一种新型商用CO_2跨临界循环压缩机开发与研究

介绍了一种新型商用跨临界CO2循环压缩机,并对此压缩机的关键部件,如壳体和连杆的设计及其应力分布进行分析,同时对压缩机内的油路进行设计,保证压缩机内油压平衡.在自行设计的跨临界CO2压缩机性能测试试验台对跨临界CO2压缩机及其热泵系统进行了系列实验研究,根据实验数据拟合出压缩机的等熵效率和容积效率公式.研究结果表明,在吸气压力为4.0 MPa,气冷器排气温度为25℃工况时,压缩机制热量在58～65 kW之间,制冷量在49～52 kW之间.跨临界CO2热泵系统在按照"一次加热"方式进行实验时,名义工况下出水温度分别为55℃和85℃时,热泵系统制热系数COPh分别为3.46和2.82.系统性能系数随着气体冷却器出水温度的升高而降低,但却随着蒸发器进水温度的升高而升高.冷却水进水温度越高,热泵系统效率越低,因此热泵热水器系统更适于"一次加热"供水系统.     

毛细管长度对热泵热水器系统动态性能的影响

对使用4种不同长度毛细管的空气源热泵热水器系统的动态性能进行了试验研究,分析了毛细管长度对压缩机排气温度、系统耗功率、蒸发压力、冷凝压力、制热量及系统性能系数(COP)等的影响.试验结果表明,在加热初始阶段,采用短毛细管的热泵热水器系统性能优于使用长毛细管的系统性能,而在加热后期则恰好相反.为了提高加热周期内热泵系统的平均性能系数,在加热过程中分别切换使用长度为150mm、250mm和350mm的3种毛细管,其动态性能试验表明,可大大提高热泵热水器系统的性能,其平均COP约为4.6.在整个加热阶段,压缩机的排气温度未超过90℃,保证了压缩机在一个安全稳定的条件下运行.     

透平压缩机迷宫密封泄漏量的数值仿真研究

给出了适用于透平压缩机迷宫密封泄漏量的修正模型,并用修正模型对变结构参数下的泄漏量进行规律研究.通过采用工程常用迷宫密封泄漏量理论公式,计算了不同压比下透平压缩机典型平滑型和曲折型迷宫密封流量系数,对比了试验结果,修正了流量系数值;在此基础上,进一步研究了不同间隙和齿数下泄漏量的规律,以研究参数变化对泄漏量的影响.研究结果表明:对于平滑型密封结构,修正模型的修正系数可选择在0.8~1.2;对于曲折型密封结构,修正模型的修正系数可选择在0.7~0.8.本文提供了一种较为准确、工程性的透平压缩机迷宫密封泄漏量模型的修正系数.     

《流体机械》2008年1～12期目次索引

题目名称期页压缩机制冷剂不冷却电动机的往复式半封闭压缩机温度系数变化规律研究1 1往复压缩机气体压缩热力过程研究1 22活塞压缩机CAD设计系统研究1 43不同叶高直板扩压器对压缩机级性能的影响3 19喷油单螺杆压缩机热力性能影响因素的试验研究4 4CO2跨临界循环双级压缩系统     

变频冰箱性能影响因素的实验研究

为了使变频冰箱的控制策略能很好地适应各种复杂多变的工况,针对影响变频冰箱性能的一些因素进行了实验研究.该实验以两温室的变频冰箱作为实验对象,以冷藏室温度作为控制目标,在不同工作环境温度和压缩机转速等变工况下,从冰箱制冷系统制冷量与热负荷的关系角度,根据冷冻室温度和冰箱能耗的不同变化分析了环境温度、压缩机转速等因素对变频冰箱性能的影响.研究结果表明,环境温度会影响冰箱制冷系统的热负荷和两温室的温度匹配关系,当冰箱处于不同环境温度时,可以通过调节变频压缩机输气量和冷藏室目标控制温度来实现冰箱两温室温度的匹配控制和改善能耗的目的.     

活塞式制冷压缩机变工况下容积效率的试验研究

研究了不同蒸发温度和冷凝温度下,活塞式制冷压缩机容积效率的变化。在现有理论的基础上,采用试验的方法,通过对不同工况下制冷剂质量流量的监测,定量分析了压缩机的容积效率变化规律。试验中采用某型号不同功率压缩机进行测试,其结果表明压缩机的容积效率随着蒸发温度的降低和冷凝温度的升高而降低,特别是在当蒸发温度低于-35℃时,压缩机的容积效率已经小于50%,严重影响了压缩机的能效。对于不同功率的压缩机,随着蒸发温度由-15℃下降至-40℃,其容积效率从70%多降至30%左右,功率越小的压缩机,容积效率下降得越快。特别是低蒸发温度对小功率压缩机的容积效率影响比较大,其下降率接近60%,容积效率只有30%左右。试验研究为制冷系统的性能改进提供参考,在低温制冷系统的设计时,一定要合理选用活塞式制冷压缩机,以实现节能的目标。     

CFA34往复压缩机排气温度高原因分析及处理

针对高压空气系统中CFA34往复压缩机末级排气温度高报警故障,通过对往复压缩机排气温度高常见原因分析,从气阀、活塞环、中间水冷器、进气缓冲罐滤网、冷干机等进行故障排查,找到故障症结并提出处理措施,为此类往复压缩机故障分析与处理提供了参考。     

往复压缩机变负荷工况阀片运动规律及气缸内状态仿真研究

为了更好地了解往复式压缩机在不同工况下阀片的运动规律以及气缸内压力、温度的变化情况,对压缩机气缸及阀片运动规律进行了模拟仿真研究。采用有限元分析手段建立了往复压缩机的三维流场模型,在变负荷工况下,运用Fluent软件模拟分析了压缩机气阀与气缸工作状态;在正常工况下,模拟了压缩机气阀的运动情况和气缸内的压力变化情况,并利用往复压缩机实验台进行了实验验证;在气量调节工况和不同的阀片顶开位移的工况下,针对压缩机进行了模拟,得到了不同工况下阀片运动规律、气缸内示功图及气缸内温度变化规律。研究结果表明:针对机组复杂运行状态可用计算机仿真研究进行深入模拟,获得贴近实际运行状态的数据,对分析压缩机运行状态,改进优化气量调节系统具有重要作用。     

涡旋压缩机的流场特性研究

涡旋压缩机工作时,内部流场存在三维非稳态特性。为了研究其特性,本文利用动网格技术对涡旋压缩机的内部流场进行了数值仿真分析,得到了不同径向间隙下工作腔内的压力及温度的分布、出口温度及输出流量曲线,研究了径向间隙对涡旋压缩机工作性能的影响。结果表明：在相同转速下,径向间隙对涡旋压缩机工作腔内的压力及温度分布、出口温度及输出流量都有一定的影响。     

叶轮损失模型对离心压缩机性能预测的影响

针对目前离心压缩机损失模型的差异性,在总结离心压缩机叶轮损失模型的基础上,提出在计算各截面参数时采用多变系数替换绝热指数的方法.并利用MATLAB编写程序计算压缩机在不同流量和不同转速下的压比和效率.通过和单级离心压缩机性能实验数值比较,分析叶轮损失模型对压缩机性能的影响,得出了采用简化的叶轮损失模型对压缩机效率影响较大而对压比影响较小的结论.     

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.