CUED Publications database

Low order modelling of direct and indirect combustion noise contributions in a gas turbine model combustor

Mahmoudi, Y and Dowling, A and Swaminathan, N (2017) Low order modelling of direct and indirect combustion noise contributions in a gas turbine model combustor. In: UNSPECIFIED.

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The present work deals with a low order modelling of combustion noise in a generic premixed pressurized combustor at École Centrale Paris. The exit of the combustor has choked convergentdivergent nozzle. The contributions of direct and indirect noise to the unsteady pressure within the combustor are obtained. The LOTAN (Low-Order Thermo-Acoustic Network model) code is used to obtain the Green's function for the supply ducting and combustor. LOTAN determines the linear acoustic, entropic and vortical waves due to a unit harmonic variation in the rate of heat release. We studied the effect of different upstream boundary conditions on the prediction of Green's function. To predict the combustion noise, the Green's functions are combined with the spectrum of heat release rate fluctuation. Two different ways of obtaining the power spectral density of the rate of heat release/unit volume were used; post-processing compressible LES data or using a spectral model based on the mean flow and turbulence statistics from a RANS calculation. Results show that the sound calculated using two approaches are in general in good agreement with the measured data, although the spectral method tends to under-predict the amplitude at low frequencies. It is seen that at some frequencies the indirect entropy noise is comparable to direct acoustic noise within the combustor. Previous high fidelity LES and experimental studies on this combustor have concluded that indirect entropy noise has a negligible role in the generation of the total noise in the combustor. This is because these studies could not discriminate fully between the direct and indirect noise elements: their analysis includes the multiple reflection of entropygenerated noise by the combustor boundaries as direct acoustic noise.

Item Type: Conference or Workshop Item (UNSPECIFIED)
Divisions: Div A > Fluid Mechanics
Div A > Energy
Depositing User: Cron Job
Date Deposited: 16 Oct 2017 20:20
Last Modified: 18 Feb 2021 16:19