Closed Loop Combustion Control - Enabler of Future Refined Engine Performance Regarding Power, Efficiency, Emissions & NVH under Stringent Governmental Regulations 2011-24-0171
Both, the continuous strengthening of the exhaust emission legislation and the striving for a substantial reduction of the carbon dioxide output in the traffic sector depict substantial requirements for the global automotive industry and especially for the engine manufacturers. From the multiplicity of possible approaches and strategies for clear compliance with these demands, engine internal measures offer a large and, eventually more important, very economical potential. For example, the achievements in fuel injection technology are a measure which in the last years has contributed significantly to a notable reduction of the emissions of the modern DI Diesel engines at favorable fuel efficiency. Besides the application of modern fuel injection technology, the linked combustion control (Closed Loop Combustion Control) opens possibilities for a further optimization of the combustion process. The availability of a highly-dynamic cylinder pressure signal makes it possible to analyze and affect the combustion characteristics based on new, advanced control algorithms even more exact than before. In order to control the temporal course of combustion, particularly a fast and precise high pressure fuel injection is qualified for dynamic adaptation by recording and evaluating the cylinder pressure signal and varying the injection accordingly. The highest degree of freedom is thereby obtained with a flexible rate shaping of the fuel introduction characteristic, which allows the realization of a pre-defined combustion pressure pattern or fuel burn rate. In this publication detailed results of experimental investigations identify the high potential of a direct fuel burn rate control, considering various possibilities with respect to the optimization of fuel consumption, the minimization of pollutant emissions and reduction of combustion noise. In the first section, the direct burn rate control is accomplished with a unique, experimental common-rail injector with specific rate shaping capabilities. In the second part of the paper an advanced control concept is presented which realizes the management of pre-defined combustion pressure traces and fuel conversion processes with a conventional, series production Piezo-injector by multiple injections. Thus control options result in the possibility of a direct cost-attractive realization of pre-defined emission-, consumption- and noise-optimal fuel rates with proven injection technology. Particularly, this technology offers the possibility of compensating different fuel properties and qualities within a large range, thus showing a large potential for a future multi-fuel diesel combustion concept.