Injection pattern design for real time control of diesel engine acoustic emission

Upcoming more stringent emission regulations throughout the world pose a real challenge, especially in regard to Diesel systems for passenger cars, where the need of additional after-treatment has a big impact in terms of additional system costs and available packaging space. Therefore, the need for strategies that allow managing combustion towards lower emissions, that require a precise control of the combustion outputs, is definitely increasing. Acoustic emission of internal combustion engines contains a large amount 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. In particular, recent research from the same authors of this paper demonstrated that combustion noise 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. Previous works showed the correlations existing between in cylinder combustion and the acoustic emission radiated by the engine, and presented a possible approach to use this signal in the engine management system for control purposes. In this work, additional experiments were carried out, in order to further investigate how to design the optimal injection pattern. The application was tested by running several experimental tests, in steady state conditions, on a Diesel engine mounted in a test cell. Tests have been run in order to identify the correlation existing between the different injection/combustion patterns that can be operated on the engine and the corresponding acoustic emission, to be used in the closed- loop combustion control based on engine noise feedback.