where the heat goes? thermal analysis of internal...

Where the Heat goes?Thermal Analysis of Internal Combustion Engines

Global Star User Conference

Marcus Ende, Carolus Gruenig, Carsten Skrobanek, Christian Schramm, René Paessler

Vienna, March 17-19, 2014

2

Thermal Analysis of IC EnginesOverview

© IAV · 03/2014 · MEn · DP-E24 · cd-adapco Global User Conference · Vienna · Where the heat goes?

Introduction

CAE Procedure

Gas-side heat transfer

Coolant-side heat transfer

Validation

Summary

3

Thermal Analysis of IC EnginesIntroduction


1990 20151995 2000 2005 2010

Year of Construction

Sp

ec.

En

gin

e P

ow

er

[kW

/l]

Four Cylinder Engines

• Downsizing of engines:

→ Increase of specific engine power

output

→ Higher thermal loading

→ Optimized and very effective

cooling system is needed

• Shorter development cycles

→ Less project time

→ Robust & accurate CAE process

→ Target for CAE

→ Predictive results are required.

→ Calculated structural temperatures within +/- 5 K from reality.

4

Thermal Analysis of IC EnginesCAE Procedure


Averaging over working cycle

αgas(x,t)

Tgas(x,t)

dm/dtCoolant

CFD Coolant Flow Simulation with solid (CHT)

STAR-CCM+

αgas*(x)

Tgas*(x)

1D Gas Exchange Simulation

GT-Power

n, P

Twall*(x)

Some Iterations

α*(x)

Tref*(x)

Thermomechanical Analysis (FEM)

ABAQUS

CFD Combustion Simulation

ES-ICE + STAR-CD

pint(t)

Tint(t)

mFuel

λ

pexh(t)

Texh(t)

5

Thermal Analysis of IC EnginesGas-side Heat Transfer



αgas(x,t)

Tgas(x,t)


ES-ICE + STAR-CDdm/dtCoolant


STAR-CCM+

αgas*(x)

Tgas*(x)


GT-Power

n, P

Twall*(x)

Some Iterations

α*(x)

Tref*(x)


ABAQUS

pint(t)

Tint(t)

mFuel

λ

pexh(t)

Texh(t)

6



− Wall heat transfer has influence on

thermodynamics, emissions, wall film, etc.

− Thermal loads are an important input for FEA

Motivation

− CFD simulation of working cycle / gas-side

heat transfer

− Cycle-averaging of heat transfer coefficients

and local gas temperatures

− Mapping to CFD-CHT model

Simulation Approach

− Detailed analysis of thermal loading

− Thermal boundary conditions for FEA

− Pre-calculation of structural temperatures

Result

�Realistic calculation of thermal loads on

engine structure is essential

CFD results working-cycle heat transfer

Cycle Averaging

CFD-CHT-Model

TGas [K]

Min.

Max.

TGasHTC

Crank Angle

7



Sensitivity analysis of combustion system parameters (Diesel)

� Combustion system specification should be considered as good as possible

� In real-life project work, these information are often not yet available

+0.07mm-0.2mm

-2°KW

1.5mg+50K +500mbar

+10%

-0.07mm

+0.2mm

+2°KW-50K -500mbar +20%

-20

-10

0

10

20

∆∆ ∆∆Q

W [%

]

-0.2mm

-2+0.2mm

+2

-100

-50

0

50

100

150

∆∆ ∆∆Q

W [%

]

8



Sensitivity analysis of basic CFD model parameters

� Turbulence model and wall function have the biggest impact

� Selection of suitable submodels is required

9



� Selection of a suitable turbulence model is mandatory

Sensitivity analysis of turbulence modelling

Turbulence model

∆∆ ∆∆Q

W [%

]

0.0 %

-100.0 %

100.0 %

50.0 %

-50.0 %

10



Sensitivity analysis of wall function

� Selection of suitable wall function model is mandatory

Experiment (Woschni)

Wall Function Model C

Wall Function Model B

Wall Function Model A

Standard Wall Function

CA[°deg] 360270 450

Wall

Heat

Tra

nsfe

r

Heat

Tra

nsfe

r R

ate

11



Cycle-averaged heat input boundary condition from working-cycle CFD

Boundary heat fluxlow high

Combustion chamber Exhaust ports

Complete 4 cyl. model

Liner

� 3d effects captured (e.g. non-symmetric heat flux distributions)

12

Thermal Analysis of IC EnginesCoolant-side Heat Transfer


dm/dtCoolant

α*(x)

Tref*(x)


ABAQUS


STAR-CCM+


αgas(x,t)

Tgas(x,t)


ES-ICE + STAR-CD

αgas*(x)

Tgas*(x)


GT-Power

n, P

Twall*(x)

Some Iterations

pint(t)

Tint(t)

mFuel

λ

pexh(t)

Texh(t)

13

Thermal Analysis of IC EnginesConjugate Heat Transfer Model


Polyhedral calculation grid with conformal interfaces

� Sufficient discretisation necessary (approx. 20 mil. cells for R4 engine model)

12 mm

3 mm

14



Coolant properties

• Chemical composition of cooling fluids affects

→ Convective heat transfer behaviour as well as

→ More important, phase change behaviour / boiling heat transfer performance

� Detailled boiling behaviour of coolant fluid should be known

• Differences of surface

temperatures up to 20

K are observed

15



Boiling modelling

• Available models

• Single-phase Rohsenow model

• To be parameterised / calibrated

• But:

• No transition / film boiling effects captured

• No boiling supression at higher velocities captured

• Multi-phase transition boiling model

• To be parameterised / calibrated

• But not intended on stationary calculations

• Developed IAV approach

• Transition boiling model equations implemented via field functions in single-phase simulation

• Boiling suppression considered

• Calibrated with measurement data

16



Heat transfer performance Cylinder-head temperatures

∆∆∆∆T approx. 20K

high

low

Tem

pera

ture

Effects of different Coolant Boiling Performances

� Accurate description of coolant boiling behaviour is necessary

17

Thermal Analysis of IC EnginesValidation


� This represents a successful simulation, but not yet in target range of +/- 5K

� Satisfying predictive simulations are still challenging

Liner Side Injector Glowplug Intake - Exhaust Exhaust - Exhaust

Differences Simulation to Measurement

18

Thermal Analysis of IC EnginesSummary


→ Not only computational power is decisive but accurate submodelling of ALL

physics.

Near-wall processes

Near-wall flame extincion

Stagnation flow

Thermal radiation, soot layers

Boiling onset / suppression

Transition / film boiling

Fluid properties

Surface conditions / depositions

Contact resistance Deformations / gaps

Material properties

Contact

Marcus Ende

IAV GmbH

Kauffahrtei 25, 09120 ChemnitzTelefon +49 371 237-34386

[email protected]

www.iav.com

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