RANS and LES of turbulent combustion based on flamelet
generated manifolds
Citation for published version (APA):
Fancello, A., Bastiaans, R. J. M., & Goey, de, L. P. H. (2011). RANS and LES of turbulent combustion based on flamelet generated manifolds. In Proceeding of the 6th OpenFoam Workshop(OFW6), 13-16 June 2011,
PennyState University, USA PennState University, USA.
Document status and date: Published: 01/01/2011
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6thOpenFOAM R Workshop PennState University, USA 13-16 June 2011
RANS and LES of Turbulent Combustion based on
Flamelet Generated Manifolds
Alessio Fancello∗, R.J.M. Bastiaans, and L.P.H. de Goey
TU/e Eindhoven University of Technology Den Dolech 2 5600MB Eindhoven -The Netherlands
March 15, 2011
Turbulent Combustion, Flamelet Generated Manifold, IGCC, Hydrogen
The continued need to use coal and, more important biomass, as a primary fuel combined with requirements to curb CO2 emissions generates a genuine demand for the development of reliable, low-emission, cost-competitive gas turbine technologies for hydrogen-rich syngas combustion. Integrated Gasification Combined Cycle (IGCC) is currently one of the most attractive technology for the high-efficiency use of coal and biomass.
The overall objective of this project [1] is to provide and demonstrate technical solutions for the development of highly efficient and reliable gas turbine in the next generation of the IGCC plants. Regarding my tasks, there will be a focus on the development and demonstration on the safe and low emission combustion technology for undiluted hydrogen-rich syngas. Hydrogen is highly diffusive, it affects chemical processes and the stability of flame. In this gas the diffusion mechanism between thermal effects and species is different with resulting in the phenomenon known as preferential diffusion effects.
The final aim of this work is to achieve at a proper combustion model in order to predict the performances in the gas turbines with good focusing on important features such as flame sta-bility and emission characteristics for future combustion designs. These appropriate modeling tools will be a good alternative for saving on costly high pressure experiments.
RANS and LES models of turbulent combustion [2] can be based on reduction techniques such as Flamelet Generated Manifold, FGM. Implementation of the models will be made with OpenFOAM R [3]. Manifolds will be created by the CHEM1D code available at the TU/e [4].
The main idea of the FGM reduction method [5, 6] comes from the fact that detailed mecha-nisms are extremely time consuming, due to the presence of a partial differential equation to be considered for each specie involved, the non-linear coupling of equations by hundreds of chem-ical reactions and finally the stiffness of the system because of the broad range of time scales. In the reaction mechanism many species are correlated and FGM use the correlation to lower
∗
the dimension of the chemical system. The starting point is to consider a multidimensional turbulent flame as a set of many one dimensional flames, called flamelets.
First of all, cold flow simulations are carried out in order to evaluate the field of velocity, pressure and density. Once the cold flow data is checked and validated, the further step involves the implementation of the FGM technique in Open FOAM. The first task is to add a new transport scalar equation for a passive scalar with a source term. The best idea is to use an existing solver from the code and to modify it, with the addition of new code lines. Considering for instance the incompressible RANS solver simpleFoam , a new one FanzySimpleFoam is created in order to be manipulated. Among all the files, the following are useful for the implementation:
• FanzySimpleFoam.C Solver file
• Yeqn.H additional file of the new scalar transport equation
• CreateFields.H declarations of the scalar and volume fields involved, such as (U ; p; Y ;...).
The Yeqn.H equation includes the source term ST. In OpenFOAM R ST can be set in an
explicit or implicit way. For stability purposes, the implicit way should be preferred. The expression of the source term for the scalar transport equation can be given in the following form: ST = Y · (1 − Y ) · Y · constant.
After some manipulations in the code, it is possible to include the new variable Y inside the Case File of the simulation and check, for instance, how this scalar quantity will be transported inside the domain. As a further step, a table provided by the TUe in-house CHEM1D, in which all the detailed chemistry data is listed, is used and uploaded during run-time. In fact, given the parameters necessary for solving the equations, values such as density and source terms of the scalar transport equation are evaluated from the table. Both terms are actually function of the scalar quantity Y which has a value between 0 and 1. Interpolation is then necessary for the values which are non included in the table because of the discrete form of the table. Some simulations with relative simple gas such as methane are carried out. Later on the future work with the FGM will be about the inclusion of hydrogen with its thermal instabilities.
References
[1] http://http://www.h2-igcc.eu/.
[2] Peters, N., Turbulent Combustion, Cambridge University Press (2000) [3] http://www.openfoam.com.
[4] http://www.combustion.tue.nl/chem1d.
[5] de Goey L.P.H. & ten Thije Boonkkamp J.H.M., A Flamelet Description of Premixed Laminar Flames and the Relation with Flame Stretch. Combust. Flame. 119(3), 253–271. (1999)
[6] J.A. van Oijen, L.P.H. de Goey, Modelling of premixed counterflow flames using the flamelet-generated manifold method. Combust. Theory Modelling, 6(3), 463-478, (2002)
