Near field aerodynamics of swirl burners. Part 1. Isothermal expanding swirling flows.

Abstract

Isothermal expanding swirling flows initially in solid body rotation with a uniform axial velocity were investigated in order to gain a better insight into the flow structure in the region near swirl burners. The velocity measurements using an LDA system revealed that two inviscid flows at different total energy flux levels were present in the regions before and after expansion, and the kinetic energy loss necessary for the transition between these flows took place at the exit of the expansion. The invisicd solution used was found to be capable of predicting the measured velocity profiles in the expansion, and hence the occurrence of a recirculation zone. The momentum theorem, with the assistance of the inviscid solution, well estimated the energy loss for the transition as a function of both the vortex diameter expansion ratio and the initial swirl number.