Large Eddy Simulation of a Syngas Jet Flame: Effects of Preferential Diffusion and Turbulence–Chemistry Interaction

Abstract

A large eddy simulation of the turbulent syngas non-premixed jet flame of Sandia ETH/Zurich B is conducted using an in-house version of FireFOAM, a fire simulation solver within OpenFOAM. Combustion is modeled using (i) the newly extended eddy dissipation concept for the large eddy simulation published by the authors’ group, (ii) the 74-step CO–H2–O2 mechanism and (iii) the relatively simple tabulated chemistry approach. The effects of the nonunity Lewis number and thermal diffusion (=Soret diffusion) are considered in the mass fraction and enthalpy equations. Systematic validation and model sensitivity studies have been conducted against published experiments of the turbulent syngas diffusion flame from the international workshop on measurement & computation of turbulent flames (TNF workshop). The predictions were in very good agreement with the relevant experimental data. The axial position of peak H2O moved toward the nozzle direction owing to the different diffusion coefficients of H2. In the radial direction, the effect of thermal diffusion was observed at x/d < 20, whereas those of the nonunity Lewis number and difference in chemistry were found at x/d < 40. After considering the effects of the nonunity Lewis number and thermal diffusion, as well as the detailed reaction mechanisms, the results were slightly better than those obtained under previous numerical conditions.

Numerical simulation of small pool fires incorporating liquid fuel motion

“…The in-house version of FireFOAM 2.2.x, which contains the authors' previous developments [12,18,19,22] is employed. The momentum and continuity equations are solved by Pressure-Implicit with Splitting of Operators (PISO) with the outer iteration (termed PIMPLE [9]).…”

“…modelling. The methodology for gas phase modelling was the same as presented in our previous studies [22]. Some further modifications to facilitate the present study will be introduced in following sections.…”

“…The minimum of the two was used as the reaction time scale. The infinitely fast chemistry was used as described in our recent paper [22].…”

“…Two further cases were simulated to test grid sensitivity of the first grid height from the interface in the gas phase, which is ∆First in Eq. (22). Equation ( 22) would be valid if the boundary layer is well resolved.…”

A Priori Modeling of NO Formation with Principal Component Analysis and the Convolutional Neural Network in the Context of Large Eddy Simulation

“…NO x include NO and NO 2 , with NO formation being dominant in most flames . Large eddy simulation (LES) is widely employed in modeling of turbulent combustion. − However, the modeling of NO formation in LES is challenging as NO formation involves various reaction pathways with different characteristic timescales, and the timescale of the dominant pathway is usually larger than that of fuel oxidation, leading to difficulties to accurately predict NO formation . Moreover, NO formation is very sensitive to local temperature and equivalence ratio in combustors, which are hard to capture precisely with existing combustion models.…”