Injection / Conc. Propagation Process

• Mass Continuity Eq.

• Momentum Eqs.

• Energy Eq.

• Species Conservation Eq.

• Turbulence Model Eqs.

• Mass Continuity Eq.

• Momentum Eqs.

• Energy Eq.

• Species Conservation Eq.

• Turbulence Model Eqs.

• Mass Continuity Eq.

• Momentum Eqs.

• Energy Eq.

• Species Transport Eq.

• Turbulence Model Eqs.

Air / Agent Gas Mixture

Eulerian Description

Liquid Agent Droplets

• Mass Transport Eq. (Evaporation)

• Momentum Transport Eqs. (Trajectories)

• Energy Transport Eq. (Heat Transfer)

• Mass Transport Eq. (Evaporation)

• Momentum Transport Eqs. (Trajectories)

• Energy Transport Eq. (Heat Transfer)

• Mass Transport Eq. (Evaporation)

• Momentum Transport Eqs. (Trajectories)

• Energy Transport Eq. (Heat Transfer)

Lagrangian Description

2-Way

Coupling

2-Way

Coupling

Injectornozzle

J. Lee 11-17-04

CFD Input Data / Solution Control

• Unsteady Vented Airflows:

Pre-Cooler Air, Bleed Air Turbine Cooling Air, Leaks

• Unsteady Agent Injection at Nozzles:

Vapor-Phase Flow Liquid-Phase Flow Droplet Size Two-Phase Flow Velocities

• Droplet Break-up Model.

• Droplet-Solid Surface Interaction.

• Non-Slip / Thermal BCs on Surfaces.

• Thermodynamic Properties of Agent.

Log-Scale

Variable Time Steps

Agent Injection

Concentration Propagation

yesBuoyancy Effect

All Transport Eqs.Under-Relaxation Scheme

Double-PrecisionCalculation Precision

2nd –Order UpwindDiscretization Schemes

SIMPLEPressure-Velocity Coupling

30 ~60Iterations per time-step

2nd–Order ImplicitTime-Marching

Eff. ConditionsSolution Controls

J. Lee 11-17-04

Volumetric Concentration

v = fh / [fh + (1 - fh) (Mh/Ma)]

where,fh = Predicted Mass Fraction of AgentMh = Mol. Weight of Agent VaporMa = Mol. Weight of Air v = Volumetric Concentration

v,

%V/V

time, sec

J. Lee 11-17-04

Validation Application - Case 1 (FAA Nacelle Fire Simulator)

Axial View

Vertical Center Plane

Pool FireTest Pan

ExhaustGas Pipe

EngineCore

FlangesFuel Nozzles

Injection Nozzles

and Orifices

airflow

Exhaustgas

J. Lee 11-17-04

Halon 1301 Concentration Histories

• Vented Airflow: Unsteady Airflow Rate: (2.2 lbm/sec @ steady-state) Temperature: 100 °F

• FireX Condition: Halon 1301 Mass: 5.2 lbm Bottle Volume: 219 in3

Bottle Charge: 812 psi, 100 °F Discharge Temp.: 100 °F

Predicted

Measured

4 Probes(12, 3, 6, 9 o’clocks)

4 Probes(4:30, 7:30, 12, 6

o’clocks)

4 Probes(12, 3, 6, 9 o’clocks)

12 Probe Locations

J. Lee 11-17-04

Validation Application - Case 2(APU Compartment)

Surface Mesh

Side View Top View

t = 0.30 sec after injection

Initial Airflow Pattern

J. Lee 11-17-04

Halon 1301 Concentration Histories

12

3

4

5

6 7

8

11

9

12

10

Probe Locations

• Agent Injection: Halon Mass: 14 lbm Charge Pressure: 600 psi Bottle Vol.: 536 In3

• Vent Air: Initial avg. Air Temp.: 125 ºF Transient Vented airflow

Measured

Predicted

J. Lee 11-17-04

Validation Application - Case 3 (Engine Core Compartment)

Surface MeshAirflow

Streamlines

• Halon 1301 Flow: Mass (CBrF3) = 22 lbm Bottle Volume = 800 in3 P (Charge) = 825 psia

• Vented Airflow: Flow Rate = 12.84 lbm/sec

t = 0.13 s t = 3.70 s t = 7.10 s

J. Lee 11-17-04

Analysis Types / Cycle Times

♣ : CPU time depends on: Total simulation time; Size of CFD mesh; No. of injection nozzles; No. of droplet sizes; No. of droplet starting locations per nozzle; No. of computer processors; Convergence criteria, etc.

1 Injection Nozzle

~1 WkORIGIN 3800

(6 cpus)

0.32 Mcells~0.5 DayORIGIN 3800

(4 cpus)

< 1 Min.SGI Octane2

400 MHz

RemarksAnalysis

Time♣

Computer Platform

Unsteady Agent Injection / Concentration

Distribution

Steady- State Initial Airflow Distribution

FireX System

Analysis Types

J. Lee 11-17-04

Key Factors for Improved Simulations

• Analysis Domain based on Fire Suppression Process.

• Advanced Flow Physics Models:

- Two-Phase Agent Jet Flow- Droplet Interaction with Solid Surfaces

• Accurate Airflow / Agent Jet Flow Boundary Conditions.

• Refined CFD Mesh including Details of Important Geometry.

• Accurate Property Correlations of Agents.

J. Lee 11-17-04

Conclusions

• Simulation Methods for Fire Suppression Process inside Aircraft Propulsion Systems have been Developed.

• The Capabilities of the Methods have been Demonstrated by Simulating the FireX Tests of Engines and APUs.

• Predicted Concentration Histories are well Correlated with Measured Data.

• The Simulation Methods need to be Improved for More Accurate Prediction of Concentration Histories.

J. Lee 11-17-04

Future Activities

• Continuous Improvement of the Developed Methods to Enhance Applicability and Practicality.

• Support the Design and Installation of FireX Systemfor Commercial, Military Airplanes, Helicopters, and for Halon Replacements.

• Complement of the FAA Certification Tests.

7E7 Dreamliner