The paper presents a non-intrusive technique in which accelerometers are used to provide information about the metric of the in-cylinder pressure development, with the final aim of using their signal as feedback in a control algorithm for the injection control unit.
Previous papers by the authors have been devoted to the evaluation of the potential of using vibration transducers; the analysis in both the time and frequency domain of the accelerometer and in-cylinder pressure signals has allowed for the separation of the vibration components caused by the combustion process from those due to other sources. The combustion related vibration has then been used to characterize the in-cylinder pressure development.
In this work, the next step of the analysis has focused on two different aspects; the former is to demonstrate the effectiveness and the repeatability of the technique for a different engine facility (that is able to reproduce the real operative conditions of the engine, mainly employed in mini-car sector application), the latter is to relate the accelerometer trace with the combustion process development by computing the rate of net heat release (ROHR). The ROHR has been calculated starting from the in-cylinder pressure signal through a thermodynamic model in which the rate of heat transfer to the walls is accounted for.