超音速燃燒衝壓引擎是迄今為止各國航太領域之重點研究項目，此設計是為了避免因氣流在進入燃燒室之溫度過高及過多壓力損失，使得燃燒室效能降低。而在超音速燃燒衝壓引擎中，在燃燒室入口處氣流必須保持在超音速狀態，此導致在燃燒室中空氣與燃料必須在極短時間內相互均勻混合並進行燃燒反應。為了使得燃燒室中有足夠的時間混合燃料及空氣，在燃燒室中加入駐焰機構如：支架、凹槽，使得燃燒室內部產生低速回流區，以利於空氣與燃料均勻的混合，最終使得燃燒反應穩定進行。本研究為了探討支架及凹槽駐焰器之幾何尺寸對超音速燃燒流場之影響，使用CFD軟體ANSYS FLUENT對具有加裝支架及凹槽之燃燒室進行數值模擬分析。本研究先針對不同支架頂角進行超音速流場分析，該支架頂角分別為18.45度、39度、60.5度，結果發現39度之總壓損失較其餘兩者大，其原因在於39度之震波結構上多了正震波，使得氣流通過正震波後，所引起的能量損失相較於斜震波來得大；緊接著固定支架頂角為60.5度及凹槽斜壁面後傾角度為22.5度，在不同凹槽L/D值下，發現凹槽尺寸的擴大僅使得支架後方至凹槽斜壁面之間之流場結構加長延伸，也因此支架後端之流場結構上並未因為L/D值的增加而有明顯改變；接下來固定支架頂角為60.5度及凹槽L/D值為5，在不同凹槽斜壁面後傾角下，發現後傾角67.5度之燃燒室兩側壁面皆出現具範圍之低速(次音速)回流區，此因後傾角的傾斜度強化了支架與邊牆之間的流場交互作用所導致。
本研究探討超音速燃燒流場，以固定支架頂角為39度、凹槽L/D值為3、後傾角為22.5度為固定條件，改變支架上之噴注質量流率，結果發現7g/s之燃燒狀況較12g/s來得好，此因為油氣當量比的分布較適合燃燒反應的進行；再以固定支架頂角為60.5度、凹槽斜壁面後傾角為22.5度下，改變凹槽L/D值，結果發現L/D值為3時，出現單一側邊近壁面點燃的現象，此因為在燃燒過程中之一特定秒數下，槽內噴注口左側及右側液滴承受氣流相對速度大小之差異所造成破碎量之不同，使得噴注口左側較右側之油氣當量比較適合點燃，最終導致單一側邊迅速燃燒，但是在L/D值為5時，在燃燒室兩邊壁面皆出現點燃區域，並在支架上之噴注口周遭各自形成一渦流使液滴在其中破碎、霧化並順勢點燃。

In this study, the ANSYS FLUENT software for numerical simulation analysis was used to analyze the supersonic combustion flow field with different geometric parameters. First, we established the mesh model, boundary conditions, and ignition method, and then modified vertex angle of the strut, L/D ratio and the ramp angle of cavity, and simulated the supersonic combustion flow field. Finally, we determined the influence of the geometric dimensions of the strut and cavity flame-holder on the supersonic combustion flow.
In the supersonic flow field, we investigated the effect of the vertex angles of strut on the total pressure loss, while the vertex angles of 18.45, 39 and 60.5 degrees, respectively. The simulation results show that the case of 39 degrees has a normal shock wave structure in flow field. Therefore, the total pressure loss of the 39 degrees case is larger than 18.45 degrees and 60.5 degrees cases.
Besides, the simulation results show that the increase of the cavity size does not significantly change the flow field structure in condition of the vertex angle of the strut is 60.5 degrees, ramp angle of the cavity is 22.5 degrees.
The study also show that when the ramp angle is changed from 22.5 degrees to 67.5 degrees, a low-speed zone appears around both side walls during the combustion process, where vertex angle of the strut is 60.5 degrees, L/D ratio of the cavity is 5. This phenomenon is due to the inclination of the strut strengthens the interaction of the flow field between the strut and the side wall.
In addition to the above results, we explore the influence of changing the injection mass flow of the strut on combustion situation. The results show that the combustion situation of 7g/s is better than that of 12g/s when vertex angle of the strut is 39 degrees, L/D ratio of the cavity is 3, and the ramp angle is 22.5 degrees. This phenomenon is because of the distribution of the fuel-air equivalence ratio is more beneficial for the combustion reaction.
The results show that the JP-4 is ignited on the single side wall of the combustion chamber occurs when the L/D ratio of the cavity is 3. It is caused by the difference in the relative velocities of the airflow on the left and right sides of the injection, while vertex angle of the strut is 60.5 degrees, ramp angle is 22.5 degrees. The results also show that the JP-4 is ignited on the two side walls of the combustion chamber when L/D ratio of the cavity is 5, while vertex angle of the strut is 60.5 degrees, ramp angle is 22.5 degrees.

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