Lifing Requirement Based Turbine Airfoil Mass Estimation Method in Conceptual Aero-Engine Design

Abstract

The presented paper describes a method developed by MTU Aero Engines to estimate the mass of turbine blades during multidisciplinary conceptual design studies based on a prescribed airfoil lifetime (Klingels, 2009, “Vordimensionierung von Turbinenschaufeln unter Berücksichtigung der Missionsanforderungen,” MTU Aero Engines, Technical Paper No. M09TET-0028, and Weisser, M., 2010, Erstellung und Implementierung eines erweiterten regelbasierten Verfahrens zur Schaufelauslegung mit Kühlluftmengenbestimmung in der Triebwerksvorauslegung, Diploma thesis, Institute of Aircraft Propulsion Systems, Universität Stuttgart, Stuttgart). For a given material, the target lifetime can be translated into a maximally allowable material temperature and stress level. While the latter has to be maintained by an appropriate mechanical design of the turbine blades, the material temperature needs to be established by sufficient cooling air. The predominant life-limiting effects are taken into account to determine the allowable temperatures and stresses as an accumulation of the varying operating condition over a flight cycle. The applicable stress levels are then used to calculate the necessary radial area distribution of the airfoil and by this a prediction of its mass is possible. Furthermore, the methodology estimates the required amount of cooling air per airfoil cascade from the computed material temperatures. Example calculations are presented and discussed which illustrate design trends and the benefits which are gained from the proposed method.