冲沙放空洞边墙空蚀破坏原因反馈分析及改造体型优化研究  

Feedback analysis on the causes of cavitation erosion on the side walls of the spillway tunnel and research on the optimization of the renovation shape

作　　者：高建标[1] 王志刚[1] GAO Jianbiao;WANG Zhigang(China Institute of Water Resources and Hydropower Research,Beijing 100038,China)

机构地区：[1]中国水利水电科学研究院,北京100038

出　　处：《水利水电技术(中英文)》2024年第S2期508-515,共8页Water Resources and Hydropower Engineering

摘　　要：为弄清冲沙放空洞边墙发生局部空蚀破坏原因,寻求切实可行的改进措施和修复方案,为修复提供技术支持,为制定合理的运行调度方式提供科学依据。以完建体型为基础,建立冲沙放空洞局部常压(1:25)、减压(1:30)水工模型,按照原型试验工况进行全面反演试验,从水流流态、掺气空腔形态、掺气效果、压强分布及水流近壁掺气浓度等综合分析论证两侧边墙发生局部空蚀破坏的原因。结果显示:侧扩水流与边墙交汇后在扩散段发生分离造成压力降低并产生较大负压,实测最大负压达-46.7 kPa,水流空化数仅0.08,水流噪声最大声压级增量达10.0 dB,远大于水流初生空化判别值5.0~7.0 dB,且洞口流速高达36 m/s左右,从而诱发边墙空化水流。另一方面边墙存在较大范围清水掺气盲区,缺乏有效的掺气保护,是发生空蚀破坏的原因之一。提出的推荐体型将原渐扩修改为突扩形式,并设置梯形突扩收缩坎控制边墙水翅的强度。在不同工况下,都能形成较长和稳定的侧空腔,下游边墙和底板压力分布合理,模型掺气浓度最小值为1.4%,说明具备较好的掺气能力。原型过流试验测量边墙水流噪声声压级最大增量仅3.5 dB,表明没有发生空化水流,经过多年运行,并末出现严重空蚀破坏情况。To search the causes of local cavitation damage on the side walls of the sand flushing and emptying spillway tunnel,seek practical and feasible improvement measures and repair plans,provide technical support for repair,and provide scientific basis for formulating reasonable operation scheduling method.Based on the completed building shape,establish a local 1:25 normal hydraulic model and 1:30 vacuum tank model for the sand flushing and emptying tunnel.Conduct comprehensive inversion tests according to the prototype test conditions,and comprehensively analyze and demonstrate the reasons for local cavitation damage on both side walls from the aspects of water flow state,aeration cavity shape,aeration effect,pressure distribution,and aeration concentration near the wall of the water flow.The result showed that after the intersection of the lateral expansion water flow and the side wall,the pressure decreased and a large negative pressure was generated in the diffusion section.The measured maximum negative pressure reached-46.7 kPa,the cavitation number of the water flow was only 0.08,and the maximum sound pressure level increment of the water flow noise reached 10.0 dB,which was much greater than the initial cavitation discrimination value of the water flow(5.0 to 7.0 dB).In addition,the flow velocity at the exit was as high as about 36 m/s,thereby inducing cavitation water flow in the side wall.On the other hand,there is a large area of blind spots in the side wall due to the lack of effective aeration protection,which is one of the reasons for the occurrence of cavitation damage.The recommended body shape will be modified from gradual expansion to sudden expansion,to set up a trapezoidal sudden lateral enlargement and gradual contraction aerator to control the strength of the downstream side wall water wing.Under different working conditions,long and stable side cavities can be formed,and the pressure distribution on the downstream side walls and bottom plate is reasonable.The minimum value of the model's aeration

关 键 词：冲沙放空洞 空蚀破坏 掺气浓度 水流空化数 突扩突跌 梯形突扩收缩坎 侧空腔 原型观测 

分 类 号：TV651.3[水利工程—水利水电工程]