A numerical study of NOx reduction by water spray injection in gas turbine combustion chambers

An Eulerian-Lagrangian model is implemented to study the process of water spray injection inside gas turbine combustors. The validation of different parts of the model and the examination of the uncertainties introduced by different assumptions in this model are presented and discussed carefully. Then, the model is used to investigate the effect of different injection parameters; including position, direction, and mass flow rate, on the performance and emission of a gas turbine combustor at different swirl numbers. The results show that the interaction between spray droplets and the flow structures inside the liner plays the key role in the effectiveness of the injection process. The spray should be injected such that droplets are not trapped in the internal recirculating zone (IRZ) since they are pushed towards the colder flow near the liner walls. On the other hand, the droplet entrapment in the swirling vortex would be favorable since it increases both the droplet residence time inside the chamber and the proximity of droplets to the hot central gas regions. It is found that the best injection location satisfying these criteria is at the end of the primary zone rather than around the inlet nozzles and is targeted at the post-ignition region.