The early and late portions of transient fuel injection have proven to be a rich area of research, especially since the end of injection can cause a disproportionate amount of emissions in direct injection internal combustion engines. The presented work simulates a gasoline direct injector operating under cavitating conditions by employing a more gradual and easily implemented model of closure that avoids spurious water-hammer effects. The results show cavitation at low valve lift for both flash-boiling and nonflash-boiling conditions. Further, this study reveals post-closure dynamics that result in dribble, which is expected to contribute to unburnt hydrocarbon emissions. Flashing versus nonflashing conditions are shown to cause different sac and nozzle behaviors after needle closure. In particular, a slowly boiling sac is observed for the flash-boiling condition which causes spurious postinjection behaviors. However, post-needle closure, traces of ambient gas and liquid fuel, which are the main source of dribble, are observed for the nonflashing condition. The current work indicates more tip wetting for the flash-boiling condition compared to the nonflashing condition during both pre- and post-needle closure phases.

中文翻译：

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闪沸条件下多孔汽油直喷器的喷油结束研究

瞬态燃料喷射的早期和晚期部分已被证明是一个丰富的研究领域，特别是因为喷射结束会导致直接喷射内燃机中不成比例的排放量。所提出的工作通过采用更渐进且更易于实施的闭合模型来模拟在空化条件下运行的汽油直接喷射器，该模型避免了虚假的水锤效应。结果表明，在闪沸和非闪沸条件下，气门升程较低时会出现气穴现象。此外，这项研究揭示了导致运球的关闭后动态，预计这将有助于未燃烧的碳氢化合物排放。闪光与非闪光条件显示在针闭合后导致不同的囊和喷嘴行为。特别是，对于导致虚假注射后行为的闪沸条件，观察到一个缓慢沸腾的囊。然而，在非闪蒸条件下，观察到针关闭后，微量的环境气体和液体燃料是运球的主要来源。目前的工作表明，在针闭合前和针闭合后阶段，与非闪蒸条件相比，闪蒸条件下的针尖润湿程度更高。