Presented By Lorenzo Andrioli Thermal Analysis in Support to Thermal Protection System Seals and...
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Transcript of Presented By Lorenzo Andrioli Thermal Analysis in Support to Thermal Protection System Seals and...
Presented By
Lorenzo Andrioli
Thermal Analysis in Support to Thermal Protection System Seals
and Interface Design of IXVLorenzo Andrioli, Massimo Antonacci
Thales Alenia Space – Turin, Italy
Alessandro Mannarelli SSE Sofiter System Engineering – Turin, Italy
Thermal & Fluids Analysis WorkshopTFAWS 2011August 15-19, 2011NASA Langley Research CenterNewport News, VA
TFAWS Paper Session
TFAWS 2011 – August 15-19, 2011 2
Outline
• Introduction• Analysis Approach• Interfaces (I/F) Thermal Mathematical Models
(TMMs) general description– Thermal network basic concept– Environment simulation– Analysis work logic– Model example
• New approach for Thermal Protection System (TPS) thermal analysis
• Summary & Conclusions
Introduction
Windward
Lateral
Nose
Flaps
Leeward
The IXV (Intermediate eXperimental Vehicle)
• An atmospheric re-entry demonstrator which will perform a suborbital flight and will re-enter in the atmosphere.
• To be launched by the ESA/Vega from the Centre Spatial Guyanais (CSG)
• It will experience the typical Low Earth Orbit re-entry thermal loads.
TFAWS 2011 – August 15-19, 2011 3
Introduction
Main objective:
To develop an analytical approach to be implemented for I/F design of IXV.
Model characteristics changes operated by means of:– algorithms
– configurations
To properly simulate behaviour of items characterized by different:– thermal properties
– thermo-mechanical properties
– permeability
Leading to different temperature requirement limits.
TFAWS 2011 – August 15-19, 2011 4
Interfaces (I/F)
External critical regions in which environmental agents can find a preferential way to dangerously affect internal environment and items.
Design requirements:
• to limit sneak flow and act as thermal barriers (proper sealing);
• to limit discontinuities (steps, gaps, and bowing) in the vehicle Outer Mould Line;
Introduction
• to allow depressurization and repressurization of IXV and TPS&H/S Assemblies.
TFAWS 2011 – August 15-19, 2011 5
Introduction
Different types of I/Fs to be designed:• among different-type Thermal Protection Systems:
– nose-to-windward– nose-to-leeward– leeward-to-windward– windward-to-hinge– hinge-to-rear– hinge-to-leeward
• between TPSs and other subsystems:– floatation system ejectable panels insulation– venting hole– protection insulation over antennas– bridle channels insulation– protection insulation on umbilical mechanisms
TFAWS 2011 – August 15-19, 2011 6
Analysis Approach
Modeling criterion• ESATAN Thermal
Lumped Parameter (TLP) solver
• Technique resembles System Thermal Mathematical Model (TMM) one improving temperature mapping capabilities
• highly customizable 2D mesh models and one 3D axisymmetric model
• depending on the I/F type, a fluid leak (sneak flow) through sealing materials is simulated
TFAWS 2011 – August 15-19, 2011 7
I/F TMMs general description
Thermal network basic concept• Thermal network organized in node blocks linked
together to establish a geometrical hierarchy → propagation of changes by acting upon relevant parameters (e.g. modification of items sizing, material properties, etc.)
• Node blocks wrapped into arithmetical nodes→ spreading effect of surface heat exchanges implicitly solved (reliable evaluation of I/F temperatures)
TFAWS 2011 – August 15-19, 2011 8
I/F TMMs general description
Environment simulation• Internal environment: radiative and convective
equivalent conductors (representative nodes defined on the basis of System TMM)
• External environment: radiative conductors and heat fluxes (ATDB, max heat load trajectory) or input from dedicated thermo-ablative software
• Sneak flow: modelled by means of a heat contribution calculated as:
)( / SCAIRIMPINGINGAIRpFLOWSNEAK TTcmQ
TFAWS 2011 – August 15-19, 2011 9
I/F TMMs general description
Air mass flow: calculated with Darcy law 1D formulation
mGap
Seal thickness
phigh plow
th
pkAm
k permeability of the seal
air kinematic viscosity
air density
Sneak flow into non-passing through slots: air filling the gap is considered as stagnating (really thin and deep slots, highly conservative boundary layer temperature)
th spatial term describing the flow path (seal thickness)
p pressure
A flow area (gap × slot width)
TFAWS 2011 – August 15-19, 2011 10
• Air flow through venting hole: equivalent thermal conductor (h × A) linking duct with a inflow boundary node
I/F TMMs general description
bush
air
r
kNuh
2
kair air conductivity
rbush duct internal radius
Nu Nusselt number
1Pr8
7.121
Pr1000Re
83
2f
fNu
264.1Reln79.0
1
f
From Petukhov-Gnielinski semi-empiric correlation:
TFAWS 2011 – August 15-19, 2011 11
I/F TMMs general description
Analysis work logic
TFAWS 2011 – August 15-19, 2011 12
I/F TMMs general description
Model example: typical TPS-to-TPS junction I/F
TFAWS 2011 – August 15-19, 2011 13
Analysis results and their application
Local vs System TMMs T are applied to overall vehicle temperature maps all along the I/Fs envelope at C/S and TPS level.
Temperature maps are used as an input for System Thermo-elastic analyses → overall steps and gaps requirements verification
TFAWS 2011 – August 15-19, 2011 14
New approach for TPS thermal analysis
Current approach modeling (ESATAN) flaws:• ESATAN-TMS GUI is in early development phase
→ code is usually written down by hand• Manual debugging and subroutine generation is the rule
→ coding is more error-prone than a robust front-end approach
• CAD interfacing tools are under development→ geometry is user discretized and modeled, usually in scripting form with graphic visualization
• Data exchange is manually managed by means of properly written routines→ a coding endeavor is required
TFAWS 2011 – August 15-19, 2011 15
New approach for TPS thermal analysis
Solution: switching to an hybrid approach tool.
• Bi-directional from/to CAD geometry interfacing, with direct user intervention for simplification purposes
• Finite element based model mesh generation
• Possibility to chose between a Finite Element Method (FEM) or a TLP solution
• Possibility to chose between FEM or TLP like postprocessing (temperatures interpolated over the node vs isothermal nodes)
TFAWS 2011 – August 15-19, 2011 16
New approach for TPS thermal analysis
FEM-TLP hybrid workflow in NX environmentAn example of hybrid approach workflow applied to a preliminary TPS-to-TPS I/F analysis.
TFAWS 2011 – August 15-19, 2011 17
Summary & Conclusions
The presented modelling approach has been developed in the frame of IXV programme resulting into a key feature of the I/F design assessment at System level.
The adopted work logic resulted in an effective approach to:• Achieve the required detail level for I/Fs design justification• Reduce development times and iterations between the different
disciplines involved• Minimize and enhance data exchange cycles among several
analysis tools
TFAWS 2011 – August 15-19, 2011 18
Improvements based on hybrid FEM/TLP analysis are being implemented to:
• Boost up detail level for I/Fs design refinement
• Further reduce development and coding endeavor (minimizing modeling mistakes)
• Enhance data exchange among several CAD/analysis suites
TFAWS 2011 – August 15-19, 2011 19
Summary & Conclusions