In-situ soot characterization of propane flames and influence of additives in a 100 kW oxy-fuel furnace using two-dimensional laser-induced incandescence

Journal article, 2019

In-situ soot characterization has been successfully performed in a 100 kW(th) down-fired oxy-fuel test furnace using laser-induced incandescence (LII) and extinction measurements. Primarily non-premixed propane flames were investigated in oxy-fuel mode with various concentrations of oxygen in the oxidant. The turbulent flame character was manifested through two-dimensional single-shot LII signals from soot showing strong spatial variations as well as local temporal variations. The LII signals were calibrated to soot volume fractions, f(v) , using in-situ extinction in the same spatial regions of the furnace. The results show increased f(v) for increasing oxygen concentration in the oxidant, which is related to increased temperatures as well as decreased mixing inside the furnace due to lowered total flow. For some measurement cases, the influence of additives was studied for flames in oxy-fuel and air environments. The results showed increased f(v) for additions of SO2 and NO for oxy-fuel conditions, while a decrease of f(v) was found for air-fed flames. Also, a large decrease in f(v) was found for water injection in the air-fed flames, and a slightly larger decrease for addition of KCl dissolved in water with the same amount of injected solution. Uncertainties in performing soot volume fraction measurements using LII and extinction in this large-scale furnace are discussed, and mainly considered to be uncertainties in E(m) for soot, the spatial variation of the laser fluence in the large imaged area, and the estimation of the absorption length during extinction calibration.