在超音速燃燒流場中，液態煤油需要經過破碎、蒸發以及點燃過程，其中點火延遲時間對超音速燃燒流場為不可忽略因素。本研究選用計算流體力學軟體ANSYS FLUENT分析超音速燃燒流場中液態燃料噴霧與點火特性。首先根據Tian等人在2019年所發表之文獻，將本研究所建立的數值模擬方法計算結果與實驗冷流場實驗之上壁面壓力分佈做比對。接著利用Zhang等人煤油反應式放入Tian等人二維超音速燃燒模型，以驗證本研究數值方法的可靠及準確性。
接著參考Tian等人之文獻，建立一組三維對稱超音速幾何模型，在凹槽後方建立一壓力偵測點，發現此模型在冷流場達到一定時間時，偵測點壓力會出現規則性震盪，此模擬結果與文獻實驗相似。此外也在開啟凹槽後方空氣噴注後，發現其對於超音速流場之穩定有莫大幫助。最後，根據不同流通量比(Flux ratio)探討對點火之影響，其火星塞(spark)設置在凹槽正中心，流通量定義為空氣噴注與自由流流量比值，其流通量比分別為12 %與24.5 %。當流通量比為12 %，點火範圍會由下游延伸至入口處；流通量比為24.5 %時，由於空氣噴注流量更高，使入口附近流場產生迴流區。當空氣噴注孔半徑固定的條件下，較大空氣噴注流量會擁有較快噴注速度，因此較能阻擋自由流，使自由流速度減緩，點火後燃燒範圍進而延伸到入口附近。結果顯示當點火完成後，其燃燒區域穩定存在於凹槽斜壁面與兩側壁面。

In a supersonic combustion flow field, liquid kerosene is required to undergo a breakup, evaporation, and ignition process. The ignition delay time is a very important factor in a supersonic combustion flow field. In this study, the computational fluid dynamics software ANSYS FLUENT is used to analyze the effects of the spray and ignition mechanism on a supersonic combustion flow field with liquid fuel injection. First, according to the Tian et al. (2019), our numerical simulation results were proven through a comparison with the top wall pressure distribution of an experimental cold flow. Then, based on Zhang et al. (2014), the kerosene reaction where cracking due to rises in the temperature was considered was put into the two-dimensional supersonic combustion model of Tian et al. (2019), and the accuracy of the proposed numerical method was proven. The numerical ignition delay time was shown to be similar to that of the experimental results.
Second, following Tian et al. (2019), we built a symmetrical three-dimensional model, where the numerical results predicted that the monitored pressure would exhibit regular oscillation. Our numerical results were similar to the experimental results. Also, the air throttling operation behind the cavity was found to be beneficial in terms of stabilizing the supersonic flow field. Finally, the effects on ignition were discussed for different flux ratios of 12% and 24. 5%. When the flux ratio was 12%, the flow field was relatively stable due to air throttling. However, when the flux ratio was 24.5%, the air throttling flow rate was higher, and the near entrance flow was affected by the ignition field, which caused a vortex to appear near the freestream inlet. When the radius of the air injection hole was fixed, the large air throttling flow rate led to a faster jet speed, which caused the free stream to be blocked and slowed it down and where the ignition field extended to the near entrance. Finally, when the ignition was stabilized, the combustion field became stable in the cavity ramp and on both side walls.

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