Numerical Simulation of Reacting Flows under Laminar Conditions with Detailed Chemistry

• Main Author: Contreras Espada, Jesús
• Format: Others
• Language: English; en
• Published: 2010
• Online Access: http://tuprints.ulb.tu-darmstadt.de/2330/2/Diss_2010_11_21.pdf; Contreras Espada, Jesús <http://tuprints.ulb.tu-darmstadt.de/view/person/Contreras_Espada=3AJes=FAs=3A=3A.html> : Numerical Simulation of Reacting Flows under Laminar Conditions with Detailed Chemistry. Technische Universität, Darmstadt [Ph.D. Thesis], (2010)

Many industrial applications deal with chemical reactive systems under laminar conditions. Processes like combustion, chemical vapour deposition, coatings, oxidations and many others often times occur in a laminar flow regime, where the reaction rates are controlled by the molecular diffusion of the reactants. Laminar flames are considered nowadays an illustrative example of the combustion phenomenon and its experimental and detailed numerical analysis is an essential part in the modelling of turbulent combustion processes as well as for pollutant formation. The coupling of an academic CFD code (FASTEST-3D) and a chemical kinetics solver (CHEMKIN) has allowed the calculation of several configurations involving combustion under laminar conditions. The results have been compared with the literature and verified against calculations carried out with a commercial code (FLUENT). In the coupling, FASTEST-3D solves the transport equations for mass, momentum, energy and species using the source terms for species and energy provided by CHEMKIN. The information required by the chemistry solver, which is provided by the CFD code, are the species concentrations and the temperature value for each control volume. The transport properties of the different species (diffusion and viscosity) are as well given by CHEMKIN as a function of temperature through its “transport database”. An “operator-splitting” procedure (Strang-Marchuk splitting) has been used for the treatment of source terms in the species and energy transport equations. This procedure consists of solving, in a first step, the mechanical problem for half of the time step, then the chemical source terms are calculated for a full time step and finally the loop is closed by solving the flow equations for the remaining half time step. The influence of critical characteristics like the Courant number or the temporal discretization has been analysed in a 1D configuration (perfectly stirred reactor) and finally some 3D cases have been calculated: · H2 diffusion flame in a micro-combustor · H2 premixed flame (lean mixture) in a Bunsen burner · Cold wall stabilized CH4 premixed flame (stoichiometric mixture) · H2 premixed flame (lean mixture) in the EKT standard burner For the sake of simplicity and to achieve a faster convergence the first three calculations were performed with constant properties (density and viscosity). For the simulation of an H2 premixed flame in the EKT standard burner, all properties were treated as temperature dependant. The simulations showed qualitative and quantitative consistency between the results provided by FASTEST-3D – CHEMKIN, the commercial code, and those available in the literature.