The Experiment Research on Early Weak Diesel Fault Diagnosis Based on Instantaneous Speed

Instantaneous speed signal included much working status information of diesel, and it has been used in severe misfire fault diagnosis successfully, but there is still lack of further research on early weak fault diagnosis. In this paper, several early faults are simulated in 6-135 type diesel through adjust cylinder fuel eject quantity, adjust exhaust valve clearance, simulate exhaust valve leak in differ degree. Experiment data is acquired at different running status, and instantaneous speed signal of diesel is calculated. Through analyzing the change rule of instantaneous speed signal in different status, it is found that the diesel instantaneous speed signal could be used in several early fault diagnosis, and the instantaneous speed unitary rise amplitude ratio P of every cylinder is a direct character parameter. At normal status, P value of every cylinder are in the range of 0.9~1.1. If the P value of certain cylinder descend over 10%,then it could be think as a fault cylinder. The method is sensitive to some fault which could influence gas press in cylinder such as fuel eject quantity not uniformity and valve leaking, and it is not sensitive to some fault which couldn't influence gas press in cylinder such as cylinder liner wear.