天然氣複循環發電方式乃是當前發電方式主流之一，但仍有燃料成本較高，氮氧化物排放抑低等問題，希望透過實務面之探討，利用空燃比方法推導燃燒器火焰溫度作為氣渦輪機進口溫度來計算熱效率，並與氣渦輪機功率輸出方法計算熱效率彼此作比較，找出設備性能評估診斷方法。
本文參考熱力學原理之應用以第一定律熱功平衡、第二定律熵增定理及天然氣成份經燃燒後擷取煙氣排放過剩氧含量推算空燃比(AFR)，以化學平衡反應式推導氣渦輪機燃燒器最大火焰溫度作為氣渦輪機進氣溫度(TIT)，並結合氣渦輪機熱力循環之運轉實例，以氣渦輪機進氣溫度(TIT) 計算熱效率及評估設備性能提供實務方法，同時以空燃比原理計算燃燒器火焰溫度，提供可應用之計算模式，也對氮氧化物排放與空燃比關係提出調整建議。
經實驗501F型GT空燃比(AFRmass)約於46及501G型GT約於42時氣渦輪機熱效率最佳。且提升燃料及燃燒空氣溫度對熱效率及氮氧化物排放濃度之降低都有極佳助益，而提升燃燒空氣溫度功能性遠大於提升燃料溫度。
利用空燃比來計算燃燒器最大火焰溫度做為TIT，以進一步評估氣渦輪機作功能力，可以獲得很高準確性，若再與氣渦輪機實際出力熱轉換效率之差異性比較，更可以做為設備熱元件或組裝時缺陷診察判斷之工具，以進一步改善提出方法。

Natural gas combined cycle power generation is one of the current power generation mainstream, but there are still higher fuel costs, nitrogen oxides emission reduction and other issues. The practical aspect of use the air-fuel ratio (AFR) method to derive the combustion flame temperature and that can be calculated as the function of gas turbine inlet temperature and thermal efficiency. In addition, we also compare with power output conversion thermal efficiency method. They can be correlated with the equipment performance and as a diagnostic method.
In this thesis, the application of thermodynamics principle to the first law of thermal balance, the second law entropy increase theorem and natural gas components after combustion of flue gas emissions from excess oxygen are adopted to calculate the air-fuel ratio(AFR) and used to chemical equilibrium reaction derived gas turbine inlet temperature(TIT), combined with the operation example of the gas turbine thermal cycle, to calculate the Brayton cycle efficiency of the gas turbine and to evaluate the performance of the equipment. At the same time, the air-fuel ratio is calculated as a function of the combustion flame temperature, to provide the application of the calculation model and the relationship between nitrogen oxide emissions and AFR adjustment is proposed.
Experimental results showed that 501F type GT AFR(kg) is about 46 and 501G GT is about 42 when the gas turbine thermal efficiency is the optimal. And the promotion of fuel and combustion air temperature on the thermal efficiency and nitrogen oxide emission concentration is very promising, and enhancement of the combustion air temperature function has greater impact than that of the fuel temperature.
The maximum flame temperature of the combustor is calculated by using the AFR as a function of TIT to further evaluate the working capacity of the gas turbine, and it is highly accurate (favorable) to compare with the actual power output efficiency of the gas turbine. Furthermore, TIT can be used as the diagnostic tool for the early monitoring of defective components or assembly of the power plant.
Keywords：Natural gas combined cycle power generation , NOx, Air-fuel ratio (AFR), Gas turbine inlet temperature (TIT), Combustor, Flame temperature

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