超音速燃燒衝壓引擎已發展了數十年，在燃料的選擇上，為了增加巡航距離與時間，由原先的氫氣，到使用氣態形式之碳氫燃料，以及發展中的液態碳氫燃料。超音速燃燒流場具有高溫及高速燃燒等特性，實驗量測上非常困難，因此相當需要在進行實驗之前，先行以數值模擬對超音速燃燒流場進行研究，以輔助規劃實驗進行。本研究使用CFD軟體ANSYS FLUENT，採用SST k-ω紊流模型以及層流有限速率燃燒模型，針對使用液態碳氫燃料之超音速燃燒流場進行模擬分析，並比對實驗數據，在壁面壓力之趨勢上大致符合。分析其流場結構後發現，燃燒室為矩形時，在角落附近之流體受到側壁面及下壁面的影響流動緩慢，加上煤油燃燒造成的高壓區，造成流場內存在逆向壓力梯度，使凹槽前端的分離點往上游移動。而產生的迴流區幫助了燃料與空氣之混合，創造了另一個高壓區，流場在高壓區與迴流區互相影響下，使得燃燒現象移動到燃料噴注口上游。

The Scramjet engine has been developed for decades. In order to increase the cruise time and distance for scramjet, gaseous and liquid hydrocarbon fuels are selected for the scramjet to replace hydrogen. Because of the high-temperature and high-speed combustion which is very hard to measure, it is needed to make a simulation of supersonic combustion flows for supporting the experiment. In this study, the FLUENT code with the SST k-ω turbulence model and the laminar finite-rate combustion model is employed for the numerical analyses of the supersonic combustion flows using liquid hydrocarbon fuels. The predicted pressure distributions at the wall are similar to the experimental data. Examining the flow structure shows that the high-pressure region caused by the combustion results in the adverse pressure gradient in the flow fields. In the rectangular combustor, the flow velocity near the corner of the walls is slow. When the two above-mentioned circumstances occur, it makes the separation point of leading edge of the cavity in the combustor move upstream. The separation of flow helps the mixing of air and fuel and creates a high-pressure region. The interaction of high-pressure region and the flow of separation lead the region of combustion to move upstream of the injection point.

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