Abstract
KEYWORDS – Transient Diesel Combustion Control, Digital Combustion Rate Shaping, Diesel Fuel Injection, Diesel Combustion Modelling, Engine Testing
ABSTRACT
The parallel optimization of combustion efficiency, pollutant- and noise emissions and thus defusing their contrary trade-offs is the main objective of modern Diesel combustion control strategies. The principle of Digital Combustion Rate Shaping (DiCoRS) is a promising way to approach this challenging development. This research study aims at developing a novel DiCoRS control strategy for diesel passenger car applications, focusing on transient engine operation conditions.
Instead of controlling distinct combustion characteristics (e.g. combustion phasing, IMEP, pmax), DiCoRS aims at controlling the full combustion process during the working cycle and therefore represents the highest possible degree of freedom for combustion control. The manipulated variable is the full injection profile, including the injection timings, the energizing durations and the number of injections. The controlled variable is the combustion rate trace. The desired combustion rate trace is predefined to exploit the thermodynamic optimum of the combustion process in dependency of the engine operation point, -condition and combustion mode. A novel DiCoRS controller is developed and implemented into the Rapid Control Prototyping environment and finally tested on a typical series type full size engine test bed.
The controller shows the realization of predefined in-cylinder pressure traces. In steady state conditions, DiCoRS is realizable via feedback based control. The feedback is obtained from typical series use in-cylinder pressure sensors. The transient DiCoRS domain is covered by the instantaneous control response of an additional, model-based feedforward precontrol path.
DiCoRS control can be considered as a tool to exploit the full thermodynamic potential of the combustion process. However, the engine operation point- and condition dependent definition of the optimal in-cylinder combustion rate trace is not focused here. Previous studies have already demonstrated the thermodynamic benefits of DiCoRS, which is therefore not discussed here in this paper.
This paper gives an insight into the development steps of a highly promising combustion control approach, which has not widely been investigated by other authors yet. Among the available literature, this research group is the first one to realize model-based DiCoRS with a series type engine in transient engine operation condition. Due to the model-based formulation of the DiCoRS controller, the control algorithm needs to inherit detailed system knowledge, for which real-time capability needs to be considered as well.