To comply with the increasingly severe regulations related to exhaust emission, internal combustion engines are required to monitor their operating conditions on a continuous basis.
Vibration-based techniques have been successfully applied in reciprocating engines to assess the condition of the machines and detect faults. Dealing with turbocharged engines, methodologies based on the employment of accelerometer signals to obtain an estimation of the turbocharger rotation have been proposed with the aim of using the instantaneous turbocharger speed for the engine function monitoring.
The present article focuses on the analysis in time and frequency domains of the vibration signals from the compressor housing of a medium-duty, four-cylinder, turbocharged common rail diesel engine aimed at indirectly evaluating the turbocharger speed in terms of its mean component and fluctuation.
Data have been acquired during experimental tests at different values of engine speed and torque. The comparison between the estimations and the direct turbocharger speed measurements demonstrated the ability of the developed methodology to track the speed fluctuation due to the exhaust process for each cylinder. This allows the methodology to be used in combustion control algorithms to detect any variation of the combustion process as regards the regular running and to detect if cylinder-by-cylinder inhomogeneity arises in the engine real-time operation.
