Soot Formation During Pyrolysis of Methane and Rich Methane/Oxygen Mixtures Behind Reflected Shock Waves

Abstract

The pyrolysis of CH₄/Ar and rich CH₄/O₂/Ar mixtures behind reflected shock waves were studied both experimentally and theoretically. The experiments were carried out behind reflected shock waves. Simulations were performed within the framework of a detailed kinetic model involving more than 260 species and 2500 elementary steps. The measured and calculated time profiles of soot yield and soot particle temperatures for CH₄/Ar and CH₄/O₂/Ar mixtures proved to be in good agreement. The proposed kinetic model can also describe the temperature and pressure dependences of the ignition delay time for stoichiometric CH₄/O₂ mixture at low pressures and for rich CH₄/O₂ mixtures at elevated pressures over a wide pressure range, as well as the promoting effect of C₂H₆ and C₃H₈ additives.

Keywords:

• Detailed kinetic modeling
• Experimental study
• Methane pyrolysis and oxidation
• Shock waves
• Soot formation

This work was supported by the Deutsche Forschungsgemeinshaft and by the Russian Foundation for Basic Research, project no. 08-08-00722.

Notes

^a Rate coefficients a presented in the form k = AT ^bexp(− Ea/RT).

^b The index n denotes the number of carbon atoms incorporated into the particle per elementary event of interaction with carbon-containing gas-phase species.

^c The rate coefficients modified in the present work.

Soot precursors with active sites on the surface are denoted as C[N], and soot precursors without active sites are denoted as CH[N]. Soot particles are large enough to expect that quasi-equilibrium between the activation and deactivation processes is attained in the reaction system. Thus, only one type of soot particles, denoted as S[N], is considered in the model. S[N] is the concentration of soot particles after N acts of interaction with various carbon-containing gas-phase species.

[a] (Agafonov et al., 2007); [b] (Appel et al., 2000); [c] (Richter et al., 2005).