排气歧管-增压器结合面密封失效分析及优化

针对某型号汽油机在排气歧管裂纹试验中出现的排气歧管-增压器结合面废气泄漏问题,从试验运行条件、试验失效件着手,分析导致其密封失效的影响因素,并借助于Abaqus软件分析引起失效的根本原因。提出强化增压器结构和优化增压器垫片回弹性能的优化方案。结构优化后的增压器垫片及局部强化的增压器,通过了排气歧管裂纹试验考核,解决了漏气问题。     

基于面心组合的排气歧管响应曲面优化设计

为解决发动机排气歧管结构优化通常采用单因素控制变量法或正交试验法带来的参数交互作用不显著等局限问题,采用中心复合试验设计(Central Composite Design)方法中的面心组合法构建响应曲面优化.以某重型载货汽车的发动机排气歧管为研究对象,实现了排气歧管38组结构参数的快速匹配,建立了多项式数学模型,得出了...     

一种新型法兰连接垫片设计

垫片是法兰连接接口的重要密封元件,在螺栓预紧力的作用下对法兰密封面施加压紧力,由垫片填塞住法兰面凹凸不平的微观几何间隙来实现密封.文中对现有的垫片进行改进,采用一种金属波齿骨架与O型圈结合,石墨填充辅助密封的垫片结构.法兰接口的螺栓拉紧后,内侧O型圈变形量可达到40％以上,外圈橡胶圈变形接近30％,垫片能达到良好的密封效果,此时法兰接口的主要密封环节是由垫片内侧的橡胶圈在起作用.当橡胶圈的变形量达到使波齿骨架变形时,金属波齿骨架、O型圈和石墨材料三者共同起密封作用.     

基于TRIZ的不锈钢歧管法兰焊后变形解决方案

近年来,我国汽车产业迅猛发展,发动机产量持续增加。而一台发动机的优劣主要从三个方面衡量,动力性、经济性和排放性能,这些都与排气歧管有着密不可分的关系。但在不锈钢排气歧管的焊接过程中,法兰与弯管(蚌壳)焊后变形严重,造成法兰平面度超差,损害了不锈排气歧管的产品质量,甚至造成装机后排气系统密封性不足,进而影响发动机动力性、可靠性以及耐久性。[1]对此,本文研究了法兰焊接后变形的原因,并采用TRIZ创新理论体系中的系统分析法、因果分析法、矛盾分析法、物场分析法等对法兰焊后变形问题进行逐步系统的分析,以便找出解决的方案。     

高温螺栓法兰连接的紧密性评价方法

提出了高温螺栓法兰连接的紧密性概念;试验研究了柔性石墨填充缠绕式垫片、金属冲齿板柔性石墨复合垫片和金属包覆垫片的压缩回弹性能、蠕变性能和基本密封性能;通过试验数据的回归分析得到了垫片高温性能表达式;将试验得到的垫片变形特性和泄漏特性统一于螺栓法兰连接中进行系统分析,建立了紧密性评价方法。该方法不仅可对在役螺栓法兰连接的泄漏状况作出评价,而且为密封连接的设计、新型垫片的开发以及垫片性能的评价提供了借鉴。     

某汽油发动机异常早燃信号问题的分析解决

保护发动机的早燃控制策略是通过爆震传感器采集到相对一般爆震的振幅增大的信号,该信号的积分值超出早燃阈值,及该信号发生在判定早燃时间窗口区域内。本文论述了一种因发动机排气歧管垫片热胀冷缩后,产生异常振动,爆震传感器将该振动信号误判为早燃导致的振动信号。通过对排气歧管垫片进行优化设计,最终解决了异常振动的产,为其他汽油发电机早燃问题、排气歧管振动问题的排查解决通过了参考依据。     

某发动机排气歧管热应力仿真与分析

运用GT-POWER、STAR-CCM+与ABAQUS软件,采用流固耦合的分析方法,对某发动机排气歧管进行温度场与热应力场分析,并针对分析结果进行若干优化改进。首先利用GT-POWER仿真得到流体计算中所需的入口条件,再利用STAR-CCM+软件对排气歧管进行流体分析,并将得到的排气歧管壁面温度以及对流换热系数映射到ABAQUS的固体网格上得到温度场,通过ABAQUS进行热应力以及热变形分析,得出排气歧管开裂是热应力过高所致。据此对排气歧管进行若干结构改进,经对比确定方案3可有效减小排气歧管热应力,说明该方案是解决排气歧管开裂问题的有效方法。     

增压发动机排气歧管开裂问题分析与解决措施

某四缸增压直喷发动机在整机台架试验过程中出现排气歧管开裂问题。为解决此问题,首先,现场确认失效排气歧管的开裂程度及位置。其次,进行失效分析,对失效样件进行断口分析、断口周边元素检测,初步确认排气歧管开裂原因。再次,通过计算机仿真分析对排气歧管开裂真因进一步确定,并制定整改对策。最后,样件整改并策划试验进行验证。结果表明:排气歧管开裂位置为热应力分布最大的区域,长期冷热冲击致使排气歧管在此位置表现为开裂失效。因此,通过排气歧管结构优化,降低开裂位置的热应力,并通过发动机可靠性试验验证确认整改方案有效,此问题最终得以解决。     

非金属垫片螺栓法兰连接寿命评价

分析非金属垫片密封的时效特性,考虑高温条件下材料退化和垫片载荷松弛过程对密封性能的影响,依据多孔介质理论,建立非金属垫片密封的时效泄漏模型.将螺栓法兰连接系统寿命划分为密封寿命和部件寿命.提出密封寿命试验方法,在考虑垫片泄漏特性变化的基础上,基于指标泄漏率分析螺栓法兰连接系统密封寿命;基于蠕变和疲劳损伤准则分析高温螺栓的剩余寿命,探讨螺栓法兰连接系统的密封寿命和各部件寿命之间的关系.建立螺栓法兰连接系统的寿命预测最弱环模型,将垫片的变形特性和泄漏特性统一于螺栓法兰连接系统中进行研究,提出基于指标泄漏率和结构完整性的螺栓法兰连接系统寿命评价方法.     

基于CAE仿真的某发动机排气歧管设计研究

以某款增压型汽油发动机的排气歧管为研究对象,运用CAE仿真软件搭建发动机仿真分析模型,比较不同排气歧管方案下的发动机性能,给出最有利于发动机性能的排气歧管连接方式和结构尺寸。文中的研究可指导发动机排气歧管设计阶段的正向开发工作,并为后期优化改善工作提供了一定的思路和方法。     

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.     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.