silencer using co-simulation Presented by: Ayyoob Zarmehri STAR - - PowerPoint PPT Presentation

Thermal soak simulation of Scania’s Eu6 silencer using co-simulation

• SCANIA CV AB

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Vehicle cooling and aerodynamics  Underhood thermal management

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Presented by: Ayyoob Zarmehri STAR Global Conference Vienna 2014

Underhood thermal management

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• 5 CFD engineers
• Technical advices for different design and test groups
• Full truck simulation :
• All external surfaces of different parts
• Heat exchangers like radiator, charge air cooler
• Fan installation
• Conjugate heat transfer for parts of interest if needed

Silencer function

• Sound absorber
• Lowering emission level, satisfying Eu6 standard:

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Inside needs to be hot enough for the chemical factory to function properly

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Requirements regarding the temperature of the external surfaces

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Heat sensitive sensors

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Heat management is necessary to handle the situation

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The structure of the silencer

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• Polyhedral mesher
• Embeded Thin mesher
• 35 million cells mesh

The thermal soak process

• Both the energy source and the cooling airflow are off
• Inherently transient process
• Complex function of heat conduction, natural convection and radiation
• Difficult to test experimentally
• Need to know the correct amount of energy stored in the system

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The interaction between the external flow and the system needs to be known

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One steady-state simulation is needed for the initial conditions

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The steady-state co-simulation

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Simulation 1:

• Internal flow
• Heat conduction within Solid

structure

• Steady-state
• Radiation included

Simulation 2:

• The external flow
• Truck speed: 30 km/h
• Steady-state

Temperature is exported to the UTM simulation Heat transfer coefficient and the reference temperature is exported

The natural convection simulation

• Test cases: flat plate of constant temperature in room temperature

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Case 1: horizontal plate with upper side heated

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Case 2: horizontal plate with lower side heated

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Case 3: vertical plate

• Physics modeling: density as a polynomial function of temperature
• Coupled solver
• Different turbulence models were tested:

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Standard K-E Low-Re:  quadratic constitutive relation  thermal stratification for buoyancy production of dissipation

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K-E two layer  buoyancy driven formulation

• Best results for a wide range of temperature difference : Standard K-E Low-Re

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The natural convection simulation

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8 The near wall mesh

Test cases: flat plate in different orientations

Vertical plate Horizontal plate, velocity Horizontal plate, wall Y+

The natural convection simulation

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Experimental values for:

• Flat plate with dimensions of 0.6m × 0.6m
• Ambient temperature: 30 °C

The thermal soak simulation

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• Solid simulation:
• Leading simulation
• Unsteady
• Time step: 5 s
• Coupling time step: 150 s
• Radiation included
• Fluid simulation:
• Lagging simulation
• Initial conditions calculated
• Steady-state
• Iterations per exchange: 200
• Exports: Specified Y+ HTC and

Reference Temperature

Conclusions:

• Thermal soak simulation has been successfully accomplished with co-

simulation

• Transient cooling of the solid mass is coupled to quasi-steady state changes of

the external natural convection flow

• Co-simulation provides an easy-to-use communication method between two

different simulations

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Future works:

• Urea spray simulation
• Calibration with experimental results

Thanks for the attention! Questions?

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