The Fault Diagnostic Studies Of Internal Combustion Engine Based On The Analysis Of Crankshaft' Speed Variation

Condition monitoring and fault diagnosis of diesel engine is crucial to improve the reliability and safety of diesel engine power plant, and meet the requirements of modern predictive maintenance and automatization. However,diesel engine is a typical reciprocating machine, its monitoring and diagnosis are very difficult because of its complex structure. Under this condition, a simplified instantaneous speed analyzing model of diesel engine has been established based on the dynamic property of crankshaft flywheel system of diesel engine. The relationship between instantaneous speed and the faults about combustion has been studied, which can be used to detect the faults and locate fault cylinders through the simulation and experimentation's signal analyses of instantaneous speed of diesel engine.Based on the dynamic property of crankshaft flywheel system of diesel engine, the parameter S of instantaneous speed variation has been developed, and diverse faults has been Simulated at varied speed at 4108YC diesel engine. By analyzing the signal at time and frequency domain, an obvious difference have been found when a fault of leakiness has happened, especially at frequence field, the configuration of harmonic orders of instantaneous speed variation is consistent with that of gas pressure torque, this pertinent correlation is intrinsical. First, the value of gas pressure torque can be estimated by the the major harmonic order amplitude of instantaneous speed variation, and the faults can be judged. second, the lower harmonic order of the instantaneous speed variation have been analyzed, and the correlation have been found between the phase of lower harmonic and the fault cylinder. This method can be used to judge the location of fault cylmder. In order to prove this conclusion, a experiment has been made at 4135 diesel engine, the outcome is coincident with the simulation. So this method is a useful tool to diagnose the fault of diesel engine.Be cause this method is simple and useful, without measuring the gas pressure and establishing the dynamic model, the location of fault cylinder can be accurately judged just by measuring instantaneous speed variation. At the same time, this method is transplantable, and can be used at diverse diesel engine, so it has a widest future.