Combustion Instabilities in Industrial Gas Turbines — Measurements on Operating Plant and Thermoacoustic Modelling FREE

[+] Author Affiliations
David E. Hobson, John E. Fackrell, G. Hewitt

PowerGen plc, Ratcliffe-on-Soar, Nottingham, UK

Paper No. 99-GT-110, pp. V002T02A015; 17 pages
  • ASME 1999 International Gas Turbine and Aeroengine Congress and Exhibition
  • Volume 2: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations
  • Indianapolis, Indiana, USA, June 7–10, 1999
  • Conference Sponsors: International Gas Turbine Institute
  • ISBN: 978-0-7918-7859-0
  • Copyright © 1999 by ASME


Measurements of vibration and combustion chamber dynamic pressures have been taken on a number of 150MW industrial gas turbines operating on pre-mixed natural gas, both during long periods of base-load operation and during short duration load-swings. The data has been analysed in terms of the frequency and bandwidth of the principle peak in the vibration and pressure spectra as a function of load and other operating parameters. It is observed that bandwidth, which is a measure of the damping of the resonant mode of the combustion chamber’s acoustic resonance, decreases towards zero as the machines approach their combustion stability limits.

A theoretical model of the thermoacoustic behaviour of the combustion system has been developed to see to what extent the observed behaviour on the operational machines can be explained in terms of an acoustic model of the ductwork and a flame characterised simply by a time-delay. This time delay is obtained from the frequency response function of the flame in response to unsteady perturbations in inlet velocity and is calculated using computational fluid dynamics.

The model has also been used to illustrate the importance of fuel supply system design in controlling combustion stability. It is shown that stability can be a strong function of the acoustic impedance of the fuel supply and that this can lead to enhanced or reduced stability depending on the flame characteristics.

Copyright © 1999 by ASME
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