An experimental and computational study of a multi-swirl gas turbine combustor

Abstract

The turbulent flow and flame dynamics within a lean direct fuel injection (LDI) multi-swirl gas turbine combustor is examined using a combination of state-of-the-art diagnostic methods, including laser doppler velocimetry (LDV), particle imaging velocimetry (PIV) and fine bead thermocouples, and modern computational methods, such as flamelet-based large eddy simulations (LES). The computations provide unsteady field data of any quantity of interest, but are to some extent model dependent, whereas the laboratory studies often can capture only end-results of the real processes with limited details. The combined perspectives can thus provide mutual validation of diagnostics and models, and a more complete understanding of the physical and chemical processes involved, including also interdependencies between processes that are very difficult to characterize in the laboratory. In turn, this provides an improved framework for modification of present gas turbine combustors and for the design of future generations. Good agreement between LES and experimental data is found both for the non-reacting and reacting regimes studied. Both cases were found to be sensitive to the inflow into the swirler, and to the confinement. The non-reacting case is dominated by an annular swirling jet, a central recirculation zone (CRZ) and a weak precessing vortex core, oscillating at ∼250 Hz. For the reacting case the CRZ remains, and dominates the flow in the upstream section of the combustor including the flame and the resulting wall jets. Longitudinal pressure fluctuations at ∼380 Hz (420 Hz in the experiments) are also observed in the reacting case.