Combustion models for CFD
[1] With the added complexity of chemical kinetics and achieving reacting flow mixture environment, proper modeling physics has to be incorporated during computational fluid dynamic (CFD) simulations of combustion.
The model should be competent enough to deliver information related to the species concentration, their volumetric generation or destruction rate and changes in the parameters of the system like enthalpy, temperature and mixture density.
The model should be capable of solving the general transport equations for fluid flow and heat transfer as well as the additional equations of combustion chemistry and chemical kinetics incorporated into that as per the simulating environment desired[1] The major consideration during any general combustion process includes the mixing time scale and the reacting time scale elapsed for the process.
But with proper simplifying assumptions Computational fluid dynamic modeling of combustion reaction can be done without substantial compromise on the accuracy and convergence of the solution.
[2] The model also takes into account an additional assumption that the mass diffusion coefficients of all species are equal.
[1] This model approximates the turbulent flame as a series of laminar flamelet regions concentrated just around the stoichiometric surfaces of the reacting mixture.
[1] This model exploits the use of experimental data for determining relations between the variables considered like mass fraction, temperature etc.
[2] The model can very well be implemented for situations where concentration of minor species in the combustion is to be computed like quantifying the generation of pollutants.
[1][5] The model can produce satisfactory results for turbulent reactive flows where convection effects due to mean and fluctuating components of velocity are dominant.
The conditional closure model solves the transport equations for the mean components of the flow properties without considering the fluctuating composition of the reaction mixture.
