Research on static characteristic of double redundance double nozzle flapper valve based on AMESim

The feedback spring rod of the armature assembly is cancelled in the double redundance double nozzle flapper valve(DRDNFV),and the difficulty of valve core displacement control is increased.Therefore,this paper intends to study the static characteristic of DRDNFV through the AMESet and AMESim simulation.It is explored under the circumstance of the fixed orifices being clogged and experimentally verified on the test bench.The results show that the pressure gain increases and the flow gain decreases with the increasing clogged degree of the fixed orifices on both sides.The zero bias increases synchronously with the increasing clogged degree of the unilateral fixed orifice.The experimental results are basically consistent with the theoretical curves and the theoretical correctness of the simulation model is effectively verified.The results can provide the theoretical reference for design,debugging,maintenance and fault diagnosis of DRDNFV.

Numerical Simulation and Experimental Study of Heat-fluid-solid Coupling of Double Flapper-nozzle Servo Valve

The double flapper-nozzle servo valve is widely used to launch and guide the equipment. Due to the large instantaneous flow rate of servo valve working under specific operating conditions, the temperature of servo valve would reach 120℃ and the valve core and valve sleeve deform in a short amount of time. So the control precision of servo valve significantly decreases and the clamping stagnation phenomenon of valve core appears. In order to solve the problem of degraded control accuracy and clamping stagnation of servo valve under large temperature difference circumstance, the numerical simulation of heat-fluid-solid coupling by using finite element method is done. The simulation result shows that zero position leakage of servo valve is basically impacted by oil temperature and change of fit clearance. The clamping stagnation is caused by warpage-deformation and fit clearance reduction of the valve core and valve sleeve. The distribution roles of the temperature and thermal-deformation of shell, valve core and valve sleeve and the pressure, velocity and temperature field of flow channel are also analyzed. Zero position leakage and electromagnet＇s current when valve core moves in full-stroke are tested using Electro-hydraulic Servo-valve Characteristic Test-bed of an aerospace sciences and technology corporation. The experimental results show that the change law of experimental current at different oil temperatures is roughly identical to simulation current. The current curve of the electromagnet is smooth when oil temperature is below 80℃, but the amplitude of current significantly increases and the hairy appears when oil temperature is above 80℃. The current becomes smooth again after the warped valve core and valve sleeve are reground. It indicates that clamping stagnation is caused by warpage-deformation and fit clearance reduction of valve core and valve sleeve. This paper simulates and tests the heat-fluid-solid coupling of double flapper-nozzle servo valve, and the obtained results provide the reference value for the design of double flapper-nozzle force feedback servo valve.

Research on valve core’s clamping stagnation of double flapper-nozzle servo valve

Due to great changing of instantaneous temperature of hydraulic oil of double flapper-nozzle servo valve, thermal deformation between valve core and valve sleeve may result in catching phenomenon of valve core, and then the reliability of servo valve could be affected seriously. The work focuses on a particular model of double flapper-nozzle servo valve and establishes three dimension couple models of liquid-solid-thermal under extreme operating condition. The transmission route and dissipative mechanism of heat is revealed and thermal deformation behavior of valve core and valve sleeve is researched. A change law of the key fit clearance under the effect of thermal expansion and warp deformation is explored, the source of catching phenomenon of valve core is identified, and then preventive measure and improvement can be proposed. In order to verify the correctness of theoretical analysis, the moving smoothness of deformed valve core and reground valve core under the circumstance of high-temperature hydraulic oil on electrohydraulic servo valve static characteristics test table is compared and tested. The results show that as oil temperature rises, relative deformations between valve core and valve sleeve in different direction at a same cross-section are not equal, and then the key fit clearance is less than the initial value. Relative deformations in the same direction at different axial position are not equal, the deformations of middle and two ends are maximum and minimum values respectively, and then warp deformation of valve core occurs. When oil temperature is higher, the relative deformations between valve core and valve sleeve is larger, the moving smoothness of valve core gets worse, and the catching phenomenon of valve core occurs. Axial deformation of valve sleeve and valve core at different axial position is different, and the opening coefficient and stability of servo valve could be affected, especially the operation circumstance of small opening. The study can provide some guidance for designing double nozzle flapper servo valves.

Dynamic Characteristics of the Jet Force on the Flapper of the Pilot Stage in a Flapper Nozzle Servo Valve Under the Flow-Solid Interaction

Nowadays,more and more attention has been paid to improve the performance of the nozzle flapper servo valve.As a core part of nozzle flapper servo valve,the armature assembly is affected by electromagnetic force,jet force and feedback force at the same time.Due to the complex structure of the pilot stage flow field and the high jet pressure,the prediction of the jet force has always been difficult in modeling the transient motion of the servo valve.Whereupon,a numerical simulation method based on the flow-solid interaction(FSI)is applied to observe the variation of the jet force when the flapper is moving.Different parameters are employed to seek a suitable numerical simulation model which can balance the accuracy and computational cost.By comparing with the experiment results,the effectiveness of numerical simulation method in predicting the variation of the jet force and cavitation is verified.By this numerical simulation model,the distribution of flow field and the force on the flapper predicted by the moving and fixed flapper are compared.The results show that more dynamic details are achieved by the transient simulation.By analyzing the numerical simulation results of different inlet pressures and flapper vibration frequencies,the relationship between the movement of the flapper,the flow field distribution,the jet force and the inlet pressure is established,which provides a theoretical basis for the subsequent modeling of the armature assembly.

Analysis of pressure characteristics under laminar and turbulent flow states inside the pilot stage of a deflection flapper servo-valve:Mathematical modeling with CFD study and experimental validation

Electro-hydraulic servo-valves are widely used components in the mechanical industry,aerospace and aerodynamic devices which precisely control the airplane or missile wings.Due to the small size and complex structure in the pilot stage of deflection flapper servo-valves,accurate mathematical models for the flow and pressure characteristics have always been very difficult to be built.In this paper,mathematical models for the pilot stage of deflection flapper servo-valve are investigated to overcome some gaps between the theoretical formulation and overall performance of the valve by considering different flow states.Here,a mathematical model of the velocity distribution at the flapper groove exit is established by using Schlichting velocity equations for incompressible laminar fluid flow.Moreover,when the flow becomes turbulent,a mathematical model of pressure characteristics in the receiving ports is built on the basis of the assumption of the collision between the liquid and the jet as the impact of the jet on a moving block of fluid particles.To verify the analytical models for both laminar and turbulent flows,the pressure characteristics of the deflection flapper pilot stage are calculated and tested by using numerical simulation and experiment.Experimental verification of the theory is also presented.The computed numerical and analytical results show a good agreement with experimental data.

Static Characteristics of the New Type Nozzle Flapper Amplifier for Double Nozzle Flapper Electro-Hydraulic Servo Valve

A new type nozzle flapper amplifier for double nozzle flapper electro-hydraulic servo valve is proposed in the paper.The electro-mechanical converter of new type nozzle flapper amplifier is designed by using the piezoelectric bimorph and beryllium-bronze materials.The structure and working principle of the new type nozzle flapper amplifier are introduced.Pressure characteristic and flowrate characteristic are analyzed by experimental method.The research results show that pressure characteristic has large amplification factor and output pressure;flowrate characteristic has large linear range and output flowrate.

Flapper Girl,重返爵士时代

2013版电影《了不起的盖茨比》中,里奥纳多·迪卡普里奥(Leonardo DiCaprio)演绎的"盖茨比"和凯芮·穆里根(Carey Mulligan)版的"黛西"被包裹在锦衣华服和声色犬马中,看得人眼花缭乱。除了文学经典被几经翻拍地热炒,吸引诸如Prada、Tiffany、Brooks Brothers等众多奢侈品牌倾力为其打造服饰造型的一个很大原因,是那个铭刻在记忆里的"爵士年代"以及在女性时尚史上留下浓墨重彩的Flapper。

浅谈“flapper girl”元素在现代设计中的影响

Flapper的本意是"刚刚学会飞的小鸟",上世纪20年代开始被美国人引用来描述美丽轻佻的年轻女郎,Flapper的诞生宣告了女性与传统女性角色的分道扬镳,强调华丽装饰的风格,在时装史上写下了华丽的篇章。

Aerodynamic force generation of an insect-inspired flapper actuated by a compressed unimorph actuator

We examined experimentally the flapping performance in terms of aerodynamic force generation of an insect-inspired flapper actuated by both of original LIPCA and compressed LIPCA. Flapping tests for two artificial wing shapes of horse botfly and hawk moth were conducted at the wing rotation angle of 60° and a flapping frequency range from 6 Hz to 12 Hz to find the optimum flapping frequency and to investigate the effect of compressed LIPCA and wing shape on the force generation. Flapping tests in the vacuum were also undertaken to measure the induced inertia force. The aerodynamic force was calculated by subtracting the inertia force from the total force measured in the air. It was found that the average inertia force was relatively small when compared with the average total force. The use of the compressed LIPCA could significantly improve the flapping angle of the flapper from 110° to 130° (18.2% increase) resulting in 24.5% increase in the average aerodynamic force. It was also found that flapper with hawk moth wings could produce larger force than the flapper with horse botfly wings.

基于Matlab的双喷嘴挡板阀检测仿真

通过对双喷嘴挡板阀的压力-流量分析,计算阀门的系统参数,在Matlab软件中建立仿真模型,根据特性使用Simulink设计函数模型,获取数据结果,得到优化的阀门状态及通用测试仿真程序,检验了传递函数的Matlab/Simulink模式的准确性,判断出喷嘴挡板阀内流量与压力有一定的对应关系,同时也为后续双喷嘴挡板力反馈型两级电液伺服阀性能优化提供了理论依据,为进一步提高电液伺服阀动作稳定性奠定了技术基础。

基于增材制造旋转直驱伺服阀的肢腿运动单元位置控制研究

液压腿足式机器人因其可承受大负载、具有更高的速度上限等优势被广泛应用于物资搬运、地形侦查等场景。伺服阀作为液压系统中的控制元件,与机器人作业过程的运动稳定性、地形适应性、节能等方面都存在着密切关联。目前腿足式机器人系统普遍应用喷嘴挡板式伺服阀,不同阀型号的选择往往只需要满足阀的频响、压力、流量等指标,并且伺服阀的数学模型也通常近似为低阶环节,这在设计中弱化了伺服阀对系统的影响。为探究不同结构伺服阀与控制系统最佳匹配问题,研究了增材制造旋转直驱式伺服阀在机器人位置控制系统中的性能,并将其与传统喷嘴式挡板阀作比较,分别建立其数学模型并在单腿试验台上完成实验验证。结果表明,在相同的流量压力需求下,应用旋转直驱阀的控制系统足端阶跃响应时间减少了14%,足端正弦轨迹跟踪误差减少了21%。

正方形射流抑制喷嘴挡板阀空化特性

喷嘴挡板伺服阀广泛应用于航空航天、工程机械、深海装备以及机器人等领域的液压伺服系统中。然而,伺服阀内流场的空化特性常常会导致流场压力脉动、高频啸叫以及气蚀损坏等问题,严重影响伺服阀的工作性能。通过采用正方形射流来改变伺服阀前置级流场的流动结构,进而改善伺服阀的空化特性。相比于传统圆形喷嘴情况,当正方形喷嘴边长与阀腔底面平行时,空化现象愈加严重;而当正方形喷嘴边长与阀腔底面成45°夹角时,空化现象得到了明显的改善。

《冰宫》的生态女性主义解读

在短篇小说《冰宫》中,菲茨杰拉德表现了他对美国南方田园的深厚情感和眷恋。从生态女性主义的视角解读《冰宫》,不仅可以深刻地洞察“冰宫”这一工业化产物所承载着的人类对自然压迫,而且有助于理解自然之女“飞女郎”莎利的探索和回归,揭示人与自然的疏离造成主人公精神世界的荒芜,从而强调人与自然、人与人和谐共处的重要性。这将从一定意义上深化对《冰宫》背后所传达的深刻意义的认识,并进一步挖掘被忽视的菲茨杰拉德的短篇小说价值。

一种低内漏喷嘴挡板压力伺服阀的探索研究

基于某型民用飞机系统架构,根据运输类飞机适航标准CCAR25部中25.735条的(h)条款关于储备能源的要求,当应急刹车系统使用刹车控制阀作为执行机构,输出与驾驶员脚蹬指令成比例的输出压力给刹车装置,应急系统中核心部件喷嘴挡板压力伺服阀的内漏将直接影响储备能源蓄压器容积的选择。根据SAE AIR5372A相关标准,一种低内漏单喷嘴阀结构压力伺服阀已在国外民用飞机刹车系统中使用。对传统四通结构和最新单喷嘴阀结构进行深入研究,对比说明单喷嘴阀在内漏、滑阀级驱动力、滑阀级零件制造及组件装配的工艺性改善等方面的优势,和传统国产阀相比,在性能稳定性、抗污染能力及整产品的可靠性方面有所提升。

压缩机阀片用高强度不锈钢材料的国产化开发

阀片是制冷压缩机的核心零部件之一。在压缩机的吸气、压缩、排气和膨胀过程中,阀片实现了工作介质在压缩机内的单向流动。阀片的性能与可靠性会直接影响压缩机的寿命。为了实现生产国产化的阀片专用材料,通过重新设定原料的化学成分配比、设计新的生产工艺路径和优化细化热处理工艺的方法,开发了高性能的不锈钢新材料。与各种进口的阀片钢材料对比显示,新材料各项力学性能和金相组织水平均已达到了行业适用的要求;针对阀片应用要求的抗冲击疲劳能力,设计了专用的试验装置进行测试对比,结果表明此产品可以满足压缩机的使用可靠性要求。综合评价各项数据,本研究开发的国产不锈钢阀片专用材料完全可以替代进口材料,并为下一代高性能阀片材料的研究与开发提供了参考。

双压电晶片驱动喷嘴挡板式伺服阀

给出了双压电晶片驱动喷嘴挡板式伺服阀的基本结构,分析了双压电晶片的频率特性和静态位移特性,针对不同基板尺寸和晶片厚度进行了静态测试,在伺服阀实验台上进行了初步验证。试验结果表明:双压电晶片驱动喷嘴挡板式伺服阀具有结构简单、响应快、分辨率高、无电磁干扰、易于控制的优点,可以满足现代精密高速控制系统的需要。

双喷嘴挡板伺服阀非线性建模及其线性化

为从理论上研究喷嘴挡板伺服阀控电液伺服系统的动静态性能,需要建立较精确的电液伺服阀数学模型。考虑伺服阀喷嘴挡板处阀口流动等非线性因素影响,分析电液伺服阀的电信号输入到阀芯位移的输出特性,建立双喷嘴挡板两级伺服阀的非线性数学模型以描绘实际系统;根据实际模型特点,采用输入/输出线性化方法中的非线性状态反馈变换获得局部线性化模型,并通过分析系统零动态稳定性,从理论上证明了线性化模型的有效性。以常规泰勒展开线性化为对象,对提出的输入/输出线性化模型的精确性进行相应的仿真和实际试验对比。结果表明,该方法所建模型更接近实际系统,具有较强的鲁棒性,可用于精确分析实现阀控液压伺服系统的动静态性能。

基于超磁致伸缩转换器喷嘴挡板阀的控制压力特性

介绍了超磁致伸缩材料的性能特点和利用国产超磁致伸缩材料研制的电-机械转换器,及喷嘴挡板阀的结构组成和工作原理,建立了数学模型。构建了基于超磁致伸缩转换器喷嘴挡板阀的控制压力测试系统,试验研究超磁致伸缩转换器喷嘴挡板阀的控制压力特性,得出了最佳控制压力时不同参数间的匹配关系。结果表明,基于超磁致伸缩转换器喷嘴挡板阀,具有较宽的控制压力特性,良好的线性度,较快的响应速度,为进一步将其应用于两级电液伺服阀提供了设计和试验依据。

基于GMA喷嘴挡板伺服阀的动态特性

提出基于GMA喷嘴挡板伺服阀的新结构,研制了GMM电-机械转换器及其喷嘴挡板伺服阀,分析其结构特点与需要解决的关键技术,建立动态数学模型。构建基于GMA喷嘴挡板伺服阀动态特性的试验系统,试验研究GMA喷嘴挡板伺服阀的阶跃和幅频响应特性,试验测得其阶跃响应上升时间为1 ms、幅频宽达680 Hz;将试验结果与仿真结果进行对比分析,两者基本吻合,论证动态数学模型的正确性。研究结果表明,用GMM设计新型电-机械转换器,可提高喷嘴挡板阀乃至整个电液伺服系统的频响和精度。

井下安全阀启闭阀板流场及应力场有限元分析

针对海上油气田常用的井下安全阀,通过有限元分析的方法对启闭阀板的流体动力学和应力应变进行了模拟分析。通过分析,得出了安全阀启闭系统结构两侧压差随开启角度的增大,两侧压差呈减小趋势,阀板的开启角度对流体速度和湍流强度的影响,得出了阀板在开启过程中最大应力出现在销轴连接处与阀板连接的过渡圆弧处,且随着阀板开启角度增大,阀板应力最大值逐渐减小。文章从理论上,为安全阀启闭系统的结构设计提供了技术参考,确保了安全阀启闭系统的可靠性。