Investigation Of The Flow Field In A Single-Cylinder Spark Ignition Engine Using OPENFOAM ”. Investigation performed on Darmstadt spray-guided research engine, using LES turbulence modelling.

1. Investigation of the flow field
in a single-cylinder Spark Ignition
engine using OpenFOAM
Antonio D’Andrea
M.Sc. Mechanical Engineering
Politecnico di Milano
Examiner: Prof. Michael Oevermann
Combustion and Propulsion system
Chalmers University of Technology

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Overview
• Introduction
• Modeling framework
• Stl Generation
• Mesh Generation
• Mesh motion strategy
• Optical research engine and
Simulation settings overview
• Results
• In-cylinder pressure
• Velocity profiles (Quantitative Analysis)
• Flow visualization (Qualitative Analysis)
• Conclusion

3. Objectives
Overall fluid-dynamic
domain
• Full-cycle 3D simulation
 Main objective is to capture the
correct in-cylinder turbulence.
• To Investigate
 In-Cylinder Pressure
Velocity field
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4. Modeling Framework - Stl Generation
stl files:
• Cylinder Head
• SparkPlug
• Injector
• Piston
• Liner
• Intake Valves (Bottom, Top, Stem)
• Exhaust Valves (Bottom, Top, Stem)
• Inlet cross-section
• Outlet cross-section
• Exhaust Manifold
• Intake Manifold
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5. Stl Foundation File
Modeling Framework - Stl Generation
• Engine Stl generation file:
 Automatic procedure adopting shell script
 5 crank angle degree step interval (full-cycle → 144 cases)
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6. Modeling Framework – Mesh Generation
• BlockMesh
• SnappyHexMesh
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7. Modeling Framework - Mesh motion strategy
• OpenFOAM dynamicFvMesh model.
• Grid motion based on displacement Laplacian Equation:
 Keeps track of grid points positions;
 Calculates grid point velocities;
 Updates grid points positions;
 Mesh deformation dealt with mapping (“mapFielDict”)
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8. Modeling Framework - Research engine overview
• TU-Darmstadt optical research Engine
Spray-Guided head geometry
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9. Modeling Framework – Simulation settings
• Numerical Set-up overview:
 OpenFOAM 2.2.2;
 LES simulation;
 Solver based on sonicEngineFoam;
 Pressure-based compressible solver;
 Unstructured hex grids;
 Mesh motion without topological changes;
 Mapping and solution in parallel;
 Backward implicit time integration;
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 Time varying pressure boundary conditions;
• Three preliminary consecutive Cycles with
fixed mesh:
 2.4 - 6.5 million cells (TDC – BDC) ducts
included;

10. Cycle 4
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Results

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Results – In-cylinder pressure

12. 60 CAD bTDC 30 CAD bTDC
15 CAD bTDC TDC
Sampling line at z = 5mm
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Results – Quantitative Analysis
Sampling line position z=5mm
z
xy
Reference U magnitude field
cycle2

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Ux[m/s]Uz[m/s]
X axis [mm] X axis [mm] X axis [mm] X axis [mm]

14. Sampling line at z = 0mm
60 CAD bTDC 30 CAD bTDC
15 CAD bTDC TDC
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Results – Quantitative Analysis
z
xy
Sampling line position z=0mm
Reference U magnitude field
cycle2

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Results – Quantitative Analysis
Ux[m/s]Uz[m/s]
X axis [mm] X axis [mm] X axis [mm] X axis [mm]

16. Sampling line at z = -10mm
60 CAD bTDC 45 CAD bTDC
15 CAD bTDC TDC
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Results – Quantitative Analysis
z
xy
Sampling line position z=-10mm
Reference U magnitude field
cycle2

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Results – Quantitative Analysis
Ux[m/s]Uz[m/s]
X axis [mm] X axis [mm]

18. Results – Flow visualization
• Tumble plane PIV
Measurements
Numerical

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Results – Qualitative Analysis
CYCLE 1 CYCLE 2PIV
300bTDC250bTDC
CYCLE 3
z
xy

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Results – Qualitative Analysis
180bTDC CYCLE 1 CYCLE 2PIV CYCLE 3130bTDC
z
xy

21. CYCLE 1 CYCLE 2PIV
50bTDC30bTDC
z
xy
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Results – Qualitative Analysis
CYCLE 1 CYCLE 2PIV CYCLE 3

22. PIV
U[m/s]
X direction
zdirection
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Results – Qualitative Analysis
• Qualitative analysis for center of tumble motion at 250°bTDC (Max valve Lift).
CYCLE 4

23. Conclusion - Future work
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• Multi-cycles simulations:
 more motored cycles to improve results
towards TDC;
• Implementation of combustion model:
 Fired engine simulations in stratified condition.
 Spray direct injection simulation within engine
model;

24. T
Conclusion – Preliminary Fired case
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• Implementation of Weller
combustion model:
 Fired engine simulation
with premixed fuel.

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Thank you for
your attention