Effect of valve train typical faults on diesel engine performance and fault isolation method

The isolation of valve train typical faults, such as abnormal valve timing, abnormal valve clearance, and valve leakage is difficult and meaningful. In this work, the identification of valve timing and the influence of valve train typical faults are studied, and an effective method for the valve train typical faults isolation is proposed. Concretely, the feature angles of valve opening and closing is defined and automatically identified, and the result shows that exhaust valve opening and intake valve closing have good repeatability, which can be combined with engine performance to distinguish valve train faults. The deviation of the intake valve closing feature angle is caused by abnormal intake timing or intake valve clearance, and with the same deviation, the former has much greater impact on engine performance. The deviation of the exhaust valve opening feature angle is caused by abnormal exhaust timing or exhaust valve clearance, but these two faults have opposite effects on the exhaust temperature. In addition, the valve leakage can be isolated according to the influence of engine speed on the fault phenomenon. Among the faults considered in this study, only the influence of valve leakage on exhaust temperature decreases with the increase of engine speed.