In this work the air flow in a furnace was computationally investigated. The furnace, for which experimental test data are available, is composed of a movable block burner connected to a cylindrical combustion chamber by a conical quarl. The apertures between the movable and the fixed blocks of the burner determine the ratio of the tangential to the radial air streams supplied to the furnace. Three different positions of the movable blocks were studied at this time. A three-dimensional investigation was performed by means of the finite volume method. The numerical grid was developed by the multiblock technique. The turbulence phenomenon was addressed by the RNG k-epsilon model. Profiles of the axial, tangential and radial velocities in the combustion chamber were outlined. The map of the predicted axial velocity in the combustion chamber was compared with a map of the experimental axial velocity. The internal space of the furnace was found to be partially filled with a reverse flow that extended around the longitudinal axis. A swirl number profile along the furnace length is presented and shows an unexpected increase in the swirl in the combustion chamber.

Computational fluid-dynamics techniques were employed to study the aerodynamics of a movable block swirl burner, developed by the International Flame Research Foundation, IFRF, which is characterized by the ability to adjust continuously and dynamically the intensity of the swirl by means of the simultaneous rotation of eight movable blocks, inserted between eight fixed blocks. Five three-dimensional grids were constructed for the burner, corresponding to five positions of the movable blocks. Both the k-e and RNG k-e isotropic turbulence models were applied. Only the latter described the existence of a central reverse flow along the annular duct. The employment of first-order and second-order interpolation schemes provided distinct results. The later provided results closer to the experimental tests. The swirl number decayed in the annular duct. The predicted swirl numbers for this movable block swirl burner were lower than the corresponding IFRF's experimental data, as was also observed by other researchers. This gave rise to the suspicion of some possible measurement error in the IFRF's experiments. On the other hand, the lack of agreement between the experimental data and the predictions regarding swirling flows could be attributed to the possible inadequate performance of the k-e model, as a consequence of its isotropic approximation. Still another possible explanation could be a phenomenon called bifurcation, in which one given swirl number can be associated with two distinct conditions of steady state flow. In addition, this complex flows requires a scrupulous development of the grids for the boundary condition and the employment of adequate interpolation schemes.