基于热经济学结构理论的燃气-蒸汽联合循环负熵分析

Negentropy Evaluation of Combined Cycle Power Plant based on the Structure Theory of Thermoeconomics

采用热经济学结构理论建立SGT5-4000F型燃气-蒸汽联合循环的生产结构图,根据“燃料-成本”概念阐述系统各个组件之间的生产关系。从机理上分析设备在三个典型工况下的负熵消耗及火用损产生的原因,采用比负熵、比火用损、火用损率等热经济学指标对系统进行评价。研究表明:燃烧室和余热锅炉在运行中存在较大的不可逆因素,使负熵消耗量较大,分别占系统全部负熵消耗的42. 37%和41. 81%,而余热锅炉和凝结水泵的火用损率较大;提升天然气的预热温度可以减少燃烧室的负熵消耗,提升系统整体的循环效率。

The structural theory of thermoeconomics is applied to establish the production structure of proposed SGT5-4000 F system,and the relationship between components is analyzed according to the concept of"Fuel-Product".Moreover,the mechanism and reason of negentropy and exergy destruction in three typical loads are analyzed.In addition,indexes such as negentropy ratio,destruction ratio and irreversibility ratio are used to evaluate the components of system.Results show that the combustion chamber and HRSG have greater negentropy rate of 42.37%and 41.81%,respectively.The largest irreversibility ratio is occurred in HRSG and condensation pump.Besides,it is revealed that improving the temperature of natural gas before burning can not only reduce the negentropy of combustion chamber but also improve the efficiency of proposed system.