Gas Turbines Cantilever Nozzles Simplified Approach for Performance and Structural Optimization

Abstract

Abstract One of the most critical phases of designing a competitive product such as a Gas Turbine is the conceptual phase, in particular the definition of the flow path, which decides the performance of the engine. Therefore, the ability to optimize the aerodynamic performance of the flow path has significant benefits, but, due to constraints related to the reduction of the time to market of new products, the optimization process is extremely limited. Typically, the definition of an acceptable flow path is an iterative process between the Aerodynamic and Structural teams, which requires a considerable amount of time leaving very little space for optimization. Considering the common architecture of a turbine, only the first stage nozzle can be supported both at inner and outer diameter, while all the other stages can be only supported at the outer. This leads to an extraordinarily strong structural and life constraint for airfoils definition because they must be properly seized to comply with creep requirements. According to the earlier design process, the aerodynamic optimization of the flow path was performed by means of a 1D tool, later on airfoils were built and analyzed from a structural standpoint to verify if they were complaint. The proposed function is based on a newly developed transfer function between the geometry parameters available from the 1D aero tool and the bending stress on the airfoils. Function has been trained on legacy engines and later verified and applied in ongoing studies. In this way the aerodynamic optimizer can obtain a preliminary mechanical assessment in real time on each configuration of the 1D flow path, allowing to generate only structurally verified configurations. The article explains how the tool works along with a case study highlighting its application. The findings confirm that this innovative tool can simplify and speed up the optimization of a 1D flow path.