超超临界机组RB过程除氧器暂态特性计算模型

Calculation Model for Transient Characteristics of Deaerator in Ultra Supercritical Unit During RB Process

针对机组甩负荷时给水泵有效汽蚀余量下降、给水泵组可能发生汽蚀的问题,在试验基础上,通过对除氧器辅机故障减负荷(RB)暂态过程的理论分析,给出了超超临界机组除氧器暂态特性和给水泵最大有效汽蚀余量ΔNa,max的计算模型,并对试验数据和试验过程模拟结果进行了比较.结果表明:所用模型精度较高;降低除氧器水容积的波动幅度,或者在除氧器布置高度不变时减小下降管长度,均能减小ΔNa,max.

To solve the problem of feed pump cavitation that may occur during load rejection process of an ultra supercritical unit due to the drop in available net positive suction head(Na)of feed pump,a mathematical model to calculate the transient characteristics of deaerator and the maximumNadecrease(ΔNa,max)of feed pump was proposed,based on theoretical analysis and experimental research on the run back(RB)transient process of deaerator.Resnlts show that comparison results between calculated and experimental data prove the proposed model to be highly accurate.To effectively reduce theΔNa,max,countermeasures may be taken by either controlling the fluctuation of water volume in deaerator,or reducing the downcomer length under the premise keeping the mounting height of deaerator unchanged.