Reliability Model Analysis Of Ship Propulsion System

Ship propulsion system is the core part of a ship,it is a complex mechanical system whose reliability directly affects the safe operation of the ship.During mission time,since ships need sail on the sea for a long time,they can't get the assistance from the shore in time when faults occur.If the reliability of ship propulsion system cannot be guaranteed,it will not only raise the cost on eliminating the fault,but also increase the maintenance labor and the ship suspended time.What's more,low reliability will reduce the using efficiency of the ship and may even lead to serious marine accident.Therefore,the reliability of ship propulsion system will be paid more and more attention in the marine field by the companies and scholars.There are few researches on the reliability model of large-scale ships propulsion system in the world at present,most of which focus on the qualitative analysis of the fault phenomenon as well as the relevant maintenance strategy.Many reliability modeling theories have not been widely used in the reliability analysis of ship propulsion systems,so it's difficult to quantitatively calculate the related reliability evaluation index.The reasons for this research status are various.On one hand,components of the ship propulsion system are numerous and their failure mode is complex.On the other hand,the lack of reliability data accumulation leads to a small sample problem when using probability and statistics mathematical model to evaluate the reliability of the ship propulsion system.Moreover,the maintainability of ship propulsion system is one of the obstacles to build a reliability mathematical model.In this thesis,the fault tree analysis was used to build the reliability model of the ship's main engine.Both qualitative and quantitative analyses were carried out to analyze the fault tree of combustion chamber assembly and fuel system which were built on the basis of detailed analysis of specific failure event.The cumulative failure probability of main engine can be obtained with this approach as well.Markov process which is suitable for establishing reliability mathematical model of repairable system was used to assess the reliability of marine propulsion shafting.The model established by Markov process can reflect the state conversion rule of the components in repairable system accurately.In order to solve the small sample problem,the model is optimized with gray theory and the result shows that theproposed modeling method can realize quantitative evaluation of the reliability of ship propulsion shafting.In the last part of this thesis,taking propeller shaft as an example,a reliability evaluation method was proposed based on stress-strength interference theory to assess the reliability of ship propulsion system under the condition of large scale deformation.The trend of propeller shaft's reliability in different sea state can be known with the method proposed.Therefore,the research results can provide a theoretical support to ensure safe and reliable operation of the ship propulsion system.