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MECHANISM ANALYSIS AND STRUCTURAL OPTIMIZATION OF SUDDEN INCREASE OF NEGATIVE PRESSURE NEAR WATER INLET PIPE OF A DROPSHAFT
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摘要: 为明晰跌流竖井进水管附近负压突增的机理以及降低竖井内的负压,基于计算流体动力学软件Fluent模拟了竖井模型内的水气两相分布规律及气压分布情况,同时对竖井模型进行了结构优化并评估了其性能。结果表明:当无量纲流量Q*w>0.08时,进水管附近的负压开始突增,而小流量下基本无变化;入流水舌是导致负压突增的主要原因,其压缩了气体流动的空间,增大了气体过流时的损失,造成水舌下方补气不足。研究还表明:优化竖井模型通过有旋分流隔板在进水口正对面形成了1个不过水的空腔区域,其强制扩大了气体过流的空间,基本保证了进水管附近气体的流动不受水流的影响,同时还降低了井内的负压和气压梯度。Abstract: To clarify the mechanism of the sudden increase of negative pressure near the water inlet pipe and reduce the negative pressure in the dropshaft, the water-air two-phase and air pressure distribution in the dropshaft model were simulated based on the computational fluid dynamics software Fluent. Then, the relationship between the water tongue and the air pressure change near the water inlet pipe was analyzed. Finally, an optimized dropshaft model was proposed and its effect was evaluated. The results showed that when the dimensionless water flow rate was greater than 0.08, the negative pressure near the water inlet pipe began to increase suddenly, and there was basically no change under a small flow rate. The water tongue was the main reason for the sudden increase of negative pressure, which occupied the space of air circulation and increased the loss of airflow. The air supply under the water tongue was insufficient, so the negative pressure would suddenly increase. The study also showed that the optimized dropshaft model formed a water-free cavity area in the space enclosed by the circular diaphragm and the shaft wall opposite the water intake pipe, which expanded the space for airflow, basically ensuring that the airflow near the water inlet pipe was not affected by the water flow, and also reduced the negative pressure and air pressure gradient in the dropshaft.
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