微型渦輪引擎環型燃燒室對使用低熱值燃料之可容許性模擬研究

Abstract

本研究以商業套裝軟體CFD-ACE+ 模擬微型氣渦輪引擎燃燒室在保持外型結構，但更換原廠預設的液態Jet A1燃料為較低熱值的氣態甲烷混合氣燃料時的燃燒流場。 所得之數值模擬計算結果在著重於經燃燒反應後所產生的推力值與熱傳效應所造成襯筒壁與燃燒室出口的高溫之探討。 研究中模擬四組的渦輪轉速條件(155000, 120000, 80000, 45000轉/分)，並分別在各組的甲烷燃料中混入六種不同二氧化碳質量濃度(0%, 10%, 20%, 30%, 40%, 50%)來做為稀釋效應的研究。 模擬結果如下: (1) 甲烷燃料加入CO2氣體後其產生的推力更低 (2) 半數襯筒壁可能會受高溫熱破壞 (3) 襯筒壁上稀釋孔所產生的噴流能有效降低燃燒室出口排氣溫度，使渦輪葉片不致產生熱破壞。由於 (2) 之模擬結果有待商確，因此有一系列的修正探討以作為未來改善之用。

This thesis applies a commercial package CFD-ACE+ to simulate the combustion flow field in combustion chamber of a micro gas turbine. The purpose is to investigate whether the original structural configuration can sustain its power performance by using the low-heating-value methane gas instead of the original liquid Jet A1 fuel. The numerical data are mainly emphasized on the thrust generated by combustion power and the temperature distributions over solid annular liners and combustor outlet. In the research, one of the parameters is the turbine rotational speed. Four rotational speeds, 155000, 120000, 80000, and 45000 rpm, are considered. The other parameter is the mass fraction of CH4 in the fuel mixture, consisting of CH4 and CO2. Six weight percentages of 100, 90, 80, 70, 60 and 50% are taken into consideration. The simulation results are as follows: (1) The thrust is reduced as a result of the addition of CO2. (2) The liner walls in half parametric studies might be burnt out. (3) The hot gas exhausted from combustor outlet is cooled down effectively by jet flow discharged from dilution holes, which prevent turbine blade from heat damage. Finally, several recommendations are suggested for the possible future improvements and extensions.