Numerical Investigation of a MILD Combustion Burner: Analysis of Mixing Field, Chemical Kinetics and Turbulence-Chemistry Interaction

摘要

A numerical study of a jet-in-hot coflow (JHC) burner emulating Moderate or Intense Low-oxygen Dilution (MILD) combustion conditions was carried out by solving the Reynolds Averaged Navier-Stokes equations in a two-dimensional axisymmetric domain and using the Eddy Dissipation Concept (EDC) for the turbulence-chemistry interaction treatment. A systematic methodology was used to analyze all possible sources of discrepancies observed between experimental and numerical data, trying to shedding light on the suitability of specific models for MILD combustion. In this regard, the deficiencies that may come from turbulence model or kinetic scheme have been shown by comparative study on four variants of the k-ε model (i.e. the standard, modified, realizable and RNG) together with the Reynolds stress model and three kinetic schemes namely KEE-58, DRM-19 and DRM-22. A variation of an EDC parameter (i.e. increasing the constant of the fine structure residence time) was proposed for better consideration of MILD combustion features and to overcome the over-prediction of peak temperature observed at downstream. In such a manner encouraging results were also obtained for the prediction of major combustion products as well as for CO and OH.