Pressure fluctuation propagation of a pump turbine at pump mode under low head condition

Pressure fluctuation at the vaneless space and vanes passages is one of the most important problems for the stable operation of a pump turbine. The fluctuation appears in any operating condition. Much research has been done on the pressure fluctuation of hydraulic machinery. However, the details of pressure fluctuation propagation of the pump turbine at the pump mode have not been revealed. The modem pump turbine with high water head requires the runner to be ＂flat＂, which would induce pressure fluctuation more easily than the low head pump turbine. In this article, a high head pump turbine model is used as the re- search object. As the pressure fluctuation at off-design point is more serious than at the design point, the low head condition is chosen as the research condition. Pressure fluctuation at the vaneless space and vanes passages is predicted by the computa- tional fluid dynamics method based on k-co shear stress transport model. The experiment conducted on the test rig of the Har- bin Institute of Large Electrical Machinery is used to verify the simulation method. It proves that the numerical method is a feasible way to research the fluctuation under this operating condition. The pressure fluctuation along the passage direction is analyzed at time and frequency domains. It is affected mainly by the interaction between the runner and vanes. In the circumferential direction, the influence of the special stay vane on the pressure fluctuation is got. The amplitude in the high-pressure side passage of that vane is lower than that in the other side. The study provides a basic understanding of the pressure fluctua- tion of a pump turbine and could be used as a reference to improve the operation stability of it.

Numerical Flow Simulation in Turbine Mode of Counter-Rotating Type Pumping Unit to Cooperate with Wind Turbine

This serial research has proposed the hybrid power system combined the wind power unit with the counter-rotating type pump-turbine unit, to provide the constant output for the grid system, even at the suddenly fluctuating/turbulent wind circumstance. In this paper, the tandem impellers prepared for the counter-rotating type pumping unit were operated at the turbine mode, and the performances and the flow conditions were investigated numerically with accompanying the experimental results. Even though providing the pumping unit for the turbine mode, the maximum hydraulic efficiency is close to one of the counter-rotating type hydroelectric unit designed exclusively for the turbine mode. Besides, the runners/impellers of the unit work evidently so as to coincide the angular momentum change through the front runners/impellers with that through the rear runners/impellers, namely to take the axial flow at not only the inlet but also the outlet, without the guide vanes. From these results, it can be concluded that this type unit is effective to work at not only the pumping but also the turbine modes.

Diode-pumped Kerr-lens mode-locked femtosecond Yb:YAG ceramic laser

We experimentally demonstrated a diode-pumped Kerr-lens mode-locked femtosecond laser based on an Yb：YAG ceramic. Stable laser pulses with 97-fs duration, 2.8-nJ pulse energy, and 320-mW average power were obtained. The femtosecond oscillator operated at a central wavelength of 1049 nm and a repetition rate of 115 MHz. To the best of our knowledge, this is the first demonstration of a Kerr-lens mode-locked operation in a diode-pumped Yb：YAG ceramic laser with sub-100 fs pulse duration.%@ 1674-1056

Effects of Driving Mode on the Performance of Multiple-Chamber Piezoelectric Pumps with Multiple Actuators

Due to the limited output capability of piezoelectric diaphragm pumps, the driving voltage is frequently increased to obtain the desired output. However, the excessive voltage application may lead to a large deformation in the piezoelectric ceramics, which could cause it to breakdown or become damaged. Therefore, increasing the number of chambers to obtain the desired output is proposed. Using a check-valve quintuple-chamber pump with quintuple piezoelectric actuators, the characteristics of the pump under different driving modes are investigated through experiments. By changing the number and connection mode of working actuators, pump performances in terms of flow rate and backpressure are tested at a voltage of 150 V with a frequency range of 60 Hz -400 Hz. Experiment results indicate that the properties of the multiple-chamber pump change significantly with distinct working chambers even though the number of pumping chambers is the same. Pump performance declines as the distance between the working actuators increases. Moreover, pump performance declines dramatically when the working piezoelectric actuator closest to the outlet is involved. The maximum backpressures of the pump with triple, quadruple, and quintuple actuators are increased by 39%, 83%, and 128%, respectively, compared with the pump with double working actuators; the corresponding maximum flow rates of the pumps are simply increased by 25.9%, 49.2%, and 67.8%, respectively. The proposed research offers practical guidance for the effective utilization of the multiple-chamber pumps under different driving modes.

Diode-pumped self-starting mode-locked femtosecond Yb:YCa_4O(BO_3)_3 laser

A self-starting mode-locked femtosecond laser is accomplished with an oxoborate self-frequency doubling crystal Yb：YCa4O（BO3）3 （Yb：YCOB） as the gain medium and a semiconductor mirror as the saturable absorber. Pumped by a 976-nm fiber-coupled diode laser with 50-ktm core diameter, stable mode-locked laser pulses up to 430 mW were obtained at a repetition rate of 83.61 MHz under 5-W pump power. The autocorrelation measurement shows that the pulse duration is as short as 150 fs by assuming the sech2 pulse shape at a central wavelength of 1048 nm. This work has demonstrated a compact and reliable femtosecond laser source for prospective low-cost applications.

Study on integrated development and hybrid operation mode of nuclear power plant and pumped-storage power station

The nuclear power plant is suitable for base-load operation, while the pumped-storage unit mainly gives play to capacity benefit in the electric power system;hence, the integrated development and hybrid operation mode of the two can better meet the needs of the electric power system. This article first presents an analysis of the necessity and superiority of such mode, then explains its meaning and analyzes the working routes. Finally, it proposes the business modes as follows: low price pumping water electricity plus nuclear power in the near term;nuclear power shifted to pumped storage power participating in market competition in the middle term;and, in the long term, nuclear power shifted to pumped storage power as primary and serving as an electric power system when needed.

光伏光热联合双源热泵系统运行模式研究(1):最佳切换模式验证

讨论了光伏光热联合双源热泵系统制热运行的最佳切换模式。利用TRNSYS软件建立了仿真模型,对双源(水源、空气源)热泵系统性能系数(COP_(s))进行了计算,提出以某时刻空气源热泵模式或水源热泵模式运行COP_(s)较大者优先运行作为COP_(s)切换模式。通过前期实验结果验证了模拟结果的正确性,并与常规的集热水箱温度切换模式进行了对比实验,验证了COP_(s)切换模式的有效性。结果表明,该实验系统以COP_(s)最佳切换模式运行时发电量和发电效率较集热水箱温度切换模式分别提高了5.35%和1.73%,耗电量降低了17.03%,COP_(s)提高了4.91%。

Diode-pumped Kerr-lens mode-locked Ti: sapphire laser with broad wavelength tunability

We report a direct blue-diode-pumped wavelength tunable Kerr-lens mode-locked Ti: sapphire laser.Central wavelength tunability as broad as 89 nm(736-825 nm) is achieved by adjusting the insertion of the prism.Pulses as short as 17 fs are generated at a central wavelength of 736 nm with an average output power of 31 mW.The maximum output power is 46.8 mW at a central wavelength of 797 nm with a pulse duration of 46 fs.

光伏光热联合双源热泵系统运行模式研究(2):供暖季系统仿真研究

使用TRNSYS软件建立了光伏光热-双源热泵(PV/T-DSHP)系统的仿真模型。选取夏热冬冷地区某一近零能耗居住建筑作为研究对象,模拟研究了供暖季PV/T-DSHP系统在COP_(s)切换模式下的运行特性和能耗。结果表明:平均光电效率为15.08%,平均光热效率为33.05%;水源热泵运行模式下供暖季平均COP为4.55,空气源热泵运行模式下供暖季平均COP为3.19,PV/T-DSHP系统的平均COP_(s)为2.98;供暖季系统自满足率为61%。

地浸采铀工艺中电潜泵内流场数值模拟研究

电潜泵是我国地浸采铀工艺中实现浸出液有效提升的主要装备,但目前针对介质举升状态下电潜泵水力部件内部流场作用机制的研究较少。试验以叶轮-导叶内部结构为研究对象,应用CFD方法对介质流动特性开展非定常分析,研究了叶轮和叶轮出口段内部的压力脉动变化规律,并利用瞬态流场数据对叶轮截面压力流场进行动模态分解(DMD)与压力流场重构,揭示了介质举升状态下由动静干涉引起的压力脉动周期性变化规律与动静部件距离对动静干涉强度的影响规律。结果表明,叶片通过频率值与快速傅里叶变换(FFT)频率值基本一致。试验结果可对减少由压力脉动引发的泵体无效震动、优化电潜泵水力部件结构参数和提升系统效率提供一定理论参考。

矿山太阳能耦合充填体热泵系统性能研究

太阳能热泵和土壤源的结合应用不仅大大提高了清洁能源的利用率,还能很好地解决土壤因冬、夏季负荷不平衡而导致的温度场降低问题。介绍了太阳能热泵系统的分类和存在的问题,提出太阳能耦合土壤源热泵系统的必要性。针对矿井条件,进一步提出了太阳能耦合充填体热泵系统的学术理念,分析了两者结合的可能性,并以石家庄为例用TRNSYS软件进行模拟。阐述了其在夏季与过渡季蓄热、在冬季供暖的运行模式,分析了输出结果以及该系统的利用价值。结果表明:相较无太阳能蓄热充填体温度场变化率为11.56%的情况,有太阳能蓄热时温度场变化率仅为3.67%。太阳能耦合充填体热泵系统中充填体总吸热量为304377.90 kW·h,充填体总释热量为222461.89 kW·h。相当于节省标煤27.36 t,减少二氧化碳排放68.21 t。为后续充填体储热及矿区热利用提供了参考。

麻雀搜索算法优化的外啮合齿轮泵泄漏量预测

预测齿轮泵泄漏量的变化趋势有助于定量分析其性能退化过程。变分模态分解(Variational Modal Decomposition, VMD)方法对齿轮泵原始泄漏量数据进行变分模态分解,得到本征模态函数IMF,提出一种结合麻雀优化算法(Sparrow Search Algorithm, SSA)和长短期记忆神经网络(Long-Short Term Memory, LSTM)的模型,建立VMD-SSA-LSTM模型预测齿轮泵泄漏量的变化情况,并对每一个分量进行单独预测,最后将预测结果进行叠加,获得完整的预测结果。通过对比不同时间段预测结果可知,VMD-SSA-LSTM模型较单一的LSTM模型预测结果的平均相对误差最高可减小25.2%,能够完成对泄漏量的有效预测。研究结论可为齿轮泵性能衰退的定量预测提供理论支持。

泵控系统的积分终端滑模位置控制

为提高执行器的响应速度、鲁棒性和控制精度,提出了一种新型控制技术,将扩张状态观测器与反步积分终端滑模预设性能控制器相结合。首先,将非线性干扰观测器与扩张状态观测器融合,实现对状态量、外部干扰和匹配干扰的观测。然后,在控制器中引入积分终端滑模和规定性能约束,以加快执行器在位移误差远离平衡点时的跟踪误差收敛速度,并确保瞬态和稳态位置响应在要求的有界范围内。最后,基于李雅普诺夫方法对控制器进行稳定性分析。结果表明:在跟踪具有外负载干扰的复合轨迹情况下,设计的控制器能保证瞬态性能和规定的跟踪精度,与反步滑模控制器和PID相比,所提出的控制器具有更佳的控制性能。

基于指数趋近率的液压机泵控伺服系统滑模控制

滑模控制方法具备较强鲁棒性,控制器结构也较简单,被广泛应用于泵控电液伺服液压系统上。在分析泵控系统原理的基础上,为克服传统PID控制很难抵抗较强外部干扰力的缺点,泵控伺服系统建立指数趋近律滑模控制器,建立泵控伺服系统MATLAB/Simulink仿真。研究结果表明:正弦信号跟踪下,滑模控制最大稳态跟踪误差与PID相比降低83.4%,同时控制器IMSE指标相对PID控制器发生了显著降低。该研究有助于提高液压机运行效率,对提高产品质量具有一定的指导意义。

可水力短路运行的三机式抽蓄机组研究综述

“双碳”发展目标的提出对电力系统中灵活调节电源的需求更为迫切。抽水蓄能电站作为当前电网中应用规模最大、技术最成熟的灵活调节电源,广泛使用的可逆式机组存在抽水工况功率不可调节的问题,限制了抽蓄电站的运行灵活性。研究证实采用三机式抽蓄机组水力短路运行可实现在抽水运行时的快速功率调节,更灵活的平衡间歇性清洁能源并网对电网的扰动,具备常规抽蓄机组所不具备的显著优势,是增强服务新型电力系统的有效手段。但具备水力短路运行模式的三机式机组在国内外仅有几个电站的应用示范,其研究在各国均处于起步阶段。我国仅有九十年代投产的羊湖电站采用了三机式机组,且由于多种原因一直未真正实现抽水调节运行。为提高新能源为主电网的灵活性,国外近年来加大了对三机式机组的研究和应用。为推动未来我国对三机式抽蓄机组的研究及应用,本文介绍了三机式机组的特点及国内外研究应用现状,对当前推动三机式机组技术应用面临的难题进行了梳理,提出了后续亟待解决的关键技术问题,可为后续开展相关研究提供参考。

基于电荷泵和电场增强层的滑动式直流摩擦纳米发电机的性能提升

针对直流摩擦纳米发电机(DC-TENG)自身性能的局限性以及静电击穿的优化,提出了一种简便、通用的将电荷泵和电场增强层与DC-TENG耦合的策略(CE-DC-TENG),以提高DC-TENG的输出性能。交流摩擦纳米发电机(AC-TENG)被用作电荷泵,在DC-TENG中引入一层增强电场的导电层并与电荷泵连接,以积累电荷和增强静电击穿的电场。在研究过程中,设置了运动频率与竖直压力这两个参数,并通过改变参数的大小测试了对应的输出性能。结果表明在1.0 Hz的运动频率和25 N竖直压力下,CE-DC-TENG输出电流约为0.67μA,七个周期的转移电荷量约为0.95μC。这个结果分别约为基于静电击穿DC-TENG的5倍和2倍。并且,该器件的输出功率在负载电阻600 MΩ左右获得最大值,达到54μW。CE-DC-TENG的峰值输出功率约是DC-TENG的18倍。通过线性滑动模式CE-DC-TENG验证了该方法的有效性。

基于集合经验模态分解和指数能量法的水泵水轮机尾水管压力脉动信号特征提取

提取水泵水轮机尾水管压力脉动信号中的动态特征信息,准确识别涡带强度,是近年来水泵水轮机工程领域的研究重点。本文基于集合经验模态分解(ensemble empirical mode decomposition,EEMD)和模态指数能量法,对某水泵水轮机发电工况不同负荷下的尾水管压力脉动信号进行特征提取,得到如下结论。首先,基于EEMD的模态指数能量能够有效地反映信号中的能量分布规律。其次,在涡带增强过程中,基于EEMD的最大模态指数能量不断升高,表明尾水管内的流动状况变得更加复杂,涡带特征信息也更加丰富。最后,使用最大与平均指数能量构建的特征向量能够准确反映不同的尾水管涡带强度,并且能够作为智能分类器的输入特征向量,有利于后续进一步的识别与诊断,具有重要的工程意义。

“双碳”目标下可再生能源与常规冷热源系统的耦合应用与运行模式分析

为了解决热泵系统存在的初投资高、产热波动大等问题,提出将空气源热泵系统与常规冷热源系统耦合。分析了计算耦合系统空气源热泵装机比值的3个维度、并联连接和串联连接2种方式的运行模式,给出了耦合系统的供回水温度建议。

双吸泵作液力透平叶轮内非定常流动DMD分析

为了精确分析双吸泵作液力透平叶轮内的非定常流动特性,采用SST k-ω湍流模型在设计工况下进行数值模拟。对一个周期的非定常速度场进行动态模态分解(DMD),并结合Q准则,得到前4阶主要模态及其相应的时空信息。分析结果表明:DMD方法将叶轮内复杂的流场特征分解为动静干扰模态、基本模态和耗散模态。其中动静干扰模态占主导地位,频率为叶轮旋转频率,反映出叶轮内流动受静止部件干扰的流动特征,涡结构主要为点状涡和不连续的管状涡;基本模态频率为0Hz,反映出叶片流道几何特征引起的稳态流场特征,涡结构主要为连续的管状涡;3阶及4阶模态为耗散模态,反映出叶轮内流动受静止部件干扰,在叶片上产生的流动分离及不稳定涡结构脱落的特征,以片状涡和不连续的管状涡为主。在特定频率下DMD方法可以对叶轮流场结构进行分解,能够清楚地分析双吸泵作液力透平叶轮内复杂流场的非定常特性。

抽水蓄能电站容量价格研究

抽水蓄能电站具有削峰填谷、调频、调相等功能,是构建新型电力系统背景下,推动新能源稳步发展和保障电网安全稳定运行的有力支撑。本文系统梳理了我国抽水蓄能电站的价格机制、运营模式及成本回收途径,并基于全国在运及2025年底前拟投运的48座抽水蓄能电站,分析了全国抽水蓄能电站容量价格的主要特点、影响因素及对电价水平的影响。研究结果表明:抽水蓄能电站的建设时间、地理区域、投资主体、设计核准角度等因素通过影响抽水蓄能电站单位千瓦投资,从而影响其容量价格;发展抽水蓄能对区域用户电价的影响程度与区域的用电水平和抽水蓄能电站的装机规模、容量价格均有较大关系。