Combustion Diagnostics of a Diesel Engine with Biodiesel Fuels based on Vibro-acoustics and In-Cylinder Pressure Measurements

Biodiesel is one of the alternative fuels which is renewable, environmentally and can be used in diesel
engines without modifications. For non-intrusive diagnosis, this study investigates the characteristics of
combustion induced vibration and noise in a diesel engine fuelled with biodiesel blends under different
operating conditions. The relationship between the engine vibro-acoustics and in-cylinder pressure was
investigated based on the analysis of the measured cylinder head vibration, engine acoustics and in-cylinder
pressure (peak pressure, pressure rise, and pressure rise rate). It has found that the biodiesel blends result
in a slight increase of peak value of in-cylinder pressure when increasing the percentage of biodiesel. The
engine running with biodiesel blends has slightly higher vibration, which is more related to the maximum rate
of pressure rise which is closely related to the combustion process. In addition, the time domain RMS values
of vibration is relating to the maximum rate of pressure rise whereas the RMS of acoustics signals is more
relating to peak pressure. These show that vibro-acoustics include good information about combustion.
However, more advanced analysis is needed to suppress noise influences for accurately representation of
combustions due to different types of fuels.