Experimental and numerical investigations of soot formation in propane laminar coflow flames in O2/N2 and O2/CO2 atmospheres

Abstract

Oxygen-rich combustion is a new type of clean combustion technology with important application prospects. At present, there are few detailed analyses on the mechanism changes of soot formation under oxygen enrichment of propane. In this paper, the effects of oxygen-rich (O2/N2, O2/CO2) combustion on soot formation in the propane laminar flow coaxial jet diffusion flame were investigated by using the experiment and numerical simulation. The flame image was taken by a color (CCD) camera in the visible band, and the two-dimensional distribution of temperature and soot volume fraction in the flame was reconstructed. In numerical simulation, the soot production model considers a detailed description of nucleation via collisions among heavy polycyclic aromatic hydrocarbons, particle aggregation, polycyclic aromatic hydrocarbons condensation, surface growth and oxidation through the hydrogen abstraction acetylene addition mechanism. The results show that the experimental results were compared with the numerical simulation results, and the numerical simulation results predict the temperature and soot change of oxygen-rich flame well. With the increase in oxygen concentration, the peaks of soot and temperature in the two oxygen-rich atmospheres gradually increased. With the increase in oxygen concentration, the peaks of soot and temperature in the two oxygen-rich atmospheres gradually increased. Comparing the combustion mechanism changes of the two oxygen-rich combustion systems, it was found that the hydrogen abstraction acetylene addition mechanism was the main cause of soot generation. The OH oxidation is dominated near the fuel nozzle side, and O2 oxidation is dominant downstream. With the substitution of CO2 for N2, the chemical effect of CO2 reduces the flame temperature and inhibits the formation mechanism and oxidation mechanism of soot to some extent. This in turn leaded to a reduction in the amount of soot produced.

Keywords

• Soot formation
• Laminar diffusion
• Oxygen-rich
• CO2 addition
• Numerical simulation