Acoustic resonances of an industrial gas turbine combustion system

A theory is developed to describe low-frequency acoustic waves in the complicated diffuser/combustor geometry of a typical industrial gas turbine. This is applied to the RB211-DLE geometry to give predictions for the frequencies of the acoustic resonances at a range of operating conditions. The main resonant frequencies are to be found around 605 Hz (associated with the plenum) and around 461 Hz and 823 Hz (associated with the combustion chamber), as well as one at around 22 Hz (a bulk mode associated with the system as a whole). The stabilizing effects of a Helmholtz resonator, which models damping through nonlinear effects, are included, together with effects of coupled pressure waves in the fuel supply system.