Research And Application Of Marine Propeller And Propulsion Device Fault Diagnosis Key Techniques

Propulsion device, which is closely related with the rapidity, economy and safety of marine navigation, is the core of marine power. As a system, marine propulsion is composed of main engine, shaft and propeller, and its faults are caused for various reasons. As an important part of propulsion, the propeller generates blade abrasion, deformation, fracture and other faults, and the propeller faults also generate the periodic variation of centrifugal force and hydrodynamic force, which will further lead to shaft and main engine faults.To achieve monitoring and diagnosis of propulsion faults and improve the safety of navigation, the key techniques of diagnosis of propeller propulsion faults caused by propeller will be studied in this paper. The idea of this study is that by analyzing the propeller hydrodynamic performance and flow characteristics under different fault conditions and studying the effect of shaft vibration and main engine matching performance, the diagnosis techniques of propeller blade fracture fault, vibration fault caused by propeller and the main engine fault caused by propeller mismatch will be presented. At present, the study of marine propulsion device fault diagnosis technique focuses on main marine engine fault diagnosis technique. However, as a power system, the three main components of propulsion device interact and influence each other, so it should be seen as a system when studying the fault monitoring and diagnosis technique The marine propeller fault diagnosis technique, the fault diagnosis and elimination techniques of marine shaft and main engine faults caused by propeller fault will be studied in this paper. Therefore, the mechanism of propulsion fault caused by marine propeller can be systematically and deeply studied in this paper. At the same time, it can improve the level of diagnosis technique, eliminate the faults more efficiently and accurately, and increase the safety of navigation.In this paper, the theoretical research, CFD and finite element numerical simulation, model testing and full scale ship application are combined to do the research. The key issues which mean to be solved are as follows: the study of the propeller hydrodynamic performance and flow characteristics under different fault conditions, the study of propeller fault diagnosis technique, and the study of the shaft fault caused by propeller. In accordance with propulsion fault, corresponding techniques and methods will be put forward and applied to full scale ships.Firstly, the study of hydrodynamic performance and flow characteristics of conventional propeller and ducted propeller under different fault conditions can help obtain the propeller's thrust, torque, lateral force and the fluctuating pressure and other variation rules of hydrodynamic loads, and the propeller flow characteristics and trends. The study of conventional propeller steady hydrodynamic performance is based on CFD methods and combines with model test.And then the relationship among fracture quantity and thrust, torque of a certain fractured blade, and the relationship among propeller diameter cutting quantity, thrust and torque will be obtained. The study of ducted propeller unsteady hydrodynamic performance is based on CFD, and then the fracture of a certain blade is numerically analyzed under different positions conditions to obtain relationship among the propeller thrust, torque, lateral force and the duct inner wall fluctuating pressure changes with period and, meanwhile, study the effect, which is performed by wake current field unsteady level and the blade gap value size,upon ducted propeller hydrodynamic performance. The hydrodynamic loads under different fault conditions obtained by the study could provide data signal and hydrodynamic loads for the further study of propulsion device fault diagnosis key techniques.Secondly, the propeller blade fracture fault diagnosis is studied. Generally, the fault diagnosis data or signal is acquired through sensors and data acquisition systems. In order to simplify the details of signal extraction and processing and focus more on the fault diagnosis technique,a ducted propeller condition motoring system based on CFD methods is established in this paper,in which propeller blade fracture faults are diagnosed by extracting the duct inner wall fluctuating pressure data and analyzing fluctuating pressure variation. CFD numerical results can be seen as the signal that the sensors and data acquisition systems obtain under the ideal state. Through contrastive analysis and FFT transform of the ducted propeller inner wall fluctuating pressure-time oscillogram of a certain blade fractured in different positions, a ducted propeller blade fracture fault diagnosis techniques which combines oscillogram analysis method with and spectrum analysis method is put forward.At the same time, in order to obtain more appropriate signal processing methods, change the window function during signal processing and comparative analysis will be tried.Thirdly,a diagnosis techniques of whirling vibration caused by propeller fracture is studied. Propeller blade fracture generates centrifugal force and hydrodynamic lateral force, which leads to a sharp shaft rotating vibration. Based on a reasonable simplified computation model, the most important factor for the study of whirling vibration of shafting is the accuracy of the hydrodynamic propeller lateral force which changes periodically and is affected by the blade fracture position and wake current field. For the study of whirling vibration of shafting diagnosis under different propeller fault conditions, the corresponding hydrodynamic loads are accurately calculated under the corresponding conditions in this paper. Finite element method is adopted to do the transient analysis of whirling vibration of shafting, and then by changing rotation rate and non-uniform wake and other parameters in different fault conditions, shaft rotating vibration time-displacement response curve by the action of centrifugal force and hydrodynamic force is obtained. Spectrum is obtained by FFT transformation of time-displacement response curve, and a propeller axis locus diagram is composed.Then a diagnosis technique of shaft vibration caused by propeller ,which combines vibration method with axis locus method, is put forward by study and analysis.Finally, combining the characteristic of marine propulsion device fault, the corresponding propulsion device fault (caused by the propeller) elimination techniques is presented, and is successfully applied to the full scale ship, which provides typical cases of fault diagnosis and fault elimination. The theory of a propulsion device diagnosis expert system based on remote network is analyzed, and a behavior-based diagnostic model is selected.The diagnosis system consists of shipboard experts, company experts and research institutions—three diagnosis subsystems, and the subsystems adopt client/server structure.