Effects of turbulence on the generation of indirect noise in an advanced gas-turbine combustor

Turbulent combustion occurring in gas turbine combustors leads to strong temperature and entropy inhomogeneities, which generate indirect combustion noise as they are accelerated through the nozzle stage of the engine. The objective of this work is to examine effects of turbulent and inhomogeneous flow field perturbation on indirect combustion noise. Due to the turbulent nature of the flow at the exit, a multimodal and non-planar thermal wave enters the nozzle downstream of the combustor. A two-dimensional linearized Euler equation (LEE) solver is employed to predict the flow field inside the nozzle, which allows for the evaluation of the generated acoustic waves. By considering canonical subsonic and supersonic nozzle geometries, the influence of the nozzle inlet and outlet Mach numbers, as well as the transverse effects inside the nozzle on the indirect noise generated by a turbulent flow field is discussed. Additionally, a transfer function based approach is assessed, as this method provides an efficient alternative for the evaluation of the indirect noise.