Using morphological analysis to tackle uncertainty at the design phase for a safety critical application

The gas turbine engine internal air system provides cooling and sealing air to a series of critical subsystems and components such as high pressure gas turbine blades, as well as controlling the thrust load on the turbine and compressor spool assembly. Many potential variations for the internal air system are possible, depending on the requirement, expertise and command of intellectual property. Some subsystems, such as rim seals, pre-swirl systems, and rotating cavities have been the subject of extensive development and analysis leading to robust design solutions. Nevertheless there remains scope for further consideration of the overall system design, and this paper explores the use of a decision analysis tool called morphological analysis applied to the internal air system. Morphological analysis provides an effective means for tackling issues where there is uncertainty, as is the case with many design scenarios, including the internal air system, with some specific parameters and information not available until later in the design phase, after the key geometry has been defined. The problem space comprising seven principal parameters, and a cross consistency matrix which allows identification of compatible and incompatible states are presented.