Abstract

The aero-engine noise due to combustion can be separated into direct and indirect sources. The first component designates the generation of pressure fluctuations due to unsteady heat released by the flame. Unsteady combustion also generates flow perturbations in the form of temperature, vorticity, and mixture-composition inhomogeneities. These perturbations, which are silent while advected by a uniform flow, generate further sound when accelerated/decelerated. This second source of noise is termed indirect combustion noise. Indirect combustion noise contributes to the total exhaust noise of aero-engines, via the downstream propagating component, and modifies the stability of the combustor, via the upstream propagating one.

To date, indirect combustion noise has been studied mostly in configurations where the flow perturbations are accelerated by nozzles. In such configurations, the flow can be described by quasi-one-dimensional and isentropic equations. Those assumptions, however, are too restrictive for realistic combustors. In this talk, we will present recent progress on the modelling of indirect noise beyond such assumptions. In particular, we will study the indirect noise generated at the turbine blade rows and area expansions with flow separation.