Empirical Equation for Self-starting Limit of Supersonic Inlets
Empirical Equation for Self-starting Limit of Supersonic Inlets
复制标题
DOI：
10.2514/1.46798
复制
发表时间：
2010-07
影响因子：
1.9
通讯作者：
Bo Sun;Kun-yuan Zhang
中科院分区：
文献类型：
--
作者：
Bo Sun;Kun-yuan Zhang
对于在大马赫数范围内工作并使用外部和内部压缩组合的高超声速进气道，必须确保进气道能够在接管马赫数时自启动。未启动的进气口与启动的进气口相比，捕获的气流更少，效率更低，气动和热负荷更高。这一起始问题最近被许多研究者研究[1-3]。术语启动用于表示在进气口内部的流动现象不会改变进气口的捕获特性的条件下的操作。有三个原因可以取消入口的启动[4，5]：1)内部收缩太大，以至于入口过度收缩到入口喉部堵塞的程度。2)将背压提高到入口所能承受的范围之外。3)大分离流的形成使流动受阻。在高马赫数时，未启动的流场通常具有较大的分离区。自启动表示进气口将在不改变进气口几何形状的情况下启动。这是固定几何形状的进气口设计中的一个重要特征，因为它表明重新启动进气口时不需要改变几何形状。自启动的内部收缩比的初步估计可以从Kantrowitz极限得到[7]。这一极限是通过假设内部收缩开始时的正常激波并计算将在喉部产生声速流的一维等熵内部面积比来确定的。对于理想气体，Kantrowitz极限的内部收缩比可计算如下：
F OR hypersonic inlets that operate over a large Mach number range and use a combination of external and internal compression, it must be ensured that inlets can self-start at takeoverMach number. An unstarted inlet captures less airflowwith lower efficiency and higher aerodynamic and thermal loads compared with a started inlet. The starting problemwas recently studied bymany researchers [1–3]. The term started is used to denote operation under conditions where flow phenomena in the internal portion of the inlet do not alter the capture characteristics of the inlet [4]. An inlet can be unstarted by three reasons [4,5]: 1) The internal contraction is so large that the inlet is overcontracted to the point where the flow chokes at the inlet throat. 2) The back pressure is raised beyond the level that can be sustained by the inlet. 3) The formation of a large separated flowmakes the flow choked. At high Mach numbers, the unstarted flowfield is usually characterized by a large separated region. Self-starting indicates that the inlet will start without a change in inlet geometry. It is a significant feature in a fixed-geometry inlet design because it indicates that variable geometry is not necessary to restart the inlet . Preliminary estimates of the internal contraction ratio that will self-start can be obtained from theKantrowitz limit [7]. This limit is determined by assuming a normal shock at the beginning of the internal contraction and calculating the one-dimensional isentropic internal area ratio that will produce sonicflow at the throat. For a perfect gas the internal contraction ratio of Kantrowitz limit can be calculated as follows: