单缸低参数汽轮机末级排汽湿度的热力分析

采用VB语言,通过动态链接库的调用,编制了低参数单缸汽轮机热力计算程序.应用此程序,在不同设计参数下,针对无抽汽除湿、级间抽汽除湿和除湿级除湿3种方案,研究了机组末级湿度的变化.结果表明,进汽压力、进汽温度和排汽压力三者对末级湿度的影响不同,进汽温度对末级湿度的影响最大,进汽压力次之,排气压力最小.在本研究所提参数条件下,满负荷运行很难保证末级出口湿度要求,需采用有效的内部除湿措施.研究也表明,在不同位置抽汽除湿和除湿级除湿对机组末级湿度影响较大,在相同的设计参数下,在机组的第四级后抽汽除湿对机组末级湿度的影响最大.在相同的除湿效率下,除湿级位置每向后移动一级,使末级湿度降低约1%,随除湿级位置后移,除湿效率对末级湿度的影响增大.

Thermodynamic Analysis of the Last-stage Exhaust Steam Wetness of a Single-cylinder Low-parameter Steam Turbine

By adopting VB language and using a dynamic-link data base,designed was a thermodynamic calculation program for low-parameter single-cylinder steam turbines.By employing this program,the change of the last-stage wetness of the turbine unit for the following three versions of wetness removal was studied at various design parameters:namely,(1) without any steam extraction,(2) by extracting steam between stages and (3) by adopting a wetness removal stage.It has been found that the inlet steam pressure and temperature as well as the exhaust steam pressure can affect the last-stage wetness in different ways,and the inlet steam temperature exercises a maximal influence on the last-stage outlet wetness with consecutively less influence being exerted by the inlet steam pressure and the exhaust steam pressure.Under the given parameter condition of the present study,it is difficult for a full-load operation to meet the requirement for the last-stage outlet wetness,making it necessary to take effective inner wetness removal measures.The research results also indicate that the wetness removal by extracting steam at different locations,and by using a wetness removal stage exercises a relatively big influence over the last-stage wetness of the unit.At the same design parameters,the wetness removal by extracting steam after the fourth stage of the unit can maximally affect the last-stage wetness of the unit.At an identical wetness removal efficiency,when the location of the wetness removal stage shifts one stage backwards each time,it will lower the last-stage wetness by about 1%.With the location of the wetness removal stage moving backward,the influence of the wetness removal efficiency on the last-stage wetness will increase.