Design and CFD Modelling of a Low Pressure Turbine for Aeroengines

During the last decades, the reduction of aeroengines fuel consumption is becoming an issue of high importance, due to economic and environmental reasons. One of the main parameters that can severely affect the fuel consumption and the whole performance of the engine is the efficiency of its turbomachinery components. In this work, a detail design study of a low-pressure turbine (LPT), which is integrated in a turbofan engine, is presented. The LPT is designed based on a thermodynamic cycle analysis of the turbofan engine, based on specific requirements such as: mass flow rate, inlet pressure, temperature, power etc, targeting always to an aerodynamic design of increased efficiency. In the first part, the development of a computational tool (0D analysis) based on the book of Saravanamuttoo et al. (2001) on gas turbine theory and the work by Kacker and Okapuu (1982) on axial-flow turbines, capable to calculate the main geometrical and thermodynamic characteristics of the turbine (e.g. inlet and outlet flow and blade angles, aspect ratio, pitch to chord ratio, root and tip radius, pressures, temperatures and densities at each stage) is presented. In order to have a proper evaluation of the design methodology, a 3D CAD of all the turbine stages is created and detailed 3D CFD computations are performed. The CFD analysis and the results are presented in the second part of this work. The ANSYS commercial software is used for the design, meshing and prediction of the flow field through the turbine. Additionally, grid independency study is conducted also, in order to determine and conclude to the size of grid that will provide grid-independent results. Finally, the results of the 0D analysis are compared with those of the 3D CFD computations. A very close agreement is achieved, with a deviation in efficiency values less than 1 %. Thus, it can be concluded that the 0D computer tool can be used as a first low-computational-cost and accurate presizing tool for the calculation of the engine turbine performance.