Turbocharger speed estimation via vibration measurements for combustion sensing

Monitoring of engine operating condition is essential to comply with severe limitations of harmful exhaust emissions and fuel consumption. Several strategies have been proposed, in which different types of sensors are used for the direct/indirect combustion sensing and to provide a feedback signal to optimize the process. It has been demonstrated that in a turbocharged engine a relationship exists between the rotational speed of the turbocharger and the thermo-fluid dynamic condition of the gases at the exhaust valve opening. Such a relation allows to establish a link between the engine operating conditions in terms of speed, load and injection settings and the turbocharger speed. This work presents a methodology devoted to extract from an accelerometer signal, the mean turbocharger rotational speed with the final aim of realizing a non intrusive control of combustion process, in which the variation of combustion development as regards nominal condition is detected via the estimation of the turbocharger speed.