基于多重分形去趋势波动分析的风力机轴承故障诊断

风力机传动轴轴承振动信号具有典型的非平稳和非线性特征,传统状态监测及故障诊断方法难以同时满足故障程度识别及部位诊断的需求。为此,针对定速轴承故障数据及变速的风力机轴承故障数据,采用多重分形去趋势波动分析方法,分析轴承在正常和不同故障状态下振动信号的多重分形特征,采用3种多重分形谱参数以表征振动信号的分形特征,结果表明:多重分形去趋势波动分析方法对于定速轴承和变速轴承均能进行有效的故障状态识别;轴承振动信号具有典型的多重分形特性,且较之正常状态,故障状态下多重分形特性更为明显,多重分形谱函数峰值对应的奇异指数更小,且当轴承处于内环故障时最小时,说明该参数可有效判断轴承运行状态及故障位置。因此,通过多重分形去趋势波动方法可获取故障特征参数,为风力机轴承故障诊断提供理论基础和实现途径。     

基于自适应变分模态分解及多重分形谱的风力机轴承故障分析

风力机齿轮箱轴承故障信号具有典型非线性及非平稳特性,采用自适应变分模态法对4种状态下振动信号进行分解,提出基于分形盒维数-峭度阈值法(Adaptived Variational Mode Decomposition,AVMD)对处理所得分量进行筛选,选取富含故障信息的分量进行信号重构,采用多重分形去趋势波分析方法,分析重构信号的分形特征并识别其工作状态,结果表明:基于多重分形去趋势波分析法对非稳定轴承可进行有效地故障识别;轴承振动信号具有典型分形特征,在不同时间尺度下,标度指数、广义Hurst指数与多重分形谱均可反应轴承工作状态;3种多重分形谱参数对故障类型敏感度不同,谱函数最大值对应的奇异指数对内圈故障较为敏感,峰值占比对外圈故障较为敏感,分形谱宽对滚珠故障较为敏感。     

基于EEMD及分形方法的轴承振动信号分析

为对具有强烈非线性特征的轴承振动信号做出准确的故障识别,基于分形理论,采用辅助经验模态分解(Ensemble Empirical Mode Decomposition,EEMD)对信号进行降噪预处理,采用G-P算法分析轴承不同状态下振动信号关联维数。研究表明:基于EEMD的降噪方法可有效对振动信号进行降噪;轴承工作状态不同,其振动信号关联维数具有明显的可区分性,当轴承处于外环故障时,其关联维数最大为4.7,当轴承处于滚珠故障时,其关联维数最小仅为3.0,当轴承处于正常/内环故障时,其关联维数分别为4.0/3.2。因此,利用关联维数能定量识别轴承的不同故障状态及位置。     

基于分形学的轴承故障诊断分析

为识别轴承的工作状态及故障类型,针对非线性振动信号,基于分形盒维数与小波降噪方法,计算了轴承正常状态及不同故障状态的振动信号盒维数。结果表明:轴承的故障类型不同,其振动信号盒维数亦不同,正常状态盒维数最大,内环故障盒维数最小,其值分别为1.6和1.4。因此,根据盒维数能定量识别轴承故障状态与故障位置,本研究可为轴承状态监测和故障诊断提供理论依据。     

一种新型改进阈值函数的第二代小波降噪方法

为了有效去除机械故障信号中含有的噪声并提取故障特征,在小波阈值降噪的基础上,提出了一种新型改进阈值函数的第二代小波降噪方法。该方法是利用第二代小波对信号进行分解,采用新型改进阈值函数对分解信号的小波系数做阈值处理,同时引入基于类可分离性测度的降噪评价准则,实现对复杂振动信号降噪效果的评价。将所提出的方法应用于仿真信号和实测信号的分析与评价,结果表明:该方法融合了第二代小波和改进阈值函数的优点,能更好地消除噪声。     

基于改进变分模态分解与支持向量机的风力机轴承故障诊断

为研究风力机齿轮箱轴承振动信号非线性及故障诊断问题,采用改进变分模态分解方法对四种状态轴承振动信号进行处理,提出无量纲参数多重分形谱值因子,联合峭度值对分解所得模态分量进行选取,剔除无效信息分量并进行信号重组,采用分形维数研究重组信号的分形特征,并通过支持向量机进行模式识别。结果表明：基于样本熵优化的改进变分模态分解方法可获得高质量的模态信息;通过多重分形谱值因子及峭度选取并重组的信号具有良好的振动特性,其分形维数可通过信号非线性程度定量区分轴承工作状态;采用支持向量机对不同轴承工作状态的重组信号进行分类,结果具有较高的准确度。     

发动机振动信号特征参数的多重分形研究

提出利用多重分形谱参数来表征发动机振动信号特征的新方法.运用多重分形理论对实测的发动机缸体振动信号进行分析,计算了振动信号的多重分形谱参数,并探讨多重分形谱参数与发动机运行状态之间的内在联系.结果表明:多重分形谱参数能定量刻画振动信号的特征.随着发动机工作状态的不同,信号的多重分形谱参数也发生变化.发动机振动越剧烈,多重分形谱参数越大,其能够反映发动机的真实运行状态,可以作为发动机状态监测和故障诊断的特征参量.     

基于KF-PP分析的风电轴承故障模式识别

针对风力发电机组滚动轴承动态信号呈非正态、非线性,故障特征提取和初期故障诊断困难的问题,提出了基于核函数的投影寻踪分析故障模式识别方法。从轴承关键部位采集振动信号,经消噪预处理后,建立能够有效表述轴承运行状态的10特征指标数据空间,以基于核函数的投影寻踪方法构建故障评价体系,将待评估样本与评价体系进行对比分析,实现轴承故障的分类与识别。利用Matlab软件平台对实验数据进行仿真验证,结果表明,基于核函数的投影寻踪分析方法是一种有效的故障模式识别方法,能够实现轴承正常运行及故障类型的准确判断,具有良好的可靠性和可行性。     

运用非线性动力系统理论进行船舶柴油机故障诊断

针对柴油机表面振动非稳态与多激励性的特点,从非线性动力系统理论角度进行信号的分析与处理。运用小波模量最大值对气缸盖螺栓表面的振动信号消噪,计算气门不同状态时的多重分形维数谱,定义故障特征向量,从而识别不同的故障。结果表明,这种方法对气门故障诊断是极为有效的。     

柴油机磨合状态下振动信号多重分形研究

为监测柴油机的磨合过程,提出利用多重分形谱参数表征柴油机振动信号特征的新方法.运用多重分形理论对柴油机磨合过程中缸体的振动信号进行分析,并计算振动信号的多重分形谱参数,探讨多重分形谱参数与柴油机磨合状态之间的内在联系.结果表明:多重分形谱参数能定量刻画振动信号的特征.随着柴油机磨合过程的进行, 振动信号多重分形谱参数出现规律性的变化.不同阶段信号的多重分形谱参数呈现出递增或递减趋势,反映了柴油机磨合状态的变化过程.     

小型锅炉烟尘测试时锅炉出力的计算

锅炉烟尘测试时,必须对锅炉出力进行测试。但监测中,许多小型锅炉往往不具备相关的计量装置和仪表,为解决这一问题,文章提出了用烟气量和空气过剩系数来计算锅炉的出力的公式,在实际使用中,该方法简单易行,其结果和实测值具有很好的一致怀。     

Unerroric of control of mutual compliance of the efficiency of hydrogen engines of unmanned vehicles in the conditions of mass production

The issues related to the reliability of hydrogen engines of unmanned vehicles and increasing the efficiency of using hydrogen as fuel when using the method of its production during the decomposition of hydrogen-containing molecules of liquid-phase organic compounds in a plasma discharge under the action of intense ultrasonic exposure are considered. Experiments have shown that as a result of decomposition in the acoustoplasma discharge of liquid hydrocarbons, solid-phase carbon-containing products are formed, chemical transformations occur in the liquid phase and hydrogen-containing combustible gas is formed. Hydrogen-containing gas can be used as fuel immediately after synthesis, i.e. it does not require separation, since in addition to hydrogen it contains only impurities of CO₂ and water vapor. The purpose of the study is to formalize the basic conditions for tightening the control of mutual compliance with the efficiency of hydrogen engines of the same series in the conditions of their mass production. Methods of mathematical statistics and hardware-software modeling were used in the study. The term “unerroric of quality mutual compliance control” is introduced to describe a set of hardware and software tools for such control. The principle of in-depth testing of the technical condition of such engines of one series is described in a multidimensional formulation of the quality control problem for three of their operating parameters at once. The conditions for increasing the mutual correspondence of the measured values of such parameters in the conditions of serial production of hydrogen engines are formalized.     

中国煤炭地下气化技术的发展

本文综述了煤炭地下汽化技术的国内外发展现状,对我国“长通道、大断面”煤炭地下气化新工艺给予了技术经济评述,并提出了发展煤炭地下汽化技术的政策建议。     

Review of theory of distortion and disintegration of liquid streams

Linear and nonlinear analyses of the instabilities and distortion of liquid streams injected into a gaseous media are discussed. The various fundamental mechanisms and the predictive capabilities for the distortions are emphasized. Round jets, planar sheets, annular sheets, and conical sheets are discussed in detail. The balance between capillary and inertial forces is primarily examined. The method for simplifying the analyses in the case of thin liquid sheets is discussed. The capabilities for representing the droplet size distribution that follows the stream disintegration are outlined.     

MgO膨胀剂细度对MgO水化和水泥浆体膨胀的影响

基于《水工混凝土掺用氧化镁技术规范》中的Ⅰ型氧化镁（MgO）,研究了该型MgO膨胀剂（MEA）细度对掺粉煤灰水泥浆体膨胀性能的影响。即采用X射线衍射分析(XRD)及同步热分析（TG DSC）分析了掺MEA水泥浆体中MgO的水化性。结果表明,养护温度相同时,MEA的细度对水泥浆体内MEA中MgO的水化和水泥浆体的膨胀无显著影响,产生的膨胀均能补偿水泥浆体的收缩;MEA的细度可从试验设计采用的45 μm筛筛余15%左右增加到30%左右,这将有利于MEA生产企业的节能降耗。     

机车车轮多轴疲劳强度安全评定的研究

使用ANSYS8.0软件对高速列车车轮进行了三维有限元分析,计算出车轮在直线、曲线和道岔条件下牵引、制动共6种工况时孔边薄弱部位的应力,分别通过Mises等效平均应力方法、Sines平均主应力方法和应力分量中考虑平均应力方法计算出应力在极值位置时的等效应力幅、等效平均应力,从而进一步算出车轮的安全系数,对其疲劳强度进行评定,并对3种方法进行了比较研究。     

Constructal optimization of the geometry of an array of micro-channels

This paper documents the geometric optimization of an array of circular and non-circular ducts. The optimization was carried out numerically using finite volume method. As optimal dimensions were independent of the array configuration, the numerical simulation was performed on a unit cell. Numerical optimization for circular, square and isosceles right triangle cross-sections of channels was performed. Based on the results of this investigation, some correlations were proposed to predict the optimal hydraulic diameter and dimensionless heat transfer per unit volume. In addition to examining the effect of pressure drop on these parameters, it was showed that among the different geometries of this study, square cross-section has the most efficiency for a given volume. The numerical results of the present study were compared with approximate results reported in the literature which a good agreement was observed.     

固体热辐射Yong性能分析

本文对漫灰均温物体在常物性条件下对外辐射传热的Ｙｏｎｇ值计算建立了数学模型。通过与物体内能Ｙｏｎｇ公式的数值计算比较,得出了辐射能量的Ｙｏｎｇ值不大于内能Ｙｏｎｇ值的结论。从初步的热射Ｙｏｎｇ值计算公式发现。Ｙｏｎｇ与物体表面辐射率有关。     

Measurements of concentration distribution of hydrogen jet using deflection of center of the laser spot

The main purpose of this work is to propose a new method to evaluate the concentration distribution of the hydrogen jet by using a He–Ne laser through the jet. This research attempts to apply the expression of concentration Gaussian distribution, the refraction formula of inhomogeneous refractive index medium, and the concentration inversion function to disclose the displacement of the center of the laser spot at different heights in the gas jet. The spot images of the laser beam passing through the gas jet at three vertical heights z = 10d, 20d, 30d, and different radial positions are obtained. The radial spatial asymmetry of the gas jet is also found in the experiment. Finally, the calculated concentration distribution curve and the fluent simulation curve, it is found that the two results are very similar. Our findings show that the error between the concentration distribution of this method and the simulated concentration distribution reaches 2.43%.     

Heat of vaporization of mixtures

General expressions for the heat of vaporization of mixtures at constant pressure; at constant temperature; and at constant pressure, temperature, and composition are proposed. The last one is related to the liquid-vapor interface where steady vaporization or condensation is taking place. Numerical examples by the proposed expressions are shown for binary mixtures of HCFC22(R22) and (HCFC123(R123) © 1997 Scripta Technica, Inc. Heat Trans Jpn Res, 25(1): 12–24, 1996