Exhaust gas recirculation effects on flame heat release rate distribution and dynamic characteristics in a micro gas turbine

Exhaust gas recirculation (EGR) is an option proposed to augment the CO₂ content in the exhaust gas for the efficient removal of CO₂. In the field of micro-gas turbine (MGT), EGR is also a feasible solution to improve the part-load performance and fuel flexibility. This research combined EGR with an adjustable fuel feeding combustor to assess the part-load performance of a 300 kW MGT and the flame spatiotemporal characteristics. The radical chemiluminescence intensity of hydroxyl is selected to represent the heat release rate (HRR) in natural gas flames. The influence of EGR on HRR was investigated experimentally under various load ratios (50%–100%) and EGR ratios (0–20%). In addition, the temperature at the combustion chamber outlet is also measured. The results show that EGR can effectively reduce OTDF when the load ratio is high. Both the spatial distribution non-uniformity and fluctuation amplitude of HRR are suppressed after applying EGR. And EGR can also reduce the influence of mixing on HRR spatiotemporal characteristics. At last, the frequency characteristics of HRR are analyzed. The result shows that the flame frequency has a strong correlation with the characteristic frequency of turbulence.