CHEMISTRY REDUCTION AND THERMOKINETIC CRITERIA FOR IGNITION OF HYDROGEN-AIR MIXTURES AT HIGH-PRESSURES

A systematic methodology consisting of sensitivity analysis, principal component analysis, quasi-steady-state analysis, and reaction path an alysis is applied at bifurcation points to deduce the kinetic and ther mal interactions at ignition of H-2-air mixtures at high pressures in a flow reactor. Singularity theory is subsequently used to derive ther mokinetic ignition criteria, capable of accurately predicting ignition temperature over a wide range of pressure along the second and third ignition limits. Comparison of thermokinetic criteria to the second ig nition branch isothermal kinetic criterion shows the importance of HO2 and H2O2 chemistry and reaction exothermicity at high pressures. Ther mally, ignition along the third branch is shown to be primarily driven by the exothermicity of the H + O-2 + M --> HO2 + M reaction. Transpo rt analysis indicates that the outflow of H2O2 becomes quite important at high pressures, causing the shift in the third ignition branch wit h respect to residence time. A revised isothermal kinetic criterion fo r the higher pressures of the second ignition limit is also proposed.