Acoustic instabilities in syngas fired combustion chambers

Abstract

Gas turbines fired on syngas may show thermo-acoustic combustion instabilities. The theory on these instabilities is well developed. From this theory it can be shown that the acoustic system of a combustion installation can be described as a control loop with a set of transfer functions. The transfer function of the flame plays a decisive role in the occurrence of combustion instabilities. It is however very difficult to predict this flame transfer function analytically. In this paper a numerical method will be presented to calculate the flame transfer function from time-dependent combustion calculations. Also an experimental method will be discussed to determine this flame transfer function. Experiments have been performed in a 25 kW atmospheric test rig. Also calculations have been done for this situation. The agreement between the measurements and CFD calculations is good, especially for the phase at higher frequencies. This opens the way to apply CFD-modeling for acoustics in a real gas turbine situation.