In recent years, an innovative system for power augmentation has been presented by the authors. The system is based on gas turbine inlet air cooling by means of liquid nitrogen sprayers. This system is not characterized by the limits of water evaporative cooling (i.e. lower temperature limited by air saturation) and refrigeration cooling (i.e. effectiveness limited by pressure drop in the heat exchangers), but the injection of a large amount of liquid nitrogen at gas turbine inlet section can be disputable.
In fact, the air composition changes, though not considerably, after nitrogen injection. The oxygen content always seems high enough to allow a regular combustion. In any case, local effects should be further investigated.
In this paper, the effect of the increase in nitrogen molar fraction of combustion air is evaluated. A micro gas turbine combustion chamber geometry (i.e. a reverse flow tubular combustor) is taken into consideration since its model has been widely validated by the authors. The analyses are performed by considering two different fuels: methane (which is the design fuel) and syngas. The results are compared in terms of overall performance (e.g. TIT, pollutant emissions) and local distributions (e.g. flow fields, flame shape and position).