汽轮机组振动信号的测量与分析

针对目前汽轮机组振动的特点,将振动信号分为两类,即轴振（相对振动）和瓦振（绝对振动）。首先分析了汽轮机组的振动概况及其对机组的影响;然后分别介绍了机组振动的测量和分析方法。具体地从传感器谈起,解释了机组的轴振和瓦振的不同测量原理。针对振动的三要素即振幅、频率及相位分别做了介绍;最后以300MW机组为例,说明其振动测点的一般布置。     

可重构振荡器与双频滤波器的协同设计

实现了一种可重构振荡器与双频率滤波器的协同设计模块。振荡器通过开关二极管的通断来实现频率的可重构,工作频率分别为1.1 GHz和2.0 GHz。与双频滤波器协同设计后,振荡器在两个频率上频偏1 MHz的相位噪声分别从-109.1 dBc/Hz和-112.9 dBc/Hz改善为-125.6 dBc/Hz和-127.9 dBc/Hz,二次谐波抑制分别由协同设计之前的-25 dB和-10 dB改善为-44 dB和-55 dB。     

基于ADF4360-8的频率合成系统

用ADF4360-8和AD8343芯片作为变频核心器件,将70MHz信号转变为具有频率稳定、波形完整的11.4MHz中频信号。实验证明,该方案设计对接收机的稳定工作起到重要的作用,变频系统具有结构简单、操作方便、稳定性高等特点。     

Tuning of multi-loop PI controllers based on gain and phase margin specifications

In this paper, a single-iteration strategy is proposed for the design of a multi-loop PI controller to achieve the desired gain and phase margins for two-input and two-output (TITO) processes. To handle loop interactions, a TITO system is converted into two equivalent single loops with uncertainties drawn from interactions. The maximum uncertainty is estimated for the initial controller design in one loop and single-input and single-output (SISO) controller design is applied. This controller is substituted to other equivalent loop for design, and finally, the first loop controller is refined on knowledge of other loop controller. For SISO controller tuning, a new method is presented to determine the achievable gain and phase margins as well as the relevant controller parameters. Examples are given for illustration and comparison.     

Adjustment of drag coefficient correlations in three dimensional CFD simulation of gas-solid bubbling fluidized bed

Fluidized beds have been widely used in power generation and in chemical, biochemical, and petroleum industries. 3D simulation of commercial scale fluidized beds has been computationally impractical due to the required memory and processor speeds. In this study, 3D Computational Fluid Dynamics simulation of a gas-solid bubbling fluidized bed is performed to investigate the effect of using different inter-phase drag models. The drag correlations of Richardon and Zaki, Wen-Yu, Gibilaro, Gidaspow, Syamlal-O’Brien, Arastoopour, RUC, Di Felice, Hill Koch Ladd, Zhang and Reese, and adjusted Syamlal are reviewed using a multiphase Eulerian-Eulerian model to simulate the momentum transfer between phases. Furthermore, a method has been proposed to adjust the Di Felice drag model in a three dimensional domain based on the experimental value of minimum fluidization velocity as a calibration point. Comparisons are made with both a 2D Cartesian simulation and experimental data. The experiments are performed on a Plexiglas rectangular fluidized bed consisting of spherical glass beads and ambient air as the gas phase. Comparisons were made based on solid volume fractions, expansion height, and pressure drop inside the fluidized bed at different superficial gas velocities. The results of the proposed drag model were found to agree well with experimental data. The effect of restitution coefficient on three dimensional prediction of bed height is also investigated and an optimum value of restitution coefficient for modeling fluidized beds in a bubbling regime has been proposed. Finally sensitivity analysis is performed on the grid interval size to obtain an optimum mesh size with the objective of accuracy and time efficiency.     

Use of chemical potential of a compound in potential phase diagrams

Potential phase diagrams, where the chemical potential of a compound is used as an axis, do not obey the usual rules for potential phase diagrams. Examples are presented in order to help the interpretation of such diagrams. The thermodynamic background of the special properties is examined.     

非线性电路的簇发现象及分岔机制

通过在立方非线性Hartley模型中引入交变的电流源,并选定适当的参数和激励频率,建立了具有快慢行为的两时间尺度周期激励电路系统．由Hopf分岔的产生条件,推导了对应自治系统Hopf分岔的第一Lyapunov系数解析表达式,并在数值计算中得到了验证．结合该系数,重点分析了系统中的快慢行为,给出了典型的周期簇发现象及其相应的分岔模式,并利用自治系统和转换相图从分岔角度指出了该种簇发现象的产生机理．     

基于TS201系列DSP的PGA算法实现

相位梯度自聚焦(PGA)算法被广泛用于机载合成孔径雷达(SAR)成像中.由于其过程复杂,数据处理量大,为满足机载SAR实时处理的要求,选用具有强大处理能力的TS201 DSP.为了充分发挥TS201的性能,利用PGA原理和TS201处理器的特点,对算法流程进行优化,并且对最耗时的FFT采用了汇编语言实现,使得运算量和处...     

窄带同步相位检测在商品电子防窃系统中的应用

给出了一种基于同步相位窄带检测电路实现的EAS系统检测器,并给出了原理和实现方法。