Effects of hydrogen on PAH and soot formation in laminar diffusion flames of RP-3 jet kerosene and its surrogate

Abstract

PAH and soot are harmful substances that can be produced in any type of combustion equipment including aircraft engines. The co-combustion of hydrogen and jet fuel has been applied in aero-engine combustors and large-scale hydrogen addition is a promising solution for reducing the consumption of fossil fuels in the aviation industry. However, it remains unclear how H2 influences the soot and PAH formation characteristics of jet kerosene. In this study, to investigate the impact of H2 on soot and PAH formation, planar laser-induced incandescence (PLII), planar laser-induced fluorescence of PAH (PAH-PLIF) and chemical kinetic simulation were conducted for the laminar diffusion flames of RP-3 jet kerosene and its surrogate S1 with different H2 doping rates. It is found that the introduction of H2 leads to the increased soot formation. However, the promotion effect of H2 on the PAH formation weakens as the number of PAH rings increases, and the formation of A4 is significantly inhibited. But the rapidly increase of benzene and alkynes in the H2-doped kerosene flame may ultimately lead to the promotion of soot formation. Furthermore, the changes in direct synthesis reactions and PAH=>PAH- jointly affect the converse changes in A1 and A4 formation. These findings will contribute to the development of the soot model and soot/PAH-reduction strategy for the co-combustion of jet fuels and hydrogen.