The Eulerian Stochastic Fields Method Applied to Large Eddy Simulations of a Piloted Flame with Inhomogeneous Inlet

Maximilian Hansinger,Thorsten Zirwes,Julian Zips,Peter Habisreuther,Feichi Zhang,Henning Bockhorn,Michael Pfitzner

doi:10.1007/s10494-020-00159-5

Abstract

Large Eddy Simulations of the Sydney mixed-mode flame with inhomogeneous inlet (FJ200-5GP-Lr75-57) are performed using the Eulerian Stochastic Fields (ESF) transported probability functions method to account for the sub-grid scale turbulence–chemistry interaction, to demonstrate the suitability of the ESF method for mixed-mode combustion. An analytically reduced 19-species methane mechanism is used for the description of the chemical reactions. Prior to the reactive case, simulation results of the non-reactive setup with cold and hot pilot stream are presented, which show differences in the jet breakup and radial species mass fluxes. The reactive case simulations are compared to experimental data and a recently conducted model free quasi-DNS (qDNS), showing very good agreement with the qDNS in terms of scatter data and radial mean values of temperature and species distribution, as well as mixture fraction conditional statistics. Further analysis is dedicated to sub-grid scale statistics, showing that mixture fraction and reaction progress variable are strongly correlated in this flame. The impact of the number of stochastic fields on the filtered temperature and species distribution is investigated; it reveals that the ESF method in conjunction with finite-rate chemistry is very insensitive to the number of employed fields to obtain highly accurate simulation results.

Highlights

Turbulent flames are usually classified into non-premixed and premixed combustion regimes
The second part compares the simulation results of the reactive case FJ200-5GPLr75-57 with the experimental data and the qDNS results of Zirwes et al (2020). It focuses on the impact and importance of the number of stochastic fields Ns and provides insights into the sub-grid statistics and joint correlations of mixture fraction Z and a reaction progress variable c
The Sydney mixed-mode flame configuration FJ200-5GP-Lr75-57 has been successfully simulated using LES with the Eulerian Stochastic Fields (ESF) transported PDF method to account for turbulence–chemistry interaction and a 19-species analytically reduced methane/air mechanism to describe the chemical reactions

Summary

Introduction

Turbulent flames are usually classified into non-premixed and premixed combustion regimes. In non-premixed flames the fuel consumption is dominated by diffusion while premixed flames can propagate into a flammable mixture (Peters 2000) Based on this classification turbulent combustion models have been developed and extensively validated, but their application is limited to their specific regime. In practical combustion devices, such as internal combustion engines or gas turbines, the fuel-oxidizer mixture is rarely perfect and events like autoignition, recirculation of hot combustion products, and extinction/reignition can be important The effect of such inhomogeneities in the fresh gas composition on the stabilization of a piloted turbulent methane/air flame has recently been investigated experimentally by Barlow et al (2015) as well as by Meares and Masri (2014). Despite the continuous efforts to model partially premixed flames (Fiorina et al 2015; Hu and Kurose 2019) there is further research required to understand the complex combustion process in these flames

Methods

Results

Conclusion