Ignition delay times of methane and hydrogen highly diluted in carbon dioxide at high pressures up to 300 atm

The need for more efficient power cycles has attracted interest in super-critical CO ₂ (sCO ₂ ) cycles. However, the effects of high CO ₂ dilution on auto-ignition at extremely high pressures has not been studied in depth. As part of the effort to understand oxy-fuel combustion with massive CO ₂ dilution, we have measured shock tube ignition delay times (IDT) for methane/O ₂ /CO ₂ mixtures and hydrogen/O ₂ /CO ₂ mixtures using sidewall pressure and OH∗ emission near 306nm. Ignition delay time was measured in two different facilities behind reflected shock waves over a range of temperatures, 1045-1578K, in different pressures and mixture regimes, i.e., CH ₄ /O ₂ /CO ₂ mixtures at 27-286 atm and H ₂ /O ₂ /CO ₂ mixtures at 37-311 atm. The measured data were compared with the predictions of two recent kinetics models. Fair agreement was found between model and experiment over most of the operating conditions studied. For those conditions where kinetic models fail, the current ignition delay time measurements provide useful target data for development and validation of the mechanisms.