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LES Modeling of the Cold Crucible Melting Process

LES Modeling of the Cold Crucible Melting Process. E. Baake , A. Umbrashko, Institute for Electrothermal Processes University of Hanover (Germany) A. Jakovics Laboratory for Mathematical Modelling of Environmental and Technological Processes, University of Latvia, Riga (Latvia).

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LES Modeling of the Cold Crucible Melting Process

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  1. LES Modeling of the Cold CrucibleMelting Process E. Baake, A. Umbrashko, Institute for Electrothermal Processes University of Hanover (Germany) A. Jakovics Laboratory for Mathematical Modelling of Environmental and Technological Processes, University of Latvia, Riga (Latvia) 2nd Sino-German Workshop on EPM Dresden 2005

  2. Contents • Introduction to the cold crucible skull melting process • Main features and optimisation potentials • Numerical modeling and results • Melt flow and temperature distribution • Particle transportation • Conclusions and Outlook Chinese-German Project

  3. vacuum chamber crucible inductor Cold crucible induction skull melting process I • Highreactive and high purity materials, e.g. TiAl • Melting, alloying, over- heating and casting in one process

  4. Cold crucible induction skull melting process II Optimisation potentials of the process • Maximisation of the overheating temperature, which is one of the key parameter • Improvement of the total efficiency and reduction of energy consumption • Control of the melt composition and reduction of skull formation • Reliable, reproducible and stable melting process

  5. skull formation liquid-solid-interface Physical Correlations magnetic field meniscus shape - distribution of power geometry of melt - electromagn. forces velocity field temperature field homogenisation of - overheating melt - heat flow alloy composition melt components optimisation of design and operating parameters

  6. start calculation of meniscus shape no stop criteria fullfilled calculation of hydrodynamic and thermal field stop criteria no fullfilled end Numerical models and numerical tools 3D-electromagnetic - Commercial software (ANSYS) 2D-meniscus shape - self-developed code Surface stability during semi-levitation process allows to uncouple electromagnetic and fluid-dynamic calculations Shape of free surface is calculated with self-developed finite-element code 3D-transient-LES - Commercial software (FLUENT)

  7. Temperature and melt flow measurements in aluminium coil Thermo-couple with ceramic protection Melt flow velocity sensor E = v x B

  8. RANS (k-ε model) • Whole energy spectrum is modelled • Relatively low mesh resolution requirements • Steady-state simulations • DNS • All scales are resolved directly • Very high requirements for computational resources • Simulations of industrial installations are impossible CFD problem Re  104 • LES • Large scales are resolved directly while only small scales are modelled • Relatively high mesh resolution requirements • Transient 3D simulations

  9. Flow pattern and temperature distribution simulated with 2D RNG k-ε turbulence model

  10. 3D LES-modeling of cold crucible melting process ~3•106 elements Time step 10 ms Smagorinsky-Lilly subgrid viscosity model Parallel computations with FLUENT 6.1 software at the HLRN* supercomputer and institute's workstation cluster (4+1 AMD64 3200+) *HLRN – scientific supercomputer network of North Germany

  11. Results of 3D transient LES modeling with aluminium melt I [m/s] vm~40 cm/s [m/s] Time-averaged flow pattern An intermediate flow pattern

  12. Results of 3D transient LES modeling with aluminium melt II ºC ºC Time-averaged temperature distribution Measured temperature distribution

  13. Velocity and temperature distribution in TiAl alloy (LES and k-ε results)

  14. Temperature oscillations in the melt of the IFCC T, K Calculated in TiAl Measured in Al

  15. 3D-instationary flow velocity distribution in the cold crucible melting TiAl alloy calculated with LES model

  16. 3D-instationary temperature distribution in the coldcrucible melting TiAl alloy calculated with LES model

  17. 3D-instationary temperature distribution in the cold crucible melting TiAl alloy calculated with LES model

  18. Melt flow velocity distribution for different crucible geometries crucible radius: 8 cm melt mass: 6 kg TiAl power in the melt: 50 kW crucible radius: 6 cm melt mass: 6 kg TiAl power in the melt: 50 kW

  19. Melt temperature distribution for different crucible geometries crucible radius: 8 cm power in the melt: 50 kW total power: 275.3 kW electrical efficiency: 18.2% crucible radius: 6 cm power in the melt: 50 kW total power: 138.6 kW electrical efficiency: 36.1%

  20. Transient 3D Particle Tracing I Starting Point Starting Point - Density of particles and melt is equal - 6 s of transient tracing in the melt

  21. Transient 3D Particle Tracing II Starting Point Starting Point - Density of particles is 10 times smaller than melt density - 3 s of transient tracing in the melt

  22. Conclusions and Outlook • Heat and mass transfer processes in the melt of induction furnaces are significantly influenced by large scale low-frequency oscillations of the recirculating flow • 3D-transient LES is a reliable numerical tool to simulate the turbulent melt flow and the heat and mass transfer in cold crucible skull melting processes • 3D-LES model will be coupled with 3D-electromagneticmodel for the induction furnace with cold crucible • Modelling of transient skull formation at the crucible wall and particle transportation by electromagnetic forces in the melt are in progress

  23. Chinese-German Projectfounded by NSFC / DFGProject Title:Cold Crucible Induction Skull Melting Process of Titanium Aluminium AlloysProject Partner Harbin Institute of Technology (HIT) School of Materials Science and Engineering Coordinator: Prof. Dr. Guo Jingjie University of Hannover Institute for Electrothermal Processes (ETP) Coordinator: Prof. Dr.-Ing. Egbert Baake

  24. Contributions of HIT and ETP to the cold crucible skull melting project • Harbin Institute of Technology (HIT) • Experimental investigations of the TiAl melting process • especially form metallurgical point of view • Investigations of the mechanism of skull formation • including the microstructure of the skull • Investigations of melt composition control and evaporation • behaviour of alloy components • Institute for Electrothermal Processes (ETP) • Numerical modeling of the skull melting process • including coupled 3D electromagnetic and 3D transient • melt flow and temperature fields • Simulation of skull formation • Investigations of design and process parameters

  25. Main Objectives of the Project (Draft) • Experimental investigation and numerical simulation of the complete cold crucible induction skull melting process of TiAl • Analysis and improvement of the process and design parameters from electromagnetic, thermal, hydrodynamic, metallurgical point of view • Optimisation of the key parameters of the melting process: overheating temperature of the melt, control of melt composition, reduction of skull formation, increasing of efficiency • Investigation of up scaling criteria from small sized units to large mass production furnaces

  26. Thank you for your kind attention!

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