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首页> 外文期刊>Experiments in Fluids: Experimental Methods and Their Applications to Fluid Flow >Experimental study of the flow regimes resulting from the impact of an intermittent gasoline spray
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Experimental study of the flow regimes resulting from the impact of an intermittent gasoline spray

机译：间歇性汽油喷雾影响下流动状态的实验研究

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The present paper reports a complete set of measurements made with a two-component phase Doppler anemometer of the two-phase flow generated at the impact of a transient gasoline spray onto a flat surface. The spray is generated by a pintle injector and the fuel used was gasoline. The measurements of droplet size-velocity were processed to provide time fluxes of number, mass, normal momentum, and energy of the poly-dispersion of droplets ejected at impact, and analyzed based on predictive tools available in the literature. The results show that splash is the dominant mechanism by which secondary droplets are ejected from the surface, either in the stagnation region or in the core region of the spray. In the stagnation region, a large fraction of each incident droplet adheres to the surface and the axial incident momentum contributes with a larger parcel than tangential momentum. As a result, the normal velocity of ejected droplets is much smaller than that of the original incident droplets, while tangential velocity is enhanced. The region near the stagnation point is immediately flooded upon impact of the leading front of the spray, forming a liquid film that is forced to move radially outwards as droplets continue to impinge during the steady period. Spray/wall interaction in the core region thus occurs in the presence of a moving thin liquid film, which enhances transfer of tangential momentum. As a result, film spreading and dynamics as a result of impingement forces are crucial to accurate model spray/wall interaction. The outer region of the spray is dominated by the vortical structure induced by shear forces, which entrains small responsive secondary droplets to re-impinge. Furthermore, prediction of the outcome of spray impact requires a precise knowledge of the two-phase flow in the presence of the target.
机译：本论文报告了使用两成分相多普勒风速计对在瞬态汽油喷雾撞击到平坦表面时产生的两相流进行的完整测量。喷雾是由针状喷射器产生的，所用的燃料是汽油。液滴尺寸-速度的测量经过处理以提供数量，质量，法向动量和冲击时所喷射液滴多分散能量的时间通量，并基于文献中可用的预测工具进行分析。结果表明，飞溅是主要的机理，通过该机理，次级液滴从表面上喷射到喷雾的停滞区或核心区。在停滞区域中，每个入射液滴的很大一部分粘附到表面，并且轴向入射动量的贡献大于切向动量。结果，喷射液滴的法向速度比原始入射液滴的法向速度小得多，而切向速度却提高了。停滞点附近的区域在喷雾前缘的冲击下立即被淹没，形成液膜，当液滴在稳定期间继续撞击时，液膜被迫径向向外移动。因此，在存在移动的液体薄膜的情况下，在芯区域中发生喷雾/壁相互作用，这增强了切向动量的传递。结果，冲击力导致的薄膜铺展和动力学对于精确的模型喷雾/壁相互作用至关重要。喷雾的外部区域由剪切力引起的涡旋结构控制，该剪切力会带走小的响应性次级液滴重新撞击。此外，对喷雾冲击结果的预测需要在目标存在的情况下对两相流的精确了解。

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