超超临界汽轮机汽流激振故障的分析研究

汽流激振是制约超超临界汽轮机安全性的关键因素之一.概括分析了国内外对汽轮机汽流激振的研究现状,并介绍了超超临界机组汽轮机汽流激振产生的原因、特征及其对轴系稳定性的影响.结合某电厂超超临界百万千瓦机组的振动实例,对汽轮机汽流激振进行了分析讨论,给出了治理汽轮机汽流激振的措施,实施后机组运行良好.     

电力系统暂态稳定风险量化分级方法研究

提出了基于风险理论的暂态稳定风险评估量化分级方法。从风险理论的角度出发,综合考虑运行方式、故障发生、故障类型、故障地点和重合闸等不确定因素计算系统失稳的概率,以暂态失稳导致的切负荷百分比作为后果,定量的得出暂态稳定风险值,并依据《国家电网公司安全事故调查规程》应用ALARP原则对风险量化分级,使风险值的意义更加清晰明确,为运行人员提供一定参考依据。最后,以WSCC3机9节点为例,说明了该方法的可行性和有效性。     

多机并网逆变器的并网／并联统一控制策略

分析了多机并网逆变器系统,得出其等效电路,推导出调节逆变器输出电压的相位可以调节逆变器输出有功功率,调节逆变器的输出电压幅值可以调节逆变器输出的无功功率.根据该理论,提出了一种多机并网逆变器的并网/并联统一控制策略,通过有功功率闭环调节逆变器输出电压的频率,通过无功功率闭环调节逆变器的幅值,给出了系统的运行流程,并分析了该方法内在的反孤岛能力.仿真和实验证明,所提控制策略在逆变器并网与并联时控制效果优良,并能实现平稳转换.     

Field plated 0.15μm GaN HEMTs for millimeter-wave application

SiN dielectrically-defined 0.15μm field plated GaN HEMTs for millimeter-wave application have been presented.The AlGaN/GaN hetero-structure epitaxial material for HEMTs fabrication was grown on a 3-inch SiC substrate with an Fe doped GaN buffer layer by metal-organic chemical deposition.Electron beam lithography was used to define both the gate footprint and the cap of the gate with an integrated field plate.Gate recessing was performed to control the threshold voltage of the devices.The fabricated GaN HEMTs exhibited a unit current gain cut-off frequency of 39 GHz and a maximum frequency of oscillation of 63 GHz.Load-pull measurements carried out at 35 GHz showed a power density of 4 W/mm with associated power gain and power added efficiency of 5.3 dB and 35%,respectively,for a 0.15 mm gate width device operated at a 24 V drain bias.The developed 0.15μm gate length GaN HEMT technology is suitable for Ka band applications and is ready for millimeter-wave power MMICs development.     

Simulation and Experimental Study on Thermal Conductivity of Nano-Granule Porous Material Based on Lattice-Boltzmann Method

Nano-porous materials have excellent thermal insulation performance,whose microstructure and physical properties,however,have great influence on the thermal conductivity.To accurately describe the stochastic phase distribution,a random internal morphology and structure generation-growth method,called the quartet structure generation set(QSGS),has been proposed in the present paper.The model was then imported into lattice Boltzmann algorithm as a fully resolved geometry and used to investigate the effects on heat transfer at the nanoscale.Furthermore,a three-dimensional Lattice Boltzmann method(LBM)D3Q15 was adopted to predict the nano-granule porous material effective thermal conductivity.This ideal method provided a significant advantage over similar porous media methods by directly controlling and adjusting of granule characteristics such as granule size,porosity and pore size distributions and studying their influence directly on thermal conductivity.To verify the accuracy of the proposed model,some experiments based on guarded hot plate meter(GHPM)were conducted.The results indicated that the simulation results agreed well with the experimental data and references values,which illustrated that this method was reliable to generate the microstructure of nano-granule.What’s more,the effects of pressure,core distribution probability,cd and density were investigated.There existed an optimal density(about 120 kg·m^-3)making the effective thermal conductivity being minimum and an optimal core distribution probability about cd=0.1 making the uniformity being the best.In addition,the present approach is applicable in dealing with other porous materials as well.     

一种改进FHN神经元滤波模型研究

突触滤波是神经元处理和传递信息的重要过程,有助于生物在复杂环境中获取所需信息.针对当前人工神经元模型中较少考虑到突触滤波机制,本文以FitzHugh-Nagumo(FHN)人工神经元模型为基础构建基于膜电势增量变化的神经元数学模型,在此基础上模拟突触滤波机制,从而提出一种改进FHN神经元滤波模型.而后,对该模型的稳定性...     

绝缘子气隙缺陷下的局部放电发展过程研究

研究了气体绝缘组合电器(gas insulated switchgear,GIS)内部绝缘子气隙缺陷局部放电(partial discharge,PD)发展过程,分析了不同发展阶段的特高频(ultra high frequency,UHF)PD信号φ-u散点图和φ-n谱图变化规律,提出了9个特征参量。研究发现：正负半周放电次数、大小具有相同的变化规律,正负半周最大放电脉冲幅值、等值累积放电量和放电信号熵特征呈指数增长趋势,相邻放电脉冲平均时间间隔呈现近似指数衰减趋势。负半周相邻放电脉冲时间间隔总是大于正半周,并且两者差异性随着PD的发展逐渐缩小。相邻放电脉冲最大时间间隔随放电发展逐渐减小。最后,本文结合PD发展物理微观过程,分析了各特征量出现相关变化规律的物理机制。     

畦灌技术研究进展

畦灌是我国北方地区目前最主要和使用最广泛的灌水方式之一,与其他灌溉技术相比其设施简单、易于运行,但浪费水量是制约该技术持续发展的关键因素。从畦灌的技术要素、水平畦灌技术、畦灌流动模拟3个方面综述了畦灌技术的现状研究进展,并总结了现有研究的不足,指出畦灌技术的发展趋势是畦灌入渗机理的完善、畦灌流动模拟的优化及畦灌技术评价体系的建立。     

大牛地气田上古生界储层粘土矿物及敏感性分析

大牛地气田上古生界储层粘土矿物组合主要为高岭石、绿泥石、伊利石和伊/蒙间层(I/S)。粘土矿物对储层的影响几乎全是负面的,致使储层的物性变差。粘土矿物的成分和含量对储层敏感性影响很大,下石盒子组砂岩储层为弱~中等水速敏、水敏、HCl酸敏,中等盐敏、碱敏和强HF酸敏;山西组砂岩储层为弱~中等水速敏、水敏、HCl酸敏、HF酸敏,中~强盐敏和强碱敏;太原组砂岩储层为弱~中等的水速敏、水敏、盐敏、HF酸敏,弱HCl酸敏和中等碱敏性。     

层状边坡的地震动输入方法研究

层状边坡是自然界中最常见的边坡之一,研究其动力响应规律对边坡的稳定性评价具有重要意义。为真实模拟弹性波在层状地基中的传播过程,首先建立层状地基的黏弹性人工边界模型,然后根据波动力学理论推导了考虑介质交界面的一次反射的等效荷载计算公式,并通过两层地基算例验证该输入方法的精度;针对层状边坡,采用本文提出的地震动输入方法和一种传统的输入方法分别研究其动力响应规律。研究表明:在两层地基算例中,本文提出的地震动输入方法能较好满足工程抗震的精度要求;在边坡的动力分析中,与传统方法相比,采用本文方法的边坡塑性应变能累积效应更加明显,且动力安全系数相对较小。