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Implementation and validation of the G-equation model coupled with flamelet libraries for simulating premixed combustion in I.C. engines

Toninel, S. and Forkel, H. and Frank, T. and Durst, B. and Hasse, C. and Linse, D. (2009):
Implementation and validation of the G-equation model coupled with flamelet libraries for simulating premixed combustion in I.C. engines.
In: SAE International Journal of Engines, pp. 674-690, 2, (1), DOI: 10.4271/2009-01-0709, [Online-Edition: https://doi.org/10.4271/2009-01-0709],
[Article]

Abstract

The G-equation model was implemented in the commercial code ANSYS CFX and validated against experimental data in order to successfully simulate turbulent premixed combustion in internal combustion engines. The model is based on the level-set approach. Two transport equations are solved respectively for the G-scalar mean value, representing the local distance function from the time-averaged mean flame front, and its variance, correlated to the turbulent flame brush thickness. The model closure for tracking the flame front is based on an algebraic expression for the turbulent burning velocity. The composition of the reacted mixture is evaluated by coupling the code with flamelet libraries generated with the ANSYS CFX-RIF package by means of a reaction progress variable computed as a function of the G-related quantities. An innovative technique for periodically re-initializing the G-scalar field, in order to enforce geometrical consistency and avoid numerical instabilities, was developed, consisting of a least-square-based interface reconstruction and a minimization of the distance from the discretized flame front. In order to make the code suitable for spark-ignition engine applications the combustion model was coupled with a spark kernel model that simulates the early stages of the ignition process at sub-grid scales. The robustness and accuracy of the level-set approach with moving structured and unstructured meshes were assessed and the parallel performance of the combustion model was optimized in order to deal with large meshes in industrial applications. Validation was carried out by comparing simulations against experimental data for three different test-cases: a steady flame in a slot-burner, a transient spark-ignited premixed combustion in a cylinder with fixed walls and optical access and a spark-ignition research engine with flat head and flat piston. The results show good numerical properties and other attractive features in terms of geometrical description of the flame front and coupling with sub-models for detailed chemistry and spark-ignition. 2009 SAE International.

Item Type: Article
Erschienen: 2009
Creators: Toninel, S. and Forkel, H. and Frank, T. and Durst, B. and Hasse, C. and Linse, D.
Title: Implementation and validation of the G-equation model coupled with flamelet libraries for simulating premixed combustion in I.C. engines
Language: English
Abstract:

The G-equation model was implemented in the commercial code ANSYS CFX and validated against experimental data in order to successfully simulate turbulent premixed combustion in internal combustion engines. The model is based on the level-set approach. Two transport equations are solved respectively for the G-scalar mean value, representing the local distance function from the time-averaged mean flame front, and its variance, correlated to the turbulent flame brush thickness. The model closure for tracking the flame front is based on an algebraic expression for the turbulent burning velocity. The composition of the reacted mixture is evaluated by coupling the code with flamelet libraries generated with the ANSYS CFX-RIF package by means of a reaction progress variable computed as a function of the G-related quantities. An innovative technique for periodically re-initializing the G-scalar field, in order to enforce geometrical consistency and avoid numerical instabilities, was developed, consisting of a least-square-based interface reconstruction and a minimization of the distance from the discretized flame front. In order to make the code suitable for spark-ignition engine applications the combustion model was coupled with a spark kernel model that simulates the early stages of the ignition process at sub-grid scales. The robustness and accuracy of the level-set approach with moving structured and unstructured meshes were assessed and the parallel performance of the combustion model was optimized in order to deal with large meshes in industrial applications. Validation was carried out by comparing simulations against experimental data for three different test-cases: a steady flame in a slot-burner, a transient spark-ignited premixed combustion in a cylinder with fixed walls and optical access and a spark-ignition research engine with flat head and flat piston. The results show good numerical properties and other attractive features in terms of geometrical description of the flame front and coupling with sub-models for detailed chemistry and spark-ignition. 2009 SAE International.

Journal or Publication Title: SAE International Journal of Engines
Volume: 2
Number: 1
Uncontrolled Keywords: Algebraic expression; Combustion model; Commercial codes; Detailed chemistry; Equation models; Experimental data; Fixed wall; Flame front; Flamelets; I.C. engine; Ignition process; Interface reconstruction; Least squares; Level set approach; Local distance function; Mean values; Numerical instability; Numerical properties; Optical access; Parallel performance; Premixed combustion; Reaction progress; Scalar fields; Spark ignition engines; Spark Kernel; Subgrid scale; Submodels; Test case; Time-averaged; Transport equation; Turbulent burning velocities; Turbulent flame; Turbulent premixed combustion; Unstructured meshes, Electric sparks; Engine cylinders; Flammability; Industrial applications; Libraries; Mathematical models; Optimization; Turbulent flow, Ignition
Divisions: 16 Department of Mechanical Engineering > Simulation of reactive Thermo-Fluid Systems (STFS)
16 Department of Mechanical Engineering
Date Deposited: 30 Nov 2017 12:03
DOI: 10.4271/2009-01-0709
Official URL: https://doi.org/10.4271/2009-01-0709
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