关于引进丹麦种猪生产性能与适应性的观察初报

足够小,否则很难保证气阀关闭时能随之关闭液阀,故要求F2m inF2m in>W2-P1(7)2气阀弹簧气阀弹簧4的上端为固定端,下端为浮动端,气门关闭,弹簧受载最小,气门完全打开,弹簧受载最大,按结构条件取气阀位移量为ΔH1,分析F1ma     

光照电厂筒形阀安装工艺

设置了筒形阀之后，筒阀随着机组开停机程序同步开闭，可以明显减少机组停机制动时间，动水关闭快速可靠，筒阀阀体紧靠导水叶外缘对称承受水压，所需启闭力小，无需充水平压开启，因而使机组开停操作程序大大简化     

“电磁阀”讲座——第十三讲 电磁组件(导阀)设计

电磁组件或称电磁铁是构成电磁阀的二大组件之一。在直动型电磁阀中,它直接与阀体组成电磁阀产品。在先导型或反冲型电磁阀中,它与主阀组件组成电磁阀产品,因它引导主阀开关动作,所以也称导阀。它是产品的关键部件,因此要求精心设计。     

怎样选用电磁阀

电磁阀的生产厂家,为了适应不同工艺过程的要求,积极研制各种规格的专用电磁阀,并提供相应的维修措施和设备。用户在选用电磁阀时,应遵循下述基本要点。1.确定阀门类别电磁阀按流通通道可分为两通、三通、四通、五通等四类,一般常用两通阀控制管路的开和关,三通和四通阀多用在以压缩气为介质的管路上。三通阀又叫单向阀,有常开和常闭两种。四通阀和五通阀有记忆功能,又称双向阀。因而在选用电磁阀时,首先根据控制管路的介     

安全阀阀瓣传感器优化设计及实验研究

为解决生产装置长周期运行与安全阀年检之间的矛盾,安全阀现场检测技术越来越重要.在将弹簧安全阀阀瓣设计成传感器的思路基础上,进一步采用方形膜片传感器结构来采集泄放口的压力变化,从而实现安全阀运行状态参数的检测.进行了结构优化设计,得到高响应传感器的设计方案,通过现场排放实验验证,表明新阀瓣传感器满足安全阀基本性能要求,同时也具有现场检测功能.     

电喷发动机怠速不良的诊断与排除

该文主要介绍一台丰田佳美轿车,由于怠速控制阀上阀体沙眼穿孔,轻微裂缝,冷却液渗漏到阀内,水垢将阀体内腔堵塞,阀轴卡死不能旋转,阀门不能开启,从而失去怠速控制功能的诊断与排除的过程。     

比例阀控制模块750-632 万可电子(天津)有限公司

正宽度仅有12mm的WAGO比例阀模块750-632可将液动或气动比例阀轻松连接到WAGO-I/O-SYSTEM,进而通过Profibus、Devicenet、Ethernet/IP等现场总线或各种工业以太网实现组网控制。无论是单向控制或双向控制,两个单向阀或一个双向阀,750-632都可提供紧凑和高性能的方案。该模块具有较高的功率输出,其中单通道模式最大可输出2A的电流,双通     

基于流固耦合的多路阀斗杆联强度分析

在挖掘机斗杆强度设计的研究中,由于多路阀斗杆联内部流道压力大、能量消耗高导致阀体变形严重,采用一般方法不能精确的分析阀内应力及变形情况.利用RNG k-ε湍流模型、结构动力学方程,采用流固耦合方法对多路阀斗杆联内部变形和应力分布进行了计算,分析了流固耦合作用对不同工况阀体强度的影响.计算结果表明:斗杆联阀体最大变形发生在油液合流通往执行机构转折处,在各油路进口处及回油处变形较小;各流道转折处及高压油口处存在明显的应力集中现象;阀体的应力和变形均随着阀内流场压力的增大而变大.计算结果将为多路阀结构的优化设计提供一定参考.     

磁阀式可控电抗器晶闸管导通角控制策略

研究了磁阀式可控电抗器的控制系统及其工作原理。提出了磁阀式可控电抗器晶闸管导通角的控制策略,利用线路检测电路、同步信号电路的拓扑结构,并利用单片机构建了微机控制系统。该控制系统采用闭环控制方式,通过其反馈部分来控制晶闸管导通角的大小以调节可控电抗器的容量。故控制系统使得磁阀式可控电抗器能够随着输电线路传输功率的变化而自动平滑地调节自身的容量,充分对输电线路进行无功补偿,为可控电抗器的工业应用提供了一定的理论依据。     

减振器环形阀片弯曲变形的有限元分析

为研究可调阻尼减振器阀系阀片变形与阀片两端压力的关系,首先对某种电磁阀控可调阻尼减振器进行试验,得到阀系两端的压强差,然后通过对阀系进行拆解在CATIA软件中分别建立复原阀阀片和压缩阀阀片的三维模型,并在ANSYS软件中进行有限元分析,得到不同压强下阀片的弯曲变形量.分析结果表明,根据有限元分析得到压强与阀片变形量关系可以有效减少阀片弯曲变形研究的计算量,对深入研究该种减振器阀片变形量与阻力关系具有重要意义.     

Passive microfluidic gas valves using capillary pressure

In this study, we developed micro gas valves which can control the gas pressure inside microfluidic systems in a simple and passive way. We designed a microfluidic chip having a liquid reservoir, a gas chamber and a microchannel connecting them to demonstrate both a micro relief valve and a micro regulator on a chip. We fabricated and tested the microfluidic chip to check the feasibility of the proposed micro valves. Test results show that when the gas pressure is greater than the relief pressure the micro relief valve discharges the gas decreasing the system pressure down to the atmospheric pressure. Also, the micro regulator kept the system pressure constant regardless of the degree of the over-pressure at pressure source. The proposed valves would be good candidates for cheap and reliable gas pressure controller in various microfluidic systems using gases.     

Passive MEMS Valves With Preset Operating Pressures for Microgas Analyzer

In this paper, we present integrated disk-in-cage poppet valves with tuned spring stiffness for gas flow control of a microgas analyzer. The valves require zero power and close at preset offset pressures (0–35 psig) to switch from gas sample loading onto a preconcentrator to concentrated constituent sample injection into a microgas chromatograph. Air flow rates of 4.5 mL/min at pressures of $-$ 2.5–$-$5 psig (vacuum sample loading) were measured. Hydrogen leak rates of 0.1 $muhbox{L}/hbox{s}$ (0.006 mL/min) were measured with valves closed at 15 psig. Analytical and numerical modeling was used to guide design of valve spring constants (ranging from 10 to 1500 N/m) that control the valve open position, flow rate, and closing pressure. The parameter design space is limited to a range of seat overlap, valve size, and spring stiffness that will allow adequate flow rate, sealing, and closing at predictable pressures. A linear curve defining closing pressure as a function of spring constant, valve gap, valve size, and seat overlap fit measured closing pressure data and can be used to predict closing pressure for future designs. $hfill$ [2008-0002]      

基于VMD-SVD的单向阀微弱故障诊断方法

针对大型往复式机械高压隔膜泵单向阀振动信号中的微弱故障特征难以提取,且磨损击穿故障、卡阀故障及正常状态振动信号难以识别的问题,提出一种基于变分模态分解和奇异值分解的单向阀微弱故障特征提取及诊断方法。首先对振动信号进行VMD分解,再借助能量百分比和方差贡献率筛选出包含丰富故障信息的模态IMF分量,其次对筛选后的IMF分量构建初始特征矩阵,然后利用SVD对特征矩阵进行分解,得到特征矩阵的奇异值作为表征微弱故障信号的特征向量,最后应用多变量预测模型对单向阀微弱故障进行诊断。工程实验结果表明,该方法能有效地提取出单向阀微弱故障信号特征并能对单向阀状态类型进行有效识别。     

Proportional directional valve based automatic steering system for tractors

Most automatic steering systems for large tractors are designed with hydraulic systems that run on either constant flow or constant pressure. Such designs are limited in adaptability and applicability. Moreover, their control valves can unload in the neutral position and eventually lead to serious hydraulic leakage over long operation periods. In response to the problems noted above, a multifunctional automatic hydraulic steering circuit is presented. The system design is composed of a 5-way-3- position proportional directional valve, two pilot-controlled check valves, a pressure-compensated directional valve, a pressurecompensated flow regulator valve, a load shuttle valve, and a check valve, among other components. It is adaptable to most open-center systems with constant flow supply and closed-center systems with load feedback. The design maintains the lowest pressure under load feedback and stays at the neutral position during unloading, thus meeting the requirements for steering. The steering controller is based on proportional-integral-derivative (PID) running on a 51-microcontroller-unit master control chip. An experimental platform is developed to establish the basic characteristics of the system subject to stepwise inputs and sinusoidal tracking. Test results show that the system design demonstrates excellent control accuracy, fast response, and negligible leak during long operation periods.     

一种供氧面罩防窒息活门测试系统的设计研究

针对供氧面罩防窒息活门性能检测,及其对人体呼吸模式影响的研究需求,研制了多参数采集、分析及统计一体的供氧面罩防窒息活门测试系统。该系统基于CompactDAQ平台,以面罩压、通气流量信号采集为基础,采用LabVIEW软件开发,可对开启压力、吸气阻力、通气流量峰值、潮气量、呼吸频率等参数进行分析统计。通过实验验证,该系统具备了对防窒息活门主要性能检测,及人体呼吸参数分析统计的能力。该系统便于携带,扩展性强,人机界面友好,运行可靠,较好的满足了防窒息活门检测、研究的需求,同时该系统的设计方法为供氧面罩其他性能参数的检测的提供了一种思路     

Dynamic analysis of a pilot-operated two-stage solenoid valve used in pneumatic system

A dynamic model was developed to study the dynamic characteristics of a pilot-operated two-stage solenoid valve used in pneumatic system. The dynamic model couples motion of the valve spindle with fluid in the system. While solving the system equations, vibration of the valve spindle, characteristics of the pressure-flow across valve orifices, pressure variation in valve chambers are taken into consideration. The model is validated by experimental results. With this model, the stability and dynamic response of the valve system for different operating conditions were discussed. The study identifies some critical parameters, which have significant effect on the dynamics of the system. A review of the obtained results indicate that the solenoid valve undergoes soft self-excited vibration, period-one hard self-excited vibration, period-two vibration, period-four vibration leading to stable working with the quasi-steadily increase in supply pressure or supply flow rate. Increasing in diameter of valve orifice d_b or decreasing in pre-compression of the valve spring z₀, half-cone angle of the valve spindle α, diameter of valve orifice d_a would improve anti-disturbance capacity and increase stable region of the solenoid valve.     

安全阀特性试验数据自动采集处理方法的研究

目前,安全阀的开启、关闭压力、压力波动值等特征参数的判断均由试验人员结合经验总结出来,准确度有待验证。针对该问题,文章提出了一种新的适用于安全阀小流量特性试验数据自动采集处理方法;以柱塞式安全阀为例分析了安全阀小流量溢流过程,给出了试验所采用的液压系统简图,详细介绍了数据采集处理软件的设计与实现。试验结果表明,该方法可直接测量安全阀溢流过程中的开启压力、关闭压力、最大压力和最小压力以及压力波动值等特征参数,并自动判断这些特征参数是否符合《MT419—1995液压支架用阀》标准的要求,具有操作简单、界面人性化等特点。     

弹簧式安全阀在线校验阀瓣微启识别技术

目前,安全阀在线校验由于没有一种有效的阀瓣微启识别技术,普遍存在校验准确性差的缺点.以高性能C8051F340单片机为控制核心,由精密拉杆式位移传感器位移变化作为触发启动附加力检测,采用安全阀弹簧受力形变特性曲线法进行阀瓣微启识别,具有准确性高、形象直观、操作方便等特点,从而提高安全阀在线校验结果的准确性和可靠性.现场实验表明,气态介质的安全阀相对于离线台测量值误差优于±2％,在行业中具有很高的推广价值.     

Characteristic studies of the piezoelectrically actuated micropump with check valve

This study presents the design and fabrication of a novel piezoelectric actuator for a micropump with check valve having the advantages of miniature size, light weight and low power consumption. The micropump is designed to have five major components, namely a piezoelectric actuator, a stainless steel chamber layer with membrane, two stainless steel channel layers with two valve seats, and a nickel check valve layer with two bridge-type check valves. A prototype of the micropump, with a size of 10 × 10 × 1.0 mm, is fabricated by precise manufacturing. The check valve layer was fabricated by nickel electroforming process on a stainless steel substrate. The chamber and the channel layer were made of the stainless steel manufactured using the lithography and etching process based on MEMS fabrication technology. The experimental results demonstrate that the flow rate of micropump accurately controlled by regulating the operating frequency and voltage. The flow rate of 1.82 ml/min and back pressure of 32 kPa are obtained when the micropump is driven with alternating sine-wave voltage of 120 Vpp at 160 Hz. The micropump proposed in this study provides a valuable contribution to the ongoing development of microfluidic systems.     

基于AMESim的安溢活门系统动力学仿真

在对安溢活门工作原理和动态特征方程研究的基础上,建立安溢活门及其试验系统的AMESim模型,对试验过程中安溢活门的动态特性进行数值仿真,从系统角度研究该安溢活门系统整体性能.仿真结果与试验测试结果吻合较好,并着重研究主副弹簧刚度、主副膜片刚度、主副膜片有效面积、主活阀摩擦阻尼、背压腔容积和泄压间隙等参数对安溢活门动态特性的影响,进而为系统整体性能优化提供分析设计支持.