戰機的性能取決於發動機的運作，供給發動機氣流的進氣道為發動機運作的關鍵因素，設計良好的進氣道必須同時兼顧多項需求，包含氣流的減速增壓、足夠的質量、低總壓損失及高均勻度等目標，過往進氣道設計中採用邊界層隔板設計以避免機首產生的邊界層氣流進入進氣道，而此設計使機身的正投影面積增加進而造成阻力值上升，複雜的外型增加後勤成本與重量，為避免邊界層隔板之缺點，無邊界層隔板超音速進氣道(Diverterless supersonic inlet, DSI)應運而生，此型設計同時具備排移低能量邊界層氣流與將氣流減速增壓的能力，進氣口前掠外罩與三維壓縮面是達成此目標之條件，簡潔的外型設計能有效降低重量與後勤維護成本。本研究利用一假想之戰機機首整合 DSI 進氣口設計作為設計目標，透過追蹤超音速流場中通過等熵錐的流線產生三維壓縮面，規劃 2 組不同的進氣口外罩設計，使用計算流體力學(CFD)方式分析設計點 2 馬赫下DSI 進氣口氣動性能，並利用不同的進氣道出口面積模擬發動機運作情形，藉由流場的馬赫數分布、總壓分布、表面壓力與表面流線圖觀察流場現象，性能指標包含進氣口處之質量流率比與總壓比。研究結果顯示與機首整合之 DSI 進氣口外型確實能排移機身前體產生的邊界層氣流，同時具備將氣流減速增壓的能力，而機首外型上下表面交界處產生之渦流結構與外罩內緣的氣流分離是造成進入進氣口氣流不均勻的主因。

This study investigates the aerodynamic characteristics for the aperture region of sidemounted supersonic inlets. Diverterless type inlet aperture region with F-35-like forebody consideration is chosen as the target of this research. The design point of freestream velocity of the inlet is Mach number 2.0. Diverterless supersonic inlet, which is usually abbreviated as DSI, consists of a 3D compression surface and a forward-swept cowling. The 3D compression surface is generated by streamline-tracing method in a conical flow field. The shape of the forward-swept cowling depends on the flow field generated by the 3D compression surface. In order to simulate the different situations of the inlet duct under different operating conditions of the engine, this study uses 4 different sizes of duct outlet area to simulate different mass flow rate conditions of the engine. The results show that the combination of the 3D compression surface and the forward-swept cowling can divert the low momentum boundary layer fluid. Meanwhile, it also decelerates and compresses the air entering the inlet duct. However, it is found that the vortex caused by the forebody of the aircraft will go into the inlet, which will reduce the flow uniformity inside the inlet. Besides, flow separation tends to occur at ? = −60° plane. To solve this problem, this study suggests that the bump should offset upward and integrate with the forebody of the aircraft. The height of transition shoulder should be decreased comparing to current design to obtain more flexibility during the cowling design process.

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