CFD RE-DESIGN OF A GAS TURBINE CAN-TYPE COMBUSTION CHAMBER HYDROGEN FIRED

Hydrogen supply in gas turbine requests the development of the combustion chamber to limit the NOx emissions avoiding flash-back and auto ignition phenomena. The object under investigation is a silo combustion chamber installed on a 10 MW class heavy-duty gas turbine. The aim of the work was to investigate some modifications for the combustion chamber 100% hydrogen fired in dry operation, in order to reduce the NOx production. The investigation was mainly focused on the burner, while the liner was not substantially changed. The swirler and the fuel injection holes were redesigned in order to achieve a better fuel-air mixing and a higher air flow rate in the primary zone of the combustor; each solution maintains a diffusion flame scheme in order to be adopted in industrial solutions. The proposed modifications were analyzed by a 3D CFD RANS reactive procedure based on commercial codes. The methodology was previously validated by a comparison with the experimental data coming from the full scale tests of the original combustor version. Full scale tests were performed also on the modified version methane fired. In house-codes were developed for the post-processing of the numerical results. The numerical analysis has shown that the modified version allows a reduction of about 30% on the NOx emissions. Finally, preliminary considerations related to the fuel injection scheme and to the effect of the main injection condition on the mixing performance, were carried out together with some estimations for NOx emissions containment.