The effects of hydrogen addition on soot formation in counterflow diffusion n-heptane flames

The effects of H2 addition on soot formation are investigated in counterflow diffusion nheptane flames. Three effects including chemical, thermal, and dilution are fully isolated and characterized by additions of H2, He, and Ar. Soot volume fractions are measured using LE-calibrated LII technique, and flame temperatures are measured using OH-TLAF method along with a thermocouple. Numerical simulations are conducted with a detailed mechanism with soot model. The simulated soot volume fractions and flame temperatures are in good agreement with experimental data. The experimental results show that H2 addition can greatly reduce the soot formation. It is also found that the chemical and dilution effects suppress soot formation, while the thermal effect with increasing flame temperature promotes soot formation. Kinetic analysis suggests that HACA growth rate could be the dominant factor that controls the final soot formation through the three effects due to H2 addition.(c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.