MSC.Marc-ATAS Advanced Thermal Analysis Software for Modeling of Rocket Motors and Other Thermal Protection Systems

Fabrice Laturelle, Snecma Moteurs

Sophie Fiorot, CS-SI

Ted B. Wertheimer, MSC.

Project OverviewThe objectives of this work is to develop new software and procedures for the analysis of thermo-structures and thermal protection systems.This is a three year project focused on :

• Thermal Degradation of Materials • Complex Thermal Boundary Conditions• Ablation / Erosion of Materials• Radiation• Numerical Efficiency• Easy of Use, Reduced Time for Data Preparation

BackgroundSnecma Moteurs, Solid Rocket Motors Division

40+ years developing, testing, and manufacturing • Solid propellant rocket motors• Thermal protection systems for reentry vehicles

Design Objectives• Replace the need for destructive full scale motor

tests with precise numerical models• Reduce time / costs for design / analysis• Implement several complexity levels of advanced

poro-thermal models• Replace multiple 1-D and 2-D in-house developed

special purpose programs with a single, easy to use, maintainable, comprehensive 3-D program

• Open the way for future coupling with CFD and radiative heat transfer codes, and fully coupled thermo-poro-mechanical analysis

Physical Problem

Materials are subjected to

– Very High Thermal Fluxes 1-100 MW/m2

– Thermochemical oxidation– (Thermo-)Mechanical and Dynamical Loads– Mechanical and Chemical Reactions with

Impacting Liquid and Solid Particles

Composite Materials

• Carbon/Carbon• Carbon/Phenolic• Silica/Phenolic• Ceramic Matrix composites• Rubber and Reinforced Rubber• Low Mass Thermal Insulators

Physics overview

Thermo-Degradation process

Modeling Levels

Level 1– Simplified Homogeneous Material Model – Effective Specific Heat which is Dependent on

the Thermal Loading Path

• Level 2– Mass Loss due to Pyrolysis– One Dimensional Fluid Flow– Advanced Material Behavior

• Level 3– Three Dimensional Fluid Flow (Darcy Law)

Advanced Material Model• Pyrolysis of Material

– Mass Density Controlled by Arrhenius Law– Thermal Properties Change based upon a

Kachanov Model between Virgin and Charred State

– Energy absorption and internal convection

• Water Vapor Creation• Coking

– Carbon comes out of the Pyrolysis Gases and Deposits onto the Solid

Arrhenius Law

Density

Temperature

Heating Rate Dependent

Arrhenius Law for j

• Dimensionless variable j that goes from 1 to 0 during pyrolysis : calculated by a law of Arrhenius:

jjsT

jaT

jBtj

,exp

Surface Energy Balance

surface

wall

flow

convection

conduction decomposition ablation by particles

ablation by gases

radiationbalance

particles impactdiffusion blowing

Ablation

• Thermochemical Ablation (Gases, Particles)

• Mechanical Erosion– Due to impacts of particles– Due to other actions such as the shear

stress of the flow and vibration of the part

S.

th = [ m.

s,th,g + m.

s,th,p ] / s

Mass Balance Equation• The mass equation of standard level 2 model is

the mass equation of the gas, written in the stationary state, with a source term of decomposition.

gm mass flow rate of the gases of decomposition.

tps

*,

source term of decomposition

tps

gm

*,

ˆ.

Energy equation

vcpsHpgHtpsT

TgmpgctT

psc

pspicis

,,,*,

ˆ*.

.*,*,

ˆ*,

ˆ

Ablation Analysis Verification

Temperature field in the material for different times while ablation .

0

500

1000

1500

2000

2500

3000

3500

0,00 0,01 0,02 0,03 0,04 0,05

radius (m) (from the initial radius)

tem

pera

ture

(K

)

marc t=0,2sec

snecma t=0,2secmarc t=1sec

snecma t=1secmarc t=2sec

snecma t=2secmarc t=5sec

snecma t=5secmarc t=10secsnecma t=10sec

marc t=20secsnecma t=20sec

marc t=30secsnecma t=30sec

marc t=40secsnecma t=40sec

Temperature VerificationComparison of the temperature between the Snecma code and Marc (MSC)

along the material at different times

40sec20sec

10sec

5 sec

2sec

1 sec

0

500

1000

1500

2000

2500

3000

0,0E+00 5,0E-03 1,0E-02 1,5E-02 2,0E-02

Coordinates (m)

Tem

per

atur

e (K

)

snecmamarc

Density Distribution

Comparison of the density field inside the material between the Snecma code and Marc (MSC)

40sec

1sec 2sec

5sec10sec 20sec

1150

1250

1350

1450

1550

0,0E+00 5,0E-03 1,0E-02 1,5E-02 2,0E-02

coordinates (m)

ma

ss d

ensi

ty (

kg m

-3)

snecmamarc

Mass Flow Rate of GasComparison of the mass flow rate at the exterior surface

between the Snecma code and Marc (MSC)

0,00

0,02

0,04

0,06

0,08

0,10

0 10 20 30 40 50 60

time (sec)

ma

ss f

low

rat

e (k

g m

-2 s

-1)

snecmamarc

Rezoning Issues

• Shaver Mesher – Rezone outer element during recession when

necessary– Update values associated with exterior SIP based

upon recession– Shift SIP when outer element removed– Remove number of SIP points

• Relax Mesher– Rezone complete mesh– Update all SIP value– Number of SIP points remain the same

Ablation

Thermal Contact

Expansion of MSC.Marc Capabilities for Thermal Contact

• No Contact– Thermal Convection to the Environment

• Close Contact– Convection, Radiation Between Surfaces

• True Contact– Conduction

Thermal Contact

• If dist < d1 then thermal conduction

• If d1< dist < d2 then near contact

• If d2 < dist then no contact

• Q = hcv*(T2-T1)+hnt*(T2-T1)ent +

sigma*eps*(T24-T14) +

(hct – (hct-hbl)*gap/dqnear)*(T2-T1)

Conclusions

Advanced Thermal Analysis Capabilities Suitable to High Temperature Applications are Being Added to MSC.Marc

• Excellent Correlation has been Observed• Increase Capability , with Less Costs• Implementation of level 3 poro-thermal model,

advanced radiation capabilities, and testing, are still in progress