汽轮机调节级变工况计算中喷嘴流量的计算方法探讨

Discussion on the Calculation Method of Nozzle Critical Flow of Turbine Control Stage

对于调节级喷嘴的流量,国内多采用喷嘴临界流量及喷嘴彭门台系数结合的方式计算,喷嘴临界流量计算公式在速度系数变动较大时会产生较大误差。通过分析喷嘴临界流量公式的推导过程及原理,类比地提出了根据水蒸汽实际工业特性进行临界流量及实际流量计算的方法及步骤。结合工程实际算例,给出了两种计算方法的计算偏差。基于计算结果分析了喷嘴临界流量随速度系数及压比的变化规律,阐述了喷嘴最大流量异于临界流量的原因。讨论结果同样适用于其它汽轮机通流压力级喷嘴流量及动叶流量的计算。

Currently calculation method combining the nozzle critical flow and Pengmentai flow coefficient is commonly used for control stage nozzle flow calculation,and there are noticeable errors found on the nozzle critical flow results when under medium speed utilizing index variation.With analyzing of the deduction process and principle of the nozzle critical flow calculation equation,method and procedures based on industrial steam properties for calculation of the nozzle critical flow and actual flow are proposed.An practical project example is provided,and the deviation of the results from two methods is illustrated.The characteristic of nozzle critical flow with the change of speed utilizing index and pressure ratio is analyzed and the reason that nozzle maximum flow is larger than nozzle critical flow is presented.The results discussed are also applicable to other steam turbine pressure stage nozzle flow and blade flow calculation.