Optimization of magnetic field design for Hall thrusters based on a genetic algorithm

Magnetic field design is essential for the operation of Hall thrusters.This study focuses on utilizing a genetic algorithm to optimize the magnetic field configuration of SPT70.A 2D hybrid PIC-DSMC and channel-wall erosion model are employed to analyze the plume divergence angle and wall erosion rate,while a Farady probe measurement and laser profilometry system are set up to verify the simulation results.The results demonstrate that the genetic algorithm contributes to reducing the divergence angle of the thruster plumes and alleviating the impact of high-energy particles on the discharge channel wall,reducing the erosion by 5.5%and 2.7%,respectively.Further analysis indicates that the change from a divergent magnetic field to a convergent magnetic field,combined with the upstream shift of the ionization region,contributes to the improving the operation of the Hall thruster.

Development and Application of a Shaft-type Tubular Pumping System with a Siphon Discharge Passage

Based on the characteristics of large flow rate , low head , short annual operation time , and high reliability of the city flood-control pumping stations , a new-type shaft tubular pumping system featuring a shaft suction box and a siphon-type discharge passage with a vacuum breaker as the cutoff device was developed , which possesses such advantages as simple structure , reliable cutoff , and high energy performance.Taking some pumping stations as the case studies , in the light of the specified operation conditions , the hydraulic optimal design of the shaft-type tubular pumping system was determined and the optimized shape of the system was recommended.The performance prediction based on the computational fluid dynamics methodology was determined and the model test verification was conducted.The results show that the predicted data agree with the experimental head and efficiency so that both methods can be used to determine the performance of a real pumping station.Finally , the in-situ measurements of a pumping station during the commissioning period further verified that the shaft-type tubular pumping station with a siphon discharge passage is of higher efficiency , more reliable and stable.

Overtopping Discharge of Wind-Waves on Simple Slope Dikes

An empirical formula for estimating the overtopping discharge of wind-waves on a smooth-impermeable-simple slope dyke is derived through model tests in this paper, it can be adopted by related design departments in the determination of the crest elevation of the dyke.

Optimization of Dielectric Barrier Discharge Process for Decolorization of Reactive Blue 19 by Means of Response Surface Methodology

The decolorization of reactive blue 19(RB-19)as a model dye from aqueous solutions has been studied by means of the dielectric barrier discharge(DBD)process.The independent parameters of input power,initial dye concentration and initial pH value were evaluated respectively.Experimental data were optimized by means of a 33 factorial design and response surface methodology(RSM).The dye was quickly removed during the treatment,yielding 96.9%of decolorization efficiency under optimized conditions.Therefore,the total organic carbon(TOC)and chemical oxygen demand(CODcr)results indicated that only the chromophore was destroyed rather than completed oxidation.This was confirmed with UV-vis and tertiary butanol assessments during the DBD treatment.

Development and Application of DC Partial Discharge Test System

Direct current (DC) partial discharge (PD) test has drawn extensive attention from world-wide electric power research institutes in recent years. However, presently, no DC PD detection device on the market has the statistical function. Thus, we developed a test system for PD detection under DC voltage, which is characterized by strong anti-jamming capability, continuous high-speed real-time data acquisi- tion and effective, complete detection of DC PD signals. The DC PD mechanism, as well as the measuring principles, software system, and hardware design of the test equipment were introduced. Adopting typical electrode pairs, we tested the statistical spectrum of PD under DC voltage. The main difference in statistical spectrums between parallel plate electrodes and needle-plate electrodes was that the time interval between two consecutive discharges for needle-plate electrodes has obviously larger variation range than that for parallel plate electrodes, which could be the convincing proof for distinguishing the type of electrodes under DC PD. Practical results indicate that the proposed sys- tem can measure time domain signals of DC PD of oil-paper insulation effectively and promptly, and it can be used to determine and detect defects in DC power transmission equipment.

A Study on Modelling Surface Finish in Electrical Discharge Machining Tablet Shape Punches Using Response Surface Methodology

This paper introduces a study on modelling surface finish in EDM （Electrical Discharge Machining） of tablet shape punches when using copper as electrode material. In this study, 27 experiments were performed based on BBD （Box-Behnken Design） and the work-piece material was 9CrSi steel. The input process parameters were the current, the pulse on time, the pulse off time and the voltage. The effects of the input parameters on the surface finish were evaluated by analysing variance. Besides, from the results of the experiments, a regression equation for determining the surface roughness is introduced. Also, the optimum input parameter values were found in order to get the minimum surface roughness.

某直列式点火器双路瞎火故障分析与改进

针对某直列式点火器在低温点火试验中出现的双路冲击片点火管瞎火问题,进行了故障定位及原因分析,提出了改进措施并对其有效性进行了试验验证。结果表明:造成双路瞎火故障的原因是点火器转接件焊点异常处的气体间隙弧光放电;提出将2个回路的触发信号时间间隔调整为50μs,按照HB 7262航空产品电装工艺的相关规定细化电装工艺,增加对能量传输通道的介质耐压检测等改进措施。验证试验表明采取改进措施后,消除了弧光放电现象,点火器内的2个爆炸箔表面均有明显的电爆炸痕迹。

卫星低气压与真空放电安全性设计分析

卫星低气压与真空放电因客观环境因素诱发,危险源无法消除,风险无法避免;但开展相关安全性设计分析可以有效降低风险。文章提出一种基于故障致因理论的安全性设计方法,以问题导向为核心,推动挖掘导致卫星低气压与真空放电故障的不同原因,深入分析每一种放电防护设计的安全性要素和风险,以便制定有效措施,防范风险。最后结合实例,采用统计分析、工程分析和数学分析等方法,挖掘和查摆卫星低气压与真空放电原因,进行风险预评和控制措施设计与验证,结果表明该方法有效可行。

我国盐穴地下储库建设的挑战与对策研究——从“金坛模式”到“XX模式”

我国盐穴地下储库建设起源于江苏金坛盐矿并获得成功,初步构建了我国盐穴储库建设首个技术标准体系。但是,我国各地盐矿的品位、埋深、矿层厚度和夹层特性等地质条件与金坛盐矿相差甚远,盐穴储库建设面临诸多挑战,不能照搬“金坛模式”。着眼于盐穴储库地质设计、造腔工程、注气排卤方案等方面,首先总结盐穴储库建库的“欧美模式”,以及基本上借鉴“欧美模式”发展形成的我国“金坛模式”的基本特征,然后结合我国已开展和正在开展的其他多座盐矿的盐穴储库建设的研究和工程实践,提出几种基于“一地一议、因矿制宜”原则的典型盐穴储库建库的“XX模式”。“XX模式”意味着是不同于金坛模式并有极大突破和变革的新型建库模式,是应对我国各地盐矿地质复杂性所带来挑战的技术方案和新思路。最后,对于下一步应对盐矿复杂地质条件带来的挑战需要突破和创新的关键理论和技术进行了展望。

国外航天器电源与供配电标准体系综述

建设完备的航天器电源与供配电标准体系是提升航天器电源与供配电系统设计正确、确保卫星能源安全可靠的重要工具。本文通过研究欧洲空间标准化合作组织ECSS(European Cooperation for Space Standardization)、美国宇航局NASA(National Aeronautics and Space Administration)、日本宇宙航空研究开发机构JAXA(Japan Aerospace Exploration Agency)、国际标准化组织ISO(International Standard Organization)和美国航空航天学会AIAA(American Institute of Aeronautics and Astronautics)等国外组织出版的电源与供配电系统标准,分析各自标准专业的侧重点,综述国外标准所包含的内容,总结各组织的标准体系,并结合我国的实际情况,提出了航天器电源与供配电标准体系建议和参考。

光热膜蒸馏水处理技术与应用研究进展

利用高效的水处理技术对海水、苦咸水脱盐淡化,以及将工业废水循环再利用,是解决水资源短缺及水污染问题的关键。目前应用较多的膜分离技术尚存在高能耗、低热效率、二次污染等问题。因此,新型的膜分离技术受到广泛关注。光热膜蒸馏技术具有热效率高、能耗低、零排放等特点,在海水淡化、水资源再利用等领域的应用已展现出良好前景。文章综述了光热膜蒸馏的基本过程和原理,光热膜材料的研发和光热膜蒸馏系统的设计研究进展,并对光热膜蒸馏的综合实际应用进行详细阐述。另外,还探讨了当前光热膜蒸馏技术的局限性及未来的挑战,以期为光热膜蒸馏系统的进一步发展及应用提供参考。

焦化废水处理工艺流程设计探索

为应对焦化废水不再用于熄焦补充水,在考察焦化项目并结合文献研究的基础上,提出焦化废水处理后直接排放工艺流程和间接排放工艺流程。间接排放采用“预处理—水解酸化—A/O生化—二沉池—活性炭加载高效沉淀池”的流程,可应用于原位提标升级改造,具有投入资金少、改造工期短、出水指标提升效果显著的特点;直接排放采用“预处理—水解酸化—A/O生化—二沉池—高效沉淀池—臭氧催化氧化—A/O生化—高效沉淀池”的流程,可应用于改扩建、新建项目,具有出水水质稳定、难降解有机物去除彻底的特点。对两种工艺流程设计的关键点和间接排放工艺流程的工程应用案例进行简要介绍,并根据工程应用中出现的问题提出“精细化运行管控”的建议。

离心腔盘挤出式油菜高速精量排肥器设计与试验

针对现有排肥装置无法满足油菜高速机直播排肥量范围且易卡顿拥堵,排肥稳定性差及肥料颗粒破碎严重的问题,该研究设计了一种离心腔盘挤出式油菜高速精量排肥器。根据高速直播作业农艺要求,结合肥料颗粒运动过程分析,确定了进肥口、离心腔盘、排肥口、动力系统等关键参数。利用离散元软件EDEM建立排肥过程仿真模型,明确了排肥器转速变化对离心腔盘转矩、肥料颗粒平均载荷、肥料破碎率的影响规律。分析结果表明,随着排肥器转速增加,离心腔盘转矩增加,腔盘内的肥料颗粒平均载荷逐渐减小,破碎率增加,破碎率不超过0.80%。排肥器性能试验表明,排肥器转速30~120 r/min(对应排量15.0~58.1 g/s),可满足最大施肥量为600 kg/hm^(2)时3.0~12.0 km/h的油菜高速机直播作业需求,排肥器各行排量一致性变异系数低于8.58%,同行排量稳定性变异系数低于6.45%,破碎率低于0.89%;正常田间作业0°~5°倾斜状态下各行排量一致性变异系数不超过8.72%。对比试验结果表明,相较螺旋扰动式排肥器,离心腔盘式排肥器适应高速作业,破碎率减少63.82%,高速大排量排肥时未出现卡肥堵塞等情况。田间试验表明,作业速度在4.1~10.1 km/h范围内,排肥器各行排量一致性变异系数不大于6.72%,同行排肥量稳定性变异系数不大于4.84%,实际排肥量相对误差小于4.54%。设计的排肥器排量范围广,排肥顺畅稳定,破碎率低,满足油菜高速直播精量排肥需求。

数值计算方法在溢洪道阶梯消能的应用设计

为研究白盆珠水库溢洪道台阶段体型参数设计方案,采用了数值计算方法,对台阶段阶梯布置长度展开了泄流消能分析。研究表明,阶梯布置长度不同,但溢洪道断面上流速、压强变化趋势仍为一致性;阶梯长度方案差异性,会改变溢洪道流速、压强量值水平,流速随布置长度为递减变化,但降幅集中在长度50~70m方案内,而压强随之为先增后减变化,长度80m方案下压强最高,同时该方案下前三级台阶流速等值线分布均匀,流态较佳。受阶梯布置长度参数影响,消力池内流速具有两种不同变化趋势,以长度80~110m方案下流速变化更能够泄流消能,且长度80~110m方案下消能率稳定在58.3%左右。结合溢洪道断面水力特性及消力池消能特征,阶梯布置长度80m方案最优。论文可为水库溢洪道阶梯式泄流消能设计提供参考。

基于几何特征分析的电火花加工区域自动识别算法

提出了一种基于几何特征分析的电火花加工(EDM)区域自动识别算法。首先,基于凹边邻接图识别模具中的凹区域,基于表面法向识别凹区域底面并进行投影,然后基于底面投影轮廓的凹凸分界点对复杂凹区域进行分割与整合,并基于4类基本特征对底面投影轮廓进行分析,从而识别电火花加工区域,最后提出了3类造型方法实现了电极的自动造型。基于UGOpen实现所提算法,使用实际工程模具进行了测试,验证了算法的可行性。

特高压直流GIL运行可靠性设计与研究

特高压直流GIL运行可靠性取决于内绝缘设计的可靠性。此外,导电元件直流电流密度的取值、弹簧触头的定位设计、GIL各元件中的绝缘件与金具连接处的楔形气隙的处理以及母线中支撑件的结构设计细节,都会对产品运行可靠性产生重大影响,不能忽视。对于运行环境十分严酷的UHV DC GIL为保证内绝缘工作可靠性和减少气体维护工作量,文中还提出了高气密性结构设计。为适应-50℃低温运行要求,产品选用了液化温度很低的N_(2)/SF_(6)混合气体,对两种气体的配比,压力特性和绝缘特性进行了讨论与计算。还有产品的局放、气体密度及微水含量的监视系统的可靠性设计,都会对产品运行可靠性产生直接影响。文中对上述问题的研究成果作了介绍,可供高压直流产品设计使用。对其中未解的新技术如基于冷镜露点测试原理、微机电技术制作的智能气体湿度和密度监测装置、高压直流复合绝缘套管伞面局放起始场强提出了研究方案。文中提出的诸多GIL运行可靠性设计要点,对于其他超/特高压直流气体绝缘电器可参考选用。

交直流输电线路混合电场的人体感受试验及设计控制值研究

交直流输电线路同走廊和同塔架设是随着我国电网技术发展而出现的新输电方式,国内外尚无相应的交直流混合电场设计控制值标准。因此,设计同走廊和同塔架设的交直流输电线路时,导线对地高度和走廊宽度的选取面临无据可依的难题。该文提出确定交直流混合电场设计控制值的原则;开展不同交流(工频)电场和直流电场组合下的人体直接感受和暂态电击感受试验;通过对试验结果的统计分析,获得不同概率下人体不出现明显感受时的交流(工频)电场和直流电场关系曲线;在此基础上,得出确定交直流输电线路混合电场设计控制值的公式。该研究可为同走廊和同塔架设交直流输电线路设计中交直流混合电场的控制提供一定技术支撑。

基于海绵城市理念的市政给排水设计

若市政给水引入点的管道位置分布混乱,会导致市政给排水流量受限,增加由于暴雨等极端天气事件或其他突发情况造成的城市损失。因此,基于海绵城市理念,优化市政给排水工程。根据给水引入点排布市政管道位置,计算市政给水余压供水区间,在区间范围内确定了市政排水管出户标高,根据市政排水管出户标高,确定了喷头流量总和与管道作用面积之间的关系,设计了平均配水量配水支管,折算每段配水支管的流量,计算了配水支管间的流量系数,以此完成市政排水设计。分割项目工程系统管道内的机械样板空间,参照管线完成水平管道施工。结果分析表明:同等效段内,基于海绵城市理念的市政给排水加压设备耐久度更高,管道排水流量较大,海绵城市理念与市政给排水设计过程的融合效果得到保证。

廉江河综合治理工程设计洪水地区组成分析

廉江河综合治理工程采用“上蓄、中疏、下拓”的防洪体系,利用上游新村水闸进行调蓄,使公园水闸-新村水闸段满足安全泄量要求。考虑新村水闸调蓄作用影响,通过“区间同频、新村相应”和“区间相应、新村同频”两种不利洪水组合进行下游控制断面的洪水计算分析,选取对工程更为不利的较大者作为控制断面设计洪峰流量。计算方法可为无资料地区洪水地区组合分析提供参考。

某污水处理厂尾水排海工程设计探讨

介绍了尾水排海工程的设计方案,包括排放方案、扩散器设计、警戒装置及标识设计,探讨了排海管管材选取、防腐设计及排海管的施工方式。设计采用I型+T型组合式扩散器、上升管顶部设置多个喷口、管道外防腐采用3PE防腐涂层加阴极保护等技术措施,对水保护的环境起到重要作用。