改造常规汽轮机电站联合循环系统的热力学分析

THERMODYNAMIC ANALYSIS OF COMBINED CYCLE-REPOWERIN OF TRADITIONAL STEAM-TURBINE PLANTS

联合循环系统改造（Ｃｏｍｂｉｎｅｄ Ｃｙｃｌｅ－Ｒｅｐｏｗｅｒｉｎｇ）是常规燃煤电站更新最科学最有效的方法之一。本文对两种典型的联合循环系统（排气助燃型ＦＦ－Ｒｅｐｏｗｅｒｉｎｇ和给水加热型ＦＷＨ－Ｒｅｐｏｗｅｒｉｎｇ）进行了热力学系统模拟研究，得到了随燃机汽机功比变化排气助燃型系统效率单调变化以及给水加热型系统效率存在极值点的现象，并发现了一定燃机汽机功比下给水加热型效率大于排气助燃型的特殊规律。通过对联合循环系统改造各种因素的综合分析，揭示了上述特殊规律的热力学机理，澄清了有关研究的误区。该理论研究对采用联合循环系统技术改造常规电站具有指导意义。

Combined Cycle-Repowering is one of the most scientific and effective way to improve the performance of existing coal based power plant. Two kinds of representative CC-Repowering (feed water heating repowering, full firing repowering) were analyzed and compared in this paper. A remarkable phenomenon was observed: Efficiency monotonously changes with work-ratio in FFRepowering system; but in FWH-Repowering system, there exists an optimal ratio at which point the efficiency is the highest. Another phenomenon to be paid attention is that under some work-ratio, the efficiency of FWH-Repowering is higher than that of FF-Repowering, giving rise to correcting the conventional concept. After synthetic analysis of every aspect, the fundamental of these phenomenons were revealed. Some valuable instructions for CC-Repowering can be drawn from this paper.