Prediction of Combustion Noise for an Aeroengine Combustor

Abstract

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 RANS simulations. The computed acoustic field for a low-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.

Acoustic and Entropy Waves in Nozzles in Combustion Noise Framework

“…This is partially because advances in the design of aircraft have reduced other noise sources such as jet, fan and external aerodynamic noise [1,2]. Furthermore, modern low-NOx combustors show a considerable increase in noise emission [3]. This is because lean premixed and stratified combustion burns more unsteadily and is also susceptible to an instability arising from the feedback interaction between unsteady combustion and acoustic waves [4,5].…”

“…Fellow AIAA. 3 Aerothermal Engineer, Combustion and Turbines Sub-System, Rolls-Royce plc. C 2 generated when the gas with a non-uniform entropy or vorticity distribution is accelerated, as it is when the unsteady products of combustion are convected through the nozzle located at the downstream outlet of the combustion chamber in a gas turbine [6].…”

Two-time correlation of heat release rate and spectrum of combustion noise from turbulent premixed flames

“…A similar spectral model was presented by Hirsch et al [21] and validated experimentally on premixed swirling jet flames [21,22] with underpredictions at low frequencies. This deficiency was improved by Liu et al [23] after a correction to the wavenumber spectrum of heat release rate and the model was applied to a realistic aeroengine combustor. However, the mapping from a local spatial power spectral density SPL sound pressure level SPL peak peak sound pressure level model spectrum of heat release rate to the temporal spectrum is an indirect way to model the frequency spectrum of combustion noise, and the spatial model spectrum based on classical turbulence theories [24] does not capture the influence of the thermochemical processes.…”

Numerical Prediction of Far-Field Combustion Noise from Aeronautical Engines

“…Future aeroengines must be designed to limit cruising speed consumption, pollutant emissions and noise at landing and takeoff phases. With the development of new low NOx-emission combustion chambers, such as lean premixed, rich-quench-lean or staged-injection combustion chambers, combustion noise is becoming a significant contributor to the overall aircraft noise and, therefore, the focus of many recent studies [1][2][3][4][5][6]. The latter show that two mechanisms creating combustion noise must be distinguished: direct and indirect noise.…”