Study of Singlet Delta Oxygen O₂(¹Δ_g) Impact on H₂–O₂ Mixture Ignition in Flow Reactor: 2D Modeling

Abstract

Influence of electron excited singlet delta oxygen (SDO) molecules produced in direct current (DC) glow discharged plasma on the induction length decrease in the H₂–O₂ mixture has been studied via comprehensive two-dimensional (2D) numerical simulations. The sensitivity analysis of the induction length on SDO mole fractions and residual mole fractions of odd oxygen was carried out. The influence of the reaction H₂ + O₂(¹Δ_g) → H + HO₂ on the ignition length was found to be negligible due to the presence of residual odd oxygen in the oxidizer flow. Two stages specify the ignition time decrease for the studied conditions: (1) chain initiation in reactions with residual odd oxygen and (2) the following chain-branching enhancement due to reaction H + O₂(¹Δ_g) → O + OH. The last reaction is the key process for studied conditions when the concentration of SDO exceeds 4%. The estimated rate constant of this reaction was found to be about 2.5 · 10⁻¹³ cm³/s at 780 K. The quenching reaction H + O₂(¹Δ_g) → H + O₂ does not affect the ignition length.

Keywords:

• Chemical reactions
• Hydrogen combustion
• Plasma-assisted ignition
• Singlet delta oxygen

ACKNOWLEDGMENTS

Authors are grateful to professor A. M. Starik for fruitful discussions. This work was supported by the Russian Key Scientific Schools Program (NSh 3322.2010.2).

Notes

*The rate constants for reactions for which the coefficients k₀, n, and E_a are not given in the Table 1 were calculated using the principle of detailed equilibrium.

Published as part of the 23rd International Colloquium on the Dynamics of Explosions and Reactive Systems (ICDERS) Special Issue with Guest Editor Derek Dunn-Rankin