The results of the numerical analysis of the flow capacity and other parameters at the different turbine vanes are presented in this paper. Two plane cascades with the same geometrical throat but with a different shape of suction surface have been investigated by means of the 2D Navier-Stokes code [1]. Stacked with these profiles two vane rows with tip meridional opening have been investigated by means of the 3D Euler code [2] and the 3D Navier-Stokes code [3]. The numerical investigation of two full-scale annular vane rows is confirmed by experimental mass flow performance, obtained in a range of exit isentropic Mach number on the mean diameter from Ma2 is = 0.7 to Ma2 is = 1.3.

This paper summarizes the development steps and measures taken for the upgrade of the GT11N2 Turbine. The main targets to be achieved were specified as follows: - GT power increase; - GT gross efficiency increase; - Flexible operation with respect to power output and service interval length. All 4 turbine stages were re-designed in order to optimize their aerodynamic performance and minimize cooling air consumption. Turbine aerodynamic efficiency improvement was achieved by means of: - Turbine stage-to-stage loading optimization; - 3D airfoil profiling; - Replacement of the damping bolt of blade 4 by a full shroud; - Stator/rotor sealing optimization. On top of that, cooling air consumption was reduced by means of cooling system optimization for Vane 1, Blade 1, Vane 2, Blade2 and SHS/A. This allowed an increase of TIT (inlet turbine mixed temperature) keeping the hot gas temperature at the turbine inlet unchanged, which is important for meeting lifetime and emission targets. One of the key requirements for this Turbine Upgrade was to use exclusively validated design approaches and design features as available from existing and proven Alstom Gas Turbines ([1], [2], [3]) in order to minimize development- and implementation risks. Manufacturing of the new turbine parts was completed in an exceptionally short time, thanks to a dedicated R&D Logistic and Manufacturing support/process, an efficient NCR (Non Conformance Report) process, early supplier involvement and a very close/open work with suppliers. The first prototype of this turbine was implemented in a GT11N2 customer engine. Performance validation runs, performed in May 2008 confirmed that the design targets for power and efficiency were fully met. The validation of the turbine parts lifetime is still ongoing.