Measuring the flame transfer function of turbulent non-premixed syngas flames

Syngas is a fuel, obtained from gasification of coal or other heavy hydrocarbons. It is used to fire gas turbines. Syngas consists of hydrogen (H₂), carbon monoxide (CO) and some inert components like nitrogen (N₂) or water vapour (H₂O). Sometimes methane (CH4) is present. It has shown in practice that syngas fired gas turbines can suffer from thermo acoustic instabilities. In case of such an instability, pressure oscillations couple with the combustion process. This can lead to extreme noise and structural damage. At the laboratory of Thermal Engineering of the University of Twente, a lab scale syngas combustor is built to measure the thermo acoustic properties of syngas flames. The passive noise of the combustion process was measured as well as the response of the flame to perturbations on the mass flow of the fuel. With the latter measurements, the so-called flame transfer function was determined. The flame transfer function is an important parameter in studying the thermo acoustic behaviour of flames. In these experiments, the flame transfer function is defined as the relation between the heat which is released by the flame and the fuel mass flow.