Pulsed liquid sprays from automotive fuel injectors are inherently complicated and the formationand development of sprays involve multiple physical processes which take place both simultaneouslyand sequentially. The pulsed spray characteristics far from the injector orifice are affectedby complicated mechanisms of primary and secondary break-up at and close to the injector tip.This complexity usually requires researchers to make assumptions about break-up mechanisms. Inaddition, several droplet collision models have been proposed for sprays, but when used in conjunctionwith break-up mechanism models, the accuracy and limitation of collision models havebeen difficult to judge. This study is intended to explore, examine and compare different collisionmodels in a pulsed fuel spray. Since trustworthy laser diffraction measurements of dropletsize distribution can be performed far from the injector orifice, these data can be used as accurateinitial conditions for simulating downstream spray development. Since the pulsed sprays from automotivefuel injectors are relatively dense ones, this study eliminates the complexity of simulatingtwo-phase flow equations for break-up and instead solves the simpler fluid mechanics problem ofthe Lagrangian trajectory of spray droplets, together with a droplet collision model. It was foundthat for the single-hole sprays of this study, when the droplet size distribution is known at someplane downstream of the break-up region, the development of the spray can be modeled accuratelyby using a simple Lagrangian model which calculates the droplet collision impact parameteranalytically at each collision.
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