超燃冲压发动机状态监测参数选择

针对超燃冲压发动机对发动机状态监测系统的需求,通过研究超燃冲压发动机的部件及整体特性,给出超燃冲压发动机性能监测所需的测量参数;根据发动机控制需求给出发动机状态监测系统所需的控制参数;最后从实际技术、物理限制等方面给出超燃冲压发动机状态监测系统需要监测的极限参数,并对这些参数的优化目标和优化方法进行简要分析.通过这些研究,给出了超燃冲压发动机状态监测系统所需的监测参数.     

拉瓦尔式燃料流量调节阀流量特性分析

燃料供给的实时、精确调节是冲压发动机技术研究的重点,对提高发动机的效率、改善发动机的工作性能具有重要的意义。为实现冲压发动机气态燃料在高温下流量的精确调节,提出了一种新型的拉瓦尔式燃料流量调节阀,以对流入发动机燃烧室的高温气态燃料进行流量调节。首先,开发了一种用于燃料供应的高温流量调节阀,然后通过采用有限元分析方法,分析了流经主阀阀口的气态燃料速度及压力的分布,从而找出了流量变化规律。研究结果表明,采用拉瓦尔管状阀口的流量调节阀,在不改变阀芯位移量以及一定入口压力条件下,流经阀口的燃料流量保持不变,且与出口压力无关。     

高温燃料流量调节发拉瓦尔管口特性分析(英文)

600～700℃高温下,冲压发动机所用燃油为完全气态。为解决气态燃料在高温下的流量精确调节,设计新式燃料流量调节阀,对流经发动机进气道的燃料进行调节。对拉瓦尔管阀口特性进行研究,采用FLUENT仿真软件,分析流经阀口的气态燃料速度及压力的分布,从而找出流量变化规律。研究结果表明,采用拉瓦尔管状阀口的流量调节阀,阀芯位移和入口压力不变时,改变出口压力,流经阀口的燃料流量保持不变。     

A mechanism of combustion mode transition for hydrogen fueled scramjet

The combustion mode transition will occur repeatedly during the real flight of a hydrogen fueled scramjet. Under the assumption of inviscid flow, a series of the equations have been developed to identify combustion mode transition in an analytical way. The processes of heating and accelerating induced mode transition are investigated, respectively. This paper presents an analytical solution to understand the conditions for the transition between ramjet-scramjet operation modes. Besides, this paper also presents a qualitative explanation of the mode transition processes in the physical point of view. The mode transition is closely related to the thermal choking effects and shock wave motion. The process of mode transition is discontinuous and very fast. There is a sudden change with the combustor entry Mach number in this process.     

Study on transient process of mode transition in a scramjet combustor with pilot hydrogen

Effective control of mode transition is one of the key technologies for dual‐mode scramjet. In this study, a 3‐dimensional unsteady Reynolds‐averaged Navier‐Stokes modeling was used to investigate the effects of equivalence ratio, inflow temperature, and pilot hydrogen on transient process of mode transition in a dual‐mode scramjet combustor. The isolator entrance Mach number was 2.5, and the fuel of vaporized kerosene was used in the combustor with pilot hydrogen. The results showed that during mode transition from ram mode to scram mode induced by reducing the equivalence ratio of kerosene, the disappearance of the high‐pressure zone around the kerosene injector was the sign of approaching the achievement of mode transition. The leading edge of the shock train moved downstream and the strength of shock train was significantly weakened. During this process, the distribution of heat release zone transformed from scattered along the combustor to being concentrated in the cavity. Then, the opposite process was studied when the inflow temperature was reduced from 1750 to 1000 K while the equivalence ratio was kept the same. The thickness of shear layers originated from the fuel injectors significantly increased. Altering the amount of pilot hydrogen can significantly influence the flow field in the combustor. It showed that the increase of pilot hydrogen could shield the kerosene vapor entering into the high‐temperature zone in the cavity and hindered the formation of concentrated heat release. Thus, the overall heat release became more dispersed.     

Numerical simulation of model scramjet combustor flowfield

A new concept has been raised and adopted in this paper to enlarge the scope of the two‐dimensional model particularly for the purpose of dealing with three‐dimensional normal injection cases. Meanwhile, the method has a very good performance for its short cyclic period. The new idea was realized through special resolution with continuity equations; i.e., mass flow was directly added in the source term of the continuity equation. To prove the robustness of this illuminating method, comparisons using calculations were carried out, and the results are satisfactory. A model scramjet combustor tested on the free‐jet scramjet test facility was illustrated and underwent numerical calculations with the two‐dimensional program, adopting the above simplified injecting method. To simulate the chemical reaction process in the scramjet tunnel, a five‐species, single‐step reaction model was introduced in the calculation process. This research presents the major aerodynamic parameters and components of mass fraction distribution within the model combustor channel, which made it easy to observe and analyze the flowfield. Finally, wall pressure comparisons between the numerical and experimental results were carried out to verify the accuracy of the calculation model. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(5): 295– 302, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20159     

Aerodynamic investigation of the shock train in a scramjet with the effects of backpressure and divergent angles

Numerical simulations are carried out to study the effect of divergence angle and adverse pressure gradient on the movement of a shock wave train in a scramjet isolator. The commercial software tool ANSYS Fluent 16 was used to simplify the two-dimensional Reynolds-averaged Navier-Stokes equation with the compressible fluid flow by considering the density-based solver with the standard k-ε turbulence model. The species transport model with a single-step volumetric reaction mechanism is employed. Initially, the simulated results are validated with experimental results available in the open literature. The obtained results show that the variation of the divergence angle and backpressure on the scramjet isolator has greater significance on the flow field. Also, with an increase in the backpressure, due to the intense turbulent combustion, the shock wave train developed should expand along the length and also move towards the leading edge of the isolator leading to a rapid rise in the pressure so that the pressure at the entrance of the isolator can match the enhanced backpressures.     

2020年国外高超声速技术发展回顾

对2020年国外高超声速飞行器技术领域的重要发展动向进行了全面梳理,分析和总结了美国、俄罗斯、印度、日本、挪威等世界主要国家在高超声速领域的发展情况和态势。美国稳步推进在研高超声速导弹项目,为后续继续开展试验做好技术储备;俄罗斯在高超声速武器部署方面取得先机,密集开展飞行试验,并披露装备部署计划;印日挪等国也通过开展飞行试验或公布研制计划等方式加快高超声速技术的发展。最后预测了未来发展动向。     

超燃冲压发动机燃烧室直连式实验研究

文中在超燃冲压发动机燃烧室直连式实验设备上,对超音速燃烧室模型进行（Ma=2．O）冷流实验研究,比较了不同的来流条件、不同的隔离段长高比和不同的燃烧室出口反压对燃烧室内部流场以及燃烧室隔离段的抗扰动能力的影响．并利用数值模拟的方法对燃烧室内部流场进行了模拟。研究结果表明：隔离段长高比增大,其容纳反压的能力相对增强;燃烧室出口堵塞导致的流场畸变越小．对燃烧室流场压力分布的影响越小。     

A new method of thermal protection by opposing jet for a hypersonic aeroheating strut

This paper presents the numerical investigation of thermal protection of scramjet strut by opposing jet in supersonic stream of Mach number 6 with a hydrogen fueled scramjet strut model using CFD software.Simulation results indicate that when a small amount of fuel is injected from the nose of the strut,the bow shock is pushed away from the strut,and the heat flux is reduced in the strut,especially at the leading edge.Opposing jet forms a recirculation region near the nozzle so that the strut is covered with low temperature fuel and separated from free stream.An appropriate total pressure ratio can be used to reduce not only aerodynamic heating but also the drag of strut.It is therefore concluded that thermal protection of scramjet strut by opposing jet is one of the promising ways to protect seramjet strut in high enthalpy stream.