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Macroscopic Behavior of Diesel Sprays in the Near-Nozzle Field
Abstract:
The objective of the paper is the characterization of the macroscopic behavior of Diesel sprays by focusing in at the first instants of the injection process at which the spray is clearly affected by the injector needle dynamic.
There are several works dealing with the characterization of Diesel sprays in stationary conditions. Most of them conclude with empirical correlations which predict spray tip penetration as a function of the most important parameters involved in the injection process, such as: injection pressure, gas ambient density, hole diameter and time elapsed from the start of injection. In all these experiments, authors find similar power law dependencies with more or less high level of confidence. Nevertheless, few works have tried to validate or to obtain new correlations for the first instants of the injection process where the spray develops in not stationary conditions because of the influence of injector needle lift.
In this paper, a wide parametrical study based on a zoomed visualization in the nozzle near-field including the first 15 millimeters of the spray has been carried out. The research has permitted the quantification of effects of the main injection parameters on spray tip penetration and spray cone angle at the initial stages of the injection process. From this study, significant differences have been found when comparing results with previous analysis based on sprays in stationary conditions especially in time dependence of spray tip penetration and injection pressure.