Prediction of Noise Source for an Aeroengine Combustor

Combustion noise may become an important noise source if not well understood in the design stage of lean burn gas turbine combustors. This work aims to predict the combustion noise source and broadband spectrum for a real aeroengine combustor, which has rarely been reported in past studies, and to compare with measured noise data on a demonstrator aeroengine. A spatial-temporal correlation model of fluctuating heat release rate is developed by analysing recent results of turbulent DNS V-flames, and the aeroengine combustor flow is calculated using RANS. A low-order linear network model is applied to the demonstrator aeroengine combustor to obtain the transfer function relating the heat release and acoustic fluctuations. The initial results for a low-medium power setting indicate that the prediction model captures the main characteristics of the broadband spectral shape of combustion noise but underestimates the spectral level. Empirical length and time scales in the correlation model are hence employed to obtain good agreement with the measured spectral level. Further work is underway to improve the model in predicting the combustion noise level

Prediction of combustion noise for an aeroengine combustor

Combustion noise may become an important noise source for lean-burn gas turbine engines, and this noise is usually associated with highly unsteady flames. This work aims to compute the broadband combustion noise spectrum for a realistic aeroengine combustor and to compare with available measured noise data on a demonstrator aeroengine. A low-order linear network model is applied to a demonstrator engine combustor to obtain the transfer function that relates to unsteadiness in the rate of heat release, acoustic, entropic, and vortical fluctuations. A spectral model is used for the heat release rate fluctuation, which is the source of the noise. The mean flow of the aeroengine combustor required as input data to this spectral model is obtained from Reynolds-averaged Navier-Stokes simulations. The computed acoustic field for a low-to-medium power setting indicates that the models used in this study capture the main characteristics of the broadband spectral shape of combustion noise. Reasonable agreement with the measured spectral level is achieved. © 2012 AIAA