Methods Of Life Prediction And Mainteance Decision Making In Civil Aeroengine Health Management

The appropriate civil aeroengine operation, maintenance and support are important for high safety, reliability and economics. Engine health management is an important method to decrease maintenance and support costs. And researchers are paying much attention to this method gradually. In this thesis, according to the features of civil aeroengine operation and maintenance, the concept of civil aeroengine health management is introduced, some involved key methods are studied in detail, and an integrated aeroengine maintenance management system is developed. The main research content is as following.(1) Holisticly, based on some famous overseas health management systems, the concept of civil aeroengine health management is introduced for engine operaton and maintenance, and main functions of this health management system are designed. After studying the involved key technologies and application system architecture based on the standards of open system architechture. So the general civil aeroengine health management method and system are established, from method to technologies, and to applications.(2) One key method of civil aeroengine health management is life on wing (LOW) prediction and control. Firstly the concept of failure intensity and two multiplative intensity models, which are proportional hazards model and proportion mean intensity model, are introduced. A specified engine operation reliability model with effect of repair numbers is studied. Then two kinds of LOWprediction models are studied detailedly. The first model is LOW prediction only using time data without condition monitoring data. This model is also called experience-based prognostics, which is a kind of statistics reliability model. Based on the failure time historyical data, the Weibull model is established and the conditional mean residual life is calculated at present time. So the LOW can be predicted. The second LOW prediction model is a kind of hybrid model which study the connection between engine conditions and performance deterioration. Using proportional hazards model (PH model) which combine the condition and reliability data, the LOW due to performance deterioration can be predicted with the engine removal control limit and condition trend. Then LOW control can be completed with the time constrains from engine manufacturer and airworthiness directives.(3) In this dissertation the other key method of civil aeroengine health management is condition based maintenance (CBM) decision-making. The relationship beween CBM and on condition maintenance is consolidated. The factors and theory of CBM decision-making model are explained. Two models are studied deeply. The first one is a dynamicly adjusted model according to the conditional residual life and conditional probability. Also based on the PH model, according to the present status, civil aeroengine removal and shopvisit can be decided with the threshold of failure intensity. And the optimal engine preventive maintenance interval is offered in term of minimal expected total maintenance cost per unit time.(4) Considering the practical demands of airlines and the fact of isolation between engine condition monitoring softwares and maintenance management softwares, based on the civial aeroengine health management system architecture, an integrated aeroengine maintenance management system is designed including the work flows, main modular functions and database. This system can implement engine condition monitoring, LOW control, maintenance decision-making and optimal engine schedule. The system is developed using Java programs and Oracle database software. And this integerated sytem is being applied to the aeroengine engineering management in airlines effectively. The work efficiency is increased and the maintenance cost is decreased.