Analysis of the relation between injection parameter variation and block vibration of an internal combustion diesel engine

The development of combustion in diesel engines is strictly dependent on injection parameters, like injection number and timings, fuel quantity and mean injection pressure. Moreover, it is well known that the variation of the injection parameters has an effect on the engine block vibration. Hence, the present work aims at investigating the possibility of using engine block vibration as a mean to diagnose, outwardly, the combustion modifications induced by these parameters. So, the possibility of following the combustion modifications by means of two accelerometers positioned at two different zones of the engine block has been analysed, defining a characteristic “signature” for each parameter. Classical Fourier analysis and time–frequency analysis were used to define the degree of correlation between in-cylinder pressure and vibration signals. It has been proved that injection pressure and injected quantities, over an energy release threshold, really affect the vibration signals in a peculiar way; injection timing affects the engine block vibration in a less evident way, but a characteristic signature was also defined for this factor.