特高压输电线路电气和电晕特性分析

特高压输电线路电气在实践中有着较为重要的作用与价值,对于整个特高压手电技术的稳定性以及可靠性有着直接的影响,对此在实践中要想提升其整体的稳定性,就要加强对特高压输电路电气的相关内容的重视,对此本文主要基于特高压分类导线表面的电场强度特性的角度对于特高压输电线路分裂导线的电晕特性进行了简单的探究与分析,通过对于在分裂导线表面中的电场强度实际体现、特高压分裂导线表面中的实际体现、特高压输电线路分裂导线的电晕特性概述以及天气因素对电晕性产生的相关影响等内容的探究对于相关内容进行了阐述,希望可以为相关研究提供一定的技术指导。     

建筑物周围风致静压场的分布及振动特性研究

对均匀流及湍流中风洞内有和无建筑物时的静压状况进行了研究,针对目前无法精确测量静压的情况,提出了一种无量纲化方法,给出了静压场的分布规律,运用幅值域及频域方法详细分析了建筑物周围各区域的流场特性,之后给出了静压场主要方向的分布函数型式,并推断了静压场的静力及动力边界。研究结果显示:在风洞中进行风压测试时,有可能激发风洞气柱自振模态并对测试结果产生误导;建筑物迎风区脉动主要取决于来流脉动;背风区脉动则与湍流来流脉动较为相像,但能引起更多非高斯特性;地面粗糙度由小变大时,建筑物侧风区脉动由小振幅周期振动向大振幅随机振动转变;地面粗糙度越大,静压场的静力作用越小而动力作用越大。所提静压场分布函数可对风工程实测参考静压的测试及建筑群体的风致干扰问题提供参考。     

立式玻璃磨边机砂轮离心振动特性分析

针对立式玻璃磨边机砂轮架的结构特点,建立其动力学模型及系统运动微分方程,导出砂轮离心力作用下砂轮架与砂轮振动的稳态响应幅值及其动力放大因子β1、β2的理论计算公式,着重分析砂轮离心力激振下砂轮架及砂轮的振动特性及规律,结果表明：β1、β2的大小和砂轮与砂轮架的质量之比µ、固有频率之比α,砂轮角频率与固有频率之比λ,阻尼比ξ等因素有关;合理选择µ、α、ξ值,可使砂轮与砂轮架具有相同且较小的动力放大因子;避免砂轮工作在λ=0.9~1.1对应的转速范围内,可有效减轻砂轮架及砂轮的振动程度。研究结果突破了现有研究将砂轮轴刚性化处理、试验测试装备复杂等缺陷,具有物理概念清晰、计算简单等特点。     

薄煤层采煤机振动特性研究

为研究复杂煤层赋存条件下薄煤层采煤机的振动特性,根据多体拓扑结构建立采煤机刚柔耦合模型,通过仿真得到采煤机在截割含夹矸韧性煤工况下前后滚筒受到冲击载荷作用时的动态特性。基于子结构模态综合方式(CMS)的振动疲劳分析方法,进行危险点动应力与模态振动的相关性分析,发现牵引部壳体在实际工作过程中产生具有3阶垂向弯曲模态特征的弹性振动;以不同测试点加速度频域响应为依据,分析采煤机振动对其电控系统以及液压系统的影响,判断测试点加速度与模态振动的相关性,同时确定出牵引部柔性壳体的高动应力区域及其结构疲劳性质。分析结果为薄煤层采煤机的优化设计、后续测试、安全性评价提供了重要的参考。     

RV减速器振动特性分析

为了研究RV减速器的振动特性,建立了RV-20E型RV减速器的刚柔耦合动力学虚拟样机模型,利用灰色关联度分析了样机的准确性。之后通过模态分析,分析了RV减速器的整机模态频率、振型等。进一步使用有限元方法对RV减速器进行了瞬态动力学分析,得到了不同工况下的仿真信号,并与试验测得的不同转速、负载下RV减速器的加速度振动信号进行对比,仿真分析结果与试验结果吻合度较高。分析结果表明负载对RV减速器振动的影响较小,而转速对于RV减速器的振动有明显影响。     

螺栓连接非线性振动特性研究

摘要：在不同的外界激励下,螺栓连接常常表现出一定的非线性。为研究螺栓连接的非线性特性,设计了一个螺栓连接系统,并对其进行不同基础激励下的正弦扫频实验。通过实验数据的分析得到了螺栓连接的共振频率和相对阻尼系数,发现其随着激励量级的不同呈现出较明显的非线性特性。在理论模型研究中,将系统简化为非线性弹簧、非线性阻尼器、质量块的单自由度模型,并利用实验数据对非线性方程中的系数进行了识别。利用此非线性模型,求出系统的主共振频率和相对阻尼系数,它们与实验结果相比差别较小,说明文中所给的非线性方程能较好描述螺栓连接的振动特性。     

纵轴式掘进机振动特性研究

为研究纵轴式掘进机截割煤岩时的振动特性,对掘进机振动源进行分析,发现截齿在截割过程中受到的非线性瞬时冲击是造成掘进机振动的主要扰动源,通过建立复杂煤岩条件下截齿的力学模型,利用MATLAB编制了计算截割头瞬时载荷的模拟程序,模拟出横摆工况下截割头受到的冲击载荷,将其导入在协同仿真环境下建立的纵轴式掘进机刚柔耦合振动模型中,对其进行受迫振动分析,识别出系统的主要模态参数以及容易被激发的振型;分析其动态响应特性,确定了对整机振动影响较大的频率;同时对回转台进行谐响应分析,找出其薄弱环节。分析结果对研究纵轴式掘进机的振动特性和耐冲击、抗振能力的提高具有重要的参考价值。     

自激振动圆柱体湍流场及发展变化的研究

采用雷诺平均法模拟低质量比弹性支撑的刚性圆柱体在均匀来流中的涡激振动问题,是近年来人们研究的热点。本文采用有限体积法结合SST k-ω湍流模型求解时间平均的纳维尔——斯托克斯方程(RANS),对低质量比弹性支撑的刚性圆柱体在均匀来流中横向振动的三个响应分支（初始分支、上端分支和下端分支）湍流场及其发展变化进行了研究,并与同等雷诺数下固定圆柱体的湍流场进行了对比。结果表明：三个响应分支的流体力系数、壁面压力系数、壁面切应力、流向平均速度、流向速度的脉动、横向速度的脉动、雷诺应力、湍流动能和涡量的分布均与固定圆柱体有明显差异。     

低温及大温差区输电铁塔螺栓扭矩及横向振动试验研究

螺栓松动是强风和舞动区输电铁塔横担损坏的主要原因,输电线路运行环境温度及其变化会对螺栓应力和防松性能产生影响。通过开展低温及大温差环境下输电铁塔螺栓扭矩试验和横向振动试验,获得了施工扭矩下-50℃～30℃的螺栓预紧力及材料强度利用系数,确定了输电线路运行环境温度及温差变化对螺栓预紧力及防松性能的影响规律,评估了输电铁塔单螺母和双螺母螺栓在低温及大温差环境下的防松效果。按照现行规范的输电铁塔螺栓施工扭矩,-50℃低温及80℃温差环境下施工不会对输电铁塔螺栓强度安全产生影响。输电铁塔螺栓按照相同扭矩在室温环境施拧后,随横向振动环境温度(30℃～-50℃)的降低,输电铁塔螺栓振后残余预紧力百分比逐渐增大,即在低温运行环境下螺栓的防松性能有所提高。其中,单螺母螺栓-50℃环境下的防松性能比室温20℃环境下提高了41.0%。     

端部激励下空间倾斜拉索非线性振动特性研究

为探讨空间倾斜拉索承受塔锚固端或梁锚固端谐波位移激励下的非线性振动特性,基于牛顿运动定律及拉索索力的状态变化,综合考虑拉索振动松弛与非松弛特性,推导了斜拉索承受端部任意方向位移激励下的三维空间非线性振动方程,并采用Runge-Kutta分段时程积分法求解该方程。研究表明：在三维空间坐标系下,拉索振动呈现面、内外耦合振动特性,且耦合振动幅值与拉索面、内外固有频率及激励频率大小有关;在面内位移激励下,增大激励幅值,拉索振动呈现面外自激振动特性;增大拉索初始垂度及激励幅值,拉索振动呈现松弛与非松弛状态交替变化过程。     

电晕处理对超高分子量聚乙烯纤维表面性能的影响

对超高分子量聚乙烯（UHMWPE）纤维表面进行了电晕处理,用XPS,FT-IR和SEM研究了处理前后纤维表面化学结构及物理结构的变化,通过单丝拔出试验和短梁剪切试验评价了UHMWPE纤维与树脂基体的微宏观界面粘接性能,结果表明：经电晕处理后,UHMWPE纤维表面含氧量增多,含氧基团数量与种类增加,表面浸润性得到改善,纤维与基体的界面粘结强度（Ts）提高幅度可达535％,短梁剪切强度TNOL提高了40％以上．     

Modeling of the production of OH and O radicals in a positive pulsed corona discharge plasma

A mathematical model was applied to describe the behavior of OH and O radicals in positive pulsed corona discharge of N₂-H₂O mixture gas. The model takes into account the generation and disappearance of radials in a pulsed corona discharge reactor by a single pulse or continuous pulses. Their concentrations were derived by considering direct electron effect on the dissociation of gaseous molecules (O₂, N₂, H₂O) and subsequent excitation transfer reaction of excited oxygen atoms to produce OH radicals. The equations promoted could be solved numerically with the FORTRAN subroutine Treanor. So as to establish the validity of the model simulation, the calculated results were compared with the experimental data. Although there is some discrepancy between the calculation and experiment, the total trend is coincident.     

Gasification of polyethylene using steam plasma generated by microwave discharge

Gasification of polyethylene (PE) pellet was studied using atmospheric argon-steam plasma generated by microwave discharge and the feasibility of the process was examined. The experimental results showed that additional steam to argon plasma promoted the weight decrease of PE and enhanced the production of H₂, CO, CO₂ and CH₄. The results confirmed that the treatment of plastics with the steam plasma was effective to obtain synthesis gas.     

填充介质对电晕放电特性的影响

为了研究填充介质对电晕放电的影响,本文采用针-板放电装置,研究了不同条件下正、负直流电晕放电的起晕电压、平均电流等特性,获得了正、负直流电晕放电和正脉冲电晕放电的时间积分图像及正脉冲电晕放电的时间分辨图像。还分析了介质尺寸、形状、填充密度以及介电常数对正脉冲电晕放电特性的影响。所得结果表明,填充介质导致正、负直流电晕起晕电压升高。正电晕放电更易于激发填充介质的表面放电,且尺寸小的介质颗粒更容易形成环绕颗粒表面的放电。在正脉冲电晕放电中,填充介质密度、介电常数越高,起晕电压越低;球状介质比圆柱形介质更容易形成表面放电。     

Numerical simulation of point-to-plane corona discharge using a Monte Carlo method

Monte Carlo simulation techniques are used to study the dynamical properties of charged particles in point-to-plane corona discharge. The numerical model includes the release of electron-ion pairs by photoionization and secondary electron emission from cathode as well as the first Townsend ionization. The simulation results of negative corona discharge in nitrogen show that electron avalanche takes place in the region of high electric field near pin electrode and the photoionization is the essential mechanism to sustain the discharge as well as electron impact ionization.     

Oxidation of nitric oxide in a two-stage chemical scrubber using dc corona discharge

The dc corona was studied as an alternative for NO oxidation in a two-stage chemical scrubber. The dc corona plasma reactor completely oxidized 150 ppm of NO to NO₂ in an air stream. The NO₂ was further oxidized at a higher voltage. For some cases, the NO₂ in the effluents of the plasma reactor was absorbed quantitatively by a caustic sodium sulfite aqueous solution in a 2 l bubble column gas absorber. The outlet concentrations of both NO and NO₂ from the plasma-scrubber combination system (corona-induced chemical scrubber) were below the detection limit of the chemiluminescent NO_x analyzer.     

Performance evaluation of two-stage electrostatic air filter with low-ozone emission corona charger

The ozone emitted from indoor air cleaners with corona chargers is harmful to the human respiratory system. In this study, a functional treatment of the discharge electrode surface was attempted to reduce the level of ozone generation from the corona discharge. The ozone emission level and charger performance were evaluated by measuring the particle removal efficiency and the pressure drop characteristics with the dust loading on the filter. Ozone production from the low-ozone discharge electrode was reduced by approximately 60% compared to conventional discharge electrode, but the corona initiating voltage and discharge current were equivalent to those of the conventional electrode. The particle removal efficiency of a low-grade filter assisted by the corona charger increased to a high-grade filter without a charger. The replacement time for the low-grade filter with the charger was approximately three times longer than that of a high-grade filter.     

高水头船闸阀门顶缝空化切片试验研究

为真实模拟泄水建筑物空蚀与冲磨复杂的破坏行为,基于Venturi空化空蚀发生器结构特点和水力学Bernoulli原理,发明了高压高速水流自动挟沙装置,设计并制作了空蚀与冲磨混合作用试验系统。利用研发的装置开展了系列试验,探讨了高速水流空蚀与冲磨混合作用机制。研究表明,空蚀与冲磨混合作用下,材料表面呈现出空蚀与冲磨复合破坏特征,混合作用下的破坏程度明显大于单独作用,空蚀与冲磨之间存在一定的促进和增强作用,空蚀的冲击在材料表面产生的孔洞及散粒体骨架结构,在冲磨切削作用下加速破坏,空蚀使冲磨破坏更加容易。     

钢桥塔涡振气动控制措施研究

杭州之江大桥桥塔为曲线型钢桥塔,刚度与阻尼较小,桥塔自立状态出现涡振的可能性较大.为确定桥塔的涡振风速锁定区间及涡振振幅,进行了全塔气弹模型试验.试验结果显示,在横桥向来流的作用下,桥塔顺桥向涡振振幅过大,需要采取气动控制措施加以控制.试验中所采用的气动措施包括:在桥塔凹角处增加扰流栏杆、多孔角型扰流器和多孔扰流板等控制措施.进一步的试验结果显示,多孔扰流板的涡振控制效果显著,能有效降低涡振振幅,满足规范的限值要求.多孔扰流板的减振机理是其允许适量的气流穿过其孔洞,从而扰乱或削弱桥塔两侧角部有规律的旋涡脱落.     

Dual needle corona discharge to generate stable bipolar ion for neutralizing electrosprayed nanoparticles

The performances of dual needle corona discharge (NCD) as bipolar ion source to neutralize the electrospray (ES) particles were characterized and optimized. The NCD was constructed from a tungsten needle and grounded mesh electrode in the needle-to-plane configuration. The dual NCD created a bipolar ion environment by mixing the balanced concentration of positive and negative ions produced by each NCD. The dual NCD was placed in an electrospray aerosol generator (EAG) apparatus to reduce the charge state of the ES particles. Polystyrene latex (PSL) suspensions having the particle size range of 96–256 nm were used as the precursor solution for the electrospray process. Some characterizations to the NCD were carried out to obtain optimum operating voltage and air flow rate. The size distribution and charge fraction of the electrospray PSL (ES-PSL) particles exiting the EAG were also investigated. The result showed the dual NCD could generate stable bipolar ions by mixing positive and negative ions with balanced concentration. The bipolar ions from the dual NCD were capable of neutralizing and reducing the charge state of highly charged ES-PSL particles larger than 100 nm. The EAG, equipped with the dual NCD, could generate ES-PSL particles with stable concentration and consistent size distribution. The charge fraction calculation of the ES-PSL particles showed that more than 80% of the particles exiting the EAG were positively charged.