压力对直射式喷嘴雾化影响的机理研究

为了揭示压力对直射式喷嘴雾化影响的雾化机理,针对D=0. 2 mm、D=0. 3 mm的直射式喷嘴采用实验和数值模拟研究。主要获得以下结论:压力是影响直射式喷嘴雾化的重要因素。压力越大,燃油液滴粒径SMD越小、喷雾锥角越大。直射式喷嘴的压力增大,雾化效果增强趋势逐渐降低;压力增大对一次雾化影响较大,对二次雾化影响较小。使用TAB模型的数值模拟结果能很好的预测出与实验一致的直射式喷嘴雾化特性,可应用于工程设计。     

高压细水雾灭火喷嘴的雾化特性研究

高压细水雾灭火系统是采用纯水液压技术的新型灭火装置,具有无环境污染、灭火迅速、用水量少和水渍损失极小等优点,是目前国际上推祟的哈龙替代系统。运用轴对称射流边界层动量积分法,对系统关键执行元件—直射式雾化喷嘴的内部流动进行分析,对边界层厚度δ和加速因子K这两个内部流动参数进行考查;同时对一些与灭火效果有关的外部雾化特性参数如出口速度和雾滴平均粒径SMD等进行分析,得出压力是影响外部雾化特性参数的最关键因素。认为8~9 Mpa是所设计喷嘴的最低稳定雾化工作压力区域。同时,喷嘴结构参数收缩角α、收缩段长度l/d对内部流动参数、外部雾化特性参数均有影响,但不明显。试验验证了上述分析结果,优选出了适合的喷嘴内部结构。     

低压旋流喷嘴喷雾特性数值仿真及结果分析

为了提高旋流喷嘴在低压下的雾化效果,对影响低压旋流式喷嘴的5个因素:旋流室直径D、旋流室高度H、喷嘴出口直径d、喷嘴出口长度l和旋流室入口数量n进行了研究.以正交试验方案确定了数值模拟的16组喷嘴结构参数组合.用Gambit进行了非结构网格划分,入口边界设为压力入口,p0=0.3 MPa,用fluent 6.3进行了仿...     

高压喷嘴几何参数对流场影响的数值模拟分析

为研究喷嘴内外部几何参数对内部流场形成的影响,在满足技术要求流量Q=0.13kg/s的情况下,分别改变喷嘴出口直径和出口圆柱段长度,用Fluent软件对圆喷嘴射流的速度变化特性进行数值模拟和分析。模拟发现,在出口直径d=0.9mm、出口圆柱段长度L=0.7mm时,速度最高;在出口直径d=1.2mm、出口圆柱段长度L=5.4mm时,出口截面速度分布最广,最为适宜枪外混合物料的喷涂操作。     

基于内外流场关联的喷嘴仿真及实验研究

针对喷嘴两级雾化之间的内部关联问题,以十字旋芯喷嘴为研究对象,对其雾滴分布特性进行了实验和仿真计算研究。首先,介绍了十字旋芯喷嘴的二维结构;然后,基于Realizable k-ε湍流模型和Pressure-swirl-atomizer雾化模型,采用Fluent软件对螺旋倾角为30°、腔体直径为6 mm、压力为4 MPa～6 MPa的喷嘴内外流场进行了仿真分析,研究了螺旋倾角大小对雾化效果的影响;最后,搭建了喷嘴雾化性能实验系统平台,用DP-02滴谱仪测得了雾化粒径分布,结合实验数据验证了仿真方法的合理性。研究结果表明：选取内流域出口流速最大值作为计算外流域入口条件更符合实际情况;随着螺旋角增大,粒径在0μm～20μm的雾滴占比越来越大,粒径在60μm～80μm的雾滴占比越来越小,该结果可以为十字旋芯喷嘴的选择提供参考。     

气体和液体压强对造雪机喷嘴雾化性能影响的仿真分析

为研究水压和气压对一种造雪机喷嘴雾化性能的影响,文中采用流体仿真的方法,建立喷嘴的三维模型,对喷嘴流域进行简化处理,通过改变喷嘴气体和液体的入口压力,运用多相流中的volume of fluid(VOF)模型和realizable k-ε模型对双流体喷嘴内流场速度进行仿真分析。由于压缩空气增加了液膜的不稳定性,利用离散相模型(DPM模型)对喷嘴外流场进行模拟雾滴的雾化情况,比较不同气、液压强下雾滴的索特平均直径(D_sm),并对结果进行分析。研究结果表明,在液体压强相同的情况下,随着气压的增大,喷射出雾滴的D_sm会出现总体减小的趋势;在气体压强相同的情况下,随着水压的增大,外流场雾滴的D_sm随着水压的增大出现增大的趋势。雾滴的D_sm受气液压强比n的影响,当n=1～2时D_sm下降幅度最大,下降幅度达到65%;当n=2～6时D_sm下降幅度较小,下降幅度达到35%,当n=1.167时,D_sm达到最大值37.63μm;n=6时,SMD达到最小值...     

气溶性射流喷嘴的结构设计及计算

设计了一种节水的气溶性射流喷嘴.该喷嘴分为进水管、进气管、混合室和Laval喷嘴四个部分.进水管在壁面上利用雾化原理加工针状小孔,使水以雾状存在于射流中,形成气溶性射流,大大的减少了用水量.根据射流清洗要求,利用雾化原理、流体力学及机械设计等相关原理,计算出喷嘴关键尺寸混合室直径、Laval喷嘴喉部直径、喷嘴出口直径分别为28mm、4mm、5.5mm.实验研究表明,证明了所设计喷嘴的射流打击能力,达到节水的目的;同时得到了该喷嘴的最佳工艺参数:在进水、进气压力分别为为0.3MPa、0.8MPa时,清洗射程达到7.2m,在喷口距测杆100mm时打击力为516.58N.     

石蜡熔融沉积的线宽试验优化设计

设计了气动式的石蜡熔融沉积装置,采用正交实验的方法,研究温度t、气压P、喷嘴直径d、喷嘴距离基板高度h和基板移动速度v等工艺参数对熔融石蜡沉积线宽的影响.实验结果分析表明:工艺参数对线宽影响的显著性由大到小依次是喷嘴直径、气压和基板移动速度,最优参数组合为t=80℃,P=0.2 MPa,d=0.4mm,v=5.4mm/s和h=0.3mm;单因素验证试验证实了正交试验结果的正确性.     

配备下限流导液管的环缝喷嘴雾化能力研究

高品质金属粉末是众多制造领域中的基础材料,微细粉末成型的关键技术在于气雾化制备阶段,而喷嘴及导液管结构和雾化工艺参数对气雾化粉末的质量有重要影响。基于高速射流流体动力学的数值模拟方法研究了雾化压力、雾化气体温度、导液管下口直径与伸出长度对配备下限流导液管环缝喷嘴雾化能力的影响,通过喷盘流场检测验证模型的可靠性。结果表明：环缝喷嘴装配下限流导液管临界入口压力为128.1 kPa,雾化压力2.0 MPa时既能有效增大雾化腔内的气体最大速度和降低最低温度,又能防止过高压力造成返喷而影响气雾化顺行。此外,在极限雾化压力2.0 MPa下,通过增大雾化气体温度、下限流导液管下口直径由5 mm降低至1 mm以及伸出长度由0 mm增大至2 mm均能继续提升气液质量流速比而提升其雾化能力。生产实践也证实了模型的预瞻性,在此优化工艺下生产顺行且粉末粒度D50仅为23.84μm。     

撞击型喷嘴雾化特性的试验研究

选用撞击型雾化喷嘴AM4进行雾化特性试验,研究了喷嘴背压对雾化液滴尺寸及分布的影响。研究发现,雾化液滴的直径随喷雾压力的增大而减小,但喷雾压力有其临界范围,该压力更有利于空气与液滴的热质交换。利用最小二乘法拟合出喷嘴雾化液滴的经验关联式,整理成韦伯数和雷诺数的函数关系,可用来预测喷嘴出口粒子的直径。     

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.