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Cavitation is the major cause of the effective flow area reduction in fuel nozzles, together with mechanical damage, which leads to an increase of pressure losses. This paper describes the effect of different geometries along the fuel nozzle holes simulated with OpenFOAM® to control the cavitation and shape of the fuel jet. Previous work has only focused on the development trend towards conical spray holes that tapers towards the outlet with a strong rounded inlet edge, to increase the static pressure and thus reduce the cavitation tendency in nozzles; however, the jet forms a very narrow cone angle. The aim of this study is to evaluate the effect of constricted, expanded and gradually wider nozzles holes. The simulation reveals that the cavitation level can be changed and controlled depending on the geometry of the nozzle holes, the wider the inlet, the less is the cavitation; at the same time, the narrower the outlet, the better is the fuel atomization.

A higher level of atomization of the fuel leads to a more homogeneous mixture with the air in internal combustion engines, whether they are equipped with direct injection or port fuel injected systems. The further break-up of the atomized fuel drops by the interaction of two fuel sprays is described in this paper. In the present research, a simulation of the collision and swirl of two fuel sprays in a double-injector engine concept is carried out through a qualitative comparison with the images obtained from the recorded video of the sprays and the results of the simulation. Previous work simulated and tested the spray interaction of fuel injectors on the top of the combustion chamber; while this research proposes a new approach to reduce the diameter of the atomized fuel drops through the direct collision of the sprays with injectors located oppositely and fully horizontally to get advantage of the flow’s momentum.

Aiming for cleaner and more efficient energy from the internal combustion engines makes necessary to ensure the special conditions for exploitation of alternative fuels. The engine vibrations are primarily understood as effects of mechanical failures, but they are also a subject of the fuel combustion effects. These effects depend on the fuel type and its ability to complete the combustion process. The vibrations of a diesel engine were measured and analyzed with a frequency spectrum calculated with fast Fourier transforms. The engine was operated with a fuel blend of 10 % recycled lubricating oil with 90% diesel fuel as well as with neat diesel. It was found that the engine operation with this fuel blend has a lower vibration level in comparison with the use of neat diesel fuel. The goal of this research is to determine the properties of the fuel blend, which provide more stability to the engine by means of vibrations reduction.

The insufficient level of atomization of the fuel drops in direct-injection engines is a major cause of pollutant emissions because of the incomplete combustion process. The fuel injection is a critical part of the homogeneous air-fuel mixture. It is well known that higher injection pressure enhances the atomization of the fuel; however, there are physical and technological limits to go further in this regard. Previous work was focused mainly on the swirl created by the spray flow, and on the avoidance of fuel drops coalescences and their impingement on the cylinder walls. This current paper proposes a new approach to reduce the diameter of the atomized fuel drops by colliding the fuel sprays in a cylinder arranged with 4 opposed injectors, in order to increase the breakup of the atomized fuel drops and therefore, to improve the homogeneity of the air-fuel mixture.

The use of alternative fuels consisting of mineral and synthetic waste substances such as recycled lubricating oil blended with diesel is a measure to mitigate the environmental impact of the fossil fuels. However, to inject these fuel blends into contemporary engines without changes to their components, it must maintain or improve the fuel injection characteristics compared to neat diesel, in order to maintain or improve the engine performance. In the present research, the spray parameters of injected fuel, such as length, angle and atomization particle diameter in terms of the Sauter mean diameter (SMD), are modeled depending on the characterization of different concentration of the recycled lubricating oil blended with diesel.