Effects of infinitely fast chemistry on combustion behavior of coaxial diffusion flame predicted by large eddy simulation

Abstract

Large eddy simulations (LES) based on turbulent combustion models aid the design and optimization of combustors. Of the various combustion models available, the eddy break up (EBU) model is widely used because it assumes an infinitely fast chemistry. However, omitting the actual chemical kinetics can cause unexpected behavior, and the characteristics of the combustion models need to be elucidated. Here, the effects of an infinitely fast chemistry on the combustion behavior of a coaxial diffusion flame as predicted by an LES were analyzed. Although the EBU model captured the overall behavior of the chemical species as well as the flow field, the gas temperature and mass fractions of the combustion products in the mixing region of the fuel and oxidizer streams were overestimated. In contrast, the flamelet/progress variable (FPV) model yielded results that were in better agreement with the experimental data, because while the EBU model assumes an infinitely fast chemistry, the look-up tables used in the FPV model are based on the actual chemical kinetics. As these models can be used for the CFD simulations of coal and spray combustion, the results of this study should be useful for efficiently simulating practical combustion systems.

Application of flamelet/progress-variable approach to the large eddy simulation of a turbulent jet flame of pulverized coals

“…The simulation was performed using our in-house code, which was developed at Tohoku University on the basis of the finite volume method [23,58]. The computational domain was constructed using unstructured grids with approximately five million grids.…”

On the interaction of wind, fire intensity and downslope terrain with implications for building standards in wildfire-prone areas

“…In the current study, to account for the effects of turbulent flow on fluid behaviour, the Large Eddy Simulation (LES)(Wang et al 2011) turbulence model is applied and the wall-adapting local eddy (WALE) viscosity method is used. The combustion model of infinitely fast chemistry(Akaotsu et al 2020) is also employed. The single-step combustion reaction of methane is used:…”