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射流预冷技术可以有效降低进气温度并提高航空发动机的性能。为探究该技术在高空环境下对流场问题的影响,采用径向均匀射流方案,模拟高空条件,结合水滴的蒸发过程以及气液两相的耦合作用对预冷段射流喷水的情形进行数值计算。结果表明,径向喷射方案能够有效降低进气温度,在各个工况中,温降系数约为8%~26.7%;在高温工况中提高喷水量可以有效提高温降效果,工况6的喷水量和工作温度都是最大的,温降系数和蒸发效率分别达到了最高值的26.7%和73.9%;预冷段的压降损失和出口流场均匀度取决于来流马赫数和喷水量,高马赫数和较大的喷水量都会加剧压损与流场的紊乱程度,由于工况6的高射流量和气流马赫数,其在喷水装置处的压降系数达到了最大值的5.8%。 相似文献
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实验研究了矩形液池中蒸发薄液居中蒸发效应与热毛细对流的耦合机理. 对于单纯的热毛细对流稳定性从实验和理论上已有深入研究,但目前国际上对带有菇发界面的热毛细对流问题尚缺乏研究. 特别是近来的研究发现,气液界面的蒸发对热毛细对流稳定性有很大的影响. 本实验以温度为主要控制参数,测量了不同工况下蒸发界面不同点的蒸发速率和表层温度,并利用 PIV 方法分析得到了液体内的嘛场分布. 实验结果发现,随着沿界面的温差增加,蒸发液体内的流型从稳定的单涡胞结构变为稳定的多祸胞结构,并最终演变为紊流结构. 综合分析以上测量结果并与理论分析结果进行了比较。 相似文献
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蒸发液滴空间实验研究的图像反馈控制系统 总被引:1,自引:1,他引:0
提出了一种利用图像反馈控制系统测量液滴蒸发速率的方法.该系统主要由图像采集、图像处理、反馈控制三个部分组成.其工作原理是对CCD采集到的液滴图像进行分析,得到液滴的物性参数,利用控制注液器动态注入来维持液滴的大小,由此得到单位时间内的注入量,即液滴蒸发速率.或通过对液滴图像几何尺寸的计算,得到单位时间内液滴的变化量,进而得到液滴的蒸发速率.为了从动态变化的图像中准确找到液滴的轮廓,简单介绍了基于拉普拉斯方程,运用牛顿法和龙格库塔法等数值方法,对图像轮廓进行拟合的算法理论.以拟合得到的液滴轮廓为基础,利用数值积分计算液滴的表面积和体积,从而由体积的变化量确定蒸发速率.介绍了图像反馈控制系统的软件结构和硬件结构.并给出了利用其进行液滴蒸发测量得到的实验结果.该系统是为我国SJ-10返回式卫星上蒸发与流体界面效应空间实验研究项目专门开发的. 相似文献
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Kaoruho Sakata Midori Mukai Govindasamy Rajesh Mukannan Arivanandhan Yuko Inatomi Takehiko Ishikawa Yasuhiro Hayakawa 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
The thermal properties of InSb, GaSb and InxGa1−xSb, such as the viscosity, wetting property, and evaporation rate, were investigated in preparation for the crystal growth experiment on the International Space Station (ISS). The viscosity of InGaSb, which is an essential property for numerical modeling of crystal growth, was evaluated. In addition, the wetting properties between molten InxGa1−xSb and quartz, BN, graphite, and C-103 materials were investigated. The evaporation rate of molten InxGa1−xSb was measured to determine the affinity of different sample configurations. From the measurements, it was found that the viscosity of InxGa1−xSb was between that of InSb and GaSb. The degree of wetting reaction between molten InxGa1−xSb and the C-103 substrate was very high, whereas that between molten InxGa1−xSb and quartz, BN, and graphite substrates was very low. The results suggest that BN and graphite can be used as materials to cover InSb and GaSb samples inside a quartz ampoule during the microgravity experiments. In addition, the difference of the evaporation rate of molten InxGa1−xSb, GaSb, and InSb was small at low, and large at high temperature. 相似文献
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某科研样机采用蒸发管回流燃烧室,其燃烧室结构复杂,燃烧机理和气流流动情况尚不清楚。在实验过程中发现,蒸发管及附近的火焰筒壁面上出现了较严重的积碳现象,影响燃烧室的性能。为了探究该型燃烧室的工作过程、分析积碳现象的原因,采用k-ε湍流模型、旋涡耗散概念燃烧模型(EDC)以及颗粒随机轨道模型对该燃烧室工作流场进行流固热耦合数值计算。结果表明,燃烧室性能参数计算值与台架试车数据较吻合,各项参数相对误差均小于1.7%。计算得到了燃烧室工作时流动和燃烧情况,同时分析出了各气孔流动情况及发挥的作用,并得出了产生积碳现象的原因,为该型燃烧室优化设计提供依据。 相似文献
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In order to accurately predict the heat and mass transfer behaviors and analyze key factors affecting pressurization process in the hydrogen tank, a comprehensive 2 D axial symmetry Volume-Of-Fluid(VOF) model is established by Computational Fluid Dynamics(CFD) method.The effects of phase change, turbulence and mass diffusion are included in the model and relationships between physical properties and temperature are also comprehensively considered. The phase change model is based on Hertz-Knudsen equation and the mass transfer time relaxation factor is determined by the NASA's experimental data. The mass diffusion model is included in gaseous helium pressurizing. The key factors including the inlet temperature, inlet mass flow rate, injector types and pressurizing gas kinds are quantitatively analyzed. Compared with the experiment, the simulation results show that the deviation of pressurizing gas mass consumption, condensing mass and ullage temperature are 3.0%, 7.5% and 4.0% respectively. The temperature stratification is existed along the axial direction in the surface liquid region and the ullage region, and the bulk liquid is in subcooled state during pressurizing. The location of phase change mainly appears near the vapor–liquid interface, and the mass transfer expressing as condensation or vaporization is mainly determined by the heat convection and molecular concentration near the vapor–liquid interface.The key factors show that increasing the inlet temperature and inlet mass flow rate could shorten the pressurizing time interval and save the pressurizing gas mass. The proportion of the total energy addition of the tank absorbed by the ullage region, the liquid region and the tank wall respectively is greatly influenced by the injector types and more heat transferred into the ullage would result in a faster pressure rising rate. Gaseous hydrogen pressurization has a higher efficiency than gaseous helium pressurization. The simulation results presented in this paper can be used as a reference for design optimization of the pressurization systems of cryogenic liquid launch vehicles so as to save the mass of pressurizing gases and shorten the pressurizing time interval. 相似文献
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The occurrence of Lean Blowout(LBO) is a disadvantage that endangers a stable operation of gas turbines. A determination of LBO limits is essential in the design of gas turbine combustors. A semiempirical model is one of the most widely used methods to predict LBO limits.Among the existing semiempirical models for predicting LBO limits, Lefebvre’s LBO model and the Flame Volume(FV) model are particularly suitable for gas turbine combustors. On the basis of Lefebvre’s and FV models, the concept o... 相似文献