Development and optimisation of a mild combustion furnace

The flow and thermal fields of reacting flows operating under MILD combustion regime within a furnace were studied. The project was divided into a developmental stage and an experimental stage. The development stage compromised a parametric study with commercially available computational fluid dynamics codes to optimize the burner and furnace configurations and aid on the design of the experimental apparatus. The parametric study utilized a three-dimensional model of one quarter of the combustion chamber to examine the turbulent reacting flow inside the furnace. The combustion chamber has a cross section of 300 × 300 sq mm and a height of 500 mm. Three combustion models were applied to simulate the combustion of methane with a relatively low level of air preheating in steady-state conditions: a finite-rate/eddy dissipation model with a two-step global reaction, an eddy dissipation concept with a skeletal chemical kinetic mechanism, and an equilibrium mixture fraction/PDF model. The main objective is to identify which parameters affect the mixing patterns in MILD combustion and to assess the suitability of existing combustion models in these types of flows. Performance is assessed based on the uniformity of the temperature profiles, the rate of heat release and operational flexibility. This is an abstract of a paper presented at the 30th International Symposium on Combustion (Chicago, IL 7/25-30/2004).