超音速燃燒衝壓引擎為自由流進入燃燒室內部時，速度維持在超音速狀態之吸氣式引擎。液態燃料注入燃燒室後，會經過霧化、破碎成小液滴，接著蒸發為氣態燃料，然後與氧氣混合，隨後燃燒。液態燃料由噴出到燃燒，中間的過程相當繁雜，但燃燒室之體積不大，且流速極快，容易造成霧化到燃燒過程尚未完成時，而流出燃燒室，甚至可能會因為流速過快使得點火不易。為了使噴霧燃料能充分進行上述提到的霧化與燃燒過程，並且可應用於超音速燃燒室中，了解超音速噴霧流場內部的構造以及流場與震波之間的關係，是一個非常重要的資訊。由於超音速噴霧流場相當複雜，藉由實驗設備觀察超音速噴霧流場細部的流場現象，難度相當高，並且實驗花費相當昂貴，因此，本研究使用ANSYS FLUENT進行數值模擬分析，藉由數值軟體探討液態噴注於超音速氣流中之細部流場，並觀察整理噴霧流量、入流馬赫速、迴流區以及震波之間的關係，提供未來設計超音速燃燒室之重要參數。
本研究使用液態水以及液態煤油垂直注入超音速燃燒室，自由流與液柱撞擊會產生高溫高壓之弓形震波，並且在液柱前方會生成迴流，而在迴流區前端會產生分離震波。使用不同噴注流量探討之結果顯示，提升噴注流量會提升弓形震波強度，並且會提升弓形震波角度，由於弓形震波增強，噴注前方的迴流區強度以及長度也會因此增加，造成分離震波高度以及強度之提升。接著，使用不同入口馬赫數之結果顯示，提升入口馬赫速，會增強弓形震波強度以及分離震波強度，但是，由於自由流流速提升，自由流往下游的動量較大，使得弓形震波角度以及分離震波高度會變小、迴流區長度會縮短。綜合不同噴注流量以及不同入口馬赫數之結果，發現隨著噴注流量提升或是入口流速的提升，弓形震波強度會越來越大，且弓形震波與分離震波強度的比值也越來越大。另外，針對注入液態煤油與注入液態水進行交叉比對，並進行相關之比較。結果顯示，由於液態煤油的密度較液態水小，在噴霧流量控制相同情況下，液態煤油的噴射速度較大，噴注動量較強，使得弓形震波強度提升，並且會提升弓形震波角度。由於弓形震波增強，噴注前方的迴流區強度以及長度也會因此增加，造成分離震波高度以及強度之提升，其流場的趨勢與不同噴注流量之結果類似。因此，液柱本身動量，可以影響震波強度、迴流區長度以及兩震波之交互作用點。本模擬之研究結果，可做為未來設計超音速液態噴霧流場之重要參數。

This study uses the numerical simulation software ANSYS FLUENT to conduct a numerical simulation of liquid-hydrocarbon fuel injected into a supersonic flow. With this numerical simulation we can investigate the detailed flow of the liquid jet into the supersonic flow, and observe the relationships among the Mach Number, flow rate of the liquid jet, recirculation zone and the shock waves. This study finds that when liquid kerosene is vertically injected into the supersonic flow, the free stream impacts the liquid column, and this produces a high- temperature, high-pressure shock wave. The flow forms a recirculation zone in front of the shock, and a separation shock results in the leading edge of the recirculation zone.
The results of using different injection flow rates show that increasing this will increase the strength of the bow shock, and also increase the angle of the bow shock. If the bow shock is enhanced then the length of the recirculation zone will increase, as will the height and strength of the separation shock. Moreover, the results of using different inlet Mach Numbers for the free stream show that enhancing the Mach Number will increase the strength of the bow shock and separation shock. However, due to the increase in inlet velocity, the flow has more momentum and thus makes the air flow downstream with greater intensity. Because of this, the angle of the bow shock will decrease, as will the length of the recirculation zone also decrease and the height of the separation shock. Moreover, when the Mach number of the free stream or the mass flow rate of injection increases, the interaction between the strength of bow shock and separation shock is strongly related to the strength of the bow shock.
Therefore, changing the momentum of injection can also change the strength of the shock, the length of the recirculation zone and the position of the interaction between the two shocks. The results of this simulation presented in this work can be used to further examine the impact of liquid jet into supersonic flow in future works.

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