Pater S., Kok J., van der Meer T.

Increasing numbers of gas turbines will be fired on syngas. This is a low calorific gaseous fuel, obtained from gasification of coal, residual oil or biomass. Syngas consists mainly of hydrogen , carbon monoxide, nitrogen, water vapor and in some cases methane. Like any combustor, syngas fired combustors can suffer from thermo acoustic instabilities, where pressure oscillations interact with the combustion process. This can lead to extreme noise levels, flame extinction and structural damage. The processes leading to thermo acoustic phenomena in a syngas combustor are different from those encountered in combustors fired with a high calorific fuel like natural gas. This is mainly due to the high relative fuel mass flows and the fast combustion chemistry. At the laboratory of Thermal Engineering of the UT a laboratory scale syngas combustor is built to measure the thermo acoustic properties of syngas flames and validate the thermo acoustic models derived earlier. The spontaneous noise generated by the turbulent combustion process was measured as well as the pressure field induced by the flame under the action of driven perturbations of the syngas mass flow. With the latter measurements, the so-called flame transfer function can be determined. The flame transfer function is an important model building block when studying the thermo acoustic behavior of flames with the use of one dimensional pressure propagation models and feed back loops. The flame transfer function is defined as the relation between the heat released by the flame and the fuel mass flow perturbation. This can not be measured directly in the flame. Using well defined model characteristics the flame transfer function is calculated on basis of the measured correlation between the induced fuel mass flow oscillation and the pressure field in the combustor. The results of these experiments will be compared with CFD model predictions.