气垫调压室体型优化与运行控制研究

With the increasing attention on development and utilization of water resource and environment protection in western China, air-cushioned surge chamber is of great value in the application of hydropower station construction that with high head and long water conveyance system. However, most of the present achievements of air cushion surge chamber are summarized from the experience on hydropower construction in the 1970s in Norway, so the material is fragmented and lacks detailed analysis and demonstration. This research is established on the basis of model experiments and analysis of fluid transient calculation. The theoretical analysis and numerical simulation methods are employed to establish the whole mathematic model of water diversion and generation system including air cushion surge chamber and units, combined with the model test results and field prototype observation data. Then the reasonable layout position in water conveyance system will be determined, as well as the selection of the closed gas room area and height, and safety water depth. Finally, according to the real dynamic characteristic of high-pressure closed gas, water hammer reflection performance, and operation stability requirements, the reasonable body-shape parameters, operation and control mode, and accident prevention of air cushion surge chamber can be determined. The achievements of this project can promote scientific innovation and provide the theoretical guidance and practical basis on optimization design, successful construction and safety operation for air-cushioned chamber.

随着我国西部地区水力资源的开发利用及对环境保护的日益重视，气垫调压室在高水头、长输水系统的水电站建设中具有重大的推广应用价值。但目前对气垫调压室的研究多为上世纪70 年代挪威的水电建设经验总结，资料较为零散，缺乏细致的分析论证。本项目拟通过理论分析与数值模拟，在模型试验与水力过渡过程计算成果分析的基础上，结合现场原型观测数据的反演分析，建立含气垫调压室及机组的输水发电系统整体数学模型，确定气垫调压室在水电站输水系统中的设置位置；制定气室面积、高度与安全水深选取原则。根据气垫调压室密闭气体真实动态特性、水锤波反射性能、运行稳定性要求，针对国内在建与拟建的含气垫调压室的水电站输水系统，合理选取气垫调压室体型参数、运行控制模式并提出事故防治对策，为气垫调压室在水电站输水发电系统中的优化设计、安全运行提供理论指导及实践依据。

长引水道、大流量引水发电系统中的调压室往往需要很大的高度和横断面积才能保证其有足够的容积容纳水体并满足波动稳定性要求，这不仅增加了工程开挖量和造价，而且也容易诱发水力共振等不利于电站安全稳定运行的现象。调压室高度通常由水位波动幅值确定，而其断面尺寸往往取决于其波动稳定断面。作为一种性能优良的平压建筑物，气垫调压室被广泛应用于引水式水电站中以控制水位波动幅值并依靠其高压气室消除共振。但是迄今为止，关于此类调压室的运行控制仍无系统的理论阐述，且存在诸多概念上的误解。另一方面，调压室波动稳定断面通常由基于一维水流特性的托马（斯韦）断面确定。但是，考虑三维流场特性的调压室临界稳定断面的研究无疑是更合理、更贴近实际的。受本项目资助，取得的成果如下：.（1）在气垫调压室紧急停机水位和压力的基础上考虑漏气、温度变化以及上游水库水位变化对气室初始压力和体积的影响，从而确定了气垫调压室在不同控制模式下的监测参数的合理变化范围，给出了空压机和排气阀的启闭依据，并建立了不同控制模式的选择标准和适用条件。依此理论控制空压机和排气阀的动作，将避免上述因素变化而导致的机组频繁停机和启动；.（2）以文献提供的试验结果为依据，选取了合适的湍流计算模型，用三维流场计算方法模拟了带长连接管的调压室的底部流场，分析了影响连接管内回流区强度和尺度的因素，给出了回流流量和与之相关的水头损失系数的计算公式，并在此基础上推导了带长连接管的调压室波动临界稳定断面；.（3）引入自由液面模拟方法，分析了阻抗气垫式调压室底部阻抗孔内回流区高度和强度的变化规律，给出了回流流量、高度和相关局部水头损失系数的计算公式，并据此推导了气垫调压室波动稳定断面，明确了调压室底部流速水头在稳定断面计算中的有利作用和取值方法。