Investigation of the relationship between engine valve leakage and acoustic emission measured on the cylinder head ignoring combustion effects

Finding leakage in valves is important to troubleshoot performance of internal combustion engines. Leakage can lead to a reduction in engine power and an increase in emissions. The main objective of the present study is to investigate relationship between valve leakage and the acoustic emission generated from the steady flow in the cylinder head of the internal combustion engine. The test rig is the cylinder head for a spark-ignited engine. The test rig simulates the valve leakage due to valve clearance. The valve clearance fault was artificially simulated by a very small lift in valve. The acoustic emission method was used to measure acoustic emission signals generated by valve flow. Characteristics of acoustic emission signals in the time and frequency domains are presented and explained. The effects of air pressure level, valve lift, and valve type on the acoustic emission signals are investigated. It is shown that acoustic emission energy and valve leakage parameters have a linear correlation. The results demonstrate the potential of the acoustic emission source identification in the practical situation of detecting valve leakage using the investigated relationship.