【作者】 王翼；

【导师】 王振国；

【作者基本信息】 国防科学技术大学 ， 航空宇航科学与技术， 2008， 博士

【摘要】 本文以高超声速进气道为研究对象,采用试验与数值模拟相结合的方法,对高超声速进气道的流动机理、启动过程、启动特性和启动性能提高方法等问题开展了研究。通过壁面压力测量、高速纹影、壁面油流和数值模拟等多种手段,详细研究了二维和三维侧压进气道启动/不启动状态的流场结构,并对比了内收缩比和唇口角对进气道启动性能的影响。在此研究的基础上,分析总结了高超声速进气道不启动流场的主要特征和能够保持稳定的原因:内收缩段入口存在大规模流动分离并在内收缩段入口前产生溢流是进气道不启动流场的主要特征;内收缩段入口分离区通过调节自身的大小和位置维持了来流动压、内收缩段反压和溢流三者之间的动态平衡,分离区通过该平衡实现“自持”是不启动流场能够稳定存在的原因。在这部分内容中还研究了侧板构型对二维进气道启动性能的影响,发现将侧板由后掠改为前掠能有效地提高启动性能。采用高速纹影观察了高超声速进气道启动过程中流场的变化情况。试验结果表明进气道的自启动过程可以分为两个阶段:分离对峙阶段和状态过渡阶段。自启动过程的临界状态在流场特征上表现为大规模分离形成的分离激波入射在内收缩段入口,溢流消失。达到这一状态后,分离区的“自持”被打破并逐渐消失,进气道继而实现自启动。在前人对一维等熵压缩进气道启动特性研究成果的基础上给出了真实飞行条件下高超声速进气道的启动特性图,将进气道的工作状态划分为不启动区、双解区和自启动区三个区域,为高超声速进气道的设计和启动性能优化工作提供了有益的参考。通过自由射流试验研究了入口开启机构对进气道启动性能的影响,并分析了进气道在入口封闭、不启动和启动三个状态下整个飞行器的力学特性。研究表明入口开启机构这一变几何方式避免了加速过程中进气道启动的迟滞现象,并在接力状态下将进气道的工作状态由自启动区转入双解区的启动状态,有效地提高了进气道的启动性能。详细研究了边界层抽吸对进气道启动性能的影响。分别在进气道前体和不启动状态大规模分离区位置考察了多种边界层抽吸方式对进气道启动性能的改善情况:边界层剥离这种集中抽吸方式在前体边界层抽吸中效果最佳;小孔抽吸这种分散抽吸方式在分离区内进行抽吸的效率最高。结果表明,边界层抽吸是一种能够以较小流量损失为代价有效提升进气道启动性能的简单易行的方法。对流线追踪Busemann进气道的设计方法、巡航状态和低马赫数下的工作特性进行了初步研究,并通过壁面小孔抽吸方法辅助过压缩的构型实现了低马赫数下的启动。更多还原

【Abstract】 The flowfield in hypersonic inlet was investigated by both experimental and numerical methods to study the starting characteristics and starting ability enhancement.Started and unstarted flowfields of 2D and 3D sidewall compression inlets were studied by wall static pressure measurement, schlieren, wall surface oil flow pattern and numerical simulation. It is achieved that the typical character of an unstarted flowfield is a large-scale flow separation near the entrance of internal compression, which causes much flow spillage. The separation keeps a balance among incoming flow, pressure rise caused by internal compression and spillage by adjusting its scale and position. And this balance forms a kind of self-sustainment of the separation which stabilizes the unstarted status. The influence of 2D inlet sidewall configuration on starting ability was also tested in this part.High speed schlieren was employed to observe the starting process of hypersonic inlets. Results show that the starting process can be divided into two parts: separation confrontment period and status transition process. The moment that separation-induced shock getting into the internal compression and spillage vanishing appears to be the critical condition of self-start.. The self-sustainment of separation is broken down when this moment occurred and then the inlet finishes the self-starting process.Based on the starting characteristics of one-dimensional, isentropic internal compression inlet, the starting characteristics of hypersonic inlet is achieved. The CR_in/Mach number diagram is divided into three distinct parts: spontaneous start region, dual solution region and cannot-start region.A 3D inlet with moving entrance door was tested in free-jet experiment and the result revealed that the moving entrance door could effectively improve the starting ability. The inlet avoids the starting hysteresis by blocking the entrance during acceleration. And the opening process after acceleration leads the inlet into dual solution region from spontaneous region which keeps the inlet started.Boundary-layer bleed was applied both on the forebody and in the separation region of unstarted flowfield. And this method is testified to be a simple but effective way to improve inlet starting ability. The results reveals that boundary-layer split on the forebody has the best effect, while the porous surface in the separation region has the highest bleed efficiency.The design method and starting characteristics of a streamline-traced Busemann inlet were investigated. The free-jet test result shows a very good performance at designed Mach number. But it cannot self-start at a lower Mach number unless with the help of bleed holes.更多还原