转速对变频涡旋压缩机压缩性能的影响研究

转速对变频涡旋压缩机压缩性能的影响规律尚不完全明确。为探寻转速对变频涡旋压缩机压缩性能的影响规律,从理论上分析了转速对变频涡旋压缩机单位曲柄转角下的排气量、压缩终了内压力及单位质量有效气体获得的多变压缩能量头的影响规律。理论分析发现,受转速引起的泄漏量变化的影响,单位曲柄转角下的排气量、压缩终了内压力及单位质量有效气体获得的多变压缩能量头均随转速的降低而减小,说明变频涡旋压缩机在低转速下的压缩性能欠佳。试验测试结果证明了理论研究所得结论的正确性。研究结果对变频涡旋压缩机的研发和使用有较强的指导意义。     

涡旋变频压缩机在空调中的应用

介绍了涡旋变频压缩机的主要特点及其优势，并列举了其在工程实践中的应用，指出了目前涡旋变频压缩机发展中的几个关键问题，对于今后涡旋变频压缩机的研发有一定的借鉴作用。     

涡旋压缩机滑动轴承间隙参数对效率的影响

涡旋压缩机中滑动轴承的间隙参数与容积效率及机械效率密切相关。本文分析了滑动轴承间隙参数与摩擦功耗、润滑油流量、含油率、容积效率的关系，并给出了合理的滑动轴承间隙参数，使涡旋压缩机效率较高。     

涡旋压缩机型线几何参数的优化设计方法研究

在涡旋压缩机的设计中,传统的设计方法是在满足设计要求和涡盘的加工工艺条件下给出型线几何参数,但这难以保证压缩机摩擦功耗和泄漏损耗较小,严重影响了压缩机的机械效率和容积效率的提高.本文在考虑使设计出的压缩机摩擦功耗和泄漏损耗最小的基础上,提出了一种涡旋型线几何参数设计的新方法.     

涡旋压缩机的虚拟建模与运动仿真

为了分析涡旋压缩机运动机构的动力特性和运动规律,根据涡旋压缩机的结构和工作原理,采用三维实体建模和虚拟样机软件对其运动机构进行了三维实体建模,通过涡旋压缩机的运动仿真,获得了准确的运动学参数曲线,保证了涡旋压缩机设计的正确性和可靠性,提高了整体设计效率和精度。     

涡旋压缩机在家用空调器中的应用与展望

通过对涡旋压缩机与往复活塞式、滚动转子式压缩机的性能比较，指出涡旋压缩机更适合在家用空调器中使用，同时指出以适应涡旋压缩机结构要求的新的环保型制冷剂的研究，以及空调热泵中涡旋压缩机变频特性的研究是涡旋压缩机在家用空调器应用领域的发展方向。     

涡旋压缩机结构设计

针对涡旋压缩机的特点,阐述了涡旋压缩机的密封性、运行压力比、涡旋盘载荷分布、噪声、启动特性、耐久性以及温度保护,为涡旋压缩机设计和制造提供了依据.     

天然气变频涡旋压缩机的密封研究

根据天然气变频涡旋压缩机的自身结构特点,重点分析了端面、结合面、间隙、径向和切向泄漏,提出了一套相应的密封方法,并在变频涡旋压缩机试验台上对样机进行了400 h测试,对采集的数据进行了分析.结果表明：该套密封方法能很好地密封天然气,保证了天然气变频涡旋压缩机的可靠性,进而为变频涡旋压缩机在天然气压缩中的广泛应用提供了理论和试验依据。     

涡旋压缩机中主要结构参数及运行参数的最佳选择

选取渐开线基圆半径、涡旋盘高和涡旋圈数作为可变参数，通过模拟计算确定出这三者之间的关系及比功率最小时的最佳参数组合，并给出了最佳参数组合下变转速运行时可确保其效率较高的转速范围。这将为涡旋压缩机的结构优化提供设计依据     

汽车空调涡旋压缩机研究

叙述了涡旋压缩机的型线理论，推导了涡旋压缩机的行程容积公式，介绍了汽车空调涡旋压缩机的基本结构，讨论了涡旋压缩机的几何参数和型线优化。     

大功率潜水电机冷却系统分析方法与试验研究

为了研究大功率潜水电机的温度分布规律,以580 kW潜水电机为例进行分析。依据工作条件建立温度场计算模型,实现流固耦合自动传热并可模拟内外冷却介质的流动;以定转子铁耗定值、油摩损耗和铜耗变量作为热源施加方式,基于冷却系统参数影响关系得到温度场与流场间双向耦合关系,由此提出一种冷却系统分析方法;采用该方法研究冷却系统结构参数影响规律,并对比不同叶轮工作特性下冷却系统计算结果以得到最优叶轮参数。室内空载试验和海边负载试验结果表明：铁耗和温度的试验值与仿真值间相对误差在5%以内,所设计冷却系统在不同负载下可稳定运行。     

捞油抽子密封橡胶筒力学性能研究

密封橡胶筒的形变、应力以及其受油管内壁摩擦力对采油漏失率和使用寿命有着直接影响.采用弹性力学中的拉梅解答经过坐标变换得到轴向应力函数表达式,再通过密封橡胶筒边界条件和物理定律建立与油管内壁受力关系.得到橡胶筒形变、应力状态、摩擦力之间的函数关系,这种函数关系将有助于对井下捞油抽子进行定量研究.     

Covariance upperbound controllers for networked control systems

This paper deals with designing covariance upperbound controllers for a linear system that can be used in a networked control environment in which control laws are calculated in a remote controller and transmitted through a shared communication link to the plant. In order to compensate for possible packet losses during the transmission, two different techniques are often employed: the zero-input and the hold-input strategy. These use zero input and the latest control input, respectively, when a packet is lost. For each strategy, we synthesize a class of output covariance upperbound controllers for a given covariance upperbound and a packet loss probability. Existence conditions of the covariance upperbound controller are also provided for each strategy. Through numerical examples, performance of the two strategies is compared in terms of feasibility of implementing the controllers.     

A robust scheduling of projects with time, cost, and quality considerations

CAM programs can generate cutting tool paths to be used by machining centres. Experience shows that CAM programmed feed rates are rarely achieved in practice during machining, especially when finishing free-form surfaces. These slower feed rates are due to the machines’ kinematic capabilities and behaviour of the numerical control (NC). To improve control over the machining process, applications need to be developed to predict the kinematic behaviour of the machines, taking the mechanical characteristics of the axes and NC capacities into account. Various models to simulate tool paths in linear and circular interpolation have been developed and are available in the literature. The present publication will first focus on the use of the polynomial model to simulate the behaviour of the machine when passing through transitions between programmed blocks with tangency discontinuities. Additional features are proposed to ensure enhancement of the match between the model and the machine’s behaviour. Analysis of machine behaviour shows that NCs do not always allow the axes to reach maximum performance levels, with an attendant loss in productivity. The present article proposes an optimisation procedure allowing control laws to be defined to reduce time spent in the transition. The contributions made by these optimised control laws are then evaluated, while impediments to their implementation are also considered.     

不同阻尼层材料对交替层合各向异性阻尼结构动态性能的影响

采用正交试验极差分析方法,研究了各阻尼层对7层各向异性交替层合阻尼结构阻尼性能和刚度的影响大小规律,并在此基础上就不同阻尼层材料对结构性能的影响进行探讨。结果表明：对于7层交替层舍的各向异性阻尼结构而言,对结构刚度影响最大的阻尼层为第4层,对结构内耗值大小与频率范围和温度范围影响最大的阻尼层分别为第2层和第6层;结构内耗的温频特性与各阻尼层材料及其厚度密切有关,一般第2层越厚,其内耗的频率特性越好。     

Cutting-system dynamics

The attractive sets formed in the vicinity of equilibrium (asymptotically stable orbital limiting cycles, two-dimensional invariant tori, and chaotic attractors) are analyzed. The bifurcations of the system in parameter space and the space of control parameters are considered. General laws of stability loss of the equilibrium in a cutting system are outlined.     

Prediction of Power Losses Due to Tooth Friction in Gears

Sliding friction between gear teeth is recognized as one of the main sources of power loss in geared transmissions as well as a potential source of vibration and noise. Its accurate modeling is therefore of primary importance in efficiency and vibration analyses of mechanical transmissions. For lubricated contacts, various empirical friction laws based on results from simulators can be found in the literature. One of their limitations comes from the specimen surface texture, which is often different to that of actual gears. Moreover, most of these models were established for high slide-to-roll ratios and cannot be used for low slide-to-roll ratios as encountered near the pitch point in gears. In this article, friction measurements were derived from an EHL simulator with contact conditions and surface finish close to those in gears and which covers a wide range of sliding/rolling conditions. A new traction law is proposed and integrated in a three-dimensional dynamic model of gears with consideration of tooth friction. The numerical results are then compared with the experimental evidence from a gear test rig. It is observed that tooth friction can strongly affect dynamic transmissibility through bearing mounts. Finally, the need of an accurate friction model for reliable power loss predictions is stressed.

     

有源声学结构次级声源的布放规律研究

有源声学结构是近年来提出的一种控制结构低频声辐射的有效方案,它是智能结构在有源噪声控制领域的具体应用。次级声源的优化布放是有源声学结构研究中的核心问题,本文对此进行了研究。首先建立了有源声学结构的计算模型,然后基于声辐射模态和结构振动模态理论,推导总结出各种情况下次级声源的最优布放规律,最后用一系列的计算机仿真实例对该规律进行了验证。     

公差设计多目标模型及其粒子群优化算法研究

为解决成本一公差设计模型中忽视产品质量的问题，以新型的田口质量观和Pareto最优解集概念为基础，提出了一种公差设计多目标模型。该模型将加工成本和质量损失分别作为设计目标，并以统计法公差装配成功率为约束条件，获得了比极值公差法更加宽松的公差限。改进了传统的粒子群优化算法，利用Pareto最优性重新定义粒子，然后采用快速非支配排序技术进行粒子的适应度排序，使其能够有效地对多目标模型进行求解。该算法对具体工程实例求解时，一次运行就可求得令人满意的Pareto最优解集，设计者可以根据生产实际和市场需求从中进行选取。通过对求得的Pareto进行最优前沿的分析，可得到该类零件公差设计的特性，其结果验证了公差诒计的一船规徨．     

采用仿生学与TRIZ相结合的水泵能效优化装置的研究

从水泵传输系统节能角度出发,运用仿生学与发明问题解决理论(TRIZ)相结合的方法,设计出一种水泵能效优化装置.利用FLUENT软件对该能效优化装置进行计算流体动力学(Computational Fluid Dynamics,CFD)对比实验分析,找出了其内部流场参数速度、压力等的变化规律.实验证明该装置能减少水泵出口处...