In-Cycle Closed-Loop Combustion Control with Pilot-Main Injections for Maximum Indicated Efficiency

An in-cycle closed-loop combustion controller is proposed in this paper. The controller uses a pilot-main injection scheme where the cycle-individual properties of the pilot combustion are estimated by in-cylinder pressure measurements, and used to predict their effect on the heat release shape of the main combustion. The prediction is used to obtain the optimal main SOI that gives the Maximum Reachable Indicated Efficiency (MRE). The optimal law was linearised to obtain a linear controller that adjusts the main SOI and main duration to obtain the MRE given the conditions of each cycle. The controller was implemented in an FPGA and tested on a Scania D13 Diesel engine. The results show that the main SOI control improves the indicated efficiency. However, the linear controller application is limited due to the non-linear behaviour of the system, which is dependent on the fuel type.