Investigating core axial power distribution with multiconcentration gadolinium in PWR

Core axial power distribution is an essential topic in pressurized water reactor(PWR)reactivity control.Traditional PWRs limit stability against axial core power oscillations at a high-cycle burnup.Because the‘‘camel’’peak power shape typically occurs with increasing depletion,the approaches used for the axial power control deserve special attention.This study aims to investigate the performance of different gadolinium rod design schemes in core axial power control during power operation based on the reactivity balance strategy,and to propose new multiconcentration gadolinium rod design schemes.In the new design schemes,low-concentration gadolinium pellets are filled in the axial hump part of the gadolinium rod,and high-concentration gadolinium pellets are filled in the other parts.The impact of different gadolinium rod design schemes on the main core characteristics was evaluated using the nuclear design code package PCM developed by CGN.The results show that the new gadolinium rod design significantly impacts the core axial power shape.The new design schemes can efficiently improve the core axial power distribution along the entire cycle by reducing the core axial power peak at the end of a cycle,enhancing the reactor operation stability,and achieving a better core safety margin,revealing a sizeable potential application.

Axial power flow distributions of ultrasonic guided waves in viscous liquid-filled pipes

The axial power flow (APF) magnitude and attenuation distributions of ultrasonic longitudinal guided waves in viscous liquid-filled elastic pipes are investigated. The optimal location, optimal mode and its frequency-thickness product (fd) for the test of pipes filled with viscous liquid are chosen according to APF and attenuation distributions. The results show that the APF magnitude distribution is an important parameter in choosing the modes and parameters. A particular mode has weak dispersion in ranges of fd values with large group velocity, while other modes with smaller group velocity in the same fd ranges have stronger dispersion. It has been observed that, within these ranges, the chosen mode has a larger APF on the (pipe’s) wall. Therefore, in the region of fd values where a particular mode has a large group velocity, this mode will be effective to be used in testing elastic pipes filled with viscous liquid. The results obtained from both the APF analysis and attenuation distribution are consistent.

A Combined-Power Model for the Distribution of Axial Force in Shaft Anchor along Its Length

The theoretical results of axial force distribution models differ greatly from tests because of the complication of the rock type material. A three-parameter combined-power model is proposed by curves fitting the test data recorded from the pull tests on anchoring bars used in different engineering projects. Based on the comparison of the mechanical characteristics of shaft anchors and prestressed tendons, a two-parameter combined-power function model for prestressed tendons is proposed. The bounded length derived from the model and the suggested values of the parameters are also proposed. Compared with the Gaussian model, the three-parameter combined-power model is more precise and simple in expression. Results also suggest that the bounded length calculated from the average stress method is not safe enough.

Optimization of Power Density for Axial-Flux Machinethrough Generalized Sizing Equations

With the cvolution of various high powerr-density machines, it beeomes important to optimize the power potential of machines of vastly different topologies with a variety of waveforms of back emf and current. The approach of tins paper is based oil the gencral-purpose sizing equations. which permit the optinlization method of machine power density to be applied to the axial-flux toroidal permanent-magnet (AFTPM) machine, and,furthermore, the power-production capabilities of the AFTPM machinc and the wen-known squirrel-cage indution machine are compared.

The Tangential Force Distribution on Inner Cylinder of Power Law Fluid Flowing in Eccentric Annuli with the Inner Cylinder Reciprocating Axially

Based on the governing equations of the inner cyinder of the unsteady flow of the power law fluid in eccentric annuli with the inner cylinder reciprocating axially in bipolar coordinate system, the calculation formulae of tangential force were established, and the relevant numerical calculation method was given. Taking the aqueous solution of partially hydrolyzed polyacrylamides (HPAM) for examples, the tangential forces were calculated by using the formulae and numerical calculation method mentioned above;the curves of the tangential force on the wall of the inner cylinder of HPAM aqueous solution were plotted;and the effects on the tangential force of the flow behavior index of the power law fluid, the stroke and the stroke frequency of the inner cylinder were analyzed.

半直驱MW级轴向磁通永磁风力发电机电磁设计与分析

在大功率直驱式风力发电机设计中,针对轴向磁通永磁发电机径向尺寸大、后期维护成本高的问题,文章将轴向磁通永磁发电机设计为大功率半直驱式风力发电机。以2 MW半直驱轴向磁通永磁发电机为研究对象,研究其参数设计原则和方法。通过探究不同极对数对发电机输出性能的影响,确定满足设计目标的发电机优选方案。采用3D有限元分析法对发电机空载和额定负载工况下的气隙磁密、电压、电流波形以及输出功率、损耗和效率进行分析,验证发电机电磁设计的正确性,发电机效率可以达到97.79%,具有损耗小、效率高的优点。通过与现有发电机进行对比,文章所提出的半直驱MW级轴向磁通永磁发电机径向尺寸显著减小,且在轴向尺寸和齿槽转矩方面比现有径向磁通结构的大功率半直驱永磁发电机表现更优。

一种降低燃气轮机试验平台启动系统功率的方法

采用轴流压气机作为负载单元的燃气轮机试验平台,启动系统-负载-燃气轮机之间采用柔性联轴器联接。启动阶段,随着机组转速的提高,轴流压气机的功耗逐渐增大。文章通过对比升速阶段燃气轮机常规启动、变工况启动两种方式对启动系统的功率需求,得出大幅降低启动功率的方式,为以后燃气轮机带负荷试验平台设计提供了参考和经验。

儿童近视发生前后的屈光度和眼生物参数变化:安阳儿童眼病研究

目的分析小学生5年间的屈光度和眼生物参数变化趋势,探讨其在近视发生前后的变化规律。方法采用队列研究方法,以“安阳儿童眼病研究”中的1年级小学生为研究对象,共纳入1986人,其中男生1126人,女生860人,均取右眼数据进行分析。每年采用1%环戊通滴眼液进行睫状肌麻痹后电脑验光获得等效球镜度(SE),采用眼生物测量仪测量眼轴长度(AL)、前房深度、晶状体厚度、平均角膜曲率(Km)等,采用Bennett公式计算晶状体屈光力(LP)。根据随访时近视发生情况将受检者分为持续近视组、非近视组和新发近视组,又根据发病年龄将新发近视组细分为8岁近视组、9岁近视组、10岁近视组、11岁近视组和12岁近视组,比较各组屈光度和眼生物参数在不同随访时间点的差异。结果随着年龄增加,所有儿童的屈光度均逐渐向近视漂移、眼轴逐渐增长,各组内相邻随访年龄间SE和AL比较,差异均有统计学意义(均P<0.05)。在相同随访年龄下,近视发生越早,其近视屈光度数越高,AL越长;各相邻组间SE比较差异均有统计学意义(均P<0.05);8~12岁随访年龄下各相邻组间AL比较,差异均有统计学意义(均P<0.05)。在非近视组,屈光度以缓慢均匀的速度向正视漂移,5年平均SE变化速度为(-0.23±0.27)D/年,AL亦缓慢均匀增长,5年平均增长速度为(0.18±0.13)mm/年;在新发近视组中,近视发生前第3年、第2年和第1年的SE年变化量分别为(-0.32±0.25)、(-0.45±0.33)和(-0.98±0.44)D,AL年增长量分别为(0.25±0.12)、(0.32±0.15)和(0.48±0.19)mm,SE和AL变化速度均在近视发生前开始加快,并于近视发生后变缓,各近视前后不同时间段SE和AL变化速度总体比较差异均有统计学意义(均P<0.001)。新发近视组中发生近视时男生的AL为(24.11±0.70)mm,明显长于女生的(23.60±0.66)mm,差异有统计学意义(t=159.71,P<0.001)。LP随年龄增加而下降,9岁前下降速度较快,9岁后下降速度变缓。持续近视组和8~11岁近视组的LP平均下降速度分别为(-0.48±0.19)、(-0.44±0.20)、(-0.49±0.16)、(-0.51±0.18)、(-0.48±0.19)D/年,明显快于12岁近视组的(-0.42±0.17)D/年和非近视组的(-0.37±0.15)D/年,差异均有统计学意义(均P<0.05)。各组不同随访年龄Km比较差异均无统计学意义(均P>0.05)。结论AL在儿童近视发生的前3年内开始加速增长,在近视发生后增长速度逐渐变缓,但仍明显快于非近视儿童;在此过程中,LP下降起到一定的代偿作用,Km无显著变化。相同年龄下男生发生近视时的AL比女生长。AL是近视防控的重要指标,评估时要考虑性别差异,更要关注AL的增长速度。

基于两点模型的堆芯功率多目标保性能控制

现阶段能源产业需要核电站能够根据实际功率需求对输出功率进行调整,因此压水堆堆芯负荷跟踪运行是现阶段压水堆商业化运行的重要需求之一.为了避免运行过程中由于堆芯功率分布不均匀导致的氙震荡、热点等问题,对堆芯运行过程中产生的轴向功率偏差进行控制也是压水堆安全运行的关键.基于中子动力学方程、反应性反馈方程和热工水力学方程,结合堆芯功率空间耦合构建了压水堆堆芯功率两节点模型,并在这一模型的基础上增加负荷跟踪和轴向功率偏差跟踪量.根据这一模型设计了能够实现负荷跟踪控制和轴向功率分布控制并且具有抗时变性的LPV-LQR多目标控制器.在经典的多个瞬态工况下进行仿真的结果表明,LPV-LQR控制器具有良好的负荷跟踪控制和轴向功率分布控制能力,并且能够更好适应堆芯功率系统的时变性.

多轴平稳非高斯随机振动试验控制方法

多轴向平稳非高斯随机振动控制试验能够对指定响应信号的时、频域特征进行同时控制。提出了一种快速生成具有指定功率谱密度、斜度和峭度的平稳非高斯随机振动信号的方法。通过频率采样方法将目标功率谱密度设计成滤波器,利用非线性变换方法获取非高斯随机信号,再将此信号经过设计的滤波器以获得满足要求的非高斯随机信号。该方法简单、快速并克服了传统非线性变换方法的缺点。进一步将此方法应用于三轴向平稳非高斯随机振动试验中,给出了三轴向非高斯随机振动控制的闭环均衡步骤,此方法能够同时对信号的功率谱自谱、相干系数、相位差以及斜度和峭度进行解耦控制。进行了三轴向平稳非高斯随机振动控制试验,三个方向上加速度信号的功率谱密度、斜度和峭度控制效果均令人满意,满足工程应用要求。

基于变流速的活动扩张角导流装置性能研究

针对导流装置型水轮机在高流速条件下叶片承受过大轴向力的问题,提出了一种自适应流速变化的导流装置解决方案。该装置能够在低流速区间保持相对稳定的增速比,而在高流速区间通过调整增速比来减轻叶片负载,提高水轮机在低流速环境下的功率输出。通过数值分析,以增速比作为评估指标,研究了扩张角的调整范围、活动装置的长度和形状,并分析了不同流速条件下的长短轴比例、水轮机所受推力及获能情况。研究结果表明:使用翼型活动装置,保持其长宽比为1.5,扩张角调整范围为0~15°,增速比的调整范围为1.10~1.57;当活动装置的长短轴比例为3.4∶1时,在高速流场中叶片相对受力可降至1.1左右,同时在低流速区域具有较好的能量转换效率。

大型管磨机驱动装置的选择及优缺点分析

大型管磨机本体及研磨体载荷大,磨机功率高,当其驱动装置采用行星减速机和齿形联轴器配合的中心传动方式时,会产生较大的轴向力,影响磨机的稳定可靠运行。分析对比了大型管磨机驱动装置采用中心传动、单边缘传动、单边缘双传动、双边缘传动、多点边缘传动等传动方式的工艺特点。以某项目ϕ5.2m大型水泥管磨机2×4000kW双边缘传动系统为例,介绍了主电机、减速机、大齿圈和小齿轮的选型设计计算及双边缘传动系统的实际应用情况。生产实践表明,大型管磨机选择双边缘传动方式安装方便、成本低、传动功率大、运行稳定可靠,是优选方案。

一种高性能功率放大器-圆极化天线的一体化设计

本文设计了一种具有圆极化辐射特性的高性能功率放大器-天线一体化电路。通过直接优化圆极化天线的输入阻抗,使之与消除输出匹配网络的功放电路直接集成。这种无缝集成方式不仅有效减少了插入和失配损耗以及整体电路尺寸,而且提高了整体的性能。采用的圆极化天线由矩形贴片和改进的地平面组成,通过在地平面上增加垂直短截线和切割水平缝隙,增强了天线的3 dB轴比带宽。为了验证,设计、制造和测量了工作在3.4 GHz~3.6 GHz的一体化电路原型。实验结果显示,功放-圆极化天线一体化电路在工作频带内的功率附加效率(PAE)超过60%,且3 dB轴比带宽达到320 MHz(相对于3500 MHz的中心频率为9.1%)。相较于传统的级联设计,PAE提高了8.5%,3 dB轴比带宽也得以改善。

110 kV单芯电缆中间接头温度轴向感知模型的材料参数敏感性

高压电缆中间接头热点温度的实时感知对电缆安全运行及动态载流能力评估具有重要意义。以110 kV单芯电缆中间接头为研究对象,构建规则化中间接头温度场仿真模型及其有限元离散边界,建立基于热流等效的结构简化方法,采用单因子变化与正交组合方式分析材料参数分散性对中间接头温度轴向感知模型的拟合度及灵敏度的影响。研究表明,提出的规则化简化建模方法适用于不同型号与结构的中间接头温度轴向感知模型,对于结构、材料及现场工艺分散性具有较好的鲁棒性。

Enhancement of Wind Energy Conversion Using Axial Flux Generator

This paper investigates the application of the axial flux machine (AFM) to the wind energy conversion systems (WECS) to obtain high power and torque at reduced cost. By developing mathematical equations using the phase and active transformations, the three-phase model is transformed to two-phase equations by making both the stator and rotor as reference frames, finally converting to arbitrary reference frame, which is useful for the modelling of the axial flux machine. The torque, current, and voltage equations are expressed to improve the simulation reliability. Based on the developed equations, the mathematical model for the axial flux machine is developed using the MATLAB/Simulink. Starting with the axial flux motor model, when the load on the motor increases, how the parameters like torque, current, and speed of the motor vary are explored in this paper. Then for the axial flux generator model, when the wind speed exceeds the rated speed how the torque, line voltages, currents, power and speed of the generator behave are investigated and presented in this paper. The developed model in this paper could be extended to a twin-rotor axial flux synchronous machine, which will lead to the development of more efficient WECS.

Modulation of absorption manner in helicon discharges by changing profile of low axial magnetic field

The modulation of absorption manner in helicon discharge by changing the profile of low axial magnetic field is explored experimentally in this work. The experiments are carried out in Boswell-type antenna driven by 13.56-MHz power source in 0.35-Pa argon environment. The peak of the external non-uniform magnetic field （Bex） along the axis is observed in a range from 0 Gs to 250 Gs （1 Gs=10^-4 T）, where the electron density varies from 0.5×10^16 m^-3 to 9×10^16 m^-3. When Bex is located near the tube upper end sealed by a dielectric plate, or near the tube bottom end connected with a diffusion chamber, the plasmas are centralized in the tube in the former case while the strong luminance appears between the edge of the tube and the axial line in the latter case. When Bex is located in the middle of the antenna, moreover, an effective resistance （Reff） peak appears apparently with increasing magnetic field. The glow moves toward first the edge of the tube and then the two antenna legs as the magnetic field increases. The discharge in this case is caused by the absorption of Trivelpiece-Gould （TG） wave. It is suggested that Bex is located in the middle of the antenna to obtain a higher efficiency of power transfer.

Novel transit-time oscillator(TTO) combining advantages of radial-line and axial TTO

A novel transit-time oscillator(TTO)is proposed in this paper.An axial cathode which has been widely used in high power microwave(HPM)source and an extractor with radial feature are adopted.In this way,the inherent advantages of axial and radial TTO,both of which can be utilized as high-quality intense relativistic electron beam(IREB),can be generated and the power capacity is also increased.The working mode isπ/2 mode of TM01 based on small-signal theory,and under the same energy storage,the maximum electric field in extractor decreases 16.3%.Besides,by utilizing the natural bending of the solenoid,this TTO saves over 60%of the length required by the uniform magnetic field,and consequently reduces the energy consumed by solenoid.The PIC simulation shows that by using 1.0-T decreasing magnetic field generated by the shorter solenoid,3.37-GW microwave at 12.43 GHz is generated with 620-kV and 13.27-kA input,and the overall conversion efficiency is 41%.

压水堆中环形轴向非均匀MA嬗变棒的中子学性能研究

为提高次锕系核素(Minor Actinides,MA)在压水堆中的嬗变效率,同时利用MA核素展平堆芯轴向功率分布,研究工作以177压水堆堆芯结构作为参考,利用蒙特拉洛程序RMC计算研究环形轴向非均匀MA嬗变棒的中子学性能。嬗变棒为中空的环形结构,嬗变材料为MA与UO2的均匀混合物,其中MA质量份额为1 wt%、3wt%以及5 wt%,MA核素在嬗变棒上沿轴向进行非均匀填充,分别开展了三、五、七段式嬗变棒的中子学性能研究。研究结果发现:(1)该嬗变棒具有优良的嬗变性能,当环形嬗变材料厚度的2 mm时,轴向分5段的环形轴向非均匀嬗变棒的嬗变率最高,可达64.55%;(2)相较于环形轴向均匀嬗变棒,该环形轴向非均匀嬗变棒具有良好的轴向功率展平效果,可将轴向功率峰因子由1.778降低至1.390;(3)压水堆堆芯装载MA嬗变棒后,可显著优化堆芯在高硼浓度下的慢化剂温度反应性效应,使堆芯在1300×10^(-6)的硼浓度下依然具有负的温度效应。

基于Simscape的APA-EPS系统建模及人机共驾转向控制策略研究

人机共驾是智能车辆实现高度自动驾驶之前的过渡阶段,由于驾驶员与驾驶辅助系统同时在环,存在驾驶权分配的问题,智能车辆的转向系统必须实时敏捷地执行驾驶员和驾驶辅助系统的转向控制指令。本文针对搭载于某智能MPV的平行轴式电动助力转向系统(APA-EPS)研究人机共驾转向控制策略。首先对APA-EPS系统进行Simscape建模,并通过台架试验验证了模型的准确度。随后基于模糊PID控制算法和模糊滑模控制算法分别设计了人驾和机驾模式下的控制策略。在驾驶员主导驾驶车辆时,根据距离影响度函数和角度影响度函数确定转向控制权重;在驾驶辅助系统主导驾驶车辆时,采用滑动时间窗口监测驾驶员的接管请求。仿真试验结果表明,人驾和机驾的控制策略均具有较好的转角跟随效果,人机共驾时转向控制权能够及时进行切换,且APA-EPS的转向盘转角响应迅速。