Predictive modeling of combustion and emissions
behavior in diesel and PPC engines
Xue-Song Bai, Mehdi Jangi
Dept of Energy Sciences, Lund University
Eric Baudoin, Raymond Reinmann, Niklas Nordin
Scania CV AB
Energirelaterad fordonsforskning 2014, oktober 8-9, Göteborg
Motivation
• Diesel engine development
– High efficiency
– Low emissions of NOx, soot
• Current solutions, among others
– Advanced injection strategy with EGR
– Non-conventional combustion mode: PPC
• R&D approaches
– Engine experiments
– CFD simulations
• CFD simulations are widely used in engine design
– Used in all major engine companies
– Cost-effective, 4-dimensional data, great potential
– In USA Wisconsin group demonstrated the potential of CFD
Energirelaterad fordonsforskning 2014, oktober 8-9, Göteborg
Engine design and optimization
• Large number of parameters, thousands CFD run cases
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Injection strategies: nozzle, angles, timing, fuel type
EGR and inlet temperature, incylinder pressure
Piston/cylinder geometry
Turbulence intensity, swirl
• Engine combustion model efficiency is of concern
– Chemistry coupling with the flow is important for PPC
– We developed a novel chemistry coordinate mapping (CCM)
• State-of-art engine combustion CFD modeling
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Considerable test of models for SI and diesel engines
Not well tested for PPC or diesel with EGR or alternative fuels
Not predictive
Accuracy and cost tradeoff
Energirelaterad fordonsforskning 2014, oktober 8-9, Göteborg
Accuracy and efficiency
accuracy
Detailed
chemistry,
LES-CCM
Detailed
chemistry,
RANS-CCM
Detailed
chemistry,
LES
Detailed
chemistry,
RANS
Simplified
chemistry,
RANS
cost
Energirelaterad fordonsforskning 2014, oktober 8-9, Göteborg
Project goals and deliverables
• Develop and systematically test the CFD tools and
models
– models used presently in industry and academics
– under challenging diesel engines/PPC engines conditions
– working with the OpenFoam platform
• Carrying out real engine experiments
– serves as validation of the CFD models
– baseline case for testing advanced engine concept
• Development of a guideline for the use of various CFD
models
– model accuracy (requiring detailed chemistry)
– computational efficiency (CCM approach, focus of this project)
– under various diesel/PPC engine-operating and fuel conditions.
Energirelaterad fordonsforskning 2014, oktober 8-9, Göteborg
Achievements
• Evaluation of RANS based chemistry coordinate mapping (CCM)
models under ECN Spray A conditions.
• Evaluation of LES-CCM models using ECN cases with nDodecane and n-Heptane fuel under varying conditions.
• A comparison of RANS-CCM and LES-CCM approaches is
investigated based on the ECN cases.
• Development of a new turbulence/chemistry interaction model,
based on CCM and transported probability density function (PDF).
• Engine experiment campaign at Scania are carried out with model
fuels.
Energirelaterad fordonsforskning 2014, oktober 8-9, Göteborg
High efficiency transported PDF approach
Notional particles are tracking in
physical space
Particles mapped to the phase-space
for solving chemistry’s ODEs
- Several particles at similar thermodynamic states grouped into one zone in the phase-space.
- Integration of the stiff ODEs is perform in the zones and the results are mapped back to the particles
- Speedup the integration of stiff ODEs by a factor of 30.
Energirelaterad fordonsforskning 2014, oktober 8-9, Göteborg
UC Berkeley viciated flame
Methane jet discharging into high temperature atmosphere
Cabra’s methane lifted flame:
Velocity [m/s] YCH4
Jet
100
0.213
Co-flow 0.9
0
YO2
0.188
0.141
T [K]
320
1310-1350
DRM22 with 22 species and 74 reactions
Energirelaterad fordonsforskning 2014, oktober 8-9, Göteborg
UC Berkeley viciated flame
(a): coflow T= 1350 K (case C50)
Energirelaterad fordonsforskning 2014, oktober 8-9, Göteborg
(b): coflow T= 1310 K (case C10)
UC Berkeley viciated flame
Energirelaterad fordonsforskning 2014, oktober 8-9, Göteborg
Sandia engine with multiple injections
J. O’Connor et al. (2013)
experiments
Engine base type: Cummins N-14, DI diesel
Bore: 139.7 mm Stroke: 152.4
Geometric compression ration: 11.2
Intake O2: 12.6 %
Injection: One main injection followed by a post injection
Energirelaterad fordonsforskning 2014, oktober 8-9, Göteborg
Sandia engine with multiple injections
Temperature field, blue-red range is 400-1100 K
Energirelaterad fordonsforskning 2014, oktober 8-9, Göteborg
Ongoing work
• Further engine experiment campaign at Scania are ongoing
• Application of LES/RANS CCM/PDF models to study of the
Scania engines, to improve the understanding of the mixing and
combustion process for improvement of the design.
Energirelaterad fordonsforskning 2014, oktober 8-9, Göteborg
Thank you for your attention
Energirelaterad fordonsforskning 2014, oktober 8-9, Göteborg