制冷用R-12热力膨胀阀流量系数的试验研究

本文通过试验研究了制冷装置中的热力膨胀阀的下述规律:(1)同一阀体不同阀针型式在开启过程中流量系统的变化;(2)比较两个通道设计几何相似而大小不同的阀体在开启过程中流量系数的变化规律;(3)研究同一工质在进、出口压力和进口过冷度变化时,对阀额定开度时流量系数的影响。     

电子膨胀阀的制冷剂流量特性的试验研究

以节流阀的水力学公式为基础,通过试验的方法研究阀开度,节流前后压差,压比,出口干度以及节流前后压力对电子膨胀阀的流量特性的影响。试验结果表明,电子膨胀阀具有良好的调节特性和较大的调节范围,阀节流前后的压差,压比,阀出口干度等因素对其流量系数和流量值都有一定的影响。     

制冷系统中电子膨胀阀流量系数的实验研究

利用自行研制的电子膨胀阀流量特性试验台对电子膨胀阀VPF-25D18在变频空调系统中的流量系数进行研究,分析了阀开度及蒸发温度对电子膨胀阀流量系数的影响,并且应用最小二乘法得出了流量系数在不同情况下的变化范围。结果表明：特定蒸发温度下不同阀门开度时的流量系数较小,特定阀门开度下不同蒸发温度对应的流量系数值较大,变化范围也较大。     

热力膨胀阀容量测试系统的设计

针对目前热力膨胀阀容量测试设备自动化程度低、测试精度低等缺点,依据国标QC/T663—2000的测试方法,设计了一套热力膨胀阀容量测试系统。在硬件设计上,该系统由开度测试装置、制冷剂流量测试装置和控制模块组成。在软件设计上,利用Visual Basic 6.0开发了一套可视化的测试软件。容量测试结果表明,该系统能较好地实现热力膨胀阀的容量测试,其测试精度达到了1.0%。     

膨胀阀动态响应特性的实验研究

介绍了对Ｈ型、Ｆ型热力膨胀阀和电子膨胀阀所进行的动态响应特性实验，验证了膨胀阀感受过热度的响应近似于一阶惯性延迟环节，给出了响应的延迟和时间常数值以及流量系数关系式。     

电子膨胀阀制冷剂流量系数经验模型的试验研究

根据黑箱理论提出将阀前压力、阀前过冷度、阀后压力和膨胀阀流通面积作为膨胀阀流量系数的影响参数。利用流量系数导出相对误差为1.97%～6.28%的电子膨胀阀流量特性专用试验台对上述四个参数进行了试验研究和趋势分析。依据试验和计算结果采用多元线性回归分析得到膨胀阀流量系数经验模型的关联式。通过对该关联式预测值的相对偏差分析说明其具有较高的预测精度,流量系数预测值的相对偏差在 –7.0%～6.6%之间。     

电子膨胀阀流量特性试验台的研制

为方便对电子膨胀阀进行性能测试及试验研究,研制了调试方便、易于操作的电子膨胀阀流量特性试验台。对DPF-2．4电子膨胀阀进行了流量随开度、蒸发温度、过冷度变化等试验。实验结果的分析表明,试验台设计合理。     

大型高压蒸汽阀流量特性的数值模拟

为提高动态工况下某蒸汽阀流量的控制精度,实现开度-流量的精确控制设计,采用CFD方法对其内部流场进行了数值模拟研究,以获取流量系数-开度的关系式。首先利用水介质的计算结果与前期试验结果进行比较,对有限元模型进行了验证。此后,采用蒸汽对不同开度及压差下蒸汽阀内部的流场进行了模拟计算,借鉴节流装置可压缩流体的流量方程式,获得了蒸汽阀流量特性曲线及关系式,并将其结果与理想气体得到的流量系数结果进行了对比分析,结果表明利用理想气体代替蒸汽进行流量特性研究具有一定的合理性。     

汽车空调用变排量压缩机动态特性的试验研究

通过大量的试验研究，找出了压缩机转速、排气压力以及负荷变化时对摇板箱压力、活塞行程、制冷剂质量流量的影响，为解决变排量压缩机和热力平膨胀阀汽车空调制冷系统的稳定性问题奠定了基础。     

热力膨胀阀失灵后的修复

热力膨胀阀是氟利昂制冷系统中控制制冷剂流量的一种节流装置。其结构如图所示。一、工作原理感温包3内装入制冷剂F-12。共数量应能保证感温包内的制冷剂在热力膨胀阀的动作温度范围内始终保持饱和状态。将感温包3平行固定在蒸发器的气体出口管路上方,使二者紧密接。若有液体制冷剂流到蒸发器出口,感温包即被冷却,感温包内的饱压力就降低。     

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.