通气对空蚀的影响及高速摄影观察

Ventilation Effects on Cavitation Erosion around a Hollow-jet Valve

为了研究通气对高速水流中发生的旋涡空化所引起空蚀的影响 ,把不同量的气体通入了射流放水阀阀针后部的旋涡空化区 ,观察了空化状态 ,测量了空化所引起的空蚀。观测表明 ,气流在水流中形成气泡分布在空化区内。部分气泡被旋涡空化团所包含 ,因此在通气条件下 ,空化涡中包含有空化泡和空气泡。空蚀实验表明 ,试片表面的质量损失均随通气量的增加而减小。分析表明 ,通气对空蚀的影响确不能完全解释为声速的减小。

To study the effects of ventilation on erosion induced by vortex cavitation occurring around a hollow jet valve,air is injected to the cavitating region around the valve.The cavitatin aspects are observed.The mass loss on eroded specimen surfaces is measured.It is indicated that the injected air forms small air bubbles in the cavitating flow field.With the motion of separating vortices,some of them flow downstreamly as a free air bubbles,and some move to the shear layer flow region entrained by cavitating vortices.The measurements of cavitation induced erosion show that,under ventilation conditions,the erosion is suppressed.The decrease of erosion is related to the reaction between air bubbles and cavitation bubbles contained in a cavitating vortex and the suppression of sonic speed in the ventilation flows.