Heavy duty gas turbines are one of the most used technologies for the power generation. Nowadays has been crucial, especially for the power generation sector, to comply a new sustainable development according to the Agenda 2030 goal 7. The main objective of this thesis is to define a 3D CFD water injection model optimizing the computational costs required by this kind of simulation. Water injection represent an answer to decrease the NOx emissions produced by a heavy-duty gas turbine. The water inside the combustor works as a heat sink, lowering the temperature of the flame with the direct consequence on the NOx abatement.