EGR混合长度对各缸不均匀性的仿真分析及优化

应用软件模拟某型电控单体泵柴油机的工作过程,研究因引入废气再循环(EGR)后进气歧管结构的改变对各缸EGR率差异的影响,找出EGR混合长度对各缸EGR率的影响规律,并结合喷油提前角的修正改善各缸排放的不均匀性。结果表明:适当地延长EGR混合长度能使各缸的EGR率差异减小,结合喷油提前角的修正能使各缸的排放更均匀,工作过程更平稳。     

基于CFD仿真分析与试验验证的EGR率均匀性研究

为满足非道路柴油机第三阶段排放法规要求,设计了一种简单、低成本的无冷却器废气再循环(EGR)系统。本文主要研究四缸非道路柴油机采用这种EGR系统的各缸EGR率分布的均匀性。首先通过一维仿真计算得到三维CFD分析计算的边界,然后通过三维AVL FIRE仿真软件计算得出进气管及EGR管路的气体流场。计算结果发现除了瞬态EGR率波动有差异外,采用和不采用EGR混合器的柴油机各缸EGR率均匀性差异不大。通过试验证明,采用和不采用EGR混合器确实对于EGR率较小的增压非中冷柴油机性能影响很小。     

基于AMESim柴油机电控单体泵喷射系统仿真研究

介绍了电控单体泵的结构组成和工作原理,针对柴油机的燃油喷射系统建立了数学模型,并利用AMESim软件建立了仿真模型,通过柴油机运行实验和喷油特性实验数据对仿真模型进行了验证,借助AMESim仿真模型展开了电控单体泵燃油喷射系统的各关键性因素(高压油管直径、高压油管长度、柱塞直径、凸轮型线速度、柴油机转速)进行了分析。     

文丘里管废气再循环系统对涡轮增压柴油机性能影响的研究

加装文丘里管的高压废气再循环(Exhaust gas re-circulation,EGR)进气系统,在兼顾柴油机经济性、动力性的前提下,研究该进气系统对NO_x排放的影响。根据一款柴油机的基本结构建立柴油机一维仿真计算模型和燃烧室的三维仿真计算模型。在对模型进行标定和对柴油机原机性能仿真计算的基础上,为进气系统引入文丘里管装置并对其结构参数进行优化设计。应用所建立的一维和三维柴油机模型,对文丘里管EGR系统柴油机的经济性、NO_x和Soot排放特性进行仿真计算研究,并对计算结果进行试验验证。研究结果表明,优化设计的文丘里管EGR系统可使柴油机在欧洲稳态循环(European steady state cycle,ESC)各工况下实现较为理想的EGR率,并在不明显影响柴油机燃油经济性的前提下,使NO_x排放量下降了约28.4%。文丘里管进气系统可以实现较为理想的高压EGR循环,在柴油机ESC工况下(怠速除外)能够达到较为理想的EGR率。     

基于EGR的高压共轨柴油机排放性能仿真研究

采用工作过程联合燃烧分析的方法,分析了EGR对TBD234共轨柴油机排放性能的影响。利用工作过程分析软件对配有EGR系统的TBD234柴油机进行建模及仿真分析,将计算结果作为初始条件对柴油机缸内燃烧过程进行燃烧计算分析,研究了不同EGR率下共轨柴油机排放特性。结果表明,随着EGR率的增加,NOx的排放显著降低,但soot生成量明显提高,燃烧过程的最高压力和最高温度降低,放热速率减小,燃烧进行变缓。当EGR率达到0.4时NO的生成量降低到原机的2.25%,但是soot的生成量几乎是EGR率为0.3时的两倍,所以在较高负荷情况下应该采用小EGR率。     

基于DOE喷油策略和EGR的耦合优化研究

利用发动机性能仿真软件GT POWER建立了某柴油机模型。选取喷油提前角、喷孔直径和EGR率为自变量,在保证动力性和经济性的基础上以降低NOx和Soot排放为目标进行实验设计(DOE),并对仿真结果进行了评估。应用多目标帕累托法进行参数寻优,得到了优化后的喷油提前角、喷孔直径和EGR率。验证表明拟合结果与模拟结果基本吻合。     

16V240ZA型柴油机多次喷射数值模拟

利用流体动力学软件FIRE对机车柴油机进行缸内多次喷射燃烧模拟,通过仿真计算,得出不同喷油方案下,柴油机各项性能参数的计算结果。研究结果表明:在总循环喷油量不变的情况下,采用预喷射喷油策略比单次喷射在控制燃烧放热率方面有明显优势;当预-主喷间隔角为5°时,能够在不恶化碳烟排放的同时降低氮氧化物的排放。     

某四缸机EGR各缸均匀性计算和结构优化

利用AVL BOOST软件针对某四缸柴油机建立带有EGR系统增压直喷柴油机的一维工作模型,根据设计好的EGR率,计算得到不同工况下的EGR流量、进排气流量等参数。根据BOOST计算结果,利用AVL FIRE软件进行EGR各缸均匀性的CFD计算,分析EGR均匀性计算结果,优化进气管结构,最终获得理想的EGR均匀性。     

车用柴油机电控高压喷油系统与欧Ⅲ排放标准

为了满足日益严格的排放控制法规,提高燃油喷射压力、控制喷油速率、控制喷油正时成为未来柴油机的发展趋势.详细介绍了电控单体泵喷油系统工作原理.采用此系统理论上可以达到欧Ⅲ排放标准.     

单体泵电控燃油喷射系统的研究

电控单体泵喷油系统是一种能够自由灵活调整喷油量和喷油正时、具有高喷射压力的新型燃油喷射系统。系统地分析了电控单体泵（EUP）燃油喷射系统的结构和原理,介绍了系统的工作过程和主要功能,对基于MC68376单片机的柴油机燃油喷射电控系统的组成及其功能进行了介绍。单体泵燃油系统成为大功率柴油机的理想燃油系统极具前景。     

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.     

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....     

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。     

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.