用于激光诱导等离子体点火技术的激光源研究进展

激光诱导等离子体点火是一种新颖的发动机点火方式,这种技术点火位置精确可控,点火延迟时间短,无烧蚀作用,还可实现同时多点点火,能够提高发动机的燃烧效率,具有良好的发展前景。主要针对用于激光诱导等离子体点火技术中的核心元件激光光源的发展状况及最新成果作了全面的综述,并对该种类型激光器的发展前景进行了展望。     

激光点火与其他点火方式在火炮中的分析研究

激光点火作为一种技术,已广泛实验应用于多个领域。激光点火应用于火炮发射技术,是对常规底部底火点火方式的革新。除激光点火方式外,还有等离子体点火方式以及场畸变点火方式等。介绍了各种点火方式的系统组成、实验结果,说明激光点火技术的可靠性和良好的弹道性能,以及激光点火、等离子体点火、场畸变点火及其组合技术在火炮发射中应用的可行性。     

激光等离子体和烧蚀对含能材料的激光点火过程的影响

通过测试激光点火的延迟时间、等离子体电荷通量和等离子体对激光的吸收能力，研究了激光等离子体和烧蚀对激光点火过程的影响。实验采用的含能材料为B／KNO3(m(B)：m(KNO3)=40：60)，外加5％的酚醛树脂，激光器为脉冲宽度为680μs的Nd：YAG固体激光器。实验结果表明等离子体密度随激光能量的提高而增大，而且激光等离子体的电荷通量大于燃烧流的电荷通量。当激光能量密度低于某一临界值时，点火延迟时间随激光能量密度的提高而线性变短，然而激光能量密度超过该临界值后，激光点火延迟时间保持恒定。在实验条件下，激光等离子体几乎不吸收入射的激光能量，但是点火延迟时间的变化规律表明了烧蚀会阻碍激光能量向含能材料注入。     

汽车发动机点火性能测试仪设计

点火系统是汽车发动机的核心部件,其工作性能直接影响汽车的动力性、燃油消耗量和尾气排放指标。点火提前角是点火系统的关键参数之一,通过对点火提前角的精确调整,能使发劝机的动力性及经济性达到最佳状态。本文介绍了汽车发动机点火性能测试仪的设计与实现,该测试仪通过测量发动机闭合角和分火角角度,分析发动机分电器和点火器性能,为调整高效的点火提前角提供关键依据。     

激光对含能材料作用特性分析

从激光特性、光的波粒二象性出发，分析了激光对含能材料的热作用、冲击作用、光化学作用、电离作用等，并做了相应的计算。对含能材料激光点火的机理作了概括。结论：通常情况下，热作用是主要的；光化学作用对激光波长有很强的选择性；电离与等离子体点火要求激光强度远大于10^10W/cm^2；临界点能量随激光强度的增大而减小。     

一种汽车发动机微波点火器的仿真研究

简要介绍了微波点火技术,对四分之一波长同轴谐振腔点火器的发展进行了概述。采用三维电磁仿真软件HFSS模拟了内导体对称环结构的耦合方式。在输入功率为400W时,内导体的顶部电场强度可达到2．3×10^7V／m左右,满足汽车发动机在高达1×10^6Pa气压下激发等离子体火焰的门限条件2．25×10^7V／m。     

半导体桥(SCB)的研究

目前常用的点火器Ｎｉ－Ｃｒ金属桥丝（热桥丝）体积较大，点火能量高（几十毫焦），作用时间长（几毫秒），且易误触发．本文中采用半导体器件和集成电路技术研制的新一代点火器——半导体桥（ＳＣＢ）体积小（为热桥丝三十分之一），结构上兼有Ｓｉ桥区倒圆点和Ｔｉ、Ａｌ金属导体倒圆点两大特点，其点火临界能量可降低到３～５ｍＪ，作用时间可缩短到５μｓ，从而能快速产生热等离子体来引爆猛炸药．同时，ＳＣＢ还具有较高的可靠性和安全性，其安全电流大于１．５Ａ．本文分析了ＳＣＢ工作原理，并研究了ＳＣＢ的结构对临界能量、点火作用时间、     

基于被动调Q固体激光器的激光点火系统的研究进展

稀薄燃烧是一种先进的燃烧方法,采用稀薄燃烧技术可以使发动机在减少废气排放的同时提高热效率。稀薄燃烧催发了激光点火技术的应用。最近几十年,脉冲宽度短、峰值功率高的被动调Q固体激光器得到了飞速的发展,特别是采用掺钕离子(Nd3+)和镱离子(Yb3+)的激光材料作为激光增益介质,用Cr4+∶YAG作为被动调Q开关的微片固体激光器在激光点火研究方面取得了长足的进展。系统地介绍了激光点火的机理和应用于激光点火的基于Nd∶YAG/Cr4+∶YAG与Yb∶YAG/Cr4+∶YAG的被动调Q固体激光器的最新研究进展,以及两类被动调Q激光器在激光点火应用中的优缺点,并指出了Yb∶YAG/Cr4+∶YAG被动调Q微片激光器在激光点火应用中的优势、需解决的问题及发展方向。     

激光二极管点火系统的设计

介绍了一种基于高功率激光二极管的激光点火系统的设计,该系统对传统激光点火系统中的光路自检功能进行了改进.在保证检测安全性的前提下提高了检测的有效性,可供武器、航空航天系统等高可靠应用系统借鉴.     

一种新型的汽车发动机微波点火器

文中设计了一种新型的同轴线谐振腔微波点火器,谐振频率为2.45 GHz.应用于汽车发动机点火,替代传统的火花塞.该设计基于四分之一波长同轴谐振腔理论,谐振腔为一端短路另一端开路的同轴线构成,内导体由两段不同直径的铜圆柱构成.通过三维电磁仿真软件HFSS得到：在输入功率为500W时,内导体的顶部电场强度可达到2.4×107v/m左右,满足汽车发动机高压下形成等离子体的门限条件-2.25×107 v/m,达到点火效果.     

低截获概率火控系统的设计

反辐射导弹技术的快速发展,给防空系统中的各种辐射源造成极大的威胁,火控系统采用低截获概率技术可以极大的提高武器系统的作战有效性和生存能力.该文论述低截获概率的原理和关键技术,探讨了一种新型火控系统的低截获概率设计方法.     

激光技术在航天航空推进系统中的应用

激光技术是第三次科技革命的标志之一,在各个方面得到广泛应用.其中激光在推进系统中的应用日益突出,引起了广泛关注.本文主要介绍激光在推进系统中的主要应用一激光推进技术,激光控制燃烧技术和激光点火技术的基本原理、应用现状及研究方向.     

MEMS: the path to large optical crossconnects

Continuous growth in demand for optical network capacity and the sudden maturation of WDM technologies have fueled the development of long-haul optical network systems that transport tens to hundreds of wavelengths per fiber, with each wavelength modulated at 10 Gb/s or more. Micro-electromechanical systems devices are recognized to be the enabling technologies to build the next-generation cost-effective and reliable high-capacity optical crossconnects. While the promises of automatically reconfigurable networks and bit-rate-independent photonic switching are bright, the endeavor to develop a high-port-count MEMS-based OXC involves overcoming challenges in MEMS design and fabrication, optical packaging, and mirror control. Due to the interdependence of many design parameters, manufacturing tolerances, and performance requirements, careful trade-offs must be made in MEMS device design as well as system design. We provide an overview of the market demand, various design trade-offs, and multidisciplinary system considerations for building reliable and manufacturable large MEMS-based OXCs     

Diagnosis from within the system [built-in test]

There has been an increasing need for technologies to better monitor the condition of their complex products and systems from the design stage, through manufacturing, to their applications. Better condition monitoring enables better quality control, which is essential for economical, environmental, availability, and safety reasons. One way to achieve such a goal is using built-in-test (BIT), which incorporates test and diagnostic functionality into a component's structure at the design stage. A system with BIT is characterized by the ability to identify operational conditions by itself, through the built-in diagnostic capabilities. Such a design philosophy has been widely applied to the design and testing of complex, mixed-signal electronic systems, such as ICs and multifunction instrumentation. Various techniques have been developed over the past three decades to implement BIT in industry, especially in semiconductors, manufacturing processes, aerospace, and transportation (Bardell and Mcanney, 1988; Baker et al., 1990; Cox et al., 1999). This article looks at BIT implementation in the IC industry, manufacturing, and the automobile industry, along with the future prospects of this technique     

Propulsion system design of electric and hybrid vehicles

There is a growing interest in electric and hybrid-electric vehicles due to environmental concerns. Efforts are directed toward developing an improved propulsion system for electric and hybrid-electric vehicles applications. This paper is aimed at developing the system design philosophies of electric and hybrid vehicle propulsion systems. The vehicles' dynamics are studied in an attempt to find an optimal torque-speed profile for the electric propulsion system. This study reveals that the vehicles' operational constraints, such as initial acceleration and grade, can be met with minimum power rating if the power train can be operated mostly in the constant power region. Several examples are presented to demonstrate the importance of the constant power operation. Operation of several candidate motors in the constant power region are also examined. Their behaviors are compared and conclusions are made     

Multiphase Power Converter Drive for Fault-Tolerant Machine Development in Aerospace Applications

This paper describes an experimental tool to evaluate and support the development of fault-tolerant machines designed for aerospace motor drives. Aerospace applications involve essentially safety-critical systems which should be able to overcome hardware or software faults and therefore need to be fault tolerant. A way of achieving this is to introduce variable degrees of redundancy into the system by duplicating one or all of the operations within the system itself. Looking at motor drives, multiphase machines, such as multiphase brushless dc machines, are considered to be good candidates in the design of fault-tolerant aerospace motor drives. This paper introduces a multiphase two-level inverter using a flexible and reliable field-programmable gate-array/digital-signal-processor controller for data acquisition, motor control, and fault monitoring to study the fault tolerance of such systems.      

Efficient Drive Cycle Simulation

Drive cycle simulations of longitudinal vehicle models are important aids for the design and analysis of power trains, and tools currently on the market mainly use two different methods for such simulations: the forward dynamic and quasi-static inverse simulations. Here, a known theory for the stable inversion of nonlinear systems is used to combine the fast simulation times of the quasi-static inverse simulation with the ability of the forward dynamic simulation to include transient dynamics. The stable inversion technique and a new implicit driver model together form a new concept: inverse dynamic simulation. This technique is demonstrated to be feasible for vehicle propulsion simulation and specifically for three power train applications that include important dynamics that cannot be handled using quasi-static inverse simulation. The extensions are engine dynamics, driveline dynamics, and gas flow dynamics for diesel engines, which are also selected to represent important properties, such as zero dynamics, resonances, and nonminimum-phase systems. It is shown that inverse dynamic simulation is easy to set up, gives short simulation times, and gives consistent results for design space exploration. This makes inverse dynamic simulation a suitable method to use for drive cycle simulation, particularly in situations requiring many simulations, such as optimization over design space, power train configuration optimization, or the development of power train control strategies.     

水滴激光辐照效应研究现状

受《水滴烧蚀激光推进性能测试[1],一文的启发,以激光与水滴相互作用在激光推进中的应用为背景,报道了国际领域内激光与水滴相互作用的实验和理论研究情况.指出了目前研究工作中存在的一些不足.为我国相关领域的研究提供了比较丰富的第一手参考资料.探讨了水滴烧蚀模式激光推进研究的广阔应用前景.     

基于红外信标网络的无线智能导游系统的设计

提出了一种新颖的红外无线智能导游系统的设计方案。基于当前先进的信标网络技术及手持移动计算技术,采用信标网络中的不同节点的红外信标信号自动选通游客手中的便携式信息终端设备,使之成为视听一体化移动的可随机点播的多媒体平台,同步提供可选的多语种语音讲解、视频播放及帮助信息功能,实现一种便携的无线智能嵌入式多媒体导游系统。介绍了总体的设计思想及系统的软硬件构成。上海科技馆、江苏周庄等地的应用实践表明,该装置稳定可靠,使用效果和社会反响良好.     

单脉冲雷达目标RCS特性测量技术研究

目前,雷达目标特性测量作为航天测控领域的一项新技术在雷达设计过程中得到广泛的应用。文中以一种单脉冲雷达散射截面(RCS)测量系统设计为背景,介绍了RCS概念及测量原理,重点从硬件设计方面阐述了RCS测量的关键技术及相关理论。从实际测量数据结果分析证明该系统具有较高的可靠性和数据获取能力,可在类似的产品设计中推广应用。