The Fault Diagnostic Studies Of Diesel Engine Based On The Instantaneous Speed Signal Analysis

In order to improve the safety and reliability of diesel engine power plant, and meet the requirements of modern predictive maintenance and automation, condition monitoring and fault diagnosis of diesel engine is crucial. However, diesel engine is a typical reciprocating machine, which is complex .Its monitoring and diagnosis are very difficult. Under this condition, this article established a simplified diesel instantaneous speed analyzing model based on the dynamic property of crankshaft flywheel system of diesel engine. This model studied the relationship between instantaneous speed and the faults about combustion, which can be used to detect the faults and locate fault cylinders through the simulation and experimentation's signal analyses of the diesel instantaneous speed.Based on the dynamic property of crankshaft flywheel system of diesel engine, this article developed the signal of instantaneous speed variation, and simulated diverse faults at 4108 diesel engine. By analyzing the signal at time field, an obvious difference was found when a fault of cylinder has happened; by analyzing the signal at frequency field, it is found that the extent value of low frequency is higher than that in normal condition. By quantificationally analyzing the signal of instantaneous speed at time and frequency field, two character parameters are found which can be used to judge the location of the fault cylinder. It is found that the methods of Bi-spectrum and STFT to analyze the instantaneous speed can be used to judge the happened of the fault and the fault degree, also and given a new way to deal with the signal of instantaneous speed. The FFT_IFFT to refine the signal of instantaneous speed has a satisfaction result. By the above methods, an experiment at 4135 diesel engine is made. The outcome is coincident with the simulation. So this method is correct.This method is simple and applicable. Without measuring the gas pressure and establishing the dynamic model, the location of fault cylinder can accurately be judge only by measuring instantaneous speed. At the same time, this method is useful, which can be used at diverse diesel engine, so it has a widest future.