高水头船闸阀门顶缝空化切片试验研究

摘要

In view of the developing problem of the valve top gap cavitation of high head single-lift ship lock, the scale 1:1 sectioning model test method which can truly describe the gap flow characteristics is adopted to study the valve top gap cavitation and the cavitation resistance mechanics of the natural aeration. It is found that three kinds of cavitation, namely the throat cavitation, the flow center cavitation and the valve plate cavitation, are taking place step by step in the gap section with the development of the cavitation. The mechanics of the natural aeration measure to prevent cavitation is that the pressure of the gap flow becomes high when the air is aerated into the gap section, and then the flow center cavitation and valve plate cavitation disappear and the throat cavitation is weakened remarkably. With the growing of the cavitation, the negative pressure zone in the gap section is gradually extending until the gap section is fulfilled with stable -10 m water head negative pressure. When the natural aeration measure is employed, the pressure in the gap section is stable in the -2 m water column and the cavitations disappear. It is nearly a quadratic polynomial relationship between the pressure of the gap section and the ventilation per meter width. The pressure of the gap is -2 m water head when the ventilation goes to the extreme value, which is the limiting equilibrium situation for the natural aeration system. When the pressure of the gap gradually increases, the ventilation volume decreases gradually until the cessation of the natural aeration. The research results are benefitcial to the cavitation resistance design of the high head valve.%针对日益严峻的高水头单级船闸阀门顶缝空化问题,采用能够真实反映缝隙流特性的1:1切片模型试验,研究阀门顶缝空化特性及门楣自然通气防空化机理.研究表明,随着空化的发展,缝隙段依次发生喉口跌坎空化、主流中心空化和阀门面板空化,缝隙段负压区不断延伸,直至整个缝隙段达到稳定的-10 m水柱负压,压力脉动很小;门楣自然通气通过增加缝隙段压力,消除主流中心空化和阀门面板空化,抑制喉口跌坎空化.当采用门楣自然通气措施后,缝隙段压力稳定在-2m水柱左右,空化消失,缝隙段水流脉动压力增大;缝隙段压力与单宽通气量近似二次多项式关系,通气量极值对应的缝隙段压力约-2m水柱,此时缝隙段压力与通气量达到平衡状态,当缝隙段压力逐渐升高时,门楣通气量逐渐降低,直至自然通气停止.