Engine Acoustic Emission Used as a Control Input: Applications to Diesel Engines

The need for strategies that allow managing combustion in an adaptive way has recently widely increased. Especially Diesel engines aimed for clean combustion require a precise control of the combustion outputs. Acoustic emission of internal combustion engines contains a lot of information related to engine behavior and working conditions. Mechanical noise and combustion noise are usually the main contributions to the noise produced by an engine. Combustion noise in particular can be used as an indicator of the combustion that is taking place inside the combustion chamber and therefore as a reference for the control strategy. This work discusses the correlations existing between in cylinder combustion and the acoustic emission radiated by the engine and presents a possible approach to use this signal in the engine management system for control purposes. The application was tested by running several experimental tests, both in steady state and transient conditions, on a Diesel engine mounted in a test cell. Tests have been run in order to first identify the correlation existing between the different injection/combustion patterns that can be operated on the engine and the corresponding acoustic emission. Once the correlation between combustion process and engine noise has been identified it can be used to set up a closed-loop algorithm for optimal combustion control based on engine noise prediction.