Pressure-based and model-based techniques for the control of MFB50 (crank angle at which 50% of the fuel mass fraction has burned) have been developed, assessed and tested by means of rapid prototyping (RP) on a FPT F1C 3.0L Euro VI diesel engine.
The pressure-based technique requires the utilization of a pressure transducer for each cylinder. The transducers are used to perform the instantaneous measurement of the in-cylinder pressure, in order to derive its corresponding burned mass fraction and the actual value of MFB50. It essentially consists of a closed-loop approach, which is based on a cycle-by-cycle and cylinder-to-cylinder correction of the start of injection of the main pulse (SOImain), in order to achieve the desired target of MFB50 for each cylinder.
The model-based technique, instead, requires the adoption of a heat release predictive model to simulate MFB50; this model is based on an improved version of the accumulated fuel mass approach, which requires the injection rate as input. This control technique is essentially based on the inversion of the heat release model, in order to identify the optimal value of SOImain that allows the desired MFB50 target to be achieved cycle-by-cycle. The approach is therefore of the open-loop type.
Both control techniques were developed and assessed by means of Model-in-the-Loop (MiL) and Hardware-in-the-Loop (HiL) techniques, and then tested on the engine using a rapid prototyping device. The experimental tests were performed on a highly dynamic test bench at the Politecnico di Torino.
These techniques have shown a good potential for MFB50 control, compared to the standard methodology implemented in the Engine Control Unit (ECU).
