Presentation on theme: "Simulation Methods for Fire Suppression Process"— Presentation transcript:
1 Simulation Methods for Fire Suppression Process inside Engine Core and APU CompartmentsBoeing Commercial Airplanes GroupSeattle, Washington, , USAJaesoo LeeThe Fourth Triennial International Aircraft Fire andCabin Safety Research ConferenceLisbon Conference Center, PortugalNovember 15-18, 2004
2 Acknowledgment FAA Tech Center: Boeing: D. Ingerson: Nacelle Fire Simulator Test DataBoeing:C. Roseburg: Thermodynamic Properties of AgentsA. Nazir: Hflowx ModificationD. Lackas, J. Petkus: Certification Test DataM. Dunn: Engine Cooling Airflow DataD. Dummeyer: APU FireX Test DataM. Grueneis, R. Moody, B. Hsiao: Mesh GenerationAcknowledgmentThis is an outline of my presentation.I will first talk about the background of this simulation work.Next, I will talk about the introduction and the objective of the simulation method developed, which will be followed by:the simulation methods of approach, includinganalysis method for FireX systemanalysis method to predict concentration distribution inside compartments.After that, I will show you some of the results of the validation analyses.And I will present the conclusions made based on the research so far and the future activity.
3 Outline Introduction / Background Engine Fire Suppression Process Simulation Methods:FireX SystemAgent Concentration DistributionExample Applications:FAA Nacelle Fire SimulatorAPU CompartmentEngine Core CompartmentConclusionsFuture ActivitiesOutlineThis is an outline of my presentation.I will first talk about the background of this simulation work.Next, I will talk about the introduction and the objective of the simulation method developed, which will be followed by:the simulation methods of approach, includinganalysis method for FireX systemanalysis method to predict concentration distribution inside compartments.After that, I will show you some of the results of the validation analyses.And I will present the conclusions made based on the research so far and the future activity.
4 Engine Fire / Overheat Detection and Fire Extinguishing Engine Fire SwitchfireXagentThermal SensorsAural / VisualWarningsJ. Lee,This slide shows the sequence of engine fire extinguishment.When a fire breaks out inside engine core compartment due to overheated parts and fuel or oil leaks, the thermal sensors detect the fire and then transmits warning signals to flight deck inside a cockpit.Based on correct judgement, pilot turns on the engine fire switch to discharge the fire extinguishing agent from storage bottle to engine.The distribution of agent from storage bottle to engine should be as fast as possible.The agent concentration level should be sufficiently high to put out fire.The agent flow pressure at the exit of the injection nozzles should be high enough to spread the firex agent over the entire compartment cavity.
5 Environmental and Physical Properties (Halon 1301 and Alternate FireX Agents)Chemical Formula CF3Br CF3CHF CF3I CH2CBrCF3Ozone Depletion PotentialMolecular WeightGlobal Warming PotentialCritical Temperature, ºFAtmospheric Lifetime, yearsLiquid Density at 77 ºF, lb/ftBoiling Point, ºFHeat of Vaporization, Btu/lbVapor Pressure at 77 ºF, psiaHalon HFC CF3I BTPProperties
6 Probe Locations inside 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 ).Range of Concentration Histories%V/VTime6.0½ secmin. conc. historymax. conc. history123456781191210Probe Locations insideAPU CompartmentInjection Nozzle
7 Technology Status and Need No Analysis Tool to Simulate the Entire Fire Suppression Processfor Engines and APUs.FireX System can be Over-Designed (Heavy, Excess Dischargeof 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.
8 Simulation of Fire Extinguishing Process Complex GeometriesUncertainties in Airflow SourcesComplicated Flow Physics:Two-Phase Agent Jet FlowDroplet Formation / Break-upDroplet Interaction with Solid SurfacesTwo-Phase CFD ProblemsCoupled Transport PhenomenaLong Analysis Cycle TimeChallenges:StorageBottleFireXAgentLiquid- / Gas-PhaseFireX Agent / N2DistributionPipeInjectionNozzlesCompartmentVentedairNon-PressurizedEngine CoreAir/AgentMixtureGas
9 Elements of the Simulation Process FireX System AnalysisCFD MeshGenerationEngine Core Compartment GeometryCFD AnalysisforConcentrationPropagationInitial Vented Airflow DistributionPost-ProcessingHistories
13 Species Conservation Eq. CFD Modeling of Agent Injection / Conc. Propagation Process•Mass Continuity Eq.Momentum Eqs.Energy Eq.Species Conservation Eq.Turbulence Model Eqs.Species Transport Eq.Air / Agent Gas MixtureEulerian DescriptionLiquid Agent DropletsMass Transport Eq.(Evaporation)Momentum Transport Eqs.(Trajectories)Energy Transport Eq.(Heat Transfer)Lagrangian Description2-WayCouplingInjectornozzle
14 CFD Input Data / Solution Control Unsteady Vented Airflows:Pre-Cooler Air, Bleed AirTurbine Cooling Air, LeaksUnsteady Agent Injection at Nozzles:Vapor-Phase FlowLiquid-Phase FlowDroplet SizeTwo-Phase Flow VelocitiesDroplet Break-up Model.Droplet-Solid Surface Interaction.Non-Slip / Thermal BCs on Surfaces.Thermodynamic Properties of Agent.Variable Time StepsAgent InjectionConcentration PropagationyesBuoyancy EffectAll Transport Eqs.Under-Relaxation SchemeDouble-PrecisionCalculation Precision2nd –Order UpwindDiscretization SchemesSIMPLEPressure-Velocity Coupling30 ~60Iterations per time-step2nd–Order ImplicitTime-MarchingEff. ConditionsSolution Controls
15 Volumetric Concentration av = fh / [fh + (1 - fh) (Mh/Ma)]where,fh = Predicted Mass Fraction of AgentMh = Mol. Weight of Agent VaporMa = Mol. Weight of Airav = Volumetric Concentrationv,%V/Vtime, sec
16 Validation Application - Case 1 (FAA Nacelle Fire Simulator)Axial ViewVertical Center PlanePool FireTest PanExhaustGas PipeEngineCoreFlangesFuelNozzlesInjectionand Orificesairflowgas
18 Initial Airflow Pattern Validation Application - Case 2(APU Compartment)Surface MeshSide ViewTop Viewt = 0.30 sec after injectionInitial Airflow PatternThe picture on the upper left, which was generated using the developed CFD mesh, shows some important parts including the injector nozzle.The 777/APU has one agent storage bottle with the volume of 536 cubic inches which carries 14 lbm of Halon charged with Nitrogen at 600 psi.The two-phase Halon liquid/vapor jet flow at the injector nozzle was predicted using the HFLOW. The nozzle injects the Halon liquid/vapor mixture over approximately 0.5 second period. The mass fraction of liquid-phase Halon was approximately 95 percent.Using the Halon flow conditions at the nozzle as the boundary condition and the airflow condition at 3 second after the engine shutdown as the initial condition, the time-dependent concentration distribution inside the compartment should be analyzed using the Fluent CFD code for approx. 10 second period. The separately analyzed initial air temperature was 125 ºF.The predicted Halon concentration distribution at 0.06 second after the Halon injection are shown by the iso-concentration contours on the right-side of the vufoil.
20 Validation Application - Case 3 (Engine Core Compartment)Surface MeshAirflowStreamlinesHalon 1301 Flow:Mass (CBrF3) = 22 lbmBottle Volume = 800 in3P (Charge) = 825 psiaVented Airflow:Flow Rate = lbm/sect = 0.13 st = 3.70 st = 7.10 s
21 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 Day(4 cpus)< 1 Min.SGI Octane2400 MHzRemarksAnalysisTime♣Computer PlatformUnsteadyAgent Injection / Concentration DistributionSteady- StateInitial Airflow DistributionFireX SystemTypes
22 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 SurfacesAccurate Airflow / Agent Jet Flow Boundary Conditions.Refined CFD Mesh including Details of ImportantGeometry.Accurate Property Correlations of Agents.
23 Conclusions Simulation Methods for Fire Suppression Process inside Aircraft Propulsion Systems have been Developed.The Capabilities of the Methods have been Demonstratedby Simulating the FireX Tests of Engines and APUs.Predicted Concentration Histories are well Correlatedwith Measured Data.The Simulation Methods need to be Improved for MoreAccurate Prediction of Concentration Histories.
24 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