一种基于级内损失理论的排汽焓计算方法

A Calculation Method of Exhaust Enthalpy Based on Stage Loss Theory

凝汽式汽轮机低压缸排汽段通常处于湿蒸汽区,排汽焓值难以直接测量。以级内损失理论为基础,将各类损失划分为与容积流量相关的排汽损失、与湿度相关的湿汽损失和与理想焓降相关的其它损失;推导了其它损失的系数与低压缸理想焓降的二次关系式;在此基础上,根据湿汽损失与排汽焓的关系提出一种排汽焓计算方法。利用该方法计算某660MW超临界汽轮机组的低压缸排汽焓,并与实际运行数据进行了对比。结果表明,提出的方法计算精度较高,所需测点少,对排汽流量的测量或计算精度要求较低,可应用于机组日常运行时对排汽焓的测算。

The exhaust enthalpy of the turbine is difficult to be measured as a result of the steam in the last one or two stages of LP cylinder is wet steam. A new approximate calculation method based on the loss theory is proposed. In this method the wet steam loss is separated from the other losses, and then the quadratic formula of the other losses and the ideal enthalpy drop in LP cylinder is deduced. Then the calculation formula of the exhaust enthalpy based on the formula mentioned above can be gotten. The exhaust enthalpy calculation of a 660MW turbine using proposed method is carried out and compared with the operated value. The resuh indicates that there are several advances in the method： the calculation process is clear; the measuring points are less ; the structure parameters need not be known ; the thermal equilibrium calculation of the turbine system does not need to be carried out. Besides,tbe influence of the exhaust mass flow on the exhaust enthalpy is less.