摘要
氣渦輪機發電機具有簡捷靈活的特性，所以非常適合當作調峰機組，但其發電效率偏低，尤其在炎熱的高溫下(也正是需電甚切期)效率與發電量都會明顯衰退，以致發電成本太高，這也使得台電所有的氣渦輪機組大都處於閒置的狀態，僅偶而作緊急調度之用。在分析各種提升氣渦輪機效率的方法中，本文選用兩種不影響主體結構，並且成效顯著、穩健可靠的改造方案，也就是蒸氣注入式(STIG)與進氣冷卻式(IAC)。
為了準確地評估這兩種改造方式的效果，吾人開發了一套模擬軟體，此軟體程式也經過模擬台電大林廠的氣渦輪機組(GE Frame 7B)來作校正與驗証之後，再模擬各改造後的性能。結果顯示利用STIG的改造方式可以將Frame 7B的發電效率從原來的29.31%提升到39.9%，而利用整合STIG與IAC的改造方式則可將發電量從原來52.14MW提升到96.78 MW。
為了更進一步地瞭解改造方案的經濟效益，本文也以實際與估算的投資成本以及估算的運轉成本並利用工程經濟來執行經濟分析，算出投資回收年限與預期獲利。
值的一提的是STIG與IAC這兩種使發電性能提升的代價是利用回收原本欲排放廢氣之能量，所以經改造後，除了有發電量與發電效率的提升之外，也減少了廢熱的排放，STIG更可使燃燒室因溫度均化，而大大地降低NOx的濃度，對環保更是具有重大的意義。

ABSTRACT
Gas turbine generation set (GENSET) is very compact and posses a very agile start-up feature, it is therefore quite suitable to be used as a load-follow unit. Unfortunately, simple-cycle GENSET has a relatively low generation efficiency, especially when the ambient weather is hot (the time when the electrical power is most needed). Therefore, the gas-turbine GENSETs are mostly put in spare state unless there is a power-shortage problem or a black-out emergency.
The reasons of having a low efficiency and a high exhausted temperature can be discerned from the fundamental thermodynamic analysis, and the methods used in the past to improve the efficiency were focused on either to increase the expansion work or to decrease the compression work. Among many performance-improvement techniques, steam-injection gas turbine (STIG) and inlet-air cooling (IAC) are considered as very effective and reliable ways without a major destruction to its original integrity. Both ways are thus analyzed further in this study for a potential retrofitting project.
In order to evaluate the effects due to STIG or/and IAC features, a general computer program was developed. The accuracy of this program was verified with the data of GE Frame 7B unit provided by Taipower Talin plant. Results from computer simulations indicated the effect of STIG can greatly improved the generation efficiency (from 29.31% to 39.9%), and the effect of combined STIG and IAC features can substantially increased the output capacity from 52.14 MW to 96.78 MW.
Beside the performance evaluations, the potential monetary benefits for the retrofitted systems are also conducted in this study. The investments of each project including capital costs and operation costs were estimated either from vender’s quotations or from some related literatures. Engineering economic analysis is then applied to calculate the rate of return and potential benefit.
It is worth to be mentioned that the energy used to improve the system performance for either the STIG or the IAC system is obtained via the recovery of waste heat from the exhaust gases. In other words, the retrofitted project cannot only promote power output and generation efficiency, but can also significantly reduce the degree of thermal pollution. Additional environmental benefit can also be realized for the system with STIG feature as the injection of steam can smooth out the local hot spots inside combustor, the emission of NOx can thus be greatly reduced.

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