基于做功曲线外推法计算汽轮机排汽焓的方法研究

Research on the calculation model based on work curve extrapolation for exhaust enthalpy of steam turbine

汽轮机排汽点常处于湿蒸汽区,由于在现场缺乏蒸汽湿度的测量手段,排汽焓难以直接确定,一直是火电机组热力系统热经济性在线分析诊断的难点之一。文章利用低压缸抽汽点参数对做功曲线进行在线拟合,并外推至湿蒸汽区,与过冷蒸汽的排汽定压线相交,由此得到汽轮机的排汽焓值;同时考虑湿汽损失的影响,对交点焓值进行修正,即为最后的排汽焓,从而提出一种排汽焓在线计算的新方法。通过对不同容量、不同工况的汽轮机进行实例计算与误差分析,结果表明:该计算方法简单,所需测点少,计算量小,计算精度高,满足在线计算的要求,适于工程实际应用。

Exhaust steam of the steam turbine is always in wet-steam region.The lack of measurement method of steam moisture at site is one of the difficulties of on-line analysis for the thermodynamic system in thermal power plants.This paper use the low pressure cylinder steam extraction point parameters in to fit the work curve,and extrapolate to the wet-steam region to interset the supercooled steam constent exhaust pressure line,to obtain the exhaust enthalpy.Meanwhile,the wet steam loss was considered to correct the intersectional exhaust enthalpy.The example calculation and error analysis of different capacity and working condition steam turbines show that this method is simple,requires less measuring points and calculation,with high calculation accuracy,which meets the requirements of online calculation and is suitable for practical engineering.