Kyoung-Su Im, Z.-C Zhang, and Grant Cook, Jr. LSTC, Livermore, CA 94551 USA 06/14/2016, Dearborn, MI
New Inflator Models! Inflator models In LS-DYNA: Pyrotechnic inflator (PI) model. Hybrid cold flow model (no reactions). Hybrid heated flow (reaction system, CO or CH 4 ). Propellant equilibrium code. Examples.! Output to Airbag simulations: Mixture based CESE compatible outputs ALE compatible outputs CPM compatible outputs; 2 nd order and 4 th order specific heat coefficients.
Physical & simulation model! Physical model: Combustion chamber Gas plenum Filter screen Rupture film #1 & #2 Discharge tank or Airbag! Simulation model: Zone 1: Combustion chamber Zone 2: Filter with rupture film #1 Zone 3: Gas plenum Zone 4: Discharge tank or Airbag with rupture film #2
Model Descriptions! Model descriptions: Based on fundamental conservation laws( Mass, Energy, 0-dimensional) Gas mixture : multiple species with well-mixed thermally perfect gas. Condensed mixture: multiple species with incompressible liquid (solid); The specific heats are functions of temperature only, given in terms of a polynomial as,!m in 1. Cold gas CV 2. Heated gas!m out Combustion Chamber Gas plenum Discharge tank or Airbag C-zone G-Zone A-Zone
Energy Conservation! Energy equations: The specific heat are not constants: => Energy equation should not be directly solved to the temperature Solve internal energy Calculate temperature by using thermodynamic relations, h = e + p/ρ
Hybrid Models! Purpose: Reduce the amount of propellants. Control the temperature and pressure. Control the particulate content of the generated gas.! Cold Gas Hybrid: Stores the pressurized inert gases in gas chamber. N 2, Ar, or/and He gases are used.! Heated Gas Hybrid: Stores the combustible gas mixture in the gas chamber. Unwanted species produced by propellant combustion are diluted by the specified chemical reactions. This requires a detailed mechanism of elementary reaction systems to calculate each species production such as H 2 /O 2 or CH 4 /O 2.!m in 1. Cold gas CV 2. Heated gas!m out
Cold Gas Hybrid! Features: Initial composition and conditions of the pressurized inert species =>*CHEMISTRY_INFLATOR_PROPERTIES, & *CHEMISTRY_COMPOSITION. Control the outflow mixture into the airbag. New species equations are added into governing equation. Chemistry input : list gas species first and then, condensed species CV!m in!m out hcold_gas.inp
Heated Gas Hybrid! Features: Initial composition and conditions of the combustible gas, =>*CHEMISTRY_INFLATOR_PROPERTIES, & *CHEMISTRY_COMPOSITION. Control the outflow mixture and species production. Requires a detailed mechanism of elementary reaction systems in the chemistry input. Must solve stiff ordinary differential equation systems 21 species CV!m in!m out adcah2.inp 52 elementary reactions CH 4 + O 2
Propellant Burning Rate! Solid propellant burning rate:! Propellant shape & regression rate: D H m p = ρ x V
Constitutive Relations! Mass flow rate from combustion chamber to gas chamber! Mass flow rate from gas chamber to airbag
What is the PEP File?! Purpose of program: To finds the equilibrium compositions for the solid (or liquid ) propellants.! Features: This program is basically the PEP program written D. R. Cruise at NWC described in NWC TP 6037, titled Theoretical Computations of Equilibrium Compositions, Thermodynamic Properties, and Performance Characteristics of Propellant Systems The theory behind the program is described in NWC TP 6037. Download zip file at ftp/anonymous/outgoing/ksim/example/inflator/ PROPEP_LSTC.zip, which includes executable, data, and sample files To run the program, users need: 1) execution file (lspropep), 2) propellant input file (sazide.pep), 3) thermodynamic binary file (jannaf), 4) propellant ingredient data file (pepcode.dat). The package also includes sample out file (sazide.out).
PEP Input File output file name pepcode.dat... propellant code.. propellant weights
PEP Output File 2 Input Deck combustion temp. Inflator_sazide.k propellant mass composition ID propellant mole fraction
Inflator Keyword file (I)! IF IOUTPUT = 1: CESE airbag compatible output mode; velocity, density, pressure load curves.! IF IOUTPUT = 2: ALE airbag compatible output mode;! IF ISOLVER = 1: temperature, velocity, and 8 main species mass flow rates.! IF IOUTPUT = 3 or 4: Pyrotechnic Inflator Models: (1) Gas phase or Mixed phase.! IF ISOLVER = 2: Hybrid Inflator Model with cold flow (no reactions are involved).! IF ISOLVER = 3: Hybrid Inflator Model with heated flow (reactions are involved). CO reactions & CH 4 reactions Currently, this model works with the gas phase model only. CPM airbag compatible output mode; mass flow rate, temperature, molar weight, 3: 2 nd order specific heat coefficients or 4: 4 th order specific heat coefficients.
Inflator Keyword file (II) sazide.inp Species should be listed gas phase first and then condensed phase All species must be listed in the thermodynamics data file tran.dat is not required for inflator models 2 sets of coefficients are used for Cp, H, S
Why 2 sets of coefficients? N2 H 2O CO2 KCL
Inflator Keyword file (III) Composition1 Composition2 Composition3 Composition4
Inflator Keyword file (IV) D H m p = ρ x V! Propellant burning rate control with setting IOUTPUT = 0: runtime (t) and propellant remaining percentage(%) are displayed on the screen. Users can optimize burning speed by controlling pressure index.
Effects of Combustion index
Results - 1! Pyrotechnic Inflator: Run time ~ 100 ms Temperature profiles at combustion chamber and gas plenum. Must be validated with experimental data
Results - 2! Pyrotechnic Inflator: Run time ~ 100 ms Pressure profiles at combustion chamber and gas plenum Must be validated with experimental data
Results - 3! Pyrotechnic Inflator: Run time ~ 100 ms Thermodynamics properties at discharge tank ( mass flow rate & temperature => inflator_outfile) Must be validated with experimental data Seeking experimental data
Airbag Deployment by CESE
Airbag Deployment by CESE
Airbag Deployment by CPM
More sample keyword files at, ftp/anonymous/outgoing/ksim/examples/inflator/ Preparing Journal paper at Prog. Energy & Combst. Sci. Looking for the experimental data collaboration Thank you!