Combustion Oscillations Diagnostics in a Gas Turbine Using an Acoustic Emissions

One of the most important areas of combustion research is the attempt to understand, and control, combustor oscillations, sometimes called hum or noise The combustion at very lean mixture produced new problems; lean systems have proven to be subject to combustion thermo-acoustic instabilities which could lead to induced pressure oscillations or a hum , the humming can increase to howling and cause serious damage to the machines involved unless power output is reduced. In order to begin to understand what humming is, it was necessary to collect and analyze the acoustic signal produced during the humming process occurs in Gas Turbine. In this paper, acoustic signals have been measured in GT combustor of the power plant at Al Rouweas (Bharat Heavy Electricals Limited BHEL, V 94.2 GT power plant) and analyzed during the humming phenomenon. The chosen method for data collection was an acoustic data acquisition system, the acquired acoustic signal was then analyzed with LabVIEW software, the software.s main feature is that capable of defining the acoustic signal (the hum) in many parameters, the most important of which were: power spectrum, auto correlation and the acoustic wave shape produced by the thermo-acoustic instability. The power spectrum gave a concise presentation of the main frequencies which constituted the hum.s acoustic wave pattern, and their relative amplitudes, this was very helpful in determining the acoustic mode of the combustion chamber.