Chemical kinetics investigation of toluene combustion in a shock tube using spectroscopic CO and H2O laser absorption

Toluene oxidation was investigated behind reflected shock waves using spectroscopic laser diagnostics to simultaneously measure carbon monoxide (CO) and water (H2O) time-history profiles. CO and H2O time histories are unique in the available database for toluene speciation as only a total of five H-atom profiles can be found in the literature and were carried out for pyrolysis instead. These new, high fidelity measurements can help in validating detailed chemical kinetics mechanisms over highly dilute conditions. The experiments cover three equivalence ratios (phi = 0.5, 1.0, and 2.0) with temperatures ranging from 1433 to 1921 K near atmospheric pressure. Comparisons with six models were conducted for a performance review: the Yuan et al. model shows the most accurate results and was selected to further understand toluene chemistry and identify the reaction pathways. Rate-of-production and sensitivity analyses support that toluene (A1CH(3) in the model) decomposes via A1CH(3) (+M) reversible arrow A1CH(2) + H (+M) and mostly produces CO and H2O with the following sequences: A1CH(3) -> A1CH(2) -> A1CH(2)O -> CH2O -> HCO -> CO and A1CH(3) -> A1CH(2) -> CH3 -> H2O, respectively.

Automated summary

Toluene oxidation was investigated using laser diagnostics to measure carbon monoxide and water profiles. The results are important for validating chemical kinetics mechanisms under highly dilute conditions.