Calculation of Gas SelfOscillations in LowEmission Combustion Chambers of Gas Turbine Power units Operating on Gaseous Fuel
M. V. Drobysh^{1}, A. N. Dubovitskii^{1}, A. B. Lebedev^{1}, D. S. Tarasov^{2}, N. I. Fokin^{2}, V. I. Furletov^{1}, K. Ya. Yakubovskii^{1}
^{1}Central Institute of Aviation Motors, Moscow, Russia ^{2}AO В«Silovye Mashiny», Saint Petersburg, Russia
Keywords: lowemission combustion chamber, turbulent combustion calculation method, thermoacoustic combustion instability, selfexcitation of gas oscillations, gas selfoscillations, oscillation modes
Abstract
An economical calculation method for selfexcitation of gas oscillations in lowemission combustion chambers of gas turbine units has been developed. The method is based on the SST SAS turbulence model and the turbulent combustion model with a modified equation for a variable degree of combustion completion. A multiplier associated with gas pressure oscillations is introduced into the source term of this equation. The tendency of the combustion chamber to excite gas oscillations is estimated by two parameters: the exponent of this multiplier (interaction index) and the logarithmic decrement of oscillation damping. When solving the problem of selfexcitation of oscillations in the case of specifying a homogeneous methaneair mixture at the combustion chamber inlet, the first radial oscillation mode with a frequency of 2700 Hz appeared. In the case of separate air and fuel supply to the combustion chamber, the first longitudinal oscillation mode with a frequency of 300 Hz was excited. The use of resonant absorbers (small antivibration screens) made it possible to completely suppress radial oscillations.
