Analysis of deformation characteristic in multi-way loading forming process of aluminum alloy cross valve based on finite element model

The deformation characteristic in the forming process of aluminum alloy 7075 cross valve under multi-way loading was investigated by numerical simulation method. The results indicate that there exist 4 deformation patterns in the multi-way loading forming process of cross valve, such as forward extrusion, backward extrusion, forward-lateral extrusion and backward-lateral extrusion; one or several patterns occur at different forming stages depending on loading path. In general, the main deformation pattern is forward extrusion or backward extrusion at the initial stage; the main deformation pattern is backward extrusion at the intermediate stage, and the backward extrusion and forward-lateral extrusion occur at the final stage. In order to improve the cavity fill and reduce the forming defects, the lateral extrusion deformation should be increased at the initial and intermediate stages, and the forward extrusion deformation at the final forging stage should be reduced or avoided.

A New Kind of Pilot Controlled Proportional Direction Valve with Internal Flow Feedback

Proportional direction valve is one of the most fundamental elements in electronic-hydraulic control technique. Its function is to control the operating speed, direction, position, and strength of output force of the hydraulic actuator continuously. Considering the different application and the cost, the existing technique mainly includes the internal feedback valve used in open loop system, and the electronic closed loop controlled valve used in closed loop system. Because of their different mechanical structure and the gre at different in performance, it brings inconvenience for customer to select, also inconvenience for enterprise to produce. Aiming at this problem, the idea of combining the above two kinds of valves into one body is proposed first, and then the new valve＇s structure to realize this target is designed. The idea intends to apply the displacement pilot flow feedback control principle in present 2-position 2-way valve system to the proportional direction valve of 3-position 4-way system. Newly designed feed forward controller can decouple the interference between the internal feedback and the electronic closed loop. Redundant conversion is designed to electronic switch mode. Experiment on dynamic and static characteristic of new proportional direction valve in internal feedback control mode and electronic closed loop control mode is discussed to prove the new theory is correct. Although the new valve is of excellent dynamic response characteristic, its steady control characteristic in open loop control mode needs to be improved further. The research results prepare one new fundamental element for electronic-hydraulic control technology.

Investigation into the Independent Metering Control Performance of a Twin Spools Valve with Switching Technology-controlled Pilot Stage

In hydraulic area,independent metering control(IMC)technology is an effective approach to improve system efficiency and control flexibility.In addition,digital hydraulic technology(DHT)has been verified as a reasonable method to optimize system dynamic performance.Integrating these two technologies into one component can combine their advantages together.However,few works focused on it.In this paper,a twin spools valve with switching technologycontrolled pilot stage(TSVSP)is presented,which applied DHT into its pilot stage while appending IMC into its main stage.Based on this prototype valve,a series of numerical and experiment analysis of its IMC performance with both simulated load and excavator boom cylinder are carried out.Results showed fast and robust performance of pressure and flow compound control with acceptable fluctuation phenomenon caused by switching technology.Rising time of flow response in excavator cylinder can be controlled within 200 ms,meanwhile,the recovery time of rod chamber pressure under suddenly changed condition is optimized within 250 ms.IMC system based on TSVSP can improve both dynamic performance and robust characteristics of the target actuator so it is practical in valve-cylinder system and can be applied in mobile machineries.

Finite element simulation of aluminum alloy cross valve forming by multi-way loading

Deformation behavior,temperature evolution and coupled effects have a significant influence on forming process and quality of component formed,which are very complex in forming process of aluminum alloy 7075 cross valve under multi-way loading due to the complexity of loading path and the multiplicity of associated processing parameters.A model of the process was developed under DFEORM-3D environment based on the coupled thermo-mechanical finite element method.The comparison between two process models,the conventional isothermal process model and the non-isothermal process model developed in this study,was carried out,and the results indicate that the thermal events play an important role in the aluminum alloy forming process under multi-way loading.The distributions and evolutions of the temperature field and strain filed are obtained by non-isothermal process simulation.The plastic zone and its extension in forming process of cross valve were analyzed.The results may provide guidelines for the determination of multi-way loading forming scheme and loading conditions of the forming cross valve components.

2D SIMPLIFIED SERVO VALVE

A novel pilot stage valve called simplified 2D valve, which utilizes bothrotary and linear motions of a single spool, is presented. The rotary motion of the spoolincorporating hydraulic resistance bridge, formed by a damper groove and a crescent overlap opening,is utilized as pilot to actuate linear motion of the spool. A criterion for stability is derivedfrom the linear analysis of the valve. Special experiments are designed to acquire the mechanicalstiffness, the pilot leakage and the step response. It is shown that the sectional size of thespiral groove affects the dynamic response and the stiffness contradictorily and is also verysensitive to the pilot leakage. Therefore, it is necessary to establish a balance between the staticand dynamic characteristics in deciding the structural parameters. Nevertheless, it is possible tosustain the dynamic response at a fairly high level, while keeping the leakage of the pilot stage atan acceptable level.

Adaptive friction compensation for large diameter electro-hydraulic proportional valve cores based on LuGre

This paper presents an adaptive friction compensation method based on LuGre model for large diameter electric-hydraulic proportional valves in which the valve core contains friction.A mathematic model of the electric-hydraulic proportional valve is established,and the friction characteristics are described based on the LuGre model.The global asymptotic stability of the control system with the adaptive friction compensation controller is guaranteed over Lyapunov theorem.The adaptive compensation of the friction on LuGre friction model is verified by simulation and experiment.The steady-state error is about [-4.23 × 10^(-5)m,5.91 × 10^(-5)m]and[-2.5 × 10^(-4)m,2.6 ×10^(-4) m] on simulation and experiment,the position tracking accuracy is higher,and the lag time of the main valve through the dead zone is shorter.The result proves that the adaptive friction compensation method can effectively compensate for the negative effects of nonlinear friction.

天然气调压橇故障分析处理

随着海外油田区块的开发,油田企业投资建设燃气轮机电站,将伴生气转化为油田生产所需的电能。由于规划中的天然气处理厂尚未建成,伴生气处理装置还不完善,伴生气含杂质多,经常出现天然气调压橇压力失调故障,直接影响燃气轮机安全运行。通过对两个不同厂商天然气调压橇的构成及调压阀工作原理的分析,分别提出采用油田伴生气调压橇的改造方案和厂商提供的指挥器装配错误修正方法,可保证燃气轮机在加速控制、一次调频、孤岛模式等工况下,天然气调压橇调整压力迅速、平稳,为海外油田区块原油产量上产稳产提供了技术支撑。

核电主蒸汽阀站中电磁先导阀的动态响应仿真研究

针对核电主蒸汽阀站中关键部件之一——大气释放阀前置隔离阀在实际工况中常出现响应超时的问题,采用数值仿真软件Fluent中的动网格以及用户自定义函数技术,对控制其启闭过程的电磁先导阀动态响应过程进行了研究。首先,研究了电磁先导阀中先导结构的动态响应过程以及阀杆的受力情况;然后,研究了电磁先导阀中主阀的动态响应过程以及主阀泄压时阀内的压力和速度分布情况;最后,综合两个动态过程,分析了电磁先导阀整阀的运动时间。研究结果表明,电磁先导阀的运动时间为8.5 ms,其中先导结构的运动时间占比较小,85%的时间集中在电磁先导阀主阀动作过程。该研究结果可对前置隔离阀响应时间的优化提供参考。

先导式安全阀整定压力预测方法研究

以自主研制的先导式安全阀为研究对象,针对先导阀的感压控制结构,开展整定压力预测方法研究。根据动作功能和结构原理分析,提出了一种测量整定预紧力的方式,并研制了专用传感器。对样机进行适应性改造和传感器安装后,开展相关冷态实验研究。结果表明,关键力值的监测数据可用于安全阀整定压力的预测,但还需进一步考虑温度等运行参数和阀门结构设计参数的影响,优化预测算法。

先导式比例电磁阀电磁力水平特性分析及优化

阻尼可调减振器作为悬架系统的核心部件,对汽车行驶平顺性至关重要,而先导式比例电磁阀作为减振器中的重要元件,对减振器性能起到关键作用。介绍了电磁阀的结构及工作原理,利用Maxwell 2D有限元仿真软件建立电磁铁仿真模型,对静态下的电磁力-位移水平特性进行仿真计算,并根据仿真结果对电磁铁隔磁环倾角、导套厚度、衔铁长度、衔铁宽度等结构参数进行调整分析,通过电磁力水平特性试验,验证仿真模型的准确性。引入正交实验法,对各参数进行协同优化,采用标准差这一指标衡量电磁力水平特性,优化后的产品电磁力标准差为0.635888,优化效果提升7.98%。为阀体的机-电-液-磁耦合仿真分析奠定了基础。

先导式节流阀比例电磁铁参数设计及优化

保证丘陵山地拖拉机在起伏山地或土质较硬地块作业时的牵引力和耕深之间的最佳匹配状态是丘陵山地拖拉机悬挂系统设计的重要指标。比例电磁铁作为节流阀电—机转换的主要元件,其性能优劣对控制节流口开度、实现流量的比例调节具有重要意义。针对丘陵山地拖拉机悬挂系统作业需求和电液比例阀设计要求,设计一种用于悬挂液压系统姿态调整的先导式节流阀比例电磁铁,对其关键结构参数进行设计,建立比例电磁铁数学模型,通过Maxwell对阀组流量特性的影响进行仿真分析。同时利用遗传算法对隔磁导向套厚度、隔磁环角度、隔磁环宽度和定子铁心深度等参数进行匹配优化,通过Maxwell对优化前后的比例电磁铁进行有限元分析。仿真结果表明:优化后的比例电磁铁在1~3 mm时电磁力几乎与X轴平行,具有更好的位移—力特性。建立先导式节流阀数学模型,通过Simulink对其进行动态特性和静态特性仿真,验证所设计的比例电磁铁参数的合理性。

农机用先导式减压阀建模及故障仿真研究

阐述农机常用先导式减压阀工作原理,利用AMESim软件建立阀的仿真模型,仿真分析主阀阻尼孔堵塞、主阀阀芯卡滞、先导阀弹簧疲劳等常见故障工况下先导式减压阀工作时的动态特性。仿真结果表明:应用AMESim软件仿真能够真实地模拟先导式减压阀实际工作时的各类故障响应,为快速、准确地诊断先导式减压阀及类似液压元件故障提供一种新的方法与依据,大大降低了故障诊断时间,提高了整机工作效率。

双阀芯先导笼式调节阀的设计仿真与试验

为解决高温高压工况下调节阀的不平衡力及密封力难以达到所需泄漏等级的问题,设计了一种大阀芯和小阀芯分段配合工作、充分利用阀前介质压力增加阀座密封力的双阀芯先导笼式调节阀。文中给出了调节阀的不平衡力计算公式、流量方程,分析了其流量特性,并对阀内流体的流动进行了仿真,分析了流体流过调节阀后的压力损失;对大阀芯内腔进行了流体流动仿真,分析了阀前压力、内腔温度以及密封力的变化;对大、小阀芯进行了运动仿真,分析了执行器驱动力、阀芯轴向合力和大阀芯速度的变化。常温介质阀体耐压试验和阀座泄漏量试验结果表明,阀体均无可见泄漏和变形,泄漏量设定为10滴/min时,3次实测泄漏量分别为1、1和2滴/min。高温介质阀座泄漏量试验结果表明,泄漏量设定为1.275 mL/min时,250℃高温水蒸气的3次实测泄漏量分别为0.11、0.11和0.13 mL/min,300℃高温水蒸气的3次实测泄漏量分别为0.19、0.19和0.22 mL/min,实测泄漏量均小于设定值。文中提出的双阀芯先导笼式结构增强了调节阀的密封力,阀体耐压强度和阀座密封性能均满足使用要求。

2D阀先导级气穴特性的可视化实验

二维(2D)阀的阀芯具有周向转动和轴向移动的2个自由度,可实现先导控制和功率放大。其先导级阀口因节流会产生气穴,引起阀芯振动并伴有噪声,直接影响阀的稳定性。为研究2D阀先导级处气穴现象及其影响因素,开发了一套可视化实验装置,结合两相流仿真研究,验证了气穴现象与阀口开度、敏感腔体积、节流口形状、入口压力关系密切。结果表明:2D阀先导级高压节流口处的气体体积随阀口开度的增加而减少,直至消失;随入口压力增加,气体体积的变化近似呈线性增长趋势;随着敏感腔体积的增大而显著增加,平均增长速度达62%,且气体分布变得不规则;矩形节流口比弓形节流口处的气穴受入口压力等因素的影响较大,弓形节流口在入口压力增加时,气体体积增量仅为矩形的8%;同时发现,随着气体在感受通道内的扩散,气体边界从最初的类矩形变成多段不规则形状。

先导式安全阀工作原理及其失效分析

针对某炼油厂蜡油加氢裂化装置的循环氢压缩机出口先导式安全阀在正常生产过程中突然失效启跳,且安全阀阀瓣不能自动回座的问题,首先从设计角度介绍了调制型先导式安全阀的结构特点和工作原理,再从工艺因素、操作因素、设备因素和失效过程四个方面进行了全面分析,最后找出了导致安全阀失效的根本原因。并基于分析结果,提出了相应的建议。旨在通过这些有效措施以减少类似安全阀失效事件的发生,确保加氢裂化装置的稳定运行,保障生产安全。

圆环型弹性阀片变形模型及厚度对溢流阀开度影响分析

先导溢流阀是阻尼连续可变减振器的关键部件,使减振器具有阻尼连续可调能力,而圆环型弹性阀片是影响先导溢流阀的开度、压力等参数的关键零件。为查明圆环型弹性阀片变形规律与先导溢流阀开度的映射机制,推导了圆环型弹性阀片变形的数学模型,在先导阀开度为0~0.25 mm,阀片厚度为0.1~0.3 mm的情况下进行计算分析,验证了变形模型的准确性,并揭示了先导溢流阀开阀压力、入口压力、溢流阀阀口内外压差和溢流阀开度的变化规律,获取了溢流阀开阀压力、压差、开度与圆环型弹性阀片厚度的关系曲线,为先导溢流阀的高精密设计及减振器阻尼匹配、优化提供理论指导。

汽车阻尼连续可调减振器先导阀参数对其性能的影响

先导阀是阻尼连续可调减振器电磁阀中的关键结构,主要调节主溢流阀的开启压力,其性能的优劣直接影响阻尼连续可调减振器阻尼特性。以一种双复位结构的阻尼连续可调减振器先导阀为研究对象,首先对比先导阀Maxwell、Femm仿真和试验数据,验证仿真模型的正确性;然后通过参数化仿真和温升试验,分析漆包线线径、漆包线耐温等级、软磁材料、结构尺寸对先导阀性能的影响。结果表明,电磁力与线径呈正相关,线径增大到0.45 mm临界点后先导阀稳恒力特性逐渐恶化,漆包线耐温等级240℃限制先导阀工作最大电流为2 A,软磁材料的膝点位置影响先导阀稳恒力特性,尽量减小侧向间隙有利于提高先导阀性能,导磁环高度对先导阀性能影响最为显著。研究旨在为阻尼连续可调减振器先导阀设计提供有益的理论参考。

先导阻尼对二通插装阀组合换向阀压力损失的影响

二通插装阀组合而成的功能阀在各类高压大流量系统中应用广泛。常用的O型机能三位四通换向功能阀由P型先导电磁阀+二通插装阀组合而成,有一种由O型先导电磁阀+二通插装阀组合而成的换向阀,不仅具有O型机能三位四通功能,同时在进油端还集成防反冲功能,在系统急停等情况下供油端已卸荷,因换向功能阀阀芯未来得及关闭到位,可有效防止液压缸压力油瞬间超大流量回流并经已卸荷的电磁溢流阀回油的情况。但这种换向功能阀在使用一段时间后出现回油压力异常增高的现象。本研究为了解异常现象的背后机理,首先通过介绍其详细工作原理,分析并定位了影响回油压力异常增高的几个可能因素,针对换向功能阀,基于AMESim软件仿真模拟不同先导阻尼孔径对插装阀压力损失的影响效果来复现故障,再通过现场试验,验证了分析结果,最后给出了设计细节方面的优化建议。

气动先导阀动态特性仿真优化研究

针对气动先导阀动态响应低的问题,在分析结构特点和工作原理的基础上,利用AMESim建立仿真模型,通过参数化仿真研究主阀弹簧刚度、弹簧预紧力、气源压力和节流孔大小对先导阀动态响应的影响,结果显示:各参数对气动先导阀动态响应特性的影响各不相同,很难通过调节某一参数得到最优解。在参数化仿真分析的基础上,基于SimV&Ver Math进行多参数优化仿真,利用贝叶斯+拟牛顿的优化算法得到最优解,将气动先导阀的总响应时间降低了7.2 ms,并通过试验验证了仿真分析的正确性。

位移-流量反馈式比例阀先导液阻匹配策略研究

高水基比例阀先导液阻桥路直接影响主阀的控制特性,多功能、多类型液阻构成的复杂先导液阻网络成为比例阀设计的关键。采用数学建模、流场仿真以及试验研究相结合的方式分析位移-流量反馈式高水基比例方向阀先导液阻桥路的液阻特性,考虑了主阀进液阀芯和阀套之间环形间隙的流量泄漏。结果表明:当环形间隙面积一定时,位移反馈槽宽度越大,位移反馈节流控制线性度越好,然而,位移反馈槽宽度越大,先导液桥流量需求越大,高速开关阀组匹配设计难度越大;回液液阻对液桥起背压作用,回液液阻尺寸越小,背压效果越好,位移反馈槽节流控制线性度越差。根据流场仿真结果,综合匹配设计高速开关阀组及进液液阻,通过试验验证了先导液阻网络各液阻尺寸匹配策略的正确性。