The usability and limits of the steady flamelet approach in oxy-fuel combustions

Abstract

This paper investigates two furnaces which work under oxy-fuel condition with natural gas. One is a 0.8 MW furnace where detailed inflame measurements are available. The other furnace is an 11.5 kW lab-scale furnace with temperature measurements. The furnaces were investigated by CFD (Computational fluid dynamics) analysis. The main focus was on using combustion models that are not computationally demanding. Therefore the SFM (steady flamelet) approach was used with two detailed mechanisms. The advantage of the SFM is that the calculation time can be reduced from 4 weeks to 4 days on 8 CPU-cores. The applicability of two detailed mechanisms under oxy-fuel condition is pointed out in this paper. The investigation showed that the skeletal25 mechanism and the SFM are in very good accordance with measurements. If the strain rate between CH4 and O2 stream is too low, the SFM fails to predict the flame shape correctly. The influence of three different turbulence models was also investigated. Furthermore simulations with the eddy dissipation model and numerically expensive eddy dissipation concept model were conducted. Different WSGGM (weighted sum of grey gases model) were applied. The comparison of the WSGGMs showed that the difference between them is insignificant for small furnaces.