Energirelaterad fordonsforskning 2014, oktober 8-9, Göteborg Predictive modeling of combustion and...

Energirelaterad fordonsforskning 2014, oktober 8-9, Göteborg

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


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


Engine design and optimization

• Large number of parameters, thousands CFD run cases– 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– 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


Accuracy and efficiency

accuracy

cost

Detailed chemistry, LES

Simplified chemistry, RANS

Detailed chemistry, RANS

Detailed chemistry, LES-CCM

Detailed chemistry, RANS-CCM


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.


Achievements

• Evaluation of RANS based chemistry coordinate mapping (CCM) models under ECN Spray A conditions.

• Evaluation of LES-CCM models using ECN cases with n-Dodecane 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.


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.

High efficiency transported PDF approach


DRM22 with 22 species and 74 reactions

Methane jet discharging into high temperature atmosphere

UC Berkeley viciated flame


(a): coflow T= 1350 K (case C50) (b): coflow T= 1310 K (case C10)



Sandia engine with multiple injections

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

J. O’Connor et al. (2013) experiments


Temperature field, blue-red range is 400-1100 K

Sandia engine with multiple injections


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.


Thank you for your attention

Energirelaterad fordonsforskning 2014, oktober 8-9, Göteborg Predictive modeling of combustion and...

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