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摘要: 首先對噴管內流動特性進行了研究，結果表明傳統拉瓦爾噴管在噴管內部易形成大量明顯的波系結構，抑制了超音速氧氣射流的初始沖擊效果，而利用特征線設計的曲線拉瓦爾噴管可有效解決該問題。其次，分析了不同供氧流量下，傳統拉瓦爾噴管及曲線拉瓦爾噴管在高溫條件下的射流馬赫數分布、動壓及射流卷吸特性。研究結果表明基于特征線法設計的曲線拉瓦爾噴管應用于轉爐氧槍噴頭時，可延長氧氣射流核心段長度，增大氧氣射流對熔池的攪拌能力，并提高氧氣在熔池內的傳質效果。Abstract: The blowing of oxygen at supersonic velocity through nozzles is a fundamental method and key technology for basic oxygen furnace process used in the steelmaking process. During the process, the high-speed oxygen jets penetrate the liquid slag leading to the formation of the impaction cavity on the surface of the molten bath. Further, the dynamic energy and mass transfer would occur at the three-phase (oxygen–liquid slag–molten steel) region. As a result, the impurity elements are removed, the temperature of molten bath is controlled, and the solid slag is melted faster. Moreover, many complex wave structures are formed in the traditional Laval nozzle depending on its gas flow field, resulting in suppression of the initial stirring ability of the oxygen jet. However, the new Laval nozzle designed by the characteristic-line method can solve this problem. Additionally, Mach number, dynamic pressure, and entrainment phenomenon of both traditional and new Laval nozzle structures were tested using various oxygen flow rates at the high-temperature ambition environment. The results prove that the new Laval nozzle structure prolongs the velocity core length of oxygen jet, increases the molten bath stirring effect, and improves the mass transfer process.
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Key words:
- supersonic jet /
- Laval nozzle /
- shock wave /
- numerical simulation
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圖 2 模型網格結構圖。（a）拉瓦爾噴管網格示意圖；（b）計算域網格示意圖
Figure 2. Schematic of the mesh distribution of the simulation model: (a) Laval nozzle; (b) computational domain
圖 3 不同類型拉瓦爾噴管的結構圖。（a）錐形拉瓦爾噴管；（b）曲線拉瓦爾噴管
Figure 3. Structure of different Laval nozzles: (a) cone-type; (b) curve-line
圖 4 錐形噴管與曲線噴管出口處徑向流場分布。（a）馬赫數分布；（b）靜壓分布
Figure 4. Mach number and static pressure distributions using various Laval nozzles at the nozzle exit: (a) Mach number profile; (b) static pressure profile
圖 5 不同氧氣流量條件下，錐形噴管與曲線噴管射流在軸向方向上的馬赫數分布。（a）低流量，即氧氣流量=2950 m3·h?1；（b）設計流量，即氧氣流量=3450 m3·h?1；（c）大流量，即氧氣流量=3950 m3·h?1
Figure 5. Mach number distributions using various Laval nozzles at centerline with different oxygen flow rate: (a) oxygen flow rate = 2950 m3·h?1; (b) oxygen flow rate = 3450 m3·h?1; (c) oxygen flow rate = 3950 m3·h?1
圖 6 不同氧氣流量條件下，錐形噴管與曲線噴管射流在軸向方向上的氧氣摩爾分數分布。（a）氧氣流量=2950 m3·h?1；（b）氧氣流量=3450 m3·h?1；（c）氧氣流量=3950 m3·h?1
Figure 6. Molar concentration of oxygen flow distribution using various Laval nozzles at centerline with different oxygen flow rates: (a) oxygen flow rate = 2950 m3·h?1; (b) oxygen flow rate = 3450 m3·h?1; (c) oxygen flow rate = 3950 m3·h?1
表 1 模型邊界條件
Table 1. Simulation boundary conditions
Inlet condition Outlet condition Flow rate/(m3·h?1) Gas composition (mass fraction) Temperature/K Static pressure/Pa Gas composition(mass fraction) Temperature/K 2950, 3450, and 3950 O2: 100% 298 101325 O2: 23%; N2: 77% 1873 
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表 2 氣相物化參數
Table 2. Parameters of the gas flow
Gas Density Viscosity/
(kg·m?1·s?1)Thermal conductivity/
(W·m?1·K?1)Air Ideal gas 1.7894×10?5 0.0242 Oxygen gas Ideal gas 1.919×10?5 0.0246
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參考文獻
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