等效焓降法效率相对变化基准的选择与分析

Selection and analysis of relative change reference of efficiency for equivalent enthalpy drop methods

等效焓降法计算汽轮机组效率相对变化量时,需选择变化基准。传统算法以净等效焓降为基准,此基准计入了给水泵焓升、轴封漏汽损失,但未计入散热、抽汽压损等常见损失,使其在计算不同类型损失时的可比性下降。选取不同的计算基准,分别建立了给水泵焓升和散热损失改变的局部定量分析模型,揭示了两种基准选择对机组效率相对变化分析结果的不同影响;算例表明,选择以毛等效焓降为基准具有更好的可比性。

In calculating the relative change of efficiency for steam turbines,it is essential to select the right change reference.The tradition algorithm applies the net equivalent enthalpy drop as the reference,which takes the feed water pump′s enthalpy rise and shaft sealing leakage loss into account but does not consider such common losses as heat loss and extraction steam pressure loss,and therefore the comparability in calculation of different types of losses was not satisfactory.In this paper,different calculation references were selected and the local-quantitative analysis model for the changes of feed water pump＇s enthalpy rise and heat loss was established respectively. Based on that, the different influences of the types of references on relative change analysis of unit efficiency were analyzed. Calculation ex- ample showed that selecting the gross equivalent enthalpy drop as reference is superior in comparability.