In this work, a series of tests have been conducted to study the aerodynamics of two typical gas turbine combustion swirlers, using Laser Doppler Velocimetry (LDV). The first swirler used is a coaxial counter-rotating, radial-radial swirler, designated as the R-R swirler. The primary swirler accounts for 40% of the total effective area of the R-R swirler. The second swirler employed consists of an inner dual-axial swirler assembly with only around 20% of total swirler effective area and an outer coaxial radial swirler, and is designated as the A-R swirler. The aim of this work is to compare the aerodynamics performance of these two different types of swirlers under similar boundary conditions, such as confinement effect, downstream exhaust nozzle, and chamber length.
The R-R swirler has a very high radial dispersing rate, and for the unconfined case, the swirling jet remained attached to the dome plate resulting in a very weak, unbound CTRZ. The swirling jet for the A-R swirler exited at a relatively low expansion angle. For confined cases, the swirling jet attached to the walls of the confinement at a certain distance downstream of the exit plane for both swirlers.
When the exhaust nozzle was applied as a downstream boundary condition, a spinning vortex core with high turbulent intensity was detected along the swirler axis for the A-R swirler, whereas the only difference for the R-R swirler was a slight reduction in the expansion angle of the swirling jet. The proximity of the exhaust nozzle to the swirlers was changed by changing the chamber length. For the R-R swirler, the effect of chamber length was only detected in the near-field region. For the A-R swirler, a reduction in chamber length caused the spinning vortex core to become more intense. Additionally, an annular CTRZ was observed for the shorter chamber lengths.