| In this paper, high-head discharge structure works with the phenomenon of cavitation was introduced briefly, the mechanism of cavitation damage and aeration mechanism also was generalized. Aeration types, working principle and application summarized fairly.By laboratory variable slope flume for small bottom slope, low-velocity flow aerator under the model experiment, to study systematically of the hydraulic characteristics of the cavity after the aerator, and analyze and explore the impact factor of cavity length and cavity backwater depth, The main contents and achievement are concluded as following:1. through the preliminary experiments and calculations to determine the size of aerator and deployment of location. According to the experimental conditions, ramp-type aerator for aeration facilities was chosen in the experiment. The choice of aerator slope:after comprehensive consideration, this experiment used 1:5,1:7,1:10 three kinds of slope, to compare the impact of aerator slope for the flow; and the choice of aerator height:according to side wall height of the Organic Glass flume, designed three kinds of aerator height (△=1cm,△=2cm,△=3cm) to mix aerator model, a total of nine different models of aerator.2. Determine the conditions of flow. The choice of flume slope:according to the present experimental conditions, regulating dual variable slope Organic Glass flume, identified three different flume bottom slope i1=0.070 (α=4°), i2=0.087(α=5°), i3=0.096(α=5.5°).According to relationship between aerator and flume slope, debugging out six appropriate different types of flow discharge (Q1=5243cm3/s, Q2=4361 cm3/s,Q3=3440 cm3/s,Q4=2662 cm3/s,Q5=2171 cm3/s,Q6=1707 cm3/s) and using right-angled triangle weir and testing thin-walled needle and valves to control the flow discharge.3.The cavity length is the most important indicator to test the effect of aeration. Experiments show that When the flume slope is unchanged, the size of aerator play a large impact on the cavity length. Improve the height and slope of aerator, can increase the cavity length, but there are certain restrictions. As Fr increases, the cavity length increases firstly, then decreases, then increases, showing "S" type characteristics. But with the addition of Re and We, the cavity length is gradually increased.4. The cavity backwater, not only affects the water aerated, but also to the stability of the cavity. The problem is inevitable of small slope flume. Analyse cavity backwater relationship between its factors. These include:the relationship between the cavity backwater and flow discharge, the cavity backwater and the slope of flume, and the cavity backwater with the jet impact angle. In this experimental condition, the jet impact angle was 5.5°when the cavity backwater has emerged. Clearly, the emergence of cavity backwater is closely related with the jet impact angle, but in the final analysis which is relevant to flow conditions, the slope of flume, and the body of aerator.5. Analyse effect of air vent on the cavity length. The size of air vent is more obvious on cavity length, other conditions unchanged, when the air vent area is smaller, the more difficult to form a stable cavity, easy to form cavity backwater; on the contrary when the air vent area is larger, the length of cavity length is longer and the depth of cavity backwater is smaller. But when the air vent area reaches a certain value, the cavity length is to the maximum. |
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