Dynamics and extinction of non-adiabatic particle-laden premixed flames

The propagation and extinction of gaseous premixed flames seeded with inert particles were analytically and numerically studied for the one-dimensional, planar H₂/O₂/N₂ and CH₄/air flames, with emphasis on the joint effects of gas-particle heat conduction, gas and particle radiation heat loss, and gas-particle velocity lag. Analytical expressions were determined for the non-adiabatic particle-laden flame speed and the state of extinction allowing for the first two effects. These findings reduced to the classical theories for the non-adiabatic particle-free flame, and the adiabatic particle-laden flame, in the limits of vanishing particle concentration and vanishing radiative heat loss, respectively. Small particles behaved like a diluent gas and induced a flammability limit based on the particle concentration. For moderate particle size, there were multiple flame regimes and extinction points because of the combined effects of the gas-particle conduction heat transfer and radiative heat loss. For large particle size, the fast flame extinction limit was extended, while the slow flame regime was narrowed. The particle velocity lag greatly affected the flame speed and the state of extinction. There was good agreement between numerical and analytical results with published data for small particle size. The existence of multiple solutions was an intrinsic feature of particle-laden flames. Original is an abstract.