Innovative design process for industrial gas turbine combustors

This thesis is tracking the design process footprints, from the wide initial scenario of a new combustor design for industrial gas turbines, down to detailed design aspects, passing through sealing system design with turbine nozzle, up to a specific liner cooling architecture and its optimization. Main effort of this job has been focused on the creation of a numerical tool, able, since the early phase of development, to analyze the liner cooling with a one-dimensional conjugate aero-thermal-strain approach: liner cold side heat transfer coefficients in a turbulated forced convection region are iteratively computed updating metal and air temperatures and the deformed geometry of coolant passages from results of a heat balance. Coolant passages, in between the deformed surfaces of liner and baffle, influence the air velocity, changing in turn heat transfer coefficients and coolant pressure losses. The computation of liner and baffle strain has been validated comparing the code results with the ones obtained by a detailed finite element model. Correlations embedded in the code have been calibrated thanks to a comparison with temperatures and pressures experimental measurements, which have been acquired in a full annular rig test campaign. The code has been provided with two additional optimization routines, developed to automatically improve the baffle design for an enhancement of the liners durability, without penalizing engine performance. Maintaining the same coolant pressure losses and minimizing the axial gradients of metal temperature by means of a variable gap baffle geometry, a reduction of thermal induced stresses can be achieved. The reader will follow problems and solutions, sizing criteria and uncertainties estimation of the combustor architecture adopted in the BHGE NovaLT industrial gas turbine class, up to reach the testing phase of the manufactured components and finally the baffle design solution optimization. Reliability of the liner cooling system depends also by the reliability of the leakage prediction across the interface between liners and turbine first stage nozzles. In parallel to the baffle design optimization, studies have been performed on this sealing systems, aimed to increase the reliability of the combustor flow split prediction and to identify areas of improvement of the sealing. The criteria for selection and design of the most suitable sealing system and related durability analyses will be presented, completing the picture of the combustor flow split and synergistically improving the reliability of the liners cooling design presented.