利用先導型貧油預混燃燒室（乾式低NOx燃燒室，Dry Low NOx (DLN) burner）及成奶j學航太中心（ASTRC）B3燃燒實驗設備，本研究完成油氣混合機構及貧油預混燃燒對NOx減量排放特性之探討。相關之設計、分析及實驗成果，可提供作為發展高燃燒效率、低污染全型燃燒室設計依據，更進而可協助業界進軍貧油預混燃燒國際市場。研究中利用噴流混合Lean Direct Injector (Jet Mix)原理，設計一包括內、外流道之燃氣與空氣混合機構，其中徑向之富油燃氣噴流(radial jets)與由外流道六個圓孔形成之軸向剪力層(shear layer)之空氣噴流(axial jets)快速混合，可有效完成油氣均勻混合。此兩段式之混合設計，可解決燃氣與空氣流量混合時兩動量相差太大問題，亦可降低火焰回火風險。實驗中曾進行兩種不同型式之混合機構；氣態丙烷噴出方向與內流道之徑向噴氣孔軸線角度為0度（型式I）及30度（型式II），其中後者之丙烷可於迴流區（由兩徑向噴氣孔所形成）與空氣先行混合，其機制優於型式I。實驗結果顯示其貧油燃燒極限與Zabetakis之經驗式吻合度良好。實驗中利用燃燒污染排放及燃燒室溫度量測值以評估DLN特性，並藉火焰觀測瞭解穩定燃燒區。在F/A=0.02（ =0.31）條件下，即有UHC及CO之排放，但直至約為 =0.268（燃料體積濃度約1.12%）才熄火，此區間為火焰可維持較低效率之穩定燃燒。經長時間燃燒（2000秒以上），燃燒室內顯示均勻之溫度分佈，其溫度量測值與CHEMKIN軟體模擬之絕熱火焰溫度吻合度良好。但當 ＜0.35時，因較低之燃燒效率造成貧油預混燃燒內之溫度量測值較絕熱火焰溫度為低。貧油預混燃燒可避免如同在擴散焰燃燒時產生之局部高溫，因此可有效抑制氮氧化物（NOx）之形成。在燃燒室出口溫度為1000℃時，貧油預混燃燒NOxC（校正至15% O2）之排放值為32ppm，較擴散焰燃燒約減少50%之排放。本研究中所建立之先導型貧油預混燃燒室及噴流混合器研製技術亦可直接應用於全型機組設計。 The performance of an indigenous Dry Low NOx (DLN) burner was examined in the ASTRC B-3 combustion facility that has already been tuned all operating parameter settings for testing lean-premixed combustion employed in the present DLN designed. In order to help the industry to expand the international market. The study conducts that combustion and pollution characteristics of this pilot DLN provide as the guideline for designing a low-emission (NOx< 20 ppm) and high combustion efficiency gas-turbine power plant. The Lean Direct Injector was used as a mixer that consisted internal and external flow channels. Propane gas was firstly premixed with limited air inside the internal channel formed as fuel rich gas that was injected radially into external channel and then mixed with 80% of the airflow passed through an outer ring of six mixing holes that would form jet shear layer. Rapid mixing of the fuel-rich radial jets and the axial air jets produces a well fuel/air mixture at the flame front for combustion. Two configurations premixed mechanism were employed to study the effect of the unmixedness on the flame stability. The lower flame limit was compared favorably with Zabetakis’s empirical equation for the better mixing case. The performance of the pilot DLN burner was characterized by the measuring data of pollutant emissions and temperature distribution in the combustor. An air-cooled periscope was employed to visualize the flame pattern to assist the judgment of the stable combustion region. A stable flame could be maintained down to =0.268 although both pollutants of UHC and CO were presented at =0.31. After passing a long time testing（over 2000 sec）, a uniform temperature distribution could be obtained at the value near to CHEMKIN’s adiabatic temperature. The lower efficiency of lean combustion caused lower but uniform combustor temperature measured as ＜0.35. As compared with diffusion flame combustion that was also conducted in the present study, NOxC (corrected to 15% O2) emitted from the indigenous DLN burner was measured at 32 ppm which showed about 50% reduction at the 1000℃ combustor temperature. Techniques of designing the pilot DLN burner developed in the present study would provide as the guideline for the scale-up application. Some specialists on lean premixed combustion can also be trained.
