An analytical study of radiation effects on the premixed laminar flames of aluminium dust clouds

Abstract

A new analytical model of a quasi one-dimensional non-adiabatic dust flame is developed with the assumption that the particle burning rate in the flame front is controlled by the process of oxygen diffusion. In this model, the flame propagation mechanism is considered to be radiation, conduction, and convection. Algebraic equations defining the laminar flame speed were obtained in two limiting cases: lean and rich mixtures. The flame structure is assumed to consist of a preheat zone, a reaction zone, and a postflame zone for lean mixtures and a preheat zone and a reaction zone for rich mixtures. Under the lean mixture approximation, values of the flame speed, lean limit, and flame temperature were calculated by adding the radiation term; flame temperature in the preheat zone increased, while it decreased in the postflame zone. This phenomenon may be attributed to the radiative heat transfer from the postflame zone to the preheat zone. Also, when the radiation term was considered, the flame speed increased but the lean limit decreased. In addition, radiation in the rich mixture resulted in the increase of the flame speed and the gas phase temperature in the preheat zone, whereas in the flame zone, the gas phase temperature decreased. Calculated values of the flame speed and flame temperature are in a good agreement with the experimental data in the literature.