基于EMD方法的柴油机振动信号去噪声处理

针对柴油机振动信号的瞬时非线性特点,提出采用柴油机振动信号的IMF分量进行特征频带识别的新方法.将柴油机振动信号经验模态分解,并去掉主要干扰因素所对应的IMF分量,再将剩余IMF分量进行重构得到柴油机振动信号.实际测试结果表明,重构后的信号能反映柴油机机身振动的真实趋势.     

基于经验模态分解方法的柴油机振动信号去噪声处理

针对柴油机振动信号的瞬时非线性特点,提出采用柴油机振动信号的本征模函数(IMF)分量进行特征频带识别的新方法。将柴油机振动信号经经验模态分解,并去掉主要干扰因素所对应的IMF分量,再将剩余IMF分量进行重构得到柴油机振动信号。实际测试结果表明,重构后的信号能反映柴油机机身振动的真实趋势。     

基于振动的汽油机爆震始点识别与强度评价研究

研究了利用振动信号进行汽油机爆震检测和强度评价的方法。通过滤波对机体振动信号进行降噪处理,利用功率谱密度估计确定了爆震特征频率。将集总经验模态分解(ensemble empirical mode decomposition,EEMD)应用到机体振动信号处理中,结合连续小波变换(continues wavelet transform,CWT)对EEMD分解得到的各本征模态函数(intrinsic mode function,IMF)分量进行时频分析,确定包含爆震特征频率成分的IMF分量,研究了利用振动信号判别爆震始点的方法,并结合缸压信号对结果进行了验证。在确定了准确的爆震窗口后,提出了爆震强度评价参数K。试验用汽油机的计算结果表明:当K值超过20,可以判断有轻微爆震的发生;当K值超过80,则代表爆震强度较强,发生明显爆震。     

基于EMD与SVM的柴油机故障诊断

对柴油机气阀间隙变化、断油等故障情况下的缸盖振动信号进行了测试分析.采用经验模式分解EMD方法对振动信号进行分解,得到固有模态函数IMF,对每一个IMF分量分别建立AR模型,以模型的自回归参数和残差的方差作为特征向量,用支持向量机SVM进行分类,判断柴油机的工作状态和故障类型.实验结果分析表明,该方法即使在小样本情况下也能准确有效地诊断柴油机故障,能实现故障的实时自动化诊断.     

基于MEEMD和KFCM的风机齿轮箱故障诊断

针对风机齿轮箱振动信号的故障特征提取与故障诊断问题,文章提出了一种基于MEEMD信号分解、样本熵和KFCM的齿轮箱故障诊断方法。首先,采用一种改进的集合经验模态分解方法(MEEMD)对采集的齿轮箱振动信号进行分解,得到了多个本征模态函数(IMF)分量;然后,计算每个IMF分量的样本熵作为齿轮箱故障诊断的特征向量;最后,使用核化的模糊聚类算法(KFCM)对齿轮箱故障样本进行聚类。通过实验数据对比表明:基于MEEMD-KFCM算法的风机齿轮箱故障诊断方法可以更加有效地识别齿轮箱故障。     

基于ＩＣＥＥＭＤＡＮ 和ＳＶＭ 的起伏振动气液两相流流型识别

针对起伏振动条件下气液两相流压差信号过于复杂难以识别的问题,提出一种基于改进的自适应噪声完备集合经验模态分解(ICEEMDAN)与支持向量机（SVM）相结合的流型识别方法。采用ICEEMDAN对小波去噪后的压差信号进行模式分解,通过求取的各本征模态函数（IMF）与原始信号进行斯皮尔曼相关系数计算,选取相关系数较大的IMF分量进行希尔伯特变换,对变换后各IMF分量的瞬时幅度进行能量熵、奇异谱熵、功率谱熵的计算,构成特征向量,带入到支持向量机中进行流型识别。结果表明：该方法能够有效识别起伏振动状态下的泡状流、弹状流、搅混流、环状流,识别准确率可达95%。     

基于CEEMDAN和混合灰狼算法优化SVM的水电机组故障诊断方法

为有效利用水电机组的振动信号诊断机组故障,提出了一种基于自适应噪声完备集合模态分解(CEEMDAN)和混合灰狼算法优化支持向量机(HGWO-SVM)的水电机组故障诊断方法.首先利用CEEMDAN方法对原始振动信号进行分解降噪,获得原始信号的各模态分量(IMF),并以IMF为基础构造各样本下机组信号的特征向量;接着在原始...     

基于EMD的水轮机空化声发射信号阈值降噪方法

针对随机噪声对水轮机空化声发射信号的影响,提出了基于经验模态分解(EMD)的水轮机空化声发射信号阈值降噪方法:首先利用EMD将水轮机空化声发射信号分解得到多个本征模态分量(IMF),然后结合给定阈值规则对前半部分IMF分量进行降噪,将降噪后的IMF分量与未处理的IMF分量重构,得到降噪后的声发射信号。采用该方法分别对仿真信号和水轮机空化试验过程中采集到的声发射信号进行了降噪处理,并与小波阈值降噪方法、小波包阈值降噪方法及传统EMD降噪方法进行了对比。结果表明:EMD阈值降噪方法有效结合了EMD自适应分解的特性和阈值降噪的良好性能优点,对水轮机空化声发射信号的降噪效果优于其他3种方法。     

基于IMF-MFDE和GRU的水电机组故障诊断

针对水电机组振动信号非平稳、非线性及强噪声的特点,提出了一种IMF多尺度波动散布熵(MFDE)结合门控循环单元(GRU)的故障诊断方法。首先,采用跳蛛优化算法(JSOA)寻找变分模态分解(VMD)最优参数,达到振动信号最佳分解降噪效果;其次,对分解得到的本征模态函数(IMF)进行重构,计算有效IMF的多尺度波动散布熵(MFDE)作为故障特征向量;最后,将特征向量输入GRU构建水电机组故障识别器。所提方法对实际水电站机组故障样本数据的故障识别率达97.83%,验证了该方法的有效性。     

EMD在LabVIEW中的实现及其在水轮机主轴振动信号分析中的应用

针对LabVIEW中缺少经验模态分解(EMD)算法模块的问题,对LabVIEW进行了二次开发,建立了基于LabVIEW的EMD模块,为振动故障信号分析提供了有效的工具,进而以水轮机故障信号的振动特征和故障产生机理为依据,将此算法运用于水轮机主轴振动信号分析,以河北省西达水电站水轮机主轴振动数据为基本资料,对分解得到的高频本征模函数(IMF)分量做包络谱分析,提取故障信息,并与轴心轨迹分析方法相结合加以验证。结果表明,该方法能够有效判别出水轮机主轴故障类型,可应用于水轮机主轴振动信号分析。     

Strategies for high-performance supercapacitors for HEV

Our paper highlights the role of supercapacitors in hybrid electric vehicles (HEVs), the current response to the worldwide demand for a clean and low fuel-consuming transport. The main strategies for increasing the specific energy of supercapacitors, which are electrochemical energy storage/conversion systems of high-specific power, are discussed, with the focus on electrode material, electrolyte and electrode/electrolyte interface properties. Particular emphasis is given to the use of ionic liquids (IL), which are attracting much attention as green and solvent-free electrolytes, and to the development of high-voltage, IL-based hybrid supercapacitor with high surface area carbon negative electrode and poly(3-methylthiophene) positive. Based on the results of laboratory cells featuring N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide and 1-ethyl-3-methyl-imidazolium bis(trifluoromethanesulfonylimide) ILs, the specific energies of hybrid supercapacitor modules are evaluated and compared to those expected for double-layer carbon supercapacitors displaying the same ILs.     

固定床反应器催化剂装填方案的优化

脱砷反应器压降升高会严重影响压缩机的安全运行,同时也制约了装置的加工量。分析认为,压降升高的主要原因是床层空隙率减小,而空隙率减小的主要原因是床层杂质增多,堵塞了颗粒间的空隙。阐述了级配剂和除垢篮在抑制压降升高方面的作用,提出级配剂加除垢篮的组合装填方案,有效解决了固定床反应器的压降问题,使撇头周期达到9个月,并对装填方案的进一步优化提出建议。     

汽轮机低压叶片材料的选择

汽轮机低压叶片的材料选择对于保证整个汽轮发电机组的安全运行至关重要。从几个方面分析讨论了汽轮机低压叶片材料选择时需要注意的问题，并提出了解决办法。     

面向2050年的中国电力发展展望

电力转型是我国能源转型的重要环节。本文基于自主开发的适合我国中长期电力发展的源网荷储协调规划模型,将各类电源、骨干电网、需求侧资源与储能等统筹考虑,在计及相关发展目标与约束条件的情况下进行系统整体优化,求解了我国当前至2050年电力系统发展优化方案,可为研判我国电力系统发展路径、制定合理转型政策提供量化参考。     

Rules for paths construction for HENs debottlenecking

This paper is based on the heat exchanger network retrofit techniques, developed by Tjoe and Linnhoff and extended by Asante and Zhu. It considers, under the Network Pinch framework, two important cases — the Retrofit Initialisation and Topology Modification when the direct application of the classic Network Pinch concept and rules is not possible. With the help of a system of simple heuristics, these limitations are overcome which extends the application range of the Network Pinch framework.     

Water-soluble binders for MCMB carbon anodes for lithium-ion batteries

We have investigated the suitability of four different binders for the conventional mesocarbon microbeads (MCMBs) anode material in Li-ion batteries. Unlike the conventional polyvinylidene fluoride (PVDF), the binders were water soluble and were either cellulose based, such as the lithium and sodium salts of carboxymethyl cellulose (NaCMC, and LiCMC) and Xanthan Gum (XG), or the conjugated polymer: poly(3,4-ethylendioxythiophene) (PEDOT, a.k.a. Baytron). All binders were commercially available except LiCMC, which was synthesized and characterized by FTIR and NMR. Thermal studies of the binders by TGA and DSC showed that, in air, the binders have a broad melting event at 100-150 °C, with an onset temperature for decomposition above 220 °C. Li/MCMB half-cell batteries were assembled using the studied binders. Slow scan voltammograms of all cells showed characteristic lithium insertion and de-insertion peaks including that of the SEI formation which was found to be embedded into the insertion peaks during the first cycle. Cycling of the cells showed that the one containing XG binder gave the highest capacities reaching 350 mAh g⁻¹ after 100 cycles at C/12, while the others gave comparable capacities to those of the conventional binder PVDF. The rate capabilities of cells were examined and found to perform well up to the studied C/2 rate with more than 50% capacity retained. Further studies of the XG-based MCMB electrodes were performed and concluded that an optimal thickness of 300-365 μm gave the highest capacities and sustained high C-rates.     

Probabilistic design factors for pipes used for hydrogen transport

Probabilistic design factors for pipes used for hydrogen transport are proposed for 3 locations: urban, peri-urban and rural areas.The used method involves a risk equation defined as the product of probability of leakage after failure, probability to have a gas flow greater than a prescribed value, probability of ignition, probability of lethal effects greater than a threshold value and probability of the presence of a person corrected by an environment factor and a risk reduction coefficient. The results obtained are less conservative than the deterministic values provided by ASME code.     

汽轮机转子临界转速计算方法

汽轮机转子临界转速分析计算是汽轮机结构设计应用中最关键的一个环节,对汽轮机转子的安全运行和全寿命管理具有非常重要的意义。分别采取能量法和分析法的方式来计算转子的临界转速,并对两种计算方法进行了相应的对比,在实际工程中具有很高的实用价值。     

Quantitative evaluation for effective removal of phosphorus for SoG-Si

Production of solar cells has increased rapidly in recent years, and metallurgical production of solar grade silicon (SoG-Si), has increased compared with more expensive processes such as Siemens process and Cz processes. It is important to understand the thermodynamic behavior of phosphorus in slag for optimized refinement of SoG-Si. In this study, the thermodynamic behavior of phosphorus in the CaO-SiO₂-CaF₂ slag system was investigated at 1773 K for various oxygen potential and slag composition. In addition, evaporation of phosphorus in the reduction process was observed during slag refining by addition of H₂ gas.Experimental results showed that the stability of phosphorus in slag depends on both the O²⁻(basicity) content of the slag and the solubility of Ca in silicon, and the dissolution mechanism of phosphorus into slag was derived. Results confirmed that phosphorus and calcium in molten silicon were also removed by acid leaching. The effective removal of phosphorus for SoG-Si using several refining processes was evaluated quantitatively.