Catalytic Cracking and Heat Sink Capacity of Aviation Kerosene Under Supercritical Conditions

Catalytic cracking of China no. 3 aviation kerosene using a zeolite catalyst was investigated under supercritical conditions. A three-stage heating/cracking system was specially designed to be capable of heating 0.8 kg kerosene to a temperature of 1050 K and pressure of 7.0 MPa with maximum mass flow rate of 80 g/s. Sonic nozzles of different diameters were used to calibrate and monitor the mass flow rate of the cracked fuel mixture. With proper experiment arrangements, the mass flow rate per unit throat area of the cracked fuel mixture was found to well correlate with the extent of fuel conversion. The gaseous products obtained from fuel cracking under different conditions were also analyzed using gas chromatography. Composition analysis showed that the average molecular weight of the resulting gaseous products and the fuel mass conversion percentage were a strong function of the fuel temperature and were only slightly affected by the fuel pressure. The fuel conversion was also shown to depend on the fuel residence time in the reactor, as expected. Furthermore, the heat sink levels due to sensible heating and endothermic cracking were determined and compared at varying test conditions. It was found that at a fuel temperature of similar to 1050 K, the total heat sink reached similar to 3.4 MJ/kg, in which chemical heat sink accounted for similar to 1.5 MJ/kg

Thermal cracking of aviation kerosene for scramjet applications

Thermal cracking of China No.3 aviation kerosene was studied experimentally and analytically under supercritical conditions relevant to regenerative cooling system for Mach-6 scramjet applications. A two-stage heated tube system with cracked products collection/analysis was used and it can achieve a fuel temperature range of 700-1100 K, a pressure range of 3.5-4.5 MPa and a residence time of approximately 0.5-1.3 s. Compositions of the cracked gaseous products and mass flow rate of the kerosene flow at varied temperatures and pressures were obtained experimentally. A one-step lumped model was developed with the cracked mixtures grouped into three categories: unreacted kerosene, gaseous products and residuals including liquid products and carbon deposits. Based on the model, fuel conversion on the mass basis, the reaction rate and the residence time were estimated as functions of temperature. Meanwhile, a sonic nozzle was used for the control of the mass flow rate of the cracked kerosene, and correlation of the mass flow rate gives a good agreement with the measurements

Heat Transfer of Aviation Kerosene at Supercritical Conditions

The heat transfer characteristics of China no. 3 kerosene were investigated experimentally and analytically under conditions relevant to a regenerative cooling system for scramjet applications. A test facility developed for the present study can handle kerosene in a temperature range of 300-1000 K, a pressure range of 2.6-5 MPa, and a mass How rate range of 10-100 g/s. In addition, the test section was uniquely designed such that both the wall temperature and the bulk fuel temperature were measured at the same location along the flowpath. The measured temperature distributions were then used to analytically deduce the local heat transfer characteristics. A 10-component kerosene surrogate was proposed and employed to calculate the fuel thermodynamic and transport properties that were required in the heat transfer analysis. Results revealed drastic changes in the fuel flow properties and heat transfer characteristics when kerosene approached its critical state. Convective heat transfer enhancement was also found as kerosene became supercritical. The heat transfer correlation in the relatively low-fuel-temperature region yielded a similar result to other commonly used jet fuels, such as JP-7 and JP-8, at compressed liquid states. In the high-fuel-temperature region, near and beyond the critical temperature, heat transfer enhancement was observed; hence, the associated correlation showed a more significant Reynolds number dependency

腹腔镜技术在肝脏和结、直肠手术中的应用(附20例报告)

目的介绍腹腔镜在肝脏、结直肠手术中的应用。方法腹腔镜下实施肝囊肿开窗术8例,肝腺瘤切除术1例,结直癌切除术11例。结果所有病例顺利恢复,无手术并发症。结论熟练掌握腹腔镜技术,严格选择病例,腹腔镜技术在肝脏、结直肠手术中的早期应用能够达到传统手术的效果

缺陷对陶瓷冷、热冲击热震裂纹扩展的影响研究

陶瓷具有较高的熔点、良好的物理化学稳定性和优异的高温耐腐蚀性,因此广泛的应用在高温环境中。但是其固有的脆性使其容易出现热震损伤,统计表明,工程陶瓷的热震损伤失效超过总失效的1/3。因此,研究陶瓷的热振开裂性能对设计和工程应用都有重要意义。在过去的几十年中,已有许多关于热震开裂的理论研究,但是,这些理论并不能证明实验的整个过程,而只能证明最终结果。为了提高理论计算与实验测量之间的一致性,我们提出了一种可以实时观测整个热震过程的方法,该方法已成功地用于定量研究裂纹扩展

Cracking in the translucent alumina ceramic during flame thermal shock

Crack measurement after thermal shock is usually considered as a replacement because real-time observation of thermal shock experiments is difficult to achieve. This paper presents an experimental approach for real-time displaying thermal shock cracking using oxygen-acetylene flame and high-speed imaging of translucent ceramic. We capture the crack propagation process, calculate the crack propagation speed, discuss the effect of sample size and flame heat flux on the crack propagation, and analyze the difference between the crack propagation under cold shock and hot shock. This paper further improves the mechanism of thermal shock damage of ceramic materials

超临界与热裂解煤油超声速燃烧性能优化研究

本文在马赫数2.5超燃模型燃烧室中研究与比较了室温、超临界态与热裂解煤油的超声速燃烧特性.针对单路燃料喷注燃料当量比的受制于容易引起边界层分离,从而导致燃烧静压向上游迅速传播跑出隔离段这一问题,以超临界态煤油为例,研究与比较了不同的喷油位置及其组合对燃烧室性能的影响,并讨论了相应的燃烧室性能优化方法

瓦面进油对推力轴承承载能力的影响分析

基于FLUENT软件建立了推力轴承瓦面进油的CFD分析模型，分析了瓦面进油槽压力、位置以及宽度对推力轴承承载能力的影响规律。研究表明，合理的瓦面进油设计有利于提高推力轴承的承载能力。当进油槽压力达到一定数值后对油膜压力具有积极的增压作用；进油槽位置应靠近推力瓦入油边侧；进油槽宽度对承载能力的影响很小。研制了采用瓦面进油的某型重载推力轴承装置，开展了性能试验和1 100 h长跑试验，为推力轴承润滑系统的设计提供了参考

伸展机构高低温力学性能测试装置

本发明涉及高低温力学性能测试系统，具体的说是一种在高低温及太空失重环境下，测试大型桁架伸展机构展开性能的伸展机构高低温力学性能测试装置，包括桁架收藏单元、力加载单元、力加载随动单元、力加载传输架体和重力平衡小车，其中力加载单元可移动地安装在所述力加载传输架体上，力加载单元通过力加载随动单元驱动移动，桁架设置于桁架收藏单元上，桁架的自由端与力加载单元相连，所述桁架伸出桁架收藏单元的部分通过重力平衡小车托举支承，力加载单元和重力平衡小车随桁架展开移动，在力加载单元上设有压力传感器、施力弹簧以及测量施力弹簧压缩量的位移传感器。本发明在测试时能够实现主动跟随及主动调节加载力等功能，测试效率高

齿轮箱双支分扭传动系统实现及转子动力学分析

为增加齿轮箱承载能力，提高功率密度，解决齿轮传动中的大功率、大转矩、大传动比问题，设计了齿轮箱双支分扭传动系统。通过人字齿轮实现系统自适应均载分流传动，并通过膜盘挠性联轴器的变形补偿误差解决瞬态偏载问题。利用DyRoBeS软件建立了含有柔性联轴器的双分支分扭传动系统模型，并对系统模型进行转子动力学分析。结果表明，所设计的双分支分扭传动系统能够满足制造要求