不同头部间距下三头部燃烧室点火过程研究

为了探讨不同头部间距对某型航空发动机燃烧室点火过程中火焰传播特性的影响,建立三头部燃烧室燃烧试验系统,开展流动与点火过程中火焰传播特性、头部间距对周向点火过程影响规律的实验研究.研究表明:燃烧室的周向点火过程具有阶段性,在初始火焰发展阶段,火焰首先顺着流线方向传递,待燃烧强度增大到一定值时,火焰才开始向其他区域延伸;在相同工况下,头部间距较小时,相邻旋流器之间的局部回流区相互影响增大,油气掺混效果增强;随头部间距增加,流动因素对火焰传播的作用减小.     

不同头部间距下三头部燃烧室点火过程研究

为了探讨不同头部间距对某型航空发动机燃烧室点火过程中火焰传播特性的影响,建立三头部燃烧室燃烧试验系统,开展流动与点火过程中火焰传播特性、头部间距对周向点火过程影响规律的实验研究.研究表明:燃烧室的周向点火过程具有阶段性,在初始火焰发展阶段,火焰首先顺着流线方向传递,待燃烧强度增大到一定值时,火焰才开始向其他区域延伸;在相同工况下,头部间距较小时,相邻旋流器之间的局部回流区相互影响增大,油气掺混效果增强;随头部间距增加,流动因素对火焰传播的作用减小.     

甲烷二次燃烧火焰传播速度的数值模拟研究

二次燃烧是常见热力设备和高速推进燃烧室内的重要现象,但目前对二次燃烧的研究较为匮乏。为了研究当量比、甲烷添加量对二次燃烧自点火火焰传播速度的影响情况,论文利用CHEMKIN软件中火焰速度反应器模拟研究了向不同当量比(0.3~0.9)甲烷/空气一次燃烧产物中添加不同量(摩尔分数0.02~0.24)甲烷时的自点火火焰传播速度。研究表明当量比主要是通过影响尾气温度和一次燃烧产物中富余氧气来影响火焰传播速度,而甲烷添加量会影响二次燃烧时局部当量比,局部当量比在1附近时火焰传播速度最大。     

一种增压直喷发动机的Miller循环燃烧室系统

该新型燃烧室系统包括屋脊型缸盖燃烧室、浅坑式活塞、Masking进气道、中置火花塞、侧置直喷六孔菱形喷油器。结合小包角进气型线形成深度Miller循环,提高发动机的几何压缩比,增大节气门开度,减小泵气损失;Masking进气道在进气行程初期组织形成高强度滚流气流,增强压缩终了时的气流湍流强度,加快火焰传播速度、缩短燃烧持续期;侧置直喷六孔菱形喷油器配合燃烧室形状,形成合适的混合气空间分布状态。综上,本燃烧室系统能够使发动机降低比油耗,提升热效率     

贫油直喷燃烧室回火的数值研究

针对燃烧稳定性中的回火问题,对贫油直喷燃烧室的回火特性进行了研究.燃烧中的回火指的是火焰从燃烧室传入到了预混区中的这样一种现象,它包含了声波、湍流、燃烧之间的复杂的相互作用,是燃烧研究中的关键问题之一.利用Fluent中的混合分数/PDF平衡化学反应模型对贫油直喷燃烧室进行了大涡模拟,分别计算了冷态和热态下的流场,捕捉了贫油直喷燃烧室内回火的动态过程,其中亚格子模型采用WALE模型,燃油射流采用离散相模型.研究结果表明,大涡模拟能够较好地反映流场分布情况,贫油直喷燃烧室内存在中心回流区,模拟结果与实验结果吻合较好;贫油直喷燃烧室中的回火发生在中心流区域,回火时,中心回流区向上游移动,这促使了火焰的向上游传播,并最终导致了回火的发生.     

某型燃机燃烧室的数值模拟

燃料喷嘴双级径向旋流器在燃烧室内形成稳定的回流漩涡结构,有助于燃烧室火焰稳定和提高燃烧效率。文中建立了计算模型,利用CFX软件进行燃烧室的燃烧模拟,研究了燃烧室中流场分布、NO含量分布、温度场分布、燃料分布。模拟计算表明,此燃烧室具有较好的气动特性、稳燃性能与冷却性能,能够在额定工况下长时间稳定工作。     

凹槽火焰稳定器前缘结构对煤油超声速燃烧的影响

采用离散液滴模型、概率密度函数紊流燃烧模型和两方程紊流模型数值,模拟了双模态冲压发动机燃烧室内不同前壁面结构凹槽的超声速燃烧火焰稳定特性。在相同的计算条件下,数值分析结果表明:与具有正规凹槽结构的燃烧室相比,具有斜面凹槽结构的燃烧室:壁面静压分布更加合理;其内涡量比较强;燃烧室出口总压恢复系数和燃烧室效率都比较大。因而认为斜面凹槽火焰稳定器提高了混合和燃烧,优于正规凹槽火焰稳定器。     

燃烧室形状对醇醚燃料发动机燃烧和排放影响的数值模拟

为了研究燃烧室形状对醇醚燃料发动机燃烧和排放特性的影响,在压缩比不变的条件下,设计了5种不同形状的燃烧室,运用AVL_Fire软件对具有不同形状燃烧室发动机的燃烧过程进行了模拟计算。结果表明,缩口燃烧室E内气流运动最强烈,缸内平均压力较高,NO和soot排放很低;直口燃烧室A的缸内压力最低,噪声小,NO和soot排放较低;敞口燃烧室B的NO排放最高,soot排放较低。尖底凸台对气流的导流效果比圆底、平底凸台要好,更利于挤流的形成和发展。缩口燃烧室内的挤流强度比直口、敞口燃烧室强烈。     

以天然气为燃料的燃气轮机燃烧室燃烧场数值模拟

某燃气轮机以天然气为燃料,对其燃烧室燃烧流场进行数值模拟,得到典型工况的速度场、温度场、CO2分布,总结了燃烧室出口温度不均匀度、燃烧效率的变化规律。结果表明:旋流器的导向作用明显,在火焰筒头部出现了明显的回流区,有利于火焰稳定;随着工况升高,燃烧室出口平均速度增大、CO2质量分数增大,燃烧效率提高;燃烧室出口温度分布均匀,掺混孔的掺混效果较好。     

提取内燃机燃烧压力高频成分进行压力高频振荡研究

研究内燃机缸内压力高频振荡的机理以及压力高频振荡对燃烧噪声的影响。利用小波分析技术确定缸内压力高频振荡出现的范围,从而确定了燃烧室空腔声模态模型的对应曲轴转角范围。用声响应法和有限元法分别测量和计算不同曲轴转角下燃烧室空腔声模态,并对测量值和计算值对应曲轴转角进行了温度修正,模态试验结果与有限元计算结果较吻合。并对测量的缸内燃烧压力信号和噪声信号进行了分析。研究结果表明：缸内燃烧压力高频振荡是燃烧室的多阶共振频率受到激励引起共振的结果,燃烧压力高频振荡是影响燃烧噪声的重要因素。     

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.