论文标题

在非蒸发操作条件下,汽油替代喷气机的主要分解的建模和详细的数值模拟

Modeling and Detailed Numerical Simulation of the Primary Breakup of a Gasoline Surrogate Jet under Non-Evaporative Operating Conditions

论文作者

Zhang, Bo, Popinet, Stephane, Ling, Yue

论文摘要

在本研究中,进行了详细的数值模拟,以研究在非蒸发的“喷雾G”工作条件下汽油替代射流的主要分裂。由发动机燃烧网络(ECN)开发的喷射G喷油器和操作条件代表喷雾引导汽油注入的早期阶段。为了将计算资源集中在解决主要分手上,对喷油器几何形状进行了简化。内部流对主要分裂的影响是通过指定入口处的非零注射角来建模的。非零注射角会导致射流渗透速度的提高以及液体射流的偏转。对注射角进行了参数研究,并将数值结果与实验数据进行比较,以识别最能代表喷雾G条件的注入角度。非零注射角在液体射流中引入了方位角不均匀的速度,这反过来又影响了射流表面上的不稳定性发育以及喷射头的变形和破裂。不对称的一级分解动力学最终导致液滴尺寸分布的方位角变化。液滴的数量随方位角的变化很大,但有趣的是,不同方位角角度崩溃的液滴大小的概率密度函数(PDF)塌陷到自相似的轮廓。还进行了分析以估计当前仿真中未解决的小滴的百分比和统计。还提出了方位角的PDF,这也显示出表现出一种自相似形式,随着时间的流逝几乎没有变化。最后,开发了一个模型来预测液滴数,这是液滴直径,液滴所在的方位角和时间的函数。

In the present study, detailed numerical simulations are performed to investigate the primary breakup of a gasoline surrogate jet under non-evaporative "Spray G" operating conditions. The Spray G injector and operating conditions, developed by the Engine Combustion Network (ECN), represent the early phase of spray-guided gasoline injection. To focus the computational resources on resolving the primary breakup, simplifications have been made on the injector geometry. The effect of the internal flow on the primary breakup is modeled by specifying a nonzero injection angle at the inlet. The nonzero injection angle results in an increase of the jet penetration speed and also a deflection of the liquid jet. A parametric study on the injection angle is performed, and the numerical results are compared to the experimental data to identify the injection angle that best represents the Spray G conditions. The nonzero injection angle introduces an azimuthally non-uniform velocity in the liquid jet, which in turn influences the instability development on the jet surfaces and also the deformation and breakup of the jet head. The asymmetric primary breakup dynamics eventually lead to an azimuthal variation of droplet size distributions. The number of droplets varies significantly with the azimuthal angle, but interestingly, the probability density functions (PDF) of droplet size for different azimuthal angles collapse to a self-similar profile. Analysis has also been conducted to estimate the percentage and statistics of the tiny droplets that are under resolved in the present simulation. The PDF of the azimuthal angle is also presented, which is also shown to exhibit a self-similar form that varies little over time. Finally, a model is developed to predict the droplet number as a function of droplet diameter, azimuthal angle where a droplet is located, and time.

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