Preliminary Thermomechanical Design for Aero-Engine combustors made of CMCs

Abstract

An efficient preliminary design is a competitive advantage in the development of an aero-engine. It has the potential of a significant decrease of development costs and time. In the frame work of the DLR programmes EVITA and PEGASUS, the software tool “CoSMA” (Combustor Strength and Modal Analysis) was developed for the thermomechanical design of lean combustors. Due to higher allowable material temperatures in comparison to state-of the art nickel-base alloys, ceramic matrix composites (CMCs) offer the chance for combustors with reduced cooling air consumption and lower NOx emissions. CMCs were implemented into the combustor design tool CoSMA. A combustor geometry and a temperature field in the combustor wall were generated by the combustor design tool “ComDAT” (Combustor pre-Design and Analysis Tool). In a first part, this paper presents the process of the CoSMA tool and the method used for calculating static thermal stresses, eigenfrequencies and failure criteria. In a second part, analytical methods for efficiently preselecting a material and for simple stress estimations in thermomechanically loaded liners are evaluated. Finally, an application example and a comparison to experimental combustor test results are detailed. This work shows the potential of cost-effective preliminary design tools for lean combustors. Moreover an analytical method is given for the stress estimation of effusion cooled combustors.