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。     

2D伺服阀矩形先导控制阀口气穴特性研究

为研究双自由度（2D）伺服阀先导控制阀口处气穴现象的影响因素及对阀芯稳定性的影响,运用Fluent软件中cavitation模型对2D伺服阀矩形先导阀口进行了气穴特性的仿真研究。研究表明,在出口压力低于1 MPa时,阀口处会出现气穴现象,且因气穴指数σ较小,故在弓形感受通道会出现气泡现象,出口压力高于5 MPa时,无明显气泡现象但阀口处的气穴仍然存在;随着入口流速增加,阀口内侧壁和外侧壁处气穴强度和分布范围增加;在出口压力0.1 MPa情况下,随着阀口开度增加气穴现象减弱。结果表明,2D伺服阀正常工作时先导阀口处会产生气穴,对伺服阀阀芯运动的稳定性产生干扰。     

偏转板射流伺服阀前置级流场分析

偏转板伺服阀已广泛应用于大型运输机、民用客机和军用飞机的各类舵机和操纵系统.本文建立偏转板伺服阀射流前置级流场模型,分析入口压力、出口压力以及接受器管路夹角对伺服阀流场特性的影响.发现压力的急剧下降和压差的急剧增大是偏转板伺服阀前置级产生气穴现象的主要原因;通过研究进口压力、结构圆角对气穴现象的影响,提出了采取适当降低进口压力和提高偏转板下端面圆角加工质量等措施来改善气穴现象的方法.     

2D伺服阀先导级螺旋阀口稳态液动力的研究

为研究二维(2D)伺服阀的稳定性及其影响因素,结合2D阀先导级螺旋阀口双流道中心对称的结构特点,通过理论分析和流体动力学仿真,得出流体流经螺旋阀口产生的稳态液动力属于空间力,且2个对称阀口处稳态液动力的径向分力大小相同,方向相反;而轴向液动分力和周向液动分力形成的力矩随着阀口开度增加逐渐减小,yoz平面的射流角度也逐渐减小,且当阀口开度小于0.1 mm时,减小幅度很大,开度大于0.2 mm时,趋于稳定;随着入口流速的增加,轴向液动力和周向液动力矩逐渐增加。结果表明稳态液动力的轴向分力及周向力矩促使先导阀口关闭,对阀芯稳定具有促进作用。     

旋转式换向阀非定常空化流动特性研究

针对旋转式换向阀空化现象会导致噪声及其性能恶化,进而影响液压激振系统的问题,对旋转式换向阀非定常空化流动特性进行了研究。利用SolidWorks软件建立了阀口的三维模型,利用前处理软件ICEM对几何模型进行了网格划分及边界条件的设置;借助Fluent软件中的Mixture气穴模型和RNG湍流模型,建立了流场数学模型,采用滑移网格技术对阀口空化流动进行了数值模拟;探究了不同开度下旋转式换向阀压力场、速度场以及气穴分布的变化趋势。研究结果表明:开度的大小会影响阀口的压力场和速度场的分布,阀芯沟槽极易出现漩涡,并且开度的变化会影响漩涡的大小;空化区域的分布也会随阀口开度的变化而变化;最大气体体积分数随入口压力和阀芯转速的增大而增大,随背压的增大而减小。     

高频电液数字转阀阀口气穴现象研究

借助FLUENT软件对高频电液数字转阀(简称2D数字阀)阀腔流场进行研究,主要对阀口极端环境时的气穴变化规律进行深入探索,揭示2D数字阀阀芯高速旋转时阀口气泡析出、发育过程及溃灭特性对阀口流量的影响。研究结果表明,气穴现象不仅会造成流量阻塞,而且气泡溃灭引起的压力脉动还会对系统形成强非线性干扰,影响阀口输出波形的精度和阀控液压缸激振系统的稳定性。     

射流管伺服阀接收口形状对阀特性的影响

射流管伺服阀的接收口形状对阀的动态特性和静态特性有着直接的影响。在喷嘴形状为矩形的情况下,通过对以圆形、矩形、三角形为接收口的射流管伺服阀前置放大器进行流场数值仿真和动态特性的仿真,获得了不同形状接收口的射流管伺服阀的压力特性、流量特性和响应频宽。通过比较,发现矩形接收口的射流管伺服阀具有较高的恢复压力和较大的压力增益,当射流管喷嘴位移较小时,矩形接收口的射流管伺服阀具有线性度较好的压力特性和流量特性,频宽响应较大。     

先导式水压溢流阀动态特性的仿真

对一种新型的先导式水压溢流阀进行了动态特性的建模和仿真研究,分析了多种因素对溢流阀动态特性的影响。仿真结果表明,先导阀尾端设置阻尼腔有利于提高先导阀的工作稳定性;在主阀口前设置合适的节流孔可降低主阀口的工作压差,减小阀口的气蚀,提高溢流阀的工作性能和使用寿命;主阀心上腔容积V12、先导阀入口容积V2、溢流阀入口容积V0对溢流阀的动态特性均有较大影响。     

2D电液压力伺服阀的实验研究

为了满足飞行器的舵机控制和刹车控制等领域的需要,特推出2D电液压力伺服阀。目前,压力伺服阀种类很少,而且多采用压力传感器作为输出进行闭环,这类伺服阀受环境温度变化影响,温漂较大。2D电液压力伺服阀采用两级结构。以LVDT传感器检测先导级阀芯位移作为反馈量,对先导级阀芯进行闭环控制,可以有效避免压力传感器温漂大的问题。实验结果表明,滞环大小为2.82%,线性度大小为3.4%,经试验研究,2D电液压力伺服阀的频宽可以达到70Hz。     

一种大流量高速开关阀的设计与实验研究

介绍了一种采用2D伺服阀作为先导控制级的双节流口并联输出结构的大流量高速开关阀的工作原理,通过理论分析和产品样机试验,研究了开关阀的泄漏特性、阀芯运动过程动态特性、阀口流动特性,并结合试验数据阐述了大流量开关阀设计中需注意的问题。该开关阀在10 MPa工作压力下,阀口开启时间约15 ms,进出口压差为2 MPa时的流量达到3000 L/min。     

不同开口度下的煤矿水液压安全阀的气蚀特性

针对煤矿水液压安全阀存在的严重气蚀问题,建立双排阀口的CFD模型,分析了不同启动次序和开口度的阀腔气相体积分数和压力分布云图,并得到其影响规律及最佳的阀口开启次序.研究表明:3种开启方式下,开口度为0.8～1.2 mm时气蚀均较为严重;同步开启时,综合抗气蚀效果最差,开口度为0.8～1.2 mm时极易形成涡旋,且对气蚀...     

2D伺服螺旋阀芯大行程位置控制的分析研究

2D伺服螺旋数字阀作为先导控制大流量高频响的换向阀,结构上利用2D阀的阀芯的双自由度运动,阀芯由步进电机驱动旋转,通过高低压孔的开口通断来改变敏感腔的压力,从而推动阀芯轴向运动。大流量高频换向阀的小阀芯与2D阀的阀芯由球头刚性连接,获得所需的大行程,驱动主阀芯运动。基于MATLAB建立2D阀的数学模型,该模型的仿真结果能较为准确地描述2D阀的动静态特征。     

Design and performance characteristic analysis of servo valve-type water hydraulic poppet valve

For water hydraulic system control, the flow or pressure control using high-speed solenoid valve controlled by PWM control method could be a good solution for prevention of internal leakage. However, since the PWM control of on-off valves cause extensive flow and pressure fluctuation, it is difficult to control the water hydraulic actuators precisely. In this study, the servo valve-type water hydraulic valve using proportional poppet as the main valve is designed and the performance characteristics of the servo valve-type water hydraulic valve are analyzed. Furthermore, it is demonstrated through experiments that a decline in control chamber pressure that follows the change of pilot flow is caused by the occurrence of cavitation around the proportional poppet, and that fundamental characteristics of the developed valve remain unaffected by the occurrence of cavitation.     

调压阀流体空化特性仿真及影响因素分析

针对船用二级调压阀空化问题,建立流域瞬态仿真模型,结合Singhal空化模型和标准k-ε湍流模型对调压阀流体空化现象进行数值模拟,通过流场气体体积分数分析,得出了流体空化强度及分布形态的演变规律,通过流体速度场和压力场分析,阐明了空化演变过程调压阀流场特性,进而研究了开度、流量和背压对调压阀流体空化现象的影响规律.结果...     

Hydrodynamic characteristics and optimization design of a bio-inspired anti-erosion structure for a regulating valve core

Cavitation is the main failure mode of coal liquefaction regulating valve, which seriously limits the service life of the regulating valve. In order to restrain cavitation in the regulating valve, a bio-inspired anti-cavitation structure inspired by the red willow of valve core is proposed. Distributions of pressure, velocity and vapor volume fraction in the bionic valve under different openings (30%, 40%, 50%, and 60%) and inlet pressures (2.0MPa, 3.0MPa, 4.0MPa, and 5.0MPa) are discussed. In addition, the parameters of bionic valve structure are optimized using NSGA-II algorithm, the field synergy principle is applied to evaluate the flow field optimization in the bionic valve. The results show that the cavitation area and cavitation length in these bionic structures are reduced significantly compared with the traditional smooth structure. And the anti-cavitation performance of the trench structure is the best, when the inlet pressure is 3 MPa and the opening is 30%, the vapor volume is 0.10 mm³, the vapor volume is reduced by 98.07% compared with traditional smooth structure. Convex hull structure is the second. When the inlet pressure is 5.0 MPa, the vapor volume of the traditional smooth structure is as high as 148 mm³, and the vapor volume of the convex hull structure is 35 mm³, the vapor volume of the trench structure is 19 mm³. Through the field synergy theory to evaluate the internal flow field, it is found that the effective viscosity coefficient in the traditional smooth structure regulating valve varies from 0.7 to 1.2, that of the bionic trench valve changes from 0.1 to 0.5, both the flow resistance and energy consumption in the trench structure valve are reduced. It is proved that the bionic trench structure of the valve core can effectively improve anti cavitation performance and optimize the internal flow resistance of the flow field, which is of great significance to the optimal design of the control valve.     

Cavitation reduction in the globe valve using oblique perforated cages: A numerical investigation

Globe valves are one of the oldest and most widely used flow control valves. However, cavitation due to high-pressure drop is a common phenomenon in such valves, reducing valve lifetime and increasing replacement costs. Recently, a series of perforated cages have been used in globe valves to reduce cavitation damage (especially in the body and disk). In this study, a globe valve is numerically investigated under four different structures, i.e., without the cage, with a perforated cage whose holes are radial, with a perforated cage whose holes are facing upwards, and with a perforated cage whose holes are facing downwards. The effects of the valve opening, inlet velocity, and holes direction on the pressure drop and cavitation incipient/intensity are investigated. The results show that cavitation is observed with the decrease of the valve opening even at the low velocities. And with increasing the velocity inlet, the pressure drop and cavitation intensity increase significantly. It can also be concluded that in the globe valve using a perforated cage with holes downwards, less cavitation is observed than in other models. Therefore, this configuration is proposed to protect the inner components of the valve (such as seat, seal, and plug) from cavitation damage.     

SIMULATION AND EXPERIMENT OF BUBBLY FLOW INSIDE THROTTLING GROOVE

The relationship between pressure distribution and cavitation (noise) inside throttling groove is investigated by numerical simulation and experimental method. A valve pocket with several transducers is performed to detect the pressure distributions inside the valve chamber, and the results fit quite well with the computational fluid dynamics(CFD) analysis. High-speed imaging techniques are employed to investigate the cavitation mechanisms, in particular bubble inception and cluster formation near the throttling groove. A spectrum analyzer is used to measure the sound pressure level of noise generated by the bubble flow. It is found that the pressure distributions inside the groove are sensitive to the valve port configuration and back pressure. The pressure distribution determines the bubble size and number passing through the valve grooves and the sound pressure level of noise induced by collapsing bubbles. The inlet pressure mainly affects the saturation degree of bubbly flow inside the groove and the intensity of sound pressure level accordingly.     

先导式水压溢流阀的设计

结合水介质的特性及典型先导式油压溢流阀的结构,分析了先导式水压溢流阀存在的关键技术难题,在此基础上设计了一种新型的先导式水压溢流阀.针对关键技术难题,在结构上主要采取了如下措施:在溢流阀入口设置固定节流孔和二级节流主阀口以减小气蚀;阀心上加组合密封件以减少泄漏和拉丝侵蚀;先导阀心尾端设置阻尼腔以抑制振动、噪声,提高先导阀的工作稳定性等.