Severity estimation and effect of operational parameters for civil aircraft jet engines

Engine maintenance costs for civil aircraft largely depend on the life consumption of critical parts like high-pressure turbine blade and disk. Severity (defined as a measure of relative damage) can be used to characterize the degree of life consumption for the parts subjected to low cycle fatigue, creep, and oxidation as predominant life-limiting modes under normal engine operation. In this context, a numerical tool has been developed to study the impact of engine-aircraft operational parameters on engine severity. This is accomplished by combining aircraft performance, gas turbine performance, component sizing, heat transfer calculation, thermal analysis, structural analysis, life and severity estimation for the high-pressure turbine, and the disk components of jet engines. Operational parameters such as take-off (TO) derate, climb derate, outside air temperature, and airport altitude have been studied for lower thrust and larger thrust engines. The observations from the study show that TO derate and outside air temperature are dominant parameters in terms of engine severity. The use of climb derate also lowers the severity and is more beneficial for larger thrust engines, while airport altitude effects could be minimized by the use of suitable TO derate. The severity characteristics estimated through the numerical tool can provide an enhanced perspective on aircraft engine maintenance.