Development of a pressure-based technique to control IMEP and MFB50 in a 3.0L diesel engine

A pressure-based technique for the control of IMEP (Indicated Mean Effective Pressure) and MFB50 (crank angle at which 50% of fuel mass fraction has burned) has been developed, assessed and tested by means of MiL (Model-in-the-Loop) on a 4 cylinder 3.0L Euro VI diesel engine. The activity was carried out in the frame of a research project in collaboration with FPT Industrial. The developed controller is of the closed-loop type. It receives, as input, the desired targets of IMEP and MFB50 for each cycle and cylinder and performs a cycle-by-cycle and cylinder-to-cylinder correction of the injected fuel quantity of the main pulse (qmain) and of the start of injection of the main pulse (SOImain), in order to reduce the deviation between the actual and target values of IMEP and MFB50, respectively. The method is referred to as “pressure-based” since it requires the measurement of the in-cylinder pressure trace for each cylinder in order to extract the actual values of IMEP and MFB50. In fact, the actual IMEP value can be estimated by integrating the pressure signal with respect to the in-cylinder volume. At the same time, the actual MFB50 value can be extracted from the heat release curve, which is obtained from the in-cylinder pressure trace by using a single-zone heat release model. The proposed control technique has been developed in Simulink environment, and has been assessed and tested on an engine emulator which is constituted by a GT-power model of the 3.0L diesel engine. The controller has been tested in transient operation over a load ramp profile at different engine speeds and over a WHTC interval, and demonstrated to have a good potential for IMEP and MFB50 control, since it is characterized by a fast response and a limited overshoot behavior.