Fault Diagnosis Of Diesel Engine System Based On Structural Theory Of Thermo-economics

Diesel engine is a common marine power machine.Because of the high thermal load and mechanical load,couple with the bad environment of the engine room,the main components are prone to failure like blocking,wear and scaling.It has a serious influence on the economy and safety of the diesel engine system,and it may even lead to the failure of the normal operation of the ship.The traditional maintenance work of diesel engine mainly depends on correction maintenance and scheduled maintenance which is short of the ability to diagnose faults in advance.It is not possible to warn the performance deterioration of the faulty components before the serious failure of the diesel engine.Therefore,it is necessary to monitor the main components of the engine system and to locate the deteriorated components in time.6PA6L-280 diesel engine is taken as the research object,and the diesel engine fault diagnosis model is set up based on the thermal-economic structure theory.The “fuel” and “product” of cylinder,air cooler,turbocharger and cylinder liner water cooler are determined according to the general principles of exergy analysis.The production structure of the diesel engine system is drawn.The "malfunction"," dysfunction" and "fuel impact" of each component are analyzed.The "malfunction" and "fault cost",which are both positive and large absolute value,are the failure components' determinant.Then,the simulation model of 6PA6L-280 diesel engine is built by using GT-Power software,and the fault simulation is carried out.The fault diagnosis model is verified by the simulated operation parameters.The results show that the fault diagnosis model based on thermo economics structure theory can locate the fault location accurately when a single fault occurs,such as compressor blockage,air cooler scaling and cylinder fuel pressure reduction.It shows high sensitivity in the air cooler component fault diagnosis.When the power of diesel engine is down 2kW,the fault cost of air cooler is amplified to 11 kW,but the diagnosis method is not sensitive to the fouling failure of the cylinder liner water cooler.The compressor block and the cylinder injection pressure reduction can be diagnosed at the same time when two or more faults occur together.But the fouling failure of air cooler is easy to be blocked by the compressor block and the cylinder injection pressure reduction because it has little effect on the efficiency of diesel engine.Its malfunction and fuel impact are only 0.06 times or even lower than that of a single fault.Therefore,we should give priority to locating the faults which have great influence on the performance of the diesel engine when using the fault diagnosis method based on the thermo economics structure theory,and the lesser faults can be located after the serious fault is removed.