Development of Liquid Atomization lnduced by Laminar-Turbulent Transition of Free Liquid Film Flow and Elucidation of the Atomization Mechanism

本文研究了由层流向湍流转变直接引起的径向变薄液膜的液滴破碎。自来水从圆管端部与圆板平面构成的薄圆柱形间隙流出形成径向液膜流，以最大限度地抑制流动的湍流。液膜在平板上径向向外流动，从平板的周边边缘脱离，然后液体在静止空气中作为径向变薄的液膜向外流动。虽然在低雷诺数流动下液体凝结是具有光滑液面的层流，但在高雷诺数流动下薄液膜的过渡开始发生在平板边缘下游几毫米的位置处，由于剪切力的消除， ...更多信息 墙上的压力。湍流的强度随雷诺数的增加而增加，并且湍流开始在板边缘的紧接下游位置处零星地扰动液体片。随着排液雷诺数的增加，穿孔数的进一步增加导致网和股的尺寸减小，最后，网股的构型在液膜中不出现，过渡导致液膜突然破碎成液滴和团块。液滴的尺寸为几十微米，团块的尺寸为几微米到几千微米，虽然随着滞止压力的增加，崩解质量进一步提高，但存在两个局限性。一是板边缘液膜流必须具有充分发展的速度分布，二是板上流动不发生转捩。流动条件的有效崩解直接由于过渡的液体片也澄清。少

The disintegration of a radially thinning liquid sheet into drops, which is induced directly by the transition from laminar to turbulent flow, is investigated.The liquid sheet in the present experiment is generated as follows ; a radial liquid film flow is formed by a tap water issue from a thin cylindrical gap, which is constructed by the end of a circular pipe and the flat surface of a circular plate, to suppress the turbulence of the flow to the utmost. The liquid film flows radially outward on the plate, detaching from the peripheral edge of the plate, and then the liquid flows outward as a radially thinning liquid sheet in still air.Although the liquid aheet is laminar with a smooth liquid surface under the low Reynolds number flow, the transition of the thin liquid sheet begins to occur at a location of several millimeters downstream of the plate edge at high Reynolds number flow, being attributable to the velocity profile having an inflection point dueto the removal of the shear … More stress on the wall. The intensity of the turbulence increases with the Reynolds number, and the turbulence begins to sporadically perforate the liquid sheet at a immediately downstream location from the plate edge. A further increase in the number of perforation with the discharge Reynolds number causes to decreasing in sizes of webs and strands, and finally, the configuration of the web of strand does not appear in the liquid sheet and the transition results in the sudden breakup of the sheetinto drolets and clumps. The sizes of droplets are several tens micrometers and those of clumps are several hurdreds to some thousands micrometers.Although the quality of the disintegration rises further with the stagnant pressure, there are two limitations. The one is that the liquid film flow at the plate edge must have a fully developed velocity distribution, and the other is that no transition occurs in the flow on the plate. Flow conditions for the effective disintegration directly due to the transition of the liquid sheet are also clarified. Less