基于Simulink仿真的SCR化学反应动力学模型研究

现阶段SCR(Selective Catalytic Reduction)技术是柴油机降低尾气中NOX的最主要手段之一。随着日趋严格的排放法规的实施,要求SCR后处理系统具备更精确更稳定的控制。基于化学反应动力学的氨储闭环模型是SCR系统尿素喷射控制策略的研究方向之一。本文基于Matlab/Simulink建立的SCR化学反应模型,结合台架及整车试验,可以更高效的优化调整各反应参数,从而使得整个SCR控制系统的精确度、灵活性以及稳定性进一步提高。     

船用低速柴油机低压SCR系统性能试验验证技术研究

船用低速柴油机低压选择性催化还原(LP-SCR)系统是一种能够显著降低氮氧化物(NOX)排放的技术。本文主要针对船用低速柴油机LP-SCR系统开展性能试验验证技术研究,并与MAN公司LP-SCR系统性能曲线进行对比分析。结果表明尿素喷射量稳态配机试验中船用低速柴油机LP-SCR系统NOX转换率与MAN公司LP-SCR系统NOX转换率性能曲线基本一致,氨逃逸水平较低,NOX减排性能及NH3泄漏控制非常出色;尿素喷射量动态响应试验在船用低速柴油机升负荷、降负荷、突降负荷和突升负荷条件下进行,尿素溶液喷射动态响应效果好,与设定值基本一致,变工况下NOX排放始终处于较低水平;在模拟海况条件下,尿素溶液喷射响应效果好,与MAN公司LP-SCR系统性能曲线吻合,NOX排放保持较低水平。     

柴油机SCR系统故障检测诊断箱的开发及试用

正柴油机用途广泛,是工程机械和各种车辆的主要动力源。国家相关法规对柴油机尾气污染物排放量要求越来越严格,仅凭机内净化技术难以达到尾气排放标准要求,必须采取机内净化技术与后处理技术相结合的措施,方可达到相关法规要求。1.开发诊断设备的重要性采用选择性催化还原(SCR)技术将是实施我国柴油机国Ⅳ排放标准的主要后处理技术。SCR系统主要由催化消声器、尿素罐、尿素喷射计量泵(简称尿素泵)、氮氧化物(NOx)传     

基于V模式的智能SCR软件开发及应用

为满足非道路国四排放标准对柴油机排气污染物NOx限值的要求,结合基于模型开发的设计思想和V模式开发流程,完成了从需求架构设计、MATLAB/Simulink建模开发、软件测试确认的智能SCR软件开发。智能SCR软件的控制策略主要包括催化器模型、前馈控制模型、氨存储计算模型、尿素量修正模型、尿素喷射控制模型等。然后将智能SCR软件与柴油机其它控制功能进行软件集成,并将生成的ECU软件刷写至非道路国四ECU。最后在试验台架上完成了多组冷机和暖机的非道路瞬态循环(NRTC循环)测试。试验结果表明:在NRTC试验循环下,NOx转化效率最高达到了94.46%,经催化还原后的NOx排放值达到了0.464g/(kW·h),低于非道路国四排放标准对排放物NOx的排放限值要求,开发的智能SCR软件可以批量应用于非道路国四柴油机。     

柴油机SCR尿素沉积物模拟分析

构建了14步反应和11种组分的柴油机SCR尿素喷射系统详细化学反应模型。考虑了氨气和异氰酸的生成,还涉及到缩二脲、三聚氰酸和三聚氰酸一酰胺等重要固体副产物的形成。就柴油机中尿素在喷射点到催化器入口前端间的排气管路中的分解过程构建三维模型,分别调入详细机理模型与总包反应机理模型进行比较,结果表明两种机理模型预测的NH3浓度生成趋势相符,详细机理模型能够预测主要沉积物缩二脲和三聚氰酸的生成规律。     

柴油机SCR尿素流量计的设计与试验

为准确快速检测柴油机SCR系统尿素喷射量,设计了尿素流量计的结构和信号处理电路,制定了尿素流量计结构和元器件参数的优化策略,并进行了参数最优匹配;对三款尿素喷射流量计进行了性能检测、尿素喷射量和NH3泄漏等测试试验.结果表明:优化后的尿素流量计线性度误差、灵敏度误差和输出信号误差率分别0.36％、0.30％和0.54％.证实了尿素流量计优化与控制策略的切实可行性;表明了设计的SCR系统尿素喷射流量计适合柴油机在线实时检测要求,为柴油机满足国Ⅳ排放标准提供了保障.     

SCR系统故障诊断策略研究

国六重型柴油机选择性催化还原(SCR)系统能有效的降低尾气中的NOx排放,若发生故障导致SCR系统无法正常运行,便会加剧对环境的影响。为了保证SCR系统可持续性的工作,需对SCR系统增加故障诊断系统OBD,其中故障诊断系统包含监控和管理,系统的诊断管理包含故障识别、故障反应、故障的存储及读取。通过MATLAB/Simlink软件建立仿真模型,使用SourceInsight工具将模型生成代码,并写入ACU(尿素喷射控制单元)中,构成控制系统。试验结果表明:诊断系统可以检测出SCR系统中的相关故障,并触发相应的故障反应,有效的避免发动机由于SCR系统问题导致尾气超标。     

柴油机SCR瞬态参数采集处理与诊断系统

基于尿素SCR系统瞬态特性,开发了适合柴油机SCR瞬态参数的测试与诊断系统;采用DASYLab软件,编写了接口、标定与诊断程序,实现了SCR系统信号显示、存储与再现等功能;依据遍历跟踪与诊断程序,实现了对柴油机SCR系统瞬态特性参数的在线测试与诊断;依据柴油机瞬态测试循环法规,进行了柴油机SCR系统的NOx转化效率、尿素喷射量和NH3泄漏量等测试与诊断试验。结果表明:与标准的AVL测试系统(AVL CBE-Ⅱ气体排放分析与测试系统)相比,所研发的系统动态最大误差为2.05%,动态平均误差为0.82%,故障诊断精确率达到了98.6%,能满足柴油机SCR瞬态测试循环要求。     

尿素喷射管路对气助式尿素喷射装置性能影响研究

SCR系统是目前较为成熟的重型柴油机尾气后处理技术,其中尿素泵、尿素喷嘴是SCR系统的核心部件,与尿素喷射管路共同组成发动机尿素喷射系统,其喷射精度、雾化质量等性能直接影响柴油机SCR系统的NOx转化率和NH3泄露量。为了探究尿素喷射管路对气助式尿素喷射系统性能的影响,搭建发动机试验台架,使用不同规格的尿素喷射管进行ESC、ETC排放试验,并通过关键过程数据的对比分析,研究尿素喷射管对气助式尿素喷射系统性能的影响。试验结果表明,采用不同规格尿素喷射管能够影响空气辅助尿素喷射系统对NOx的处理效果以及氨气的泄漏量;尿素管路内径较粗,会影响尿素的正常喷射,导致ESC循环各工况点NOx尾气浓度不稳定,带来氨泄漏的增加,尿素喷射量较大的高负荷工况更加明显;喷射管长度较长会影响尿素喷射的瞬态响应性,适当减小尿素管长度有助于提高气助系统对NOx的转化效果、降低氨泄漏风险。搭建的常用气助式尿素喷射系统,使用内径3 mm,长度1.5 m以内的尿素喷射管最优。     

选择性催化还原反应器数值模拟及仿真研究

以柴油机为动力装置排放的氮氧化物是大气的首要污染物,选择性催化还原技术(SCR)是控制氮氧化物的主流技术.文中建立了耦合计算流体动力学和化学动力学的实际柴油机尿素-SCR反应系统的三维数值模型,对SCR系统的内部工作过程进行了模拟仿真.分析各种参数的变化对尿素-SCR系统NOx转化率的影响,为优化尿素SCR反应器的结构指出研究方向,使其在各种环境下,氮氧化物的转化率都能达到比较理想值,以降低氮氧化物的排放,减小对环境的污染和破坏.     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

ANGULAR DISTORTION ALLOWABLE VALUE AND ASSESS METHOD OF WELD ON COKE TOWER

A graph as the new engineering method for estimate the safety of bulging deformation of coke tower is proposed. Through stresses analysis of circumferential weld of coke tower and comparing the stresses produced by pressure with heat stress of steady state, residual stress, bending stress produced by both itself weight and wind loads, it showed that the stresses produced by pressure on the angle distortion are the main factor of equivalent stress of the combined stress. After comparing four kinds of stress controlling conditions, the relation to stress with depth of angular distortion, grade of curvature of angular distortion and half of region of angular distortion has been inferred. Graph of deformation allowable value of coke tower for different condition by angular distortion and half of region of angular distortion has been plotted. The five steps for its engineering use have been explained. The lighter the grade of curvature is, the larger of bulge allowance, may be, and the bigger of depth of angular distortion may pose too. For the coke tower with a popular structure of Dg 5 400 mm×28 mm, the result by graph is nearly more than the result of two formulas formed by other research, the error is less than 7.0%. But, the graph can be easily applied to different size of angular distortion.