Numerical simulation of gas turbine swirl-stabilized injector dynamics

A comprehensive numerical analysis has been conducted to investigate the vortical flow dynamics and acoustic response of a gas-turbine swirlstabilized injector. The theoretical formulation is based on the complete conservation equations of mass, momentum, and energy in three dimensions. Turbulence closure is achieved by means of the large-eddy-simulation (LES) technique. The compressible version of the Smagorinsky eddyviscosity model is employed to describe the subgridscale turbulent motions and their effect on large-scale structures. The governing equations and the associated boundary conditions are solved by a finitevolume, Adam-Bashforth predictor-corrector scheme along with the implementation of the message passing interface (MPI) parallel computing architecture. Detailed flow structures are studied for two different swirl numbers. Results show that the internal flowfield in the injector is intrinsically unsteady and subject to shear and centrifugal instabilities. The unsteady flow evolution and vortex breakdown are clearly visualized and can be explained on theoretical bases. The unsteadiness may be related to periodic vortex shedding, vortex breakdown and breakup, mode competition, and other phenomena that are sensitive to the swirl number.