CFD simulation of combustion and water injection in a gas turbine burner

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. Also, the water introducing is an additional working fluid inside the combustor and that produce a turbine power output increase. The main cost to pay by introducing water inside the combustor is an overall efficiency decrease. There are many possibilities to simulate the water injection inside the combustor of a gas turbine. The first one is represented by the VOF (Volume of Fluid) simulation, the second one by modelling the spray using ELSA spray atomization strategy. In this work, to avoid the computational effort required by these two strategies, a study of water injection as a simple heat sink is proposed. A first preliminary study on the NASA LDI gas turbine has been conducted to study how the ELSA spray atomization works and to have the reference to reproduce the water injection as a boundary condition. From this analysis, the water injection study has been moved on the TG - 20 gas turbine real combustor with a process of optimization concerning the concentration of water and the influence of this boundary condition on the primary recirculation zone. The model has been validate comparing the results in terms of NOx, UHC, CO coming from experimental results.