via STAR-Cast Santhanu Jana, Access e.V., Aachen Talk overview - - PowerPoint PPT Presentation

Simulation of Centrifugal Casting via STAR-Cast

Santhanu Jana, Access e.V., Aachen

 Centrifugal casting  STAR-Cast‘s modelling basis  Motivation for centrifugal investment casting  Centrifugal investment casting of

• Low pressure turbine blades
• Turbocharger wheels

 Future work

Talk overview

 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 Mould Coating Liquid metal Bottom rollers

Introduction to centrifugal casting

Schematic of horizontally rotated bimetallic casting

Modelling basis in STAR-Cast

 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 10.000 cells per processor: STAR-Cast Power Version

STAR-Cast‘s modelling approach

 Advanced liquid-solid state transition model

• Resistance to flow is a function of secondary dendrite arm

spacing Liquid Mushy Solid fL= 0.0 fL= 0.3 fL= 1.0

STAR-Cast‘s modelling approach

Motivation for centrifugal investment casting

 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

Casting of TiAl components with centrifugal investment process

 But a difficult material to cast

• Potential of misrun
• Components like LPT blades have trailing edges of around 0.5 mm

Near-net-shape parts manufacture of Titanium Aluminides

HPC Vanes LPT Blades Medical Implant

Turbocharger Wheel

Centrifugal Investment Casting of Low Pressure Turbine (LPT) Blades

Typical casting defects in LPT blades

Misruns Porosity

The foundry engineer faces an uphill task!!!!

Gas entrapments Ceramic Particles Ceramic breakouts Hot tearing

Induction Skull Melting Copper Crucible Tilting Melt Separation valve (open) Heating box Melting chamber Casting chamber Sprue Melt distributor Rotating table Rotation

Process characteristics Two chamber system Melting capacity: 10.0 kg (optional 25 kg) Rotation speed:0-400 rpm Mould filling in 1.5 seconds

Centrifugal investment casting  LPT Blades

 STEP 1: Simulate the crucible pouring process moving grids Metal flow Velocity field

Simulation of the pouring process

Wetting

Simulation of the pouring process

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

 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

Simulation of the casting cluster of LPT blades

LPT blade Distributor Runner Ingates Inlet Typical casting cluster of LPT Blades

Rotating at 200 RPM

Polyhedral mesh on shell mould Total mesh size :3 million cells

Generation of shell mould and mesh

Simulations of casting cluster

Rotating at 200 RPM

Simulations of casting cluster

Rotating at 200 RPM

Result from Casting Trials

Comparison of casting trials and simulation predictions

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

Centrifugal investment casting of TiAl turbocharger wheels

Centrifugal investment casting  TiAl turbo charger wheel

Centrifugal investment casting furnace, shell mold and turbocharger wheel

Centrifugal investment casting  TiAl turbo charger wheel

Process characteristics Melting capacity: 2.0 kg (max) 1 Chamber process

Wrapping around parts slows down the solidification process Ceramic shell mold calculated using the STAR- Cast shell mold generator

Centrifugal investment casting  TiAl turbo charger wheel

Centrifugal investment casting  TiAl turbo charger wheel

Centrifugal investment casting  TiAl turbo charger wheel

spinning

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

Future work

Special Thanks !!