Reliability Analysis Of Multi-state Aero Engines

With the rapid development of technology and industry,people are increasingly demanding complex systems,and most complex systems are multi-state systems.Multi-state complex systems are very popular in the field of reliability research in recent years.All components of the traditional two-state system consider that there are only two states of normal and fault.However,if some components in the system have multiple working states,they exist.In addition to normal and fault intermediate states,such as wear,cracks,etc.,such systems are considered to be multi-state systems.As a mechanical system for both military and civilian use,the aero-engines reflect the comprehensive strength of a country.In recent years,there have been many incidents of aircraft crashes,which have gradually attracted people's attention to the safety and reliability of aircraft.Due to the complex structure and working process of aero-engines,components and systems often have multiple working states.It is a typical multi-state system.When performing reliability analysis,the reliability model has a large state space and is difficult to carry out.In addition,the structure of the aero-engine system is complex,with many components,and there is often a fault correlation between its components,resulting in inaccurate results in the preventive maintenance analysis of the aeroengine.In this thesis,the following three aspects of research and application are carried out for these two problems in aeroengine:(1)Aiming at the problem that the state space of multi-state system is difficult to analyze reliability,an improved multi-state multi-valued decision graph(MMDD)model is proposed for multi-state system reliability analysis.Firstly,a sorting heuristic algorithm based on the number of component states is proposed to reduce the MMDD model.Secondly,the state space size and minimum cut set of the MMDD model before and after the improvement are analyzed from the perspective of qualitative analysis.The state space of the obtained MMDD model is reduced,and the optimization effect is achieved,and the minimum cut set is consistent with the improvement.Finally,the system is analyzed based on the MMDD model before and after the improvement from the perspective of quantitative analysis,and the system state obtained by the improved algorithm is improved.It is also consistent with the improvement,which verifies the correctness of the algorithm.(2)Aiming at the problem of fault correlation between components in complex systems,a comprehensive importance analysis method based on fault correlation is proposed.In the reliability analysis of the system,it is necessary to perform preventive maintenance before the system failure to moderately improve the reliability of the system.When performing maintenance,it is often desirable to achieve higher reliability while reducing maintenance costs.In this thesis,considering the component maintenance cost,the component integration importance of the spare parts system with fault correlation is calculated.It is verified by experiments that the preventive maintenance strategy considering the fault correlation is more reasonable than the maintenance strategy without considering the fault correlation.(3)Based on the research contents of the first two parts of this thesis,the reliability analysis and preventive maintenance strategy of the rotor system and the lubrication system in the aeroengine are studied respectively,and the minimum cut set and system state probability under the multi-state of the rotor system are obtained,as well as lubrication.Preventive maintenance strategy for the system.There are many failure modes in the aero-engine rotor system,and most of its components are multi-state components,so it is very important to carry out multi-state reliability analysis.Firstly,the state performance of each system of multi-state rotor system components is divided,and its MMDD model is established and qualitatively analyzed.Then,the probability of each state of the component is calculated according to the component's failover and repair transfer matrix,and the rotor system is obtained.State probability.In addition,the aero-engine lubrication system is susceptible to wear and affects the operation of the engine.Therefore,it is necessary to study the preventive maintenance method of the lubrication system,reduce maintenance costs,and improve reliability.Spare parts are often included in the engine lubrication system,and there is generally a certain correlation between the spare parts and the main parts.Based on the comprehensive importance of considering the fault correlation,the maintenance strategy of the engine lubrication system is obtained through experiments.