Experimental study on anti-cavitation mechanism of valve lintel natural aeration of high head lock

In view of the serious valve top gap cavitation problem of Datengxia high head single-lift ship lock, the 1:1 scale slice experimental method, which can truly describe the gap flow characteristics, has been adopted for the investigation of the valve top gap cavitation characteristics and the anti-cavitation mechanism of natural aeration. Three kinds of cavitation, namely, throat, mainstream inner, and valve plate, are determined and have occurred step-by-step in the gap section because of the development of the cavitation. The anti-cavitation mechanism of the natural aeration measure increases the pressure of the gap flow through ventilation, eliminates the mainstream inner and valve plate cavitation, and weakens the throat cavitation. The negative pressure zone of the gap section gradually extends with the development of cavitation until the gap section is filled with a stable -10 m water head. When the natural aeration measure is employed, the pressure of the gap section approximately reaches the -2 m water head, and the cavitation disappears. The systematic tests reveal the quadratic polynomial relationship between the pressure of the gap and the ventilation per meter width. The pressure, which corresponds to the maximum value of ventilation at the beginning of the gap, approximately reaches the -2 m water head, and pressure and ventilation reach the equilibrium state limit. When the pressure of the gap increases when the valve is opened, the ventilation gradually decreases until the natural aeration stops. The gap section length for high head valves has a great effect on natural aeration and should be long enough to maintain the stable negative pressure of the gap, whereas the throat width has minimal effect. Results are beneficial to the anti-cavitation design of the high head lock valve.