RANS AND LES SIMULATION OF A SWIRLING FLOW IN A COMBUSTION CHAMBER WITH DIFFERENT SWIRL INTENSITIES

A numerical study of the effect of the swirl intensity on the turbulent flow inside an isothermal model combustor is conducted. The study started with a non-reacting swirling flow, in a combustion chamber, generated by a radial-type swirl generator with a Reynolds number, based on the outer radius of the annular inlet and the bulk inlet velocity, equal to 61090. Similarly to what is found in the literature, a lack of accuracy was observed starting at a distance equal to 120 mm from the inlet for the mean flow field and the situation was even worse for the turbulent field. The results showed remarkable improvement when the LES turbulence model was used. The mean and turbulent flow field exhibited remarkable differences between the low and high swirl flows. The axial velocity component decays rapidly from the inlet, for the high swirl case whereas the situation inverts for the tangential velocity component. The low swirl generates a conical inner recirculation zone and a large outer one while the high swirl generates an annular and conical inner recirculation zones and a smaller outer one. For the high swirl case, inner and outer shear layers were generated immediately downward of the inlet annular slot. The low swirl case exhibited disordered turbulent structures. In both cases a precessing vortex core with high frequency oscillations is noticed for the low swirl, close to the inlet.