Analysis On The Common Cause Failure Of Diesel Engine Cooling System

Common cause failure is one of the important reasons that cause the failure of components in mechanical systems.It will increase the joint failure probability among all kinds of failure modes and reduce the reliability of redundant systems.In the analysis and calculation of the reliability of the system,it is considered that the failure of each part of the system is independent of each other,which will leads to too large error in calculation results,or even the wrong conclusion.Due to the complexity of the structural components and the correlation of the working process,the influence of the common cause failure on the reliability of the diesel engine is more important.In addition,due to the multi-state and multi-stage of diesel engine system,the common cause failure will produce superimposed effect on the original failure,which will further affect the reliability of diesel engine.In this dissertation,the cooling system of diesel engine is taken as the research object.The common cause failure problem in the cooling system of diesel engine is analyzed by using BN,UPM,common cause failure parameter model and BDD etc.To evaluate the effect of common cause failure on system reliability,which can provide theoretical support for system design,fault diagnosis and maintenance.The main work of this paper is as follows:(1)Study on analysis method of common cause failure.Based on the introduction of the basic concept of common cause failure and the analysis process of common cause failure system,this paper makes a research on the data analysis model and processing steps of common cause failure.Moreover,the parameter model involved in the common cause failure analysis is enumerated.These contents are prepared for the follow-up study of common cause failure(2)Analysis of common cause failure of diesel engine cooling system.The structure of the cooling system of a diesel engine is analyzed,and the structure principle diagram of the system is drawn.Moreover,the failure modes of the main components are analyzed,and the fault tree analysis of the whole cooling system is carried out.The common cause failure problem in the cooling system is quantified by the ?-factor model,based on the analysis of common cause failure process.The UPM is used to estimate the factor values accurately.(3)A reliability analysis model of multi state common cause failure system based on BN is proposed.The multi state Bayesian network model of diesel engine cooling system is established,and the ?-factor model is used to quantify the common cause failure.The results show that the proposed method can clearly express the common cause failure in the system.This method does not need to calculate the minimum cut set,and the system reliability is not required to be expressed by complex mathematical expressions.This method is applicable to the common cause failure of complex mechanical systems.(4)A reliability analysis model of multi stage common cause failure system based on the BBD is proposed.The BBD is used to analyze and model the multi stage system,which can effectively deal with the relationship between stages of components.The common cause failure of the system is quantified by introducing the propagation failure probability,and the BBD of system is generated.The system reliability function is generated according to the BBD of system,and then the reliability of the system is evaluated.