Investigation of a Novel Combustion Stabilization Mechanism and Combustion Characteristics of a Multi-Nozzle Array Model Combustor

Higher combustor temperatures, extended fuel flexibility, and lower NOx and CO emissions are the trends in the development of industrial gas turbines. The multi-nozzle array burners with short and evenly distributed flames shorten the residence time in the combustor to solve the problem of higher NOx emissions at high combustor temperature. At the present stage, the nozzle jet velocity of multi-nozzle array burner is basically lower than 50m/s with a narrow stability range. To achieve stable combustion at higher nozzle jet velocity, a novel combustion stabilization mechanism has been applied in a multi-nozzle array model combustor based on the principle of high-speed jet induced flue gas recirculation. Combined PIV experiments with numerical simulations, the flame stabilization mechanism of the model combustor fueled methane was verified considering a high flame speed of hydrogen-rich fuel is more conducive to extend the lean blowout (LBO) than methane. The effects of nozzle jet velocity and air temperature on combustion characteristics were investigated, including pollution emissions and reaction zone distribution. A combination of experiments and theoretical calculations by Chemkin was used to analyze the effect of heat loss on NOx emissions. The results show that the stable combustion is achieved by the interaction of the inner and outer recirculation vortex during the condition of high injection velocity. NOx emissions are less than 20 ppm@15%O2 and CO emissions are less than 30 ppm@15% O2 under non-adiabatic conditions in the adiabatic temperature range of 1500K to 2100K. The predicted NOx emissions by Chemkin are less than 20 ppm@15% under adiabatic conditions when the adiabatic temperature is less than 1885K. The LBO of the combustor trends to the high equivalent ratio at the velocity of 60m/s. The CO emission decreases and the combustion stability expands with increasing air temperature. The nozzle velocity and the air temperature mainly affect the downstream of the reaction zone, and the root of the reaction zone remains largely unchanged due to the inner recirculation. The novel stabilization mechanism is potentially very promising for use in multi-nozzle combustor, and further apply for industrial gas turbines using hydrogen enriched fuel with non-swirling high-speed nozzle