Research On Monitoring And Diagnosing For Marine Diesel Engine Based On Instantaneous Angular Speed And Thermal Parameters

Marine diesel engines, due to their superior effeiciency compared to otherthermal engines, are widely used for propulsion of vessels, so the conditions ofmarine diesel engines are important to keep vessels' safety. With the development ofthe marine diesel engines, they tend to high-power, heavy-load and intelligence.Monitoring and diagnosing technology for the marine diesel engines is the one of themain three technologies of the morden intelligent diesel engines, so it is necessaryand significant to research on the monitoring and diagnosing technology for themarine diesel engines. As a reciprocating machine, the fault diversity makes thedetection of engine faults extremely difficult, it is a complex project to generallymonitor and diagnose the condition of the marine diesel engines. According to thefeatures of the marine diesel engines, a new monitoring and diagnosis method ofusing instantaneous angular speed and thermal parameters about the faults ofunderpower and misfire of single cylinder is proposed through theorical analysis andexperiment research. The main conclusions of this paper are listed below.(1) After analyzing the characteristics and shortcomings of the simpleinstantaneous angular speed calculation model for diesel engine, a new instantaneousangular speed calculation method based on the flexible body model is proposed. Theprocess of the calculation is that the harmonics of exciting forces are forced on theequivalent model of the propulsion shaft, the instantaneous angular speed of eachnode in the equivalent model is calculated from the torsional response. It is provedthat the calculation result from the new model is more consistent with the testing data,compared to the simple model. The results from different calculation solutions alsoshow that the precision of the instantaneous angular speed of the marine diesel enginebased on the flexible body model is mainly correlated to the rigidity matrix and theinertia of moment matrix of the equivalent model.(2) The instantaneous angular speed based on the flexible body model underdiffierent faults simulated is calculated, which shows the rule of the instantaneousangular speed fluctuation ratio due to the underpower of a single cylinder. Therefore,the maximum power fluctuation ratio of the instantaneous angular speed is proposed to diagnose the fault of single cylinder's underpower.(3) As an object of 6L16/24 type marine diesel engine, the one-dimensionnumeric model of the marine diesel engine is built by using the software of AVLBoost, and its correction is verified by the experiment. Based on the verified model, 8faults simulated are conducted, which analyzes the influence of varied faults on thecylinder pressure. 6 cylinder pressure parameters are extracted to show theunderpower fault of cylinder. The rule is acquired, which is that the different faultshave different effects on the cylinder pressure parameters, and the rule is not varywith different fault degrees of the same fault.(4) A numeric monitoring and faults diagnosis system for the marine dieselengine is developed based on the virtual instruments. This system employed multipleparameters and the multiple methods to realize the function of monitoring thecondition of the cylinder, the shaft power, the turbocharger performance, the fuel oilsystem and the inlet-exhaust system In the system, all the data are managed by thedatabase technology. Especially, the measurement & analysis modules of theinstantaneous angular speed and the cylinder pressure fulfill the measuring and theanalysis of the instantaneous angular speed and the cylinder pressure.(5) Based on the numeric monitoring and diagnosis system for 6L16/24 typemarine diesel engine, the instantaneous angular speed and the cylinder pressure areapplied to the monitoring and diagnosing of the marine diesel engine through theartificial faults experiments in laboratory. The experiments results show that theintegrated motheds both the instantaneous angular speed and the cylinder pressurecan effectively diagnose the underpower fault of single cylinder, and detects whichcylinder occurs.(6) Based on the relation between the performance parameters of cylinderpressure and the single cylinder fault of underpower, a fuzzy diagnosis system formarine diesel engine by using fuzzy interfere principle is investigated, which canautomatically identify the single cylinder underpower. The researches provide thefoundation for the practical application of the instantaneous angular speed and thecylinder pressure methods.