The Effect of Pressure on Detailed Soot Formation Processes in Laminar Coflow Diffusion RP-3 Kerosene Flames

This paper aims to provide a physical understanding of the pressure effect on soot formation in laminar diffusion flames. Soot formation in laminar coflow diffusion flames is strongly influenced by pressure. Although predicting soot formation at atmospheric pressure has been very accurate in literatures, there is still a lack of understanding of multiple soot formation processes at high pressures. However, few researches studied the effects of pressure on multiple steps in the soot formation. This work studies the pressure effect on detailed soot formation, which includes multiple physical processes of surface growth, surface OH oxidation, surface O₂ oxidation, and collision kinetics. A pressure-dependent model is proposed by analyzing the pressure-dependent surface reactivity in surface reactions and the pressure-dependent collision kinetics in soot formation. Simulation is conducted in the pressure range from 1 atm to 20 atm, with experimental validation in the pressure range from 1 atm to 3.5 atm. In the pressure range from 1 atm to 3.5 atm, the predicted primary soot particle diameter and soot yield of cases with the pressure-dependent model are validated by experimental result. As pressure further increases from 5 atm to 20 atm, the pressure dependence of soot yield and surface reaction rate decreases due to the limit of oxidation. This study contributes to the understanding of the pressure effect on soot formation at high pressures in soot formation.