Vortex ring-like structures in gasoline fuel sprays under cold-start conditions
Vortex ring-like structures in gasoline fuel sprays under cold-start conditions
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DOI：
10.1243/14680874jer02809
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发表时间：
2009-08
影响因子：
2.5
通讯作者：
S. Begg;F. Kaplanski;S. Sazhin;M. Hindle;M. Heikal
中科院分区：
文献类型：
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作者：
S. Begg;F. Kaplanski;S. Sazhin;M. Hindle;M. Heikal
摘要本文对两种类型的喷油器进行了汽油喷雾涡环结构的现象学研究：低压进气道喷油器（PFI）和高压雾化器（G-DI），后者将燃油直接喷入发动机燃烧室。采用高速摄影和相位多普勒测速技术（PDA）对燃油喷雾进行了研究。在一般情况下，每个喷雾被视为包括三个不同的时期：一个初始的，不稳定的阶段;准稳定的注射阶段;和指数拖尾阶段。对于两个喷嘴，涡环状结构可以清楚地跟踪在喷雾的尾部。液滴和气体混合物的最大涡度区域的位置被用来计算涡环状结构的平移速度的径向和轴向分量的时间演化。在这两种情况下，该速度的径向分量保持接近于零。实验结果被用来评估以前开发的层流和湍流涡环模型的鲁棒性。引入了归一化时间和归一化轴向速度，其中t init是涡环结构的初始观测时间。对PFI和G-DI喷雾的时间依赖性分别近似为和。与分析涡环模型相比，G-DI喷雾的预测结果更好，在长时间范围内，层流情况下α = 3/2，考虑湍流影响时α = 3/4。PFI喷雾的结果似乎与现有理论模型的预测不相容。
Abstract A phenomenological study of vortex ring-like structures in gasoline fuel sprays is presented for two types of production fuel injectors: a low-pressure, port fuel injector (PFI) and a high-pressure atomizer that injects fuel directly into an engine combustion chamber (G-DI). High-speed photography and phase Doppler anemometry (PDA) were used to study the fuel sprays. In general, each spray was seen to comprise three distinct periods: an initial, unsteady phase; a quasi-steady injection phase; and an exponential trailing phase. For both injectors, vortex ring-like structures could be clearly traced in the tail of the sprays. The location of the region of maximal vorticity of the droplet and gas mixture was used to calculate the temporal evolution of the radial and axial components of the translational velocity of the vortex ring-like structures. The radial components of this velocity remained close to zero in both cases. The experimental results were used to evaluate the robustness of previously developed models of laminar and turbulent vortex rings. The normalized time, , and normalized axial velocity, , were introduced, where t init is the time of initial observation of vortex ring-like structures. The time dependence of on was approximated as and for the PFI and G-DI sprays respectively. The G-DI spray compared favourably with the analytical vortex ring model, predicting , in the limit of long times, where α = 3/2 in the laminar case and α = 3/4 when the effects of turbulence are taken into account. The results for the PFI spray do not seem to be compatible with the predictions of the available theoretical models.