Generation characteristics of thermal NOx in a double-swirler annular combustor under various inlet conditions

Abstract

The NOx emission of gas turbine is a key factor of air pollution. It is still a challenge to realize low-NOx generation for all the gas turbines with diverse types of combustors and operation schemes. In this study, a three-dimensional simulation of the internal flow and combustion in a double-swirler annular combustor of a heavy-duty gas turbine was carried out. The realizable k-ε turbulent model and finite rate/eddy dissipation combustion model were employed for the numerical calculation. The effects of the swirl number and temperature of the inlet premixed gas flow on the thermal performance and the relationship between the velocity-temperature field synergy and the thermal NOx formation were investigated on the basis of field synergy principle. The results indicated that the change of the outer swirl number had a greater impact on thermal NOx generation than the change of the inner swirl number. The velocity-temperature field synergy in the combustor became better as the inlet swirl number or the inlet gas temperature increased. This synergy had a correlation with the thermal NOx generation. The formation rate of thermal NOx in the combustor should be controlled with the optimized velocity-temperature field synergy rather than the sole reduction of inlet gas temperature by considering the required thermal uniformity and capacity. The adopted field synergy is a promising concept to evaluate the thermal related performance of combustor. The obtained results on the generation characteristics under various inlet conditions may guide the design and operation of gas turbine combustors.