Numerical Simulation of Combustion Instabilities in a Lean Premixed Combustor With Finite Rate Chemistry

Abstract

Combustion instabilities in lean premixed gas turbine combustors remain a major limitation in decreasing NOx emissions. Computational Fluid Dynamics (CFD) has become an important design and analysis tool that is often used to predict thermoacoustic oscillations caused by these instabilities. Limitations to prediction accuracy are imposed by the choice of chemistry and combustion model. The focus of this study is to compare CFD calculations using Eddy Dissipation and Finite Rate Chemistry models to experimental data reported by Richards and Janus (1997) on the single-injector lean premixed DOE-NETL combustor. The computational domain consists of an annular swirl inlet, fuel injection, a can combustor, a plug for reduced flow area, and an exhaust plenum. The numerical calculations were done using a RANS solver. A 2D axisymmetric-swirl model with RANS turbulence model was employed. The Eddy Dissipation Model has become popular largely because of its robust performance. It is shown that this model does not predict combustion instabilities for the present case. On the other hand, the Finite Rate Chemistry Model is numerically stiff, but is capable of capturing the onset of combustion instabilities.