Experimental Observation and Numerical Modelling of a Laminar Double Coflow Methane/Air Diffusion Flame

Abstract

The effect of the central air flow rate on the structure and sooting characteristics of a laminar double coflow methane/air diffusion flame was experimentally observed and recorded by a digital camera. The double diffusion flame was generated using a modified Gu¨lder laminar coflow diffusion flame burner by introducing an air flow in the centre of the fuel pipe. Numerical calculations of the double diffusion flame at different central air flow rates were conducted by solving the elliptic conservation equations of mass, momentum, species, and energy in axisymmetric cylindrical coordinates using a standard control volume method. Detailed multi-component thermal and transport properties and detailed combustion chemistry were employed in the modelling. Soot formation was modeled using a semi-empirical acetylene based model in which two transport equations for soot mass fraction and soot number density per unit mass were solved. Thermal radiation was calculated using the discrete-ordinates method and a 9-band non-grey model for the radiative properties of the CO-CO2-H2O-soot mixture. The numerical model reproduced qualitatively the experimental observations of the effect of central air flow rate on the structure and sooting characteristics.