超音速燃燒流場之物理現象極為複雜，涉及噴注與自由流之間的交互作用，包括震波、邊界層分離產生的迴流區與噴注後方的燃燒等現象。因為自由流流速為超音速，且受限於燃燒室長度，故自由流與燃料燃燒反應需在極短的時間完成，否則空氣與燃料便會流出燃燒室，導致燃燒效率不佳。為了提升整體燃燒效率，因此燃料注入的方式多採用多孔噴注，使燃料能平均分佈於燃燒室內。為了分析多孔噴注間之交互作用，本文採用氣態燃料噴注，探討多孔噴注之幾何及操作參數對噴注所產生之震波與迴流區之影響，進而分析超音速流場之燃燒現象。本文使用ANSYS FLUENT，並以噴注距離與噴注孔徑之比值(l/d) 為參數進行數值分析。在孔徑分別為0.5mm及1mm時，分析l/d=2、5及8之流場變化。研究結果顯示，當噴注動量保持不變時，不管孔徑是1mm或0.5mm，其流場型態差異不大。但隨著兩噴注間的距離較近時，兩噴注互相干擾的程度也隨之增加。當l/d=2時，煤油氣體流動的方向受到改變，造成兩噴注前方之迴流區匯流成一，故迴流區比l/d=5及8時大。若進一步探討物質成份分佈的情況則可發現，當l/d=2時，因兩噴注距離較近，造成噴注前方煤油氣體堆積，使空氣無法順利進入兩噴注間之區域。因此，沒有足夠之空氣可以參與反應，造成兩噴注間的區域的燃燒現象比較不明顯。當l/d=2時，弓形震波壓力值較兩噴注間距較遠(l/d=5、8)時低。因為l/d=2時噴注間距較近，使前方迴流區匯流成一個，當自由流流經迴流區最上側，因迴流區高度影響，造成自由流局部流體減速，自由流撞擊噴注形成之高壓區也相對下降。若將兩噴注合而為一，即單噴注面積是l/d=2時的兩倍，並比較單噴注與雙噴注之流場變化。結果顯示，單噴注之煤油氣體流動較為完整，燃燒室流場較為穩定；反觀當l/d=2時，兩噴注互相干擾，煤油氣體流動的方向受到改變，使燃燒現象較不穩定。因此，改變噴注間距，可以影響迴流區的大小、弓形震波的強度及燃燒現象。

Shocks and recirculating flows will be induced by individual fuel-injections into supersonic flow, and their interaction will significantly affect the supersonic combustion flow. In order to improve combustion efficiency, multiple injections will be used in supersonic combustion flow. The present simulation analyses are aimed toward developing an understanding of how the geometric and operating parameters of multiple fuel injectors affect the shocks and recirculating flows generated by fuel injections. They are also intended to help develop an understanding of the impact of the interaction on the supersonic combustion flow behind the fuel injections. The simulation employs ICEM to establish the model, and ANSYS FLUENT software is used for the simulation. The SST k-ω turbulence model is adopted as the numerical method. We use different distances between jets to investigate the interaction among the jets, such as l/d=2, 5, or 8, where l represents the distance between the jets, and d represents the jet width. The results show that when two jets are far apart, such as l/d=5 or 8, the interaction between the two jets is weak. When we change the distance between the jets to l/d=2, and as the distance between the two jets becomes too close, these distances enhance the interaction of the jets, so the recirculation zone in front of the jets is longer and higher than l/d=8 and l/d=5, respectively. When l/d=2, because the recirculation zone is longer and higher, some part of the air will be affected by this recirculation zone. Its momentum will in turn be reduced, and then the strength of the bow shock will be decreased. When l/d=2, the kerosene vapor changes its flow direction due to obstruction from the other jet, so the kerosene vapor stacks in front of the jet. Therefore, changing the distance between the jets can also change the flow structure, including the recirculation zone, bow shock, and the combustion phenomenon behind the jets. The results will help lead to an understanding of the interaction mechanism for multiple fuel injections and its influence on supersonic combustion flow.

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