A shock tube and modeling study on ignition delay times of pyridine under O2/CO2 atmospheres at elevated pressures

Pressurized oxy-fuel combustion has been attracting increasing attentions due to its improved efficiency and low cost. The present study reports ignition delay times (IDTs) of pyridine under O₂/CO₂ atmospheres within a temperature range from 1202 to 1498 K at pressures from 2.2 to 10 bar for equivalence ratios of 0.5, 1.0, and 2.0. The experimental results were compared with the IDTs of pyridine under O₂/Ar atmospheres from MacNamara et al.. The comparison results indicate that the IDTs of pyridine under O₂/CO₂ atmospheres are evident longer than those under O₂/Ar atmospheres even at low pressure. A modified kinetic model (HUST pyridine Model) was proposed based on our previous mechanism. HUST pyridine Model predicted well the IDTs under both O₂/CO₂ and O₂/Ar atmospheres obtained in shock tubes and the species profiles under both O₂/CO₂ and O₂/N₂ atmospheres obtained in plug flow reactors. HUST pyridine Model, Alzueta Model, and Pyridine LTO Model were evaluated. The results show that the performance of HUST pyridine Model is much better than Alzueta Model, and Pyridine LTO Model. The main reason is that the net reaction rate of C₅H₅N + O = C₅H₄N + OH in HUST pyridine Model is much faster than that in Aluzeta Model. The effect of CO₂ on the ignition of pyridine at elevated pressures has been analyzed in detail. The oxidation pathways of pyridine are also analyzed at different pressures.