現代的超音速進氣道不僅需具備捕獲氣流、減速壓縮空氣並維持高總壓恢復之氣流提供發動機正常運作，匿蹤進氣道外型同樣成為設計的一大考量。早期的進氣口構型通常以邊界層隔板(Diverter)裝置排除低能量之氣流，然而該裝置的設計造成設備維護成本及重量的增加，因此在目前的五代戰機為達到設備維護成本的減少，且保有良好的氣動性能及匿蹤特性的考量，取消邊界層隔板設計採用新的進氣口設計構型，該構型於進氣口安裝三維幾何曲面，搭配前掠外型的進氣道外罩，此新型進氣道構型稱之為無分流隔板超音速進氣道(Diverterless supersonic inlet, DSI)，三維幾何曲面亦可稱之為壓縮面(Bump)，其作用為壓縮空氣及排開近壁面處的低能量氣流，壓縮面的設計是利用錐形流(Conical flow)作為基礎流場進行流線追蹤生成的幾何曲面。如何在特定機身設計符合發動機需求的DSI進氣道，以及DSI外型對於氣動與匿蹤的性能分析為本研究的探討重點，本研究採用設計點馬赫數2.0的等熵錐(Isentropic cone)進行流線追蹤生成兩組不同外形的壓縮面，並利用流體力學工具(CFD)分析壓縮面在設計點的基準流場進行進氣道外罩及次音速管道設計，後續利用CFD模擬兩組DSI在設計點及設計點外的氣動特性，在滿足氣動特性的條件下利用高頻電磁模擬軟體(HFSS)計算雷達散射截面(Radar Cross Section, RCS)。研究結果顯示兩組DSI在設計點上能滿足本研究之發動機氣流量需求，等熵壓縮面的外型能提供進氣道良好的總壓恢復性能，使得兩組DSI在設計點2馬赫能維持90%以上的總壓恢復係數，匿蹤特性上結果表明兩組DSI在前向區域的RCS皆低於傳統邊界層隔板進氣道，DSI的壓縮面搭配S型進氣道能將雷達波在進氣道內多次反射，避免雷達對發動機入口產生強烈回波，且前掠外罩的外型亦能減少唇口處的邊緣繞射。本研究從兩組DSI之氣動與匿蹤結果發現壓縮面的高度差異影響進氣道的氣流捕獲面積、阻力及RCS的大小，在足夠的高品質氣流捕獲條件下，較小的壓縮面外型亦能維持良好總壓恢復，並能獲得更小的阻力與更低的RCS表現。

Fifth-generation fighters feature a new air intake design called Divertless Supersonic Inlet (DSI), which provides excellent aerodynamics and stealth while reducing maintenance costs and aircraft weight. This study proposes the design of DSI in a specific forebody and matchs the performance requirements of the engine. And investagation the characteristic analysis of DSI on aerodynamics and stealth. DSI is composed of a three-dimensional (3D) bump and a cowling. The 3D bump geometry can be designed by tracing the streamlines released from curve forebody surface in conical flow with two different offsets, resulting in height differences for the bumps. Use CFD to analyze the flow field of the bump mounted on the fuselage and investigate flow field over the 3D bump before the cowling and the subsonic diffuser design. The flow field over the 3D bumps determines DSI cowling size, causing discrepancies in the capture area. The simulation results indicate that the two DSIs can satisfy the engine airflow requirements of this study at the design point. The isentropic compression surface can provide high total pressure recovery performance. Two DSIs in this study can provide a total pressure recovery coefficient of more than 90% at the design point Mach 2. The results of the stealth characteristics show that RCS of the two DSIs in the forward region is lower than the traditional boundary layer divert inlet. The bump of DSI and the S-shaped inlet can reflect the radar wave multiple times in the duct, avoiding the strong echo of the radar to the engine inlet. This study found from the aerodynamic and stealth results of the two DSIs that the height difference of the bump affects the airflow capture area, drag and RCS.

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