Parametric analysis of core-noise from a realistic gas-turbine combustor for cruise and take-off conditions

Combustion noise from a realistic gas-turbine combustor geometry is investigated parametrically using a hybrid simulation framework that combines large-eddy simulation and a linearized Euler formulation. The effect of operating conditions on the relative noise-source contributions arising from direct and indirect noise is examined by considering take-off and cruise conditions. To quantify the predictions of the combustion flow field, comparisons with available experimental data for velocity and spray droplet diameter are performed. Analysis of combustion dynamics shows that tonal combustion noise from a thermoacoustic instability is present at both operating conditions, which is consistent with experimental data. The unsteady combustion and dilution are the main sources for the fluctuations of pressure, temperature and mixture composition at the combustor exit. While the thermo-chemical properties do not significantly change between the two operating conditions, the simulation results show that the level of unsteadiness in the flow field is significantly higher for the take-off condition. This leads to an overall increase in the noise emissions by up to 20 dB at take-off compared to the cruise condition. Indirect noise arising from compositional inhomogeneities is found to exceed the entropy noise for both operating conditions. Phase cancellation between composition noise and temperature-induced noise is shown to result in an overall reduction of the indirect combustion-noise emissions.