Eliminating bad vibrations
Gas turbine engines are the most efficient engines for power generation on a large scale. However, the engine has a major risk of failure due to feedback between the fuel combustion process and pressure waves. This leads to violent oscillations known as 'thermo-acoustic instabilities’, resulting in profound damage to a gas turbine that is expensive to replace. To improve the reliability of gas turbines for power generation was the aim of the EU-funded 'Limit cycles of thermo-acoustic oscillations in gas turbine combustors' (LIMOUSINE) project. Its objective is to predict the mechanical vibration in a gas turbine engine, the resulting fatigue and the time to failure. A general combustor was designed specifically for the project to explore the phenomenon of thermo-acoustic oscillations. The project has already developed models to analyse and to predict acoustics, liquid fuel combustion and crack propagation. Numerical simulation tools were designed to predict transient heat transfer in an oscillating combustion flow. An experimental test was developed to explore the effect of heat transfer to the combustor’s structure. Finally, the geometric design of a full size engine was digitised in preparation for simulations using computational fluid dynamics. Further work is being carried out to improve the reliability of gas turbine power generation. It will also reduce the emissions of carbon dioxide and nitrogen oxides. Finally, project developments will lead to an increased use of sustainable gaseous and liquid fuels.