大型水力机组中空化现象的比尺效应

The Scale Effect of Cavitation in the Large Hydraulic Unit

大型水力机组中的空化比尺效应关系到真机的空化性能和水电站装机高程的确定．影响水力机组空化比尺效应的主要因素有：机组运行水头、转轮直径、液体中的空气含量以及流动介质本身的性质等等．本文在前人研究的基础上推导出真机与模型机之间的空化相似率，提出了水力机械模型试验台上空化试验应遵循的相似准则．以岩滩电站为例，根据其模型转轮的空化试验和流场理论分析结果推算了岩滩电站真机的空化特性．建议在确定大型水力机组，尤其是三峡机组的吸出高度时，较多的考虑初生空化系数的影响，取用较接近于真机实际的初生空化系数值，从水电站的设计和机组安装上保证转轮内良好的流态，避免空化引起的破坏．

The cavitating scale effect in the large-scale hydraulic unit influences the cavitating property ofthe prototype and the elevation of the hydraulic power plant- The main elements influencing the cavitating scaleeffect of the hydraulic unit include: operating head of the unit, diameter of the runner, air content and otherproperties of the fluid. Based on the results of the predecessor, the cavitating similar transformation formulafrom the model runner to the prototype and the similar rules for the cavitating model test are provided in thispaper. The cavitating property of the Yantan power plant's prototype is predicted as an example on the base ofthe results of the cavitating model test and the flowfield analysis for the corresponding model runner' It is suggested that the initial cavitating coefficient should be paid more attention and the one closed with it is recommended when the H. of the large-scale hydraulic units is determined, especially for the Three-Gorge unit. Anda reasonable flowfield in the runner will be realized when the plant is designed and assembled in this way andthe cavitating damage will be avoided in a large degree.