Combustion and Ignition of Thermally Cracked Kerosene in Supersonic Model Combustors

A series of experiments were conducted to characterize the self-ignition and combustion of thermally cracked kerosene in both a Mach 2.5 model combustor with a combustor entrance height of 51 mm and a Mach 3.0 model combustor with an entrance height of 70 mm. A unique kerosene heating and delivery system was developed, which can prepare heated kerosene up to 950 K at a pressure of 5.5 MPa with negligible fuel coking. The extent of China no. 3 kerosene conversion under supercritical conditions was measured using a specially designed system. The compositions of gaseous products as a result of thermal cracking were analyzed using gas chromatography. The mass flow rates of cracked kerosene were also calibrated and measured using sonic nozzles. With the injection of thermally cracked kerosene, the ability to achieve enhanced combustion performance was demonstrated under a variety of airflow and fuel conditions. Furthermore, self-ignition tests of cracked kerosene in a Mach 2.5 model combustor over a range of fuel injection conditions and with the help of different amounts of pilot hydrogen were conducted and discussed.

20～21世纪的力学

<正> 一、力学发展的趋势 1.20世纪力学的巨大成就 本世纪初边界层理论的提出,对力学的发展起了划时代的作用。从此,流体力学能够成功地解释流动对物体的阻力与升力,为航空、航天的发展奠定了科学基础。这个典型也影响与推动了其他力学分支的发展,使力学研究的内涵有了空前的充实、扩大与深化。早在20年代初便形成了活跃于整个20世纪内容广泛的应用力学,成为工程与应用科学的支柱。人们把空气动力学的研究看作是本世纪以科学为基础将航

电液伺服材料试验机的动力学响应特性研究

对MTS810电液伺服材料试验机在位移控制和载荷控制两种控制方式下的动力学响应特性进行了研究。以岩石压缩测试数据为例,对载荷-时间曲线、位移-时间曲线进行了对比分析,发现岩石破坏过程中,位移控制方式下可以观察到岩石的局部损伤至破坏的演化过程,载荷在岩石破坏时刻突然降为0;而载荷控制方式下看不到损伤演化过程,载荷未突然降为0。说明试验机本身的结构响应会影响对试样力学性能的测试。

Pressure Drop Studies of Gas-Liquid Bubbly Flow in Vertical Upward Pipeline

This paper describes the experimental and theoretical studies of gas-liquid bubbly flow in vertical upward pipeline carried out at Institute of Mechanics, Chinese Academy of Sciences. Bubbly flow in a vertical pipe with a 3 m long and 5 cm inner diameter plexiglass pipe was experimentally investigated, and studies carried out on the relationship between superficial velocities of the liquid and gas phases and pressure gradient is described. The developed drift-flux model applied to gas-liquid bubbly flow is presented, and the results are compared against the experimental data measured by ours in air/water vertical pipes.

Pipeline Corrosion Analyzed by Fuzzy Reliability Methods

Fuzzy reliability methods are used to study the corrosion of pipelines. Three methods are used. They consist of using fracture failure modes, failure assessment diagram (FAD) and residual strength for establishing fuzzy reliability. Calculations are made by application of JC, improved GA-JC and Mente-carlo methods. Examples for oilfield injecting water pipeline show the residual strength well agree with field data. Mente-carlo methods appear to yield results that have better agreement with field data.

High-Strength Composite Fibers: Realizing True Potential of Carbon Nanotubes in Polymer Matrix through Continuous Reticulate Architecture and Molecular Level Couplings

Carbon nanotubes have unprecedented mechanical properties as defect-free nanoscale building blocks, but their potential has not been fully realized in composite materials due to weakness at the interfaces. Here we demonstrate that through load-transfer-favored three-dimensional architecture and molecular level couplings with polymer chains, true potential of CNTs can be realized in composites as Initially envisioned. Composite fibers with reticulate nanotube architectures show order of magnitude improvement in strength compared to randomly dispersed short CNT reinforced composites reported before. The molecular level couplings between nanotubes and polymer chains results in drastic differences in the properties of thermoset and thermoplastic composite fibers, which indicate that conventional macroscopic composite theory falls to explain the overall hybrid behavior at nanoscale.

紧聚焦的超短超强激光脉冲在真空中加速斜入射的相对论电子

研究了紧聚焦的线偏振飞秒超强高斯激光脉冲俘获并剧烈加速斜入射低能相对论电子的效应，发现被俘获的电子在激光脉冲纵向有质动力的强大加速作用下，可以获得GeV量级的能量，并详细研究了入射电子的初能量、斜入射角、电子与激光脉冲的相对延迟时间和激光脉冲宽度等条件对电子能量增益的影响，发现当激光脉宽超过10λ时，脉宽对电子能量增益影响不大．

7.3 W国产单频光纤放大器

报道了一种MOPA式国产单频光纤放大器。该放大器采用连续波单频激光器作为主振荡器，采用我国自行设计和制造的大模场面积掺Yb双包层光纤作为功率放大器，在波长1064 nm处实现了最高7.3 W的连续激光输出，斜率效率为39%，光－光转换效率为26%。此外，对光谱特性及放大的自发发射的抑制也进行了探讨。

Propagation of flat-topped beams

The propagation of flat-topped beams passing through paraxial ABCD optical system is investigated based on the propagation formulas of Gaussian beam. The focal shift of focused coherent flat-topped beam is also studied in detail. Analytical expressions of the M-2 factor and the far-field intensity distribution for flat-topped beams are derived on the basis of second-order moments. (C) 2007 Elsevier Ltd. All rights reserved.