Influence of Thickening Factor Treatment on Predictions of Spray Flame Properties Using the ATF Model and Tabulated Chemistry

Abstract

Different strategies to account for the heat and mass transfer between liquid droplets and their carrier phase within the Artificially Thickened Flame (ATF) approach are analyzed and compared. Herein, two approaches are introduced to take into account the droplet movement relative to the thickened flame front orientation. While the first approach achieves this behavior through scalar modifications in the droplet temperature and mass evolution equations, the second one introduces a trajectory modification within the thickened flame front. Both approaches, referred to as projection and refraction correction, are first compared to state of the art methods in a simplified two-dimensional configuration, and then in a complex turbulent spray flame. The investigated spray flame corresponds to the operating condition EtF6 of the Sydney Spray Burner. The analysis showed that: (1) A consideration of a simplified configuration is insufficient to fully uncover the performance of the different approaches. (2) While the proposed approaches performed best in the two-dimensional configuration, only the projection method outperforms the remaining ones in the turbulent spray flame. (3) The formulation to consider the flame thickening has a strong effect on global flame properties, combustion regime distribution as well as carrier and liquid phase statistics.

Effects of Reaction Mechanisms and Differential Diffusion in Oxy-Fuel Combustion Including Liquid Water Dilution

“…Following typically applied strategies in complex flows [6,24], the two other procedures chosen to characterize the diffusion transport refer to the Hirschfelder-Curtiss formulation (hereafter, denoted as the mixture averaged approach; [22] and a unitary Lewis number approach. In both, thermal diffusion effects are not considered.…”

“…However, for the unitary Lewis numbers approach, the simplifying condition is not only specified by setting Le i = 1, but also considering that Pr i = Sc i = 0.7. This is a typical strategy applied to address turbulent combustion simulations based on tabulated chemistry [24,25]. As a consequence, diffusion velocities and heat flux are written as…”

Identification of Flame Regimes in Partially Premixed Combustion from a Quasi-DNS Dataset

“…Historically, the first flame regime marker was developed by Yamashita et al (1996) and is based on the alignment of gradients of the fuel and oxidizer mass fractions. In the last few years alone, a large number of works has used the concept of the Takeno flame index to study flames and improve their prediction: it was used to understand the structure of blue swirling flames (Chung et al 2019), identify flame regimes in thickened flame simulations of spray flames (Hu and Kurose 2019b;Dressler et al 2020) and study the influence of evaporation (Wei et al 2018) as well as devolatilization . Premixed and non-premixed regions in swirl spray flames were analyzed with the flame index concept (Eckel et al 2019;Paulhiac et al 2020) and the influence of swirl number on the combustion regime (Fredrich et al 2019) was evaluated.…”

Numerical Prediction of Turbulent Spray Flame Characteristics Using the Filtered Eulerian Stochastic Field Approach Coupled to Tabulated Chemistry

“…The solution of transport equations for each of these species is unfeasible for large scale application due to the stiff coupling of the equations being solved. To avoid the expensive consideration of the detailed kinetics, various chemical reduction mechanisms [4] and chemistry tabulation approaches have been suggested and successfully applied [5][6][7][8][9]. In this regard, various methods, including the intrinsic low-dimensional manifold (ILDM) by Maas and Pope [10], the reaction-diffusion manifold (REDIM) [11], the flamelet progress variable approach (FPV) [12], the flame prolongation of ILDM (FPI) [13,14] or the flamelet generated manifold (FGM) [15], among others, have been proposed.…”