Plasma-assisted ignition and combustion

The use of a thermal equilibrium plasma for combustion control dates back more than a hundred years to the advent of internal combustion (IC) engines and spark ignition systems. The same principles are still applied today to achieve high efficiency in various applications. Recently, the potential use of nonequilibrium plasma for ignition and combustion control has garnered increasing interest due to the possibility of plasma-assisted approaches for ignition and flame stabilization. During the past decade, significant progress has been made toward understanding the mechanisms of plasma–chemistry interactions, energy redistribution and the nonequilibrium initiation of combustion. In addition, a wide variety of fuels have been examined using various types of discharge plasmas. Plasma application has been shown to provide additional combustion control, which is necessary for ultra-lean flames, high-speed flows, cold low-pressure conditions of high-altitude gas turbine engine (GTE) relight, detonation initiation in pulsed detonation engines (PDE) and distributed ignition control in homogeneous charge-compression ignition (HCCI) engines, among others. The present paper describes the current understanding of the nonequilibrium excitation of combustible mixtures by electrical discharges and plasma-assisted ignition and combustion.     

9原子荧光法同时测定土壤中的砷、锑

研究了以王水分解样品,硫脲-抗坏血酸作为还原剂,用双道原子荧光光度计断续流动进样方式同时测定土壤中的砷、锑。实验结果表明,砷、锑的检出限分别达到0．8μg/g、0．42μg／g,相对标准偏差分别为2．94％、3．17％;经标准物质验证,测定结果与标准值相符。     

一起空压机未遂事故原因解析与对策

分析解决了空气压缩机因直连拖动同步电动机投励时间滞后引起的启动失败故障,以及设备制造、安装质量造成的运行安全隐患,提出了空压机电气设计、安装与运行安全对策措施。     

汽轮发电机与工厂电网中的无功补偿

汽轮发电机是工厂中常见的利用余热发电的设备,它对工厂电网无功功率的调节有非常重要的意义.文章对无功功率的概念、作用、负面影响和补偿方法进行了简要描述.重点介绍了工厂中汽轮发电机对无功功率调节的原理和方式,并分析了无功功率异常与发电机励磁故障之间的联系.     

基于虚拟同步发电机的逆变电源控制策略研究

针对采用常规下垂控制方法的逆变电源存在稳定时电压和频率的偏移,不能完全满足电网运行要求的问题,采用了一种新的逆变电源控制方法即虚拟同步发电机(VSG)控制策略。建立了虚拟同步发电机的模型,参考同步发电机控制理论,重点设计了功频控制器和励磁控制器,搭建了以大容量汽轮发电机模拟电网的逆变器并网发电系统。通过Matlab/Simulink仿真验证了虚拟同步发电机中转动惯量的作用和虚拟同步发电机的并网调节特性,仿真结果表明,基于虚拟同步发电机的逆变电源在外特性上近似等效为一个同步发电机,具有良好的调频调压性能,能很好地适应电网的运行要求。     

60Hz与50Hz中小型汽轮发电机之比较

阐述了中小型60 Hz空冷汽轮发电机的方案设计,针对30 MW以下的中小型机组,从设计角度与国内50 H z同等容量的产品进行比较,探讨两种频率发电机主要电气性能参数及结构特点的异同。     

一起机组进相试验时失磁保护动作原因分析

通过一起发电机进相试验过程中发生的失磁保护动作事件,详细分析机组失磁保护整定计算过程、机组进相试验工况的确定及校核情况以及试验过程中低励限制参数设置情况,分析出本次失磁保护动作原因:REG126保护说明书中失磁保护整定计算方法有误、试验工况校核过程计算有误以及失磁保护装置本身存在一定误差。最后,为避免发生类似事件,提出防范的技术措施,建议对国外某公司生产的REG126型保护进行全面核查失磁保护定值,并提出进相试验工况失磁保护校核中电压值和裕度设置。     

基于变压器动态非线性模型励磁涌流的研究

基于变压器铁芯拓扑结构建立了电路方程和磁路方程并进行了深入分析,然后将电路方程和磁路方程结合起来,利用Jiles-Atherton铁磁磁滞原理模拟变压器铁芯磁滞特性曲线,建立了计及剩磁的变压器非线性模型。基于所建立的变压器模型研究了在不同剩磁不同合闸角情况下变压器空载合闸的励磁涌流,结果显示了剩磁和合闸角对磁滞曲线和励磁涌流都有很大的影响,磁滞曲线的畸变程度则决定了励磁涌流的大小。     

千兆瓦静态励磁发电机高频轴电流调谐滤波器研究

在大型发电机广泛应用的静态励磁系统晶闸管换相引发幅值较高的高频轴电压脉冲,使得轴电压成为影响大型发电机安全可靠运行的主要问题之一。文章在现场实测1 000 MW发电机轴电压的基础上,建立了基于Matlab Simulink Power System的大型静态励磁发电机轴电压仿真模型,分析得出静态励磁系统输出共模电压基频及其奇次高频谐波轴电压应为大型汽轮发电机轴电压的防治重点,研究提出了一种选择滤除千兆瓦静态励磁发电机高频轴电流的调谐滤波器,仿真表明该滤波器对所选择的高频轴电流滤除效果良好。     

Identification of stiffness and periodic excitation forces of a transverse switching crack in a Laval rotor

This work involves model‐based identification of rotor crack. A Laval rotor with a transverse surface crack and disc unbalance is studied. Viscous damping, disc eccentricity and additive stiffness due to crack are the parameters considered for identification. The linear system equations of motion together with the switching crack excitation function are used for developing the identification algorithm. Furthermore, the algorithm is extended for a novel attempt of estimating the coefficients of switching crack excitation function, which constitute the crack excitation force. This estimation could be used to provide valuable information on the actual opening/closing profile of the switching crack. The proposed algorithms are illustrated through numerical examples. They are tested against measurement noise and found to be reasonably robust.