Simulation of Centrifugal Casting via STAR-Cast. Santhanu Jana, Access e.v., Aachen

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2 Simulation of Centrifugal Casting via STAR-Cast Santhanu Jana, Access e.v., Aachen

3 Talk overview Centrifugal casting STAR-Cast s modelling basis Motivation for centrifugal investment casting Centrifugal investment casting of Low pressure turbine blades Turbocharger wheels Future work

4 Introduction to centrifugal casting Centrifugal forces distributes the molten material in the mould Rotation axis may be horizontal, vertical or inclined Preferred for high quality cast parts Rolls, nozzles, wheels, jewellery, etc Casting materials: iron,steel, alloys of Aluminium, Copper, Titanium etc Top rollers Casting Bottom rollers Schematic of horizontally rotated bimetallic casting Liquid metal Mould Coating

5 Modelling basis in STAR-Cast

6 STAR-Cast s modelling approach Coupled flow and solidification model : Multi phase approach: gas, liquid and solidified metal HRIC: ensures sharp resolution of free surface, entrapped gas bubbles Porous walls: Escape of gas through shell moulds Interfacial forces: Surface tension and wetting angle effects Rotational forces : are modeled based on rotating frame of reference Moving grids: to model crucible tiling and pouring into the funnel Polyhedral meshes: for complex geometries and multiphysics simulations Material data: Comprehensive and fully documented data dedicated for casting simulation High performance computing: Scales almost linear on parallel machines down to cells per processor: STAR-Cast Power Version

7 STAR-Cast s modelling approach Advanced liquid-solid state transition model Resistance to flow is a function of secondary dendrite arm spacing Solid Mushy Liquid f L = 0.0 f L = 0.3 f L = 1.0

8 Motivation for centrifugal investment casting

9 Casting of TiAl components with centrifugal investment process Aero-engine manufacturers are introducing using new light weight materials Intermetallic TiAl alloys 50% lower weight compared to conventional Ni-based alloys. Centrifugal investment casting can deliver high quality requirements Ni basis Vs. TiAl blades

10 Near-net-shape parts manufacture of Titanium Aluminides HPC Vanes LPT Blades Turbocharger Wheel Medical Implant But a difficult material to cast Potential of misrun Components like LPT blades have trailing edges of around 0.5 mm

11 Centrifugal Investment Casting of Low Pressure Turbine (LPT) Blades

12 Typical casting defects in LPT blades Misruns Porosity Ceramic Particles Hot tearing Gas entrapments Ceramic breakouts The foundry engineer faces an uphill task!!!!

13 Centrifugal investment casting LPT Blades Separation valve (open) Heating box Tilting Induction Skull Melting Copper Crucible Melt Melting chamber Casting chamber Sprue Process characteristics Two chamber system Melting capacity: 10.0 kg (optional 25 kg) Rotation speed:0-400 rpm Mould filling in 1.5 seconds Rotation Rotating table Melt distributor

14 Simulation of the pouring process STEP 1: Simulate the crucible pouring process moving grids Metal flow Velocity field Wetting

15 Simulation of the pouring process Obtain inlet mass flow rate for the casting cluster Optimize the pouring process Funnel outflow Skull weights on funnel

16 Simulation of the casting cluster of LPT blades STEP 2: Simulate the casting cluster Generate the shell mould and mesh Apply inlet, initial and boundary conditions Use appropriate time step size (around 1.0e-4s) Solve on a high performance computing cluster (With around 72 processors total computing time is 4 days) Objectives: Predict misruns : i.e., if a fully filled blade is achievable or not

17 Typical casting cluster of LPT Blades Inlet LPT blade Distributor Ingates Rotating at 200 RPM Runner

18 Generation of shell mould and mesh Polyhedral mesh on shell mould Total mesh size :3 million cells

19 Simulations of casting cluster Rotating at 200 RPM

20 Simulations of casting cluster Rotating at 200 RPM

21 Result from Casting Trials

22 Comparison of casting trials and simulation predictions

23 Final outcome!!!! Simulations Casting designs Next time anyone flying on an aircraft fitted with these blades be assured it has been developed using state-of-the-art tool STAR-Cast

24 Centrifugal investment casting of TiAl turbocharger wheels

25 Centrifugal investment casting TiAl turbo charger wheel Centrifugal investment casting furnace, shell mold and turbocharger wheel

26 Centrifugal investment casting TiAl turbo charger wheel Process characteristics Melting capacity: 2.0 kg (max) 1 Chamber process

27 Centrifugal investment casting TiAl turbo charger wheel Ceramic shell mold calculated using the STAR- Cast shell mold generator Wrapping around parts slows down the solidification process

28 Centrifugal investment casting TiAl turbo charger wheel

29 Centrifugal investment casting TiAl turbo charger wheel spinning

30 Future work Multiple frame of references coupled with solidification Centrifugal casting of multiple alloys Particle tracking during mould filling Coupling to thermomechanics

31 Special Thanks!!