Development of a Novel Approach for Non-Intrusive Closed-Loop Heat Release Estimation in Diesel Engines

Over the past years, policies affecting pollutant emissions control for Diesel engines have become more and more restrictive. In order to meet such requirements, innovative combustion control methods have currently become a key factor. Several studies demonstrate that the desired pollutant emission reduction can be achieved through a closed-loop combustion control based on in-cylinder pressure processing. Nevertheless, despite the fact that cylinder pressure sensors for on-board application have been recently developed, large scale deployment of such systems is currently hindered by unsatisfactory long term reliability and high costs. Whereas both the accuracy and the reliability of pressure measurement could be improved in future years, pressure sensors would still be a considerable part of the cost of the entire engine management system. In the light of these remarks, and especially with regard to light duty applications, research is being conducted in order to develop non-intrusive methodologies for the extraction of relevant information about the combustion process. This work presents a methodology for heat release estimation through a proper analysis of the signals coming from a set of accelerometers and the engine speed sensor already present on-board. The presented algorithm is mainly composed of two steps: the first step is an open-loop pressure estimation based on a zero-dimensional model of the combustion process, while the second one consists in a closed-loop correction based on the analysis of the signals coming from the above mentioned sensors. This paper also reports the results obtained applying the whole estimation methodology to a light-duty turbocharged Common Rail Diesel engine.