Equivalent low-order angular flux nonlinear finite difference equation of MOC transport calculation

The key issue in accelerating method of characteristics(MOC)transport calculations is in obtaining a completely equivalent low-order neutron transport or diffusion equation.Herein,an equivalent low-order angular flux nonlinear finite difference equation is proposed for MOC transport calculations.This method comprises three essential features:(1)the even parity discrete ordinates method is used to build a low-order angular flux nonlinear finite difference equation,and different boundary condition treatments are proposed;(2)two new defined factors,i.e.,the even parity discontinuity factor and odd parity discontinuity factor,are strictly defined to achieve equivalence between the low-order angular flux nonlinear finite difference method and MOC transport calculation;(3)the energy group and angle are decoupled to construct a symmetric linear system that is much easier to solve.The equivalence of this low-order angular flux nonlinear finite difference equation is analyzed for two-dimensional(2D)pin,2D assembly,and 2D C5G7 benchmark problems.Numerical results demonstrate that a low-order angular flux nonlinear finite difference equation that is completely equivalent to the pin-resolved transport equation is established.

Multi-layer Quasi Three-dimensional Equivalent Model of Axial-Flux Permanent Magnet Synchronous Machine

Axial-flux permanent magnet synchronous machine(AFPMSM)enjoys the merits of high torque density and high efficiency,which make it one good candidate in the direct-drive application.The AFPMSM is usually analyzed based on the three-dimensional finite element method(3D FEM)due to its three-dimensional magnetic field distribution.However,the 3D FEM suffers large amount of calculation,time-consuming and is not suitable for the optimization of AFPMSM.Addressing this issue,a multi-layer quasi three-dimensional equivalent model of the AFPMSM is investigated in this paper,which could take the end leakage into consideration.Firstly,the multi-layer quasi three-dimensional equivalent model of the AFPMSM with single stator and single rotor is derived in details,including the equivalent processes and conversions of structure dimensions,motion conditions and electromagnetic parameters.Then,to consider the influence of end leakage on the performance,a correction factor is introduced in the multi-layer quasi three-dimensional equivalent model.Finally,the proposed multi-layer quasi three-dimensional equivalent model is verified by the 3D FEM based on an AFPMSM under different structure parameters.It demonstrates that the errors of flux linkage and average torque obtained by the multi-layer quasi three-dimensional equivalent model and 3D FEM are only around 2%although the structure parameters of the AFPMSM are varied.Besides,the computation time of one case based on the multi-layer quasi three-dimensional equivalent model is only 6 min,which is much less than that of the 3D FEM,1.8 h,under the same conditions.Thus,the proposed multi-layer quasi three-dimensional equivalent model could be used to optimize the AFPMSM and much time could be saved by this method compared with the 3D FEM.

The voltage-current relationship and equivalent circuit implementation of parallel flux-controlled memristive circuits

A flux-controlled memristor characterized by smooth cubic nonlinearity is taken as an example, upon which the voltage-current relationships （VCRs） between two parallel memristive circuits - a parallel memristor and capacitor circuit （the parallel MC circuit）, and a parallel memristor and inductor circuit （the parallel ML circuit） - are investigated. The results indicate that the VCR between these two parallel memristive circuits is closely related to the circuit parameters, and the frequency and amplitude of the sinusoidal voltage stimulus. An equivalent circuit model of the memristor is built, upon which the circuit simulations and exper/mental measurements of both the parallel MC circuit and the parallel ML circuit are performed, and the results verify the theoretical analysis results.

Analysis of Permanent Magnet-assisted Synchronous Reluctance Motor Based on Equivalent Reluctance Network Model

In this paper,the equivalent reluctance network model(ERNM)is used to calculate the magnetic circuit of a permanent magnet-assisted synchronous reluctance motor(PMASynRM)and calculate no-load air-gap magnetic field and electromagnetic torque.Iteration method is used to solve the relative permeability of iron core.A novel reluctance network model based on actual distribution of the magnetic flux inside the motor is established.The magnetomotive force(MMF)generated by armature winding affects the relative permeability of iron core,which is considered in the calculation of ERNM to improve the accuracy when the motor is under load.ERNM can be used to measure air-gap flux density,no-load back electromotive force(EMF),the average value of motor torque,the armature winding voltage under load,and power factor.The method of calculating the motor performance is proposed.The results of calculation are consistent with finite element method(FEM)and the computational complexity is much less than that of the FEM.The results of ERNM has been verified,which will provide a simple method for motor design and analysis.

基于气隙磁密差信号峭度因子的永磁同步电机局部退磁故障诊断

该文提出一种新型基于气隙磁密信号差峭度因子的永磁同步电机局部退磁故障诊断方法。首先,建立永磁同步电机等效磁路模型,根据简化模型分析局部退磁故障后各极主磁路下径向气隙磁密的变化规律。然后,将预存健康电机空载状态下气隙磁密信号与测量的在线状态下气隙磁密信号作差并计算其峭度值,作为故障特征值。取健康电机空载状态下气隙磁密信号与不同工况下气隙磁密信号差峭度值的最大值作为参考值,根据故障特征值与参考值的大小诊断出局部退磁。最后,仿真和实验结果均验证提出的局部退磁故障诊断方法的有效性。

一种球形光度计等价光谱透射比的测量方法

本文提出一种球形光度计等价光谱透射比的原位测量方法。使用球形光度计测试光源总光通量,因标准灯与被测灯的光谱差异进行光谱失配修正,等价光谱透射比是计算该修正的输入参数之一。为避免对积分球上的毛玻璃和球壁上的涂层样品拆卸安装,使用原位方式,通过比较毛玻璃漫透射出口处和积分球中心标准灯的光谱差异,计算等价光谱透射比的值。应用该方法,使用球形光度计测试白、红、绿、蓝四色LED样品的总光通量,与分布光度计的测试结果比较,实验数据显示两者在不确定度内一致,验证了所提出的等价光谱透射比测量方法可行性。

基于径向气隙磁密和定子电流的永磁同步电机均匀退磁故障诊断研究

该文提出一种基于径向气隙磁密和定子电流的永磁同步电机均匀退磁故障诊断方法。首先,建立电机的d轴等效磁路模型,分析均匀退磁故障后径向气隙磁密的变化规律;然后,获取电机的径向气隙磁密和定子电流信号,对各极下径向气隙磁密幅值进行归一化处理,并绘制雷达图,根据雷达图和比较相同定子电流幅值下健康电机和故障电机的各极下径向气隙磁密幅值的平均值,来诊断均匀退磁故障;利用空载各极下径向气隙磁密幅值的平均值计算故障程度。最后,仿真和实验结果均验证所提均匀退磁故障诊断方法的有效性。

九寨黄龙机场一次长时间雷雨过程成因分析

本文利用NCEP/NCAR1°×1°再分析资料、常规资料、多普勒天气雷达资料等对九寨黄龙机场2021年9月25日的一次长时间雷雨过程的天气形势、物理量场及航班影响情况进行分析。本次雷雨天气受500hPa波动槽和700hPa低涡共同影响,孟加拉湾和南海的暖湿气流持续输送,高层抽吸作用增强抬升,为此次雷雨的发生、发展和维持提供了有利条件。雷雨过程持续时间长达5小时以上,造成3个航班取消。雷雨前期由500 hPa波动槽东移带来的冷空气与高压外围暖湿气流交汇引起,雷雨中后期主要受700 hPa低涡东移的影响。雷暴云团在水汽积聚的区域发展增强,在水汽流失的区域逐渐消亡。

等值反磁通瞬变电磁在既有铁路路基岩溶探查中的应用

灰岩地区由于其地下空洞、溶洞和裂隙等地质特征,对既有铁路路基的稳定性构成严重威胁。本文采用等值反磁通瞬变电磁法进行探测,结合区域地质资料,圈定了既有铁路路基下方病害的分布位置、大小及形态,通过钻探资料验证了物探结果的可靠性,表明使用等值反磁通瞬变电磁法探测铁路路基岩溶分布是可行且高效的。

开槽盘式磁力耦合器径向不对中时传动性能分析

为了研究开槽盘式磁力耦合器径向不对中时的传动性能,以等效磁荷理论为基础,将运动中切割磁力线产生磁场的铜导体涡流区域等效成永磁体,结合库伦定律,建立开槽盘式磁力耦合器径向不对中时的输出转矩计算模型;通过有限元软件对开槽盘式磁力耦合器径向不对中时的磁感应强度、铜层功率损耗、输出转矩进行有限元分析,确定了耦合器径向不对中量所允许的最大值。研究结果表明,随着径向不对中量的增大,磁力耦合器工作过程中的感应磁场减小,从而引起耦合器最大磁感应强度增大,铜层功率损耗以及输出转矩逐渐减小;同时,二者随时间变化的曲线波动也越来越显著,当径向不对中量不超过6 mm时,开槽盘式磁力耦合器工作过程中依然能够保证较为准确地输出转矩,其转矩波动也相对稳定。

低轨星座对静止轨道卫星同频干扰指标研究

随着全球低轨星座系统的快速部署及应用,非静止轨道卫星对静止轨道卫星系统的同频干扰问题日益凸显。为保护静止轨道卫星系统不受有害干扰,国际电联现行无线电规则中规定了非静止轨道卫星系统应满足的等效功率通量密度限值或干扰噪声比限值,但所适用频段及限值标准仍在不断修订完善中。为了精确定量评估低轨星座对静止轨道卫星的同频干扰,通过对等效功率通量密度限值和干扰噪声比限值的确定方法及演进历程进行研究,分析了上述限值与静止轨道卫星实际被干扰的对应关系,并以典型倾斜轨道星座和极地轨道星座为例,分析了不同干扰指标对卫星系统间干扰判定结果的影响,当静止轨道卫星系统的实际被干扰门限低于国际电联制定等效功率通量密度限值选用的参考门限时,建议低轨星座选择干扰噪声比限值作为开展频率干扰分析与判定的依据。

新型交流调磁型永磁同步电机基本机理及运行特性

以提升永磁同步电机广速域运行性能为目标,提出一种新型交流调磁型永磁同步电机(AC flux-regulation permannent magnet synchronous motor,ACFR-PMSM),相较于传统永磁同步电机,所提电机拥有独立的轴向定子及轴向交流绕组,且转子上设计有凸出的轴向导磁极。该电机的数学模型、等效磁路模型和三维有限元模型分别被建立,并通过对比计算证明了所搭建模型的准确性。另外,通过对该电机等效磁路模型的分析,归纳了电磁性能与径向定子裂比、电机轴径比、永磁体参数的关系,进而完成了该电机关键尺寸参数的优选设计。采用三维有限元分析进行了所设计电机与传统永磁电机的电磁性能对标,结果表明,ACFR-PMSM拥有更优秀的磁场调节能力、更低的永磁体退磁风险及更宽的恒功率运行范围。最后,制造了一台ACFR-PMSM样机并搭建了测试平台,经验证,所制造样机的实测结果与有限元仿真结果的吻合度良好。样机的性能测试结果展现了ACFRPMSM在诸如电动汽车驱动、航空起动/发电系统、新能源发电等需要进行高效磁场调节及高性能宽速域运行领域的广阔应用前景。

基于等效传热和动态热流分配的限滑离合器温度场研究

针对限滑离合器多工况宽时长滑摩状态流、固传热及实际热流输入对温度场的非线性影响,考虑恒定热流分配模型无法满足接触界面温度连续的局限,提出以摩擦副间隙油膜等效假设计算等效对流传热系数的新方法。建立动态热流分配过程中限滑离合器全润滑状态温度场预测模型,搭建滑摩试验台并开展了6组不同润滑油温、相对转速差试验测试。研究结果表明:所建立模型有效降低了温度计算偏差,预测最大误差为7.6%,为非稳态连续滑摩离合器温度场研究提供了理论依据;将离合器温升分为快速增加阶段A和平稳变化阶段B,随着相对转速差提升,对偶钢片在阶段A输入热流降低值、对流传热等效功率递增值变化明显,平均温升速率随总滑摩热流密度增加而加快,并在阶段B热流输入与传热输出达到了稳态并趋于平衡。

多层绕组盘式横向磁通电机及建模分析

针对低速大转矩用盘式横向磁通电机中存在的C型定子结构不稳定,电机尺寸过大和生产效率低,U型定子和E型定子槽满率低、转矩密度小等问题,提出一种将绕组绕制在U型定子铁心两端的多层绕组盘式横向磁通电机拓扑结构。介绍了电机的结构和原理,并建立该电机基于磁阻的三维等效磁网络模型。在考虑永磁体空间漏磁的情况下,对主磁通进行计算并推导了空载磁链、空载反电动势和主要尺寸的关系。通过与双层绕组盘式横向磁通电机齿槽转矩、转矩密度和功率因数三维有限元结果的对比研究,分析所提出电机结构的优越性和有效性。试制出一台样机并进行空载反电动势的实验测试,通过仿真和实验测试的结果对比,验证该建模分析方法的准确性。性。

轴向磁通永磁同步电机快速等效磁路分析

轴向磁通永磁同步电机具有轴向长度短、结构紧凑、体积小、转矩密度高等特点。然而其磁场为三维磁场,模型过于复杂,难以直接运用经典解析法进行快速求解与计算。为快速完成轴向磁通永磁同步电机的前期估算,文中提出一种简化等效磁路模型来快速计算轴向磁通永磁同步电机的基本性能。该磁路模型通过合理的等效,将三维轴向磁通永磁同步电机模型转化为多层二维等效模型,进而运用等效磁路法和叠加法实现电机性能的计算。最后,以10极12槽双定子单转子轴向磁通永磁同步电机为例,运用文中所述模型计算其气隙磁密,永磁磁链和空载反电动势并对不同分层数的电机模型进行了有限元的仿真。结果表明,本文等效磁路模型的计算精度与三维有限元法相近,且耗时极短,更有利于该类电机的工程初算。

无铁心轴向磁通永磁电机的磁场解析计算

轴向磁通永磁电机磁场呈三维结构且磁路复杂,采用有限元法求解电机的气隙磁场将会耗费大量的建模及仿真时间,针对该问题,采用解析法对电机的空载磁场进行计算,通过将电机沿径向分成多个截面,使三维的轴向磁通电机等效为多个二维直线电机的组合体,在直角坐标系中求解拉普拉斯方程,得到矢量磁位,代入边界条件对磁场进行求解。计算电枢反应磁场时,采用多层电流片法进行求解,与有限元仿真结果对比,验证了解析法的可行性,提高了无铁心轴向磁通永磁电机磁场计算和电机参数设计的速度。

Bearingless motor’s radial suspension force control based on flux equivalent with virtual winding current analysis method

A bearingless motor has two sets of intercoupling stator windings, namely torque windings and sus-pension force windings. The decoupling control of the two sets is difficult and a key technology to stable operation for a bearingless motor. In this paper, a simple, reliable and accurate analysis method is put forward using the concept of flux equivalent with virtual winding currents. By this method, the suspension operation condition PB=PM±1 for bearingless motors is testified, and under the rotation condition of the motor, it is also proved that currents in suspension force windings must have the same phase sequence and frequency as torque windings to generate a stable single direction radial force in the rotor's whole circumference. On this basis, the control strategy of realizing the suspension opera-tion of the bearingless motor is presented, and a prototype of the bearingless surface-mounted per-manent magnet synchronous motor is tested. The research results have indicated that the experimental results correspond with theoretical analysis adopting this method, a stable and reliable radial suspen-sion force can be generated, and the validity and feasibility of this control strategy are confirmed.

以磁通等效实现磁悬浮轴承磁极容错控制

针对8磁极电磁轴承容错控制问题,文中提出了一种基于磁通等效的电磁轴承容错控制方法。该方法首先通过仿真得到磁通的电流-磁通影响系数,利用线性代数理论计算得到电流分配矩阵。当某一个磁极回路发生故障时,利用电流分配矩阵计算重构电流,使8个磁极端面的磁通在故障前后保持不变,即磁通等效,从而实现容错运行。在ANSYS有限元仿真平台进行仿真,用磁通等效方法可以较好地还原故障前的端面磁通和磁力线分布,并计算得到了磁通误差(最大不超过3.2%,绝大部分小于0.5%)和力误差(最大不超过7%,绝大部分小于1.5%),证明了所提出磁通等效容错控制方法的有效性。

高密度电法在水库工程勘探中的应用探析

高密度电法是浅层地球物理勘察的主要手段。文中通过该方法,基本划分出云南省镇雄县苏木水库库区第四系全新统、三迭系飞仙关组、二迭系长兴组、龙潭组的岩层分界面,推测出断层的分布情况,并结合现有矿洞的延伸情况和钻孔地质资料,呈现出矿洞、采空区域存在于有煤层的龙潭组地层地质特征。

综合勘察方法在岩溶区桥梁勘察中的应用分析

在高速公路建设过程中,岩溶发育带来的各种问题频发,受各种自然条件的限制,单一的勘探技术具有局限性,加大了岩溶区勘察难度,对现有勘察技术提出了新的要求。文中以云南某高速公路岩溶区桥梁勘察为研究对象,通过工程地质调绘、等值反磁通法、地质雷达法、钻探、孔内测试等勘探手段的综合应用,对勘探成果进行对比分析,提高了岩溶区勘探资料的准确性,为岩溶地区的勘察提供经验参考,为桥梁设计提供可靠的地质依据。