Combustion and Vibration Characteristics in a Small Displacement Diesel Engine Fueled with Biodiesel Blends 2013-01-1902

This paper presents the results of an experimental study on the application of an engine block vibration transducer. The aim of the study was to accomplish a real time management of the control unit using the vibration signal as a feedback to correct the injection parameters setting.

The continuously strengthened exhaust emission regulations and the constrains related to the fuel consumption and noise, vibration and harshness (NVH) characteristics, have determined increasing interest towards investigation of the potentiality of new combustion technologies and fuel blends capable of reducing particulate matter and NOx emissions. Focus has also been paid to non-intrusive techniques for the combustion process characterization by means of sensors, such as microphones and accelerometers. The signal of these sensors can be profitably used for the optimization of the injection strategy (e.g. number of injections, quantity of fuel delivered in each shot, injection timings) under stationary and transient engine's operation.

The results here presented are a part of a wide research program where the vibration signal of the engine block is used to fully characterize the combustion development of conventional diesel fuel. Through the vibration signal is possible to identify the crank angle values corresponding to the subsequent combustion phases and to estimate the maximum value of the pressure trace during the combustion process.

During the present study, an enhancement and an extension of such technique was obtained which demonstrated its suitability to be applied in the real engine operation to optimize the injection process through the control unit, accounting for the fuel properties.

The experimentation was performed on a small displacement two cylinder common-rail diesel engine fueled with different biodiesel blends. The complete engine operative field was investigated under stationary conditions.