Calculation of Gas Self-Oscillations in Low-Emission Combustion Chambers of Gas Turbine Power units Operating on Gaseous Fuel
M. V. Drobysh1, A. N. Dubovitskii1, A. B. Lebedev1, D. S. Tarasov2, N. I. Fokin2, V. I. Furletov1, K. Ya. Yakubovskii1
1Central Institute of Aviation Motors, Moscow, Russia
2AO В«Silovye Mashiny», Saint Petersburg, Russia
Keywords: low-emission combustion chamber, turbulent combustion calculation method, thermoacoustic combustion instability, self-excitation of gas oscillations, gas self-oscillations, oscillation modes
Abstract
An economical calculation method for self-excitation of gas oscillations in low-emission 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 self-excitation of oscillations in the case of specifying a homogeneous methane-air 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 anti-vibration screens) made it possible to completely suppress radial oscillations.
|
