Online detection of cylinder-to-cylinder variations by a vibration analysis system

Imbalance between cylinders is a major concern of a proper operation of reciprocating engines. An engine reliability and performance envelop, including life span, fuel consumption and emission, are strongly affected by an improper operation of the cylinders. To improve the engine quality, there is a strong need for a closed-loop control system to manage the amount of fuel injected to each individual cylinder. An advanced system to detect imbalance related faults in reciprocating engines which is based on the analysis of the engine's mechanical vibrations have been developed. The system is based on a firm theoretical background that provides a fundamental relation between the engine's vibration pattern and the relative characteristics of the combustion process in the different cylinders. With a single accelerometer mounted on the engine's block, online information related to the combustion process in each cylinder is provided by the system. This information can be used to control the injection quantity and timing to the individual cylinders. It was demonstrated in a series of experiments that the system provides sensitive yet robust data concerning the momentarily relative contribution of each cylinder.