Marine gas turbines pollutant emissions assessment

Although gas turbines are less frequently used than diesel engines for ship propulsion and present generally lower emissions, the issue of estimating and reducing emissions is becoming topical also for this type of engine, because of the adoption of increasingly stringent regulations in the shipping sector. In the paper the authors propose corrections to be applied to some empirical equations, of the few published in literature, in order to improve their ability to calculate the extent of the main pollutants contained in exhaust gas of gas turbines. The improvements of the correlations have been based on the availability of a reliable and detailed database concerning the pollutant emissions, determined in a wide range of working conditions, of a naval, aero-derivative gas turbine. As shown in the paper, the improved correlations have allowed a consistent increase of the accuracy in quantifying the gas turbine emissions in every operating condition. As a first application of the study, the improved emission correlations have been included in a numerical simulator, already developed by the authors, for the CODLAG propulsion system of an Italian frigate. The simulation results relative to the main polluting substances emitted during some frigate maneuvers are presented and discussed in the paper.