【作者】 王卫东；

【导师】 过增元； 张振家；

【作者基本信息】 清华大学 ， 工程热物理， 1997， 博士

【摘要】 采用氢燃料的冲压组合式发动机是空天飞机等高超声速飞行器最有希望的推进系统，氢冲压燃烧室研究的难关在于如何使氢与空气均匀混合，虽然国外对此进行了一些研究，但气氢燃烧恶化的问题仍没解决。本文详细讨论了流向旋涡增强氢燃料和空气混合的物理机制，并将这种方法应用于突扩燃烧室和钝体稳定器燃烧室中。 在突扩燃烧室研究中，提出了壁面垂直喷氢方案，以代替国外常用的直杆式喷氢，利用横喷氢射流产生的流向旋涡对来增强氢燃料和空气的混合，并通过冷态试验、数值模拟和燃烧试验相结合对此问题进行了详细研究。研究了几何参数和流动参数对单孔、二维和单排多孔受限垂直射流的穿透深度和穿透轨迹的影响，结果表明孔距与通道高度的比和动量比的平方根之积是决定多股受限射流穿透深度的物理量。在试验中发现难于测量射流最大速度穿透轨迹，提出了以流向旋涡的涡心连线来定义的射流穿透轨迹，并解释了射流浓度轨迹线比最大速度轨迹线低的原因。垂直射流与来流的混合程度取决于其形成的流向旋涡的位置、作用范围和强弱，本文得出了使流向旋涡涡心位于通道半边的中央位置，流向旋涡能最大程度地强化射流与来流混合的最佳混合准则。但突扩台阶后的回流区旋涡将破坏垂直射流形成的流向旋涡，在实际设计中，应增加氢喷嘴离突扩截面的距离。本文设计了带有石英观测窗口的氢冲压燃烧试验室模型，对各种垂直喷氢的喷孔布列方案进行了燃烧试验，还进行了带有固体旋涡发生器和喷氢直杆的突扩燃烧室试验。试验结果表明只有接近最佳混合准则的喷孔布列方案才能获得高的燃烧效率；直杆喷氢方式的燃烧室总压损失太大，证明本文提出的壁面垂直喷氢方案的正确性；固体旋涡发生器和垂直喷氢方式相结合进一步强化了气氢与空气的混合。 用数值方法研究了主流、射流进口温度比对二维受限通道垂直射流轨迹和穿透深度的影响，表明了进口温度比是独立于动量比以外的重要影响参数。射流进口温度比对射流穿透影响的物理机制可用热阻力的概念来分析。 V型火焰稳定器用于气氢燃烧时会在稳定器后形成燃料浓度集中，从而燃烧恶化，这成为阻碍氢冲压发动机发展的难题。本文为此设计了一种新型火焰稳定器-流向旋涡火焰稳定器(SVGs)。研究揭示了SVGs所产生的复杂流场，一是气流在SVGs台阶背风区形成展向回流流动，可用于火焰稳定；二是气流流经SVGs形成了流向旋涡，用于增强燃料混合；可根据稳定和混合的不同需要，调节二种旋涡强弱。燃烧试验结果表明，采用扁长的氢射流喷孔的SVGs混合最好，而且总压损失低，圆孔SVGs稳定器略逊，V型稳定器最差。更多还原

【Abstract】 Air-Turbo-Ram Engine is regarded as one of the most prospective engines for a hypersonic vechicle .The technical barrier of hydrogen fueled ram-combustor research is how to improve the fuel distribution and enhance the fuel/air mixing. Although some research has recently been performed in the area of enhanced H₂/Air mixing, poor combustion of gaseous hydrogen is still not resolved. This paper discuses the physical mechanism of streamwise vortex enhanced H₂/Air mixing and deals with a practical study for the hydrogen fueled dump combustor and bluffbody flameholder combustor.In the research of dump combustor,the concept of gaseous hydrogen injected traversely into the subsonic air flow is put forward. Streamwise Vortex produced by traverse jets improved H₂/AIr mixing. The cold and combustion experiments and numerical modelling have been carried out.The effect of the geometric and jet flow variables on the jet penetration depth and trajectory is investigated. Rresults show that the penetration depth depends mainly upon the product of squre root of the momentum ratio and the ratio of orifices spacing and duct height. A new well-definition is suggested --Vortex Jet Trajectory defined by the locus of streamwise vortex core. Then the reason that the jet concenration trajectory is below the jet velocity trajectory is explained. The mixing of traverse jet and coming flow depends upon the scope and strength of streamwise vortex. A criterion of optimization mixing is put forward. According with this criterion the streamwise vortex core should be located in the center of duct cross section in order to achieve the best mixing to achieve . Gaseous hydrogen fueled combustor model with quartz glass windows was designed.Vanous traverse H₂ injection model experiments were carried out. Experimental results indicate that only the model according with the demands of the optimization critertion can be reached high combustion efficiency.Large total presure loss has been found in the experiment of dump combustor with straight pipes injection.In this paper numerical study is conducted on the influence of temperature ratio on the penetration depth of two dimensional confined Jet flow and it is found that the jet to main flow temperature ratio is a important parameter independent of momentum rato. The physical mechanisim can be explained by using the concept of thermal drag.Gaseous hydrogen concentrated in the recirculation zone behind the V-gutter lead to a bad combustion. A new concept flameholder - SVGs was designed to produce streamwise vortex for the enhancement of mixing. Research clarified the complex flow fields produced by SVGs. The flow structure behind SVGs can be divided into two parts, one is spanwise recirculation flow, the other is streamwise vortex formed by the stream flowing across sweep slope. Experimental results show that the mixing of SVGs with square injector hole is the best, SVGs with circular hole is the better, V-gutter is the worst.更多还原