The Research on Weak Fault Time Domain Feature Extraction of Diesel Engine Instantaneous Speed

Abstract

Instantaneous speed signal is a new information source for diesel fault diagnosis. It has been used in critical fault diagnosis successfully such as misfire. But the occurrence rate of early weak diesel fault is high, and can’t be diagnosed easily by other information source, so it has high value to research on the weak fault feature extraction method of transient speed. Due to the difficulty in setting up effect and accurate mathematic model for diesel engine instantaneous speed under weak fault conditions, so in this paper the early fault simulated experiments are proceed in 6-135 type diesels. Many early faults are simulated by adjusting cylinder fuel eject quantity, adjusting exhaust valve clearance, simulating exhaust valve leak in differ degree. Through analyzing the variation rule of instantaneous speed signal in different status, the direct time domain fault feature is extracted. It is the instantaneous speed unitary rise amplitude ratio of every cylinder, the value of each cylinder is named as Pi. The experiments outcome shows that if Pi descend over 10%, then the No.i cylinder exist fault. The feature is very sensitive to some fault which influence gas press in cylinder such as fuel ejects quantity not uniformity and valve leaking.