Numerical investigation of a lifted methane/air jet flame using stochastic map-based turbulence modeling

Abstract

Turbulent combustion processes are ubiquitous phenomena and play a fundamental role in a wide range of industrial applications, transportation, and energy production. The accurate numerical investigation of turbulent reacting flows is particularly challenging owing to the wide range of spatial and temporal scales involved. Here, the nonpremixed chemically reacting flow of a lifted methane/air jet flame in a vitiated coflow is studied using the map-based stochastic one-dimensional turbulence (ODT) model. The ODT model is efficient in terms of computational costs and provides nonetheless full-scale resolution along a notional line of sight crossing the turbulent reactive flow field. ODT uses a stochastic formulation for the turbulent advection and considers diffusion and reaction effects along the one‐dimensional domain by temporally advancing deterministic evolution equations. In the considered Cabra burner configuration [Combust. Flame 143 491‐506 (2005)], a jet flame issues from a central nozzle into a vitiated coflow of hot reaction products generated from an array of lean hydrogen/air flames. For the representation of the methane/air combustion, a reduced and detailed reaction mechanism with 19 and 53 species is used, respectively. The centerline profiles for mixture fraction, temperature and species mass fractions reveal reasonable agreement with the experimental measurements. Scatter plots and two-dimensional visualizations of the jet flame are also given including an assessment of an autoignition index used to differentiate between autoignition-driven and flame-propagation-dominated reaction zones. A parametric study is performed to examine the sensitivity of the flame to variations in jet velocity, coflow velocity, and coflow temperature. The results highlight the critical role of the interaction between the hot vitiated coflow and the cold unburnt jet in governing ignition, stabilization, and overall reaction dynamics. Despite its reduced-order formulation, the ODT model captures the essential physics of turbulent nonpremixed combustion and provides predictions that compare favorably with experimental observations at a significantly reduced computational cost.