A single-step chemistry mechanism for biogas supersonic combustion velocity with nitrogen dilution

Abstract

The application of one-step irreversible Arrhenius kinetics to the numerical description of biogas supersonic combustion (also known as detonation) with nitrogen N2 dilution is investigated in this study. The three model parameters: the temperature exponent n, the activation energy Ea, and the pre-exponential factor Ar are chosen to describe biogas detonation velocities. It can be seen that as the N2 dilution reached 50%, changes in Ea caused a significant drop in biogas detonation velocity, which was also observed in the current biogas detonation experiment, demonstrating that the dependence of high and low Ea values could appropriately tailor for changes in the thermodynamic condition of the reaction zone behind the detonation fronts as the N2 dilution increased. Via the validation feedback loop processes with the experimental and detailed chemistry (GRI Mech 3.0) results as the main validation basis, the resulting chemistry description in the one-step model is able to reproduce biogas detonation velocities with reasonable accuracy (< 15% discrepancy). Hence, the model overcomes the known gap of prior establishments of one-step Arrhenius kinetics for detonation by incorporating the N2 dilution effect and biogas as a fuel for detonation emergence.