Research On Vibration Diagnosis Method Of Valve Leakage For Diesel Engines

Because of their high specific power, high thermal efficiency and easy starting characteristics, diesel engines are widely used in generator sets, heavy-duty vehicles, ship and other fields. The working conditions of the diesel engine are seriously poor, the diesel engines prone to failure and easily lead to a fatal accident. So the research on the monitoring and diagnosing technologies of the diesel engine becomes the significance and the engineering application value. The vibration diagnosis method of the valve leakage based on support vector machine is investigated on a4120SD diesel engine. The main research concludes are shown below:1) A diesel engine static test bench is set up. The vibration diagnosing mechanism of the valve leakage is investigated and verified by using static test results.2) A diesel engine dynamic test bench is set up and the experiments with five fault conditions of the valve leakage are carried out. The vibration signals on the cylinder head are measured, and the characteristic parameters of the vibration signals used to diagnose the valve leakage are extracted.3) The basic principle of the support vector machine and the construction of classifier is analyzed. Compared to the traditional diagnosis methods and standards-based neural network, the support vector machine method has the feasibility and superiority of applied to diesel engine small sample fault diagnosis, and a technical road map is gave for the practical application.4) The vibration diagnosis of the valve leakage technology based on support vector machine is investigated. The vibration characteristic parameters on the cylinder head used in support vector machine are extracted, a fault diagnosis model based on support vector machine is built up and the correctness of the diagnosis model is verified by the experiments.