Mixing Process
Laser Doppler and Phase Doppler Velocimetry have been extensively used at Istituto Motori within optical accessible engines to obtain detailed measurements of one or two components of the velocity field and size of fuel droplets, joined to a planar technique, the Particle Image Velocimetry (PIV), to provide a clearer illustrations of the flow field structure and allow a better understanding of the physical process implied.
Additional experimental investigation tools, based on non interfering light-based or non-conventional sources (X-ray), have been used to scan the pulsed phenomenon while mineral based, vegetal derivate or nanoparticle additivate fuels have also been investigated.
Sensor-devoted activities and innovative actuators for injection command and monitoring complete this part of activities.
Multi injection strategies have been implemented on a complete programmable ECU using the last generation Common Rail (CR) high pressure injection system typical of new generation EURO5 diesel engines. Studies involving the injections in the spray bomb and in single-cylinder research engine have been made in order to assess the behaviour of the fuel dispersion for mineral diesel and different biodiesels.
For the formation process of the air-fuel mixture, optical diagnostic techniques are used; they are based on the interaction of light-material in the UV-visible field and allow to follow, temporal and spatial resolved, the liquid and vapour phases which precede the priming of the combustion. These techniques are applied both to quiescent high pressure vessels, optically accessible, and to prototypes engines, optically modified in order to get a wide field of view for optical diagnostic application.
The experimental analysis for the characterisation of the fuel/wall impingment, for the identification of droplet rebounding phenomena, splashing and liquid film formation is carried out by means of imaging optical techniques. Moreover, aiming at optimizing the engine control strategies to meet European emission standards, the measure of size and fuel droplets velocity associated to functional parameters of the injection system, may contribute to clarify theorethical aspects of spray atomization and breakup as well make the data base for CFD codes calibration.