Isothermal Modelling of a Combustion System With Swirl: a Computational Study

Isothermal physical scale models, employing an equivalent jet radius, are used to simulate combusting flows in furnaces. Computational fluid dynamics is used to assess the isothermal analogues of combustion systems with and without swirl. The accuracy of representation of the flow in the isothermal analogue depends on the swirl number, S, and the ratio of the equivalent jet radius to chamber radius, re / rc. The representation was good without swirl, S=0, and with swirl for S up to 0.12 with re/ rc >0.16 and for S up to 0.24 with re rc > 0 08. This behaviour was assessed through the normalised recirculation mass flow and the points of separation and reattachment of the main eddy, and should extrapolate to higher swirl numbers as re/rc is reduced. The differences between the combusting and isothermal flows arise from a shifting of the eddies in the enclosure flow.