Comparison of external and internal EGR concepts for low emission micro gas turbines

The external recirculation of exhaust gases represents an effective tool for approaching an almost flameless regime and controlling the nitric oxide formation, like demonstrated by a number of authors' papers. Such a system penalizes, on the other hand, the micro-gas turbine performance due to the high EGR rates that are needed for the pollutant reduction. Basing on this consideration, the author consider, in this paper, the possibility of exploiting the internal combustion fluid-dynamics for achieving the same level of pollutant abatement. The comparison of the combustion regimes that are induced by either the external or internal EGR adoption are carried out on a CFD basis. The results refer to different load conditions of the micro-gas turbine, with both gaseous and liquid fuel supply.