Structure and sooting limits in counterflow methane/air and propane/air diffusion flames from 1 to 5 atmospheres

The structure of counterflow methane/nitrogen and propane/nitrogen diffusion flames for pressures from 1 to 5 atm was investigated experimentally and computationally. The temperature and major species concentration profiles were measured with spontaneous Raman scattering and computationally simulated with detailed kinetics and transport. Good agreement was found between the experimental data and the computational simulation. It was further shown that the previously developed global and local sooting limit correlations are again applicable, respectively relating the density-weighted strain rate at the sooting limit with the global parameters of the system pressure and the fuel mole fraction in the fuel stream, and with the local flame parameter of the peak acetylene partial pressure. In addition, the local correlations for the propane and ethylene flames collapse into a single relation. An interpretation of these correlations is provided, and their fundamental importance is emphasized.