The silencing of the exhaust from industrial gas turbines is an important element of
current designs as it can affect efficiency, space, noise and gas emissions. However,
exhausts are very costly and the lower the frequency, the higher is the cost involved in
trying to attenuate the noise due to the amount of material and space necessary to
implement the exhaust system.
In this work, the sources of noise from an exhaust system of a particular gas turbine are
investigated. Improvements in understanding the unsteady behaviour of the flow in the
exhaust system could potentially lead to an increase in efficiency, a reduction in noise
emissions, a decrease in the cost of exhaust mufflers and improved location for the
This work presents the experimental approach used to identify the major sources of
noise and how these results were then used to create a model that could represent the
sources identified. As the frequency components generated by the flow are low, this
work concentrates on understanding the mechanisms that generate the low frequency
Results show that the major source of noise is the jet leaving the engine exhaust and
that the main acoustic source is of dipole nature.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.