Preliminary Aero Engine Life Assessment via Techno-Economic Environmental Risk Analysis
Significant progress has been made towards the improvement of engine efficiency through the increase in overall pressure ratio (OPR) and reduction in specific thrust (SFN). The implications of engine design extend beyond thermodynamics and should include the consideration of multi-disciplinary aspects related to operation, emissions, lifing and cost. This paper explores the relationship between fuel burn and engine life across the design space of a typical aircraft engine integrated system. In this context the Cranfield University Techno-economic Environmental Risk Analysis (TERA) methodology allows for the assessment of environmental and economic risk when the design of an engine system is at its conceptual stage. It is essentially a multi-disciplinary optimization framework which can be used for design space exploration. Such an approach is necessary in order to assess the trade-off between asset life and powerplant efficiency at the preliminary stage of the design process. A parametric study was conducted in order to assess the sensitivity of major design parameters on engine life and specific fuel consumption (SFC) for a given engine type. The principal failure modes of creep, fatigue and oxidation, were considered for engine life estimation. In addition an optimization study was carried out in order to investigate the trade-off between fuel burn and engine life as Time Between Overhaul (TBO). This was accomplished by integrating aircraft performance, engine performance and lifing models in the TERA Framework. An increase in turbine entry temperature (TET) is required to maintain efficiency at OPR. However, as TET has a strong influence on engine life there is an important trade-off to be made against engine efficiency. The parametric study outlined in this work explores the design space both with respect to engine life as well as efficiency. The optimization study showed that a penalty of 1.42kg additional fuel is required per additional hour of TBO. The fuel penalty is a consequence of sub-optimal design parameters with respect to engine efficiency and is applicable for the presented engine aircraft combination.