基于LMD边际谱的柴油机气门故障诊断

针对柴油机气门间隙故障诊断问题,在WP7柴油机上模拟了多种气门间隙故障,测取了正常及故障条件下的缸盖振动信号。考虑柴油机缸盖振动信号具有非平稳的特点,提出一种基于局部均值分解边际谱和马氏距离的故障诊断方法。该方法在LMD边际谱的基础上定义了频率中心,并以此作为柴油机气门间隙的故障特征,利用马氏距离判断柴油机气门的工作状态。试验结果表明:该方法可以有效地提取柴油机气门间隙故障特征,实现柴油机气门机构故障诊断。     

基于平行因子分析的振动信号盲分离方法研究

发动机缸盖振动信号为卷积混合信号,为消除延时滤波的干扰,提出了平行因子分析和快速独立成分分析结合的盲源分离方法,并对振动仿真信号与缸盖振动信号进行分析,结果表明:消除干扰后,分离得到的信号有更高的信噪比。利用分离信号的奇异值特征向量动态聚类对发动机进行故障诊断,应用实例表明:消除延时滤波影响后,发动机故障诊断精度提高47.17%。     

柴油机气门故障特征提取方法研究

针对柴油机气门故障诊断问题,在柴油机上模拟了气门间隙异常、气门漏气故障,同步测取了正常和故障情况下的缸盖振动与瞬时转速信号,提出了基于阶比跟踪的振动信号等角度重采样方法,准确地实现了振动信号时间域到角度域的转换,避免了频谱泄漏及混叠。考虑到缸盖振动信号的非平稳特性,应用经验模态分解法将振动信号分解成一系列具有不同尺度的内禀模态函数,利用三维Hilbert谱提取了反映柴油机故障的特征参数。试验结果表明:研究方法可以有效地提取柴油机振动信号的故障特征,从而实现柴油机配气机构故障诊断。     

局域波边界谱在缸盖振动信号分析中应用研究

提出了一种新的谱分析方法－局域波边界谱，分析研究了柴油机缸盖表面振动信号的特性，较为详细地讨论了激励源及其响应，指出了基于傅立叶变换之上频谱分析的不足，同时对试验数据进行了有效的分析和比较，结果表明，在柴油机状态监测和故障诊断中，利用局域波边界谱对缸盖表面振动信号进行分析是有效的和可行的。     

基于粗糙集和神经网络的柴油机故障诊断

介绍了粗糙集理论的核心内容和ROSETTA软件的特点,给出了基于粗糙集理论的柴油机缸盖振动信号的故障诊断系统。以某型号大功率柴油机为例,首先将提取的缸盖振动信号经过小波包消噪和时域、频域分析,构造出用于故障诊断的特征值,然后应用ROSETTA软件约简特征属性,最后通过神经网络进行故障模式分类。通过对比ROSETTA软件处理前后神经网络的输出结果,表明粗糙集理论能优化特征属性,有效地减少神经网络的输入节点数,提高故障分类的准确率。     

基于双谱的柴油发动机活塞销故障诊断

为了从柴油发动机振动信号中提取出活塞销故障特征,采用双谱对振动信号进行了分析,并在双谱模域内沿平行于对角线的直线,按特定步长搜索双谱特征频率面,计算其平均幅值得到号特征参数,最后利用GA-BP神经网络成功地对故障进行了模式识别.试验结果表明,对于EQ6BT发动机,诊断活塞销故障的最佳部位为发动机缸体下部左右两侧机体,最佳转速为1 800 r/min,特征频率为1.3～3 kHz;信号特征不仅存在于对角线上,还大量存在于对角线以外的区域;采用双谱分析提取故障特征,结合神经网络进行故障诊断,效果良好.     

基于粗糙集和神经网络的内燃机转子振动故障诊断方法研究

提出了一种基于粗糙集和神经网络的柴油机转子振动故障诊断方法。首先计算传感器采集数据的小波包,提取振动信号能量特征,其次粗糙集对不同振动信号能量特征数据离散方法的基础上,针对数据结构特征确定了等频离散法与公平尺度法相结合的离散方法,最后以获取的规则为输入,利用BP神经网络进行故障诊断。将我们建立的故障诊断方法应用到柴油机转子振动系统中去,表明了该种方法的有效性。     

遗传算法在气门机构故障诊断中的应用

通过模拟柴油机气门机构的2种主要故障-气门漏气和气门间隙异常进行试验,采集柴油机缸盖表面的振动信号,计算 了柴油机缸盖振动信号的小波包能量、时域能量、最大幅值和奇异性指标。建立了振动信号的AR和ARMA模型,最后利用遗传算法进行自动再生最佳特征参数,得到了优化的气门机构故障诊断表达式,结果表明利用该表达式可以更简捷有效地进行故障诊断。     

CMI发动机燃油喷射系统工作原理及故障诊断技术分析

基于CMI发动机燃油喷射系统的系统构造,通过对该型发动机燃油喷射系统的驱动燃油泵、燃油计量组件、燃油分配器和燃油喷嘴等主要部件的系统构造和工作原理进行分析,深入阐述了该燃油喷射系统各部件的故障机制及故障表征现象,提供了该燃油喷射系统常见故障的诊断方法及故障排除措施,为该型发动机燃油喷射系统的日常维护、故障诊断及排除和故障预防提供了有力依据。     

基于图像识别技术的旋转机械振动故障诊断方法

目前振动信号的分析主要是针对特定测点在某一瞬间采集的一段振动波形,提取其中的特征量来进行故障诊断,这种基于状态信息的诊断方法对故障类型的辨别能力有限。通过构造基于归一化幅值谱的三维矩阵来刻画旋转机械振动故障的过程变化规律,并引入图像识别技术,在此基础上建立了一种基于归一化幅值谱图识别的旋转机械振动故障诊断方法。并通过该方法对试验台获取的振动故障信号进行分析,计算结果表明该方法是一种有效的故障诊断方法。     

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.     

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。     

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.     

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     

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%.