Experimental and Computational Study of Nonreacting Vortex Breakdown in a Swirl-Stabilized Combustor

Abstract

Non-reacting flow experiments are conducted in a swirl-stabilized combustor with several configurations of a triple annular research swirler (TARS) fuel injector. Particle Imaging Velocimetry (PIV) is used to measure mean axial and radial distribution of the velocity field from which swirl ratio and position of vortex breakdown are calculated for each injector configuration. The numerical simulat ions are based on the ReynoldsAveraged-Navier-Stokes (RANS) model equations of non-reacting flows, and provide insight into the characteristics of the axisymmetric vortex breakdown phenomenon in a circular, finite-length pipe with a sudden expansion downstream of a concentric, circular inlet pipe. Results show that flow states with vortex breakdown can be simulated numerically. Good agreement is found between the results of the simul ations and available theoretical predictions for the first appearance of breakdown downstream of the pipe expansion plane as well as its first appearance in the inlet pipe s ection as upstream swirl level is increased. We also show good agreement between the measured experimental data, simulations, and theoretical predictions. It is demonstrated that th e theoretical criteria and numerical simulations can be used to predict the appearance a nd location of vortex breakdown for several different nozzles of varying swirl numbers relevant to the stability of lean, premixed combustion.