| Summary: | The need to diversify the fuels used in gas turbine power generation has driven forward the development of fuel – flexible combustion systems. However, the change in chemical, thermal and transport properties of fuels due to the variation of the constituents can have a significant effect on the performance of the combustor. It is known that the fuel properties have a strong influence on the dynamic response of flames. One of the key parameters required to enable detailed understanding of the flame response is heat release rate. To date there are no measurements that can directly provide this quantity. Simultaneous OH/H2CO PLIF (HRX – pixel by pixel product of LIF signals) can provide planar local heat release rate and it has shown to work on premixed hydrocarbon flames (methane, propane and ethylene air flames) and ethanol. For the first time this method was extended to biogas/syngas type flame application. Here H2/CO/CH4/CO2 flames are investigated and the heat release response was measured under high curvature and rates of strain. In the case of laminar flames the results suggest that simultaneous OH/H2CO PLIF can be used to provide information about the heat release rate in methane and methane/carbon-dioxide (biogas) flames. The trend in spatial distribution of HRX agrees well with the one-dimensional flame calculations. The spatial distribution of the HRX is of great interest for studying combustion modelling and instabilities. Therefore the measurement technique was extended to turbulent flames on a laboratory scale gas turbine combustor to study the flame response of multi-component fuels. The HRX technique was found to be suitable to study biogas flames subjected to flow perturbations. The measurements allowed to spatially resolve the heat release region under different perturbation conditions, especially in the region where the vortex is formed. These measurements were also carried out for methane/carbon-monoxide/hydrogen (syngas) flames. For the first time experimentally, spatially resolved heat release regions of biogas and syngas were measured and compared to aconventional natural gas (methane). Also part of the study was to investigate the flame response while the flame speed of the different fuels were matched. In the case of biogas and methane flames, provided the flame speed and the overall bulk velocity were similar, the same flame responses were observed at all forcing frequencies. In the case of syngas and methane flames, a similar response was observed at higher forcing frequency but not for low frequency.
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