一种集成Herschel-Quincke管的双调谐内插管扩张室液压脉动衰减器的设计与分析

目前,基于平面波理论的一维解析法已成为气体消声器声学特性研究中最常使用的计算方法,现将其推广到简单扩张室(SEC)和双调谐扩张室(DTETC)压力脉动衰减器的理论建模,并与实验测量结果进行对比,证明了该理论在截止频率范围内用于液压系统也是可行的。之后,应用该理论对设计的一种集成Herschel-Quincke管(HQ管)的双调谐内插管扩张室液压脉动衰减器进行声学模拟,并对可能影响传递损失(TL)的HQ管分支管道长度以及截面积进行了参数化分析。最后,将这种新型结构与SEC、DTETC脉动衰减器的传递损失性能进行了对比比较。     

一种复合式广谱液压脉动衰减器的设计与分析

为了降低液压泵出口的压力脉动,设计了一种复合式广谱液压脉动衰减器。该衰减器由1个扩张室、2个容积室、2个限流管和8个质量室构成。通过对复合式广谱液压脉动衰减器的参数进行合理配置,可实现对多个频率段的脉动进行衰减。采用插入损失来评价复合式广谱液压脉动衰减器的衰减效果,利用MATLAB软件对其衰减效果进行仿真,并分析了脉动衰减器主要结构参数与衰减效果的关系。结果显示,该液压脉动衰减器在20～1000 Hz的脉动频率范围内具有良好的衰减效果。复合式广谱液压脉动衰减器结构紧凑,衰减频率带变宽,衰减效果好,符合设计要求。     

基于耳蜗基底膜仿生原理的液压脉动衰减器滤波特性研究

为解决液压系统中由于压力脉动引起的振动和噪声问题,从仿生学角度出发,根据人耳听觉形成过程及耳蜗基底膜的宽频振动响应特征,研究耳蜗基底膜振动的"空间-频率"特性,提出一种仿耳蜗基底膜振动特性的液压脉动抑制方法。设计一种以仿生膜片为共振体的结构紧凑灵巧的液压脉动衰减器,克服了传统液压脉动衰减器结构复杂、体积庞大的缺点。基于流固耦合原理,分析仿生膜片在压力流体中的振动特性;结合管路动态特性,建立脉动衰减器的传递矩阵模型,用插入损失对脉动衰减性能进行评价;通过脉动衰减器样机的试验检验其滤波减振性能。理论和试验结果表明该液压脉动衰减器能够有效衰减液压系统有效频率的压力脉动,并且在较宽频带内有较好的滤波效果,实现了广谱滤波。     

抗性消声器插入损失的有限元法的探讨

插入损失作为消声器的主要评价指标,优点是比较直观、实用。不过插入损失往往不仅决定于消声器本身的性能,而且与系统总体装置的情况密切相关。插入损失对消声器性能的预测比传递损失更接近实际情况。应用四端子网络法与有限元相结合法对有连接管的抗性消声器的插入损失进行计算,说明了一维波动理论在消声器性能方面的缺陷。建立了简单抗性消声器的插入损失测量的试验模型,用直接模拟试验的方法,获得消声器的插入损失。结果表明,四端子法计算得到的加连接管的消声器插入损失与直接模拟试验方法所得的结果吻合良好。     

Herschel-Quincke管用作液压脉动衰减器的滤波特性研究

Herschel-Quincke管（HQ管）广泛用于气体消声系统，且该结构声学特性研究也已成熟。鉴于此，将这种结构引入液压系统，采用一维解析法构建其数学模型，再利用三维有限元法进行验证。两种理论方法传递损失计算结果在平面波域内吻合较好，证明了截止频带内采用一维解析法研究液压脉动衰减器声学特性是可行的。利用一维解析法对HQ管用作液压脉动衰减器的滤波特性进行了研究，结果表明，只要分支管道长度以及横截面积选取合理，HQ管是可以用于液压系统压力脉动衰减的。     

声学对称特性消声器传声损失测量方法

为了实现对具有声学对称特性的消声器传声损失的快速测量,结合其声传递矩阵内部各元素之间的数学关系,提出了一种能够消除消声器下游透射反射波对上游声场耦合的四传声器单载传声损失测量的新方法。以赫姆霍兹共振式消声器为例,基于边界元法对其传声损失进行虚拟测量,虚拟实验结果与理论结果吻合良好,验证了其正确性。该方法通过一次测量即可获得传声损失,具有测量设备简单、速度快、精度高、更易于使用等诸多优点。     

薄板振动式液压脉动衰减器滤波特性

为解决液压系统中由于压力脉动而引起的振动和噪声问题,提出一种薄板振动式液压脉动衰减原理,用弹性薄板代替结构振动式液压脉动衰减器的振动质量块,使静力平衡孔和平衡腔的流体构成一个赫姆霍兹谐振系统,弹性薄板与流体耦合振动构成一个受迫振动系统,实现了结构谐振与流体谐振的共同滤波,解决了传统液压脉动衰减器体积庞大的缺点.基于管路动态特性,结合具体的负载,建立薄板振动式液压脉动衰减器的传递矩阵模型,对压力脉动的衰减特性进行仿真,分析主要结构参数与压力脉动衰减性能的关系.根据仿真分析结果完成了流体滤波器样机的制作,对样机进行相关的试验研究,并将理论计算与试验结果进行比较分析.理论和试验研究表明薄板振动式液压脉动衰减器在很宽的频率范围内有良好的滤波效果.     

轮式挖掘机复杂结构抗性消声器研究及设计

针对某型轮式挖掘机发动机排气噪声的频率组成分布在低中高全频段的特点,根据共振腔消声器和扩张室消声器这两种基本消声单元结构特性,提出了一种恰当结合两种基本消声单元结构进行复杂结构抗性消声器设计的方法,使得消声器在全频段具有良好的消声效果,运用GT-power仿真软件对挖掘机发动机和消声器进行了耦合仿真,预测了复杂结构抗性消声器的性能,利用正交实验的方法对消声器内部结构参数进行了优化,最后通过实车测试进行了验证。实验及研究结果表明,所设计的复杂结构抗性消声器声学性能和空气动力性能良好,发动机排气噪声在全频段均有所下降,消声器插入损失平均达到18 d B(A),压力损失在许可范围内。     

内燃机抗性排气消声器插入损失的计算

本文推导了抗性排气消声器的插入损失的计算公式，对Ｓ１９５柴油机两种结构的排气消声器的消声性能进行理论计算，并进行了消声器的发动机台架试验，结果表明理论计算值和实测值吻合良好。     

薄板振动式广谱流体脉动衰减器实验研究

该文针对流体脉动的消减要求,在分析各种流体脉动消声器的基础上,设计一种薄板振动式广谱流体脉动衰减器结构。其作用机理类似于有阻尼的结构共振式吸振器,以载流弹性薄板为共振体,减小了滤波器的重量和体积。设计不同的薄板共振半径可以方便实现脉动衰减器的多共振频率,从而达到广谱滤波。应用ANSYS软件Workbench、ANSYS Mechanical和CFX的流固耦合功能对流体脉动衰减器进行流固耦合分析,并进行了实验研究。研究结果表明,该流体脉动衰减器结构简单,体积小,而且在较宽频带内都有较好的滤波效果,为流体脉动抑制技术提供了一种新的模式。     

Research Status,Critical Technologies,and Development Trends of Hydraulic Pressure Pulsation Attenuator

Hydraulic pumps are a positive displacement pump whose working principle causes inherent output flow pulsation.Flow pulsation produces pressure pulsation when encountering liquid resistance.Pressure pulsation spreads in the pipeline and causes vibration,noise,damage,and even pipeline rupture and major safety accidents.With the devel-opment of airborne hydraulic systems with high pressure,power,and flow rate,the hazards of vibration and noise caused by pressure pulsation are also amplified,severely restricting the application and development of hydraulic systems.In this review paper,the mechanism,harm,and suppression method of pressure pulsation in hydraulic sys-tems are analyzed.Then,the classification and characteristics of pulsation attenuators according to different working principles are described.Furthermore,the critical technology of simulation design,matching method with airborne piston pumps,and preliminary design method of pulsation attenuators are proposed.Finally,the development trend of pulsation attenuators is prospected.This paper provides a reference for the research and application of pressure pulsation attenuators.     

共振型液压脉动衰减器研究现状及展望

压力脉动通常被认为是振动和噪声的主要来源,使用合适的方法衰减压力脉动对液压系统的减振降噪有着十分重要的意义。共振型液压脉动衰减器由于能够有效衰减固有频率附近的压力脉动、压力损失小、变换类型多、成本低、可靠性高,在实际中得到了广泛的运用。在归纳总结国内外研究现状的基础上,将共振型脉动衰减器分为H型、多腔体型、流体-结构耦合振动型三类,并分别阐述各个类别的研究进展及使用性能。对各个类别的共振型脉动衰减器性能特点进行比较以方便用户合理选用设计。针对现存技术存在的不足,阐述今后研究的重点方向并指出紧凑性好、通用性高、频率适应性强是未来共振型液压脉动衰减器的发展趋势。提出一种新型拓扑结构的共振型脉动衰减器,该种衰减器能够灵活调整自身形状以适应严苛的安装空间要求。     

Experimental and numerical crashworthiness investigation of combined circular and square sections

Quasi-static experimental and nonlinear finite element analyses are performed to compare the energy absorption and initial peak load of combined circular and square sections with those of regular circular and square sections. The combined circular and square sections have higher energy absorption and lower initial peak load. These tubes can be widely used to ensure passenger safety in automotive and aerospace landing structures. The predicted numerical crushing load and fold pattern are in good agreement with experimental results. The specific energy absorption capability of the combined tube is significantly higher than that of the square tube and is close to that of the circular tube. The initial peak load of combined tube is significantly lower than that of the circular tube and somewhat lower than that of the square tube. Changing the section dimensions and their length results in higher energy absorption of the combined section than that of circular and square sections. Moreover, the initial peak load in the combined section is lower than that of the circular and square sections in all cases.     

板坯形状对方截面无模旋压轴向可旋深度的影响

利用实验方法对比了方形和圆形板坯形状对方截面无模旋压轴向可旋深度的影响,并对其影响机理进行了理论分析。首先采用确定初始步长的方法推导了可无限扩展的方截面旋轮路径公式,在此基础上分别模拟了方形和圆形板坯的无模旋压过程,并对模拟结果进行实验验证。然后提出了轴向可旋深度的评估方法,并以此为判据,对比分析了同轴向旋压深度下圆形和方形板坯工况的后续可旋性,发现方形板坯工况优于圆形板坯工况,进而揭示其机理为：方形板坯工况旋压过程中剩余法兰形状与旋轮路径切合性较好,促进了金属径向流动均匀化。     

Upper bound analysis of extrusion from square billets through circular and square/rectangular dies

Upper bound elemental technique (UBET) for prediction of extrusion pressure in three-dimensional forward extrusion process is presented. Using square/rectangular billets, the study of the effect of die land length has been extended for the evaluations of extrusion pressures to extrude sections such as circular, square and rectangular shaped sections with power of deformation due to ironing effect at the die land taken into account. The extrusion pressure contributions due to the die land evaluated theoretically for these shaped sections considered are found to increase with die land lengths for any given percentage reduction and also increase with increasing percentage die reductions at any given die land length. The effect of die land lengths on the extrusion pressures increases with increasing complexity of die openings geometry with rectangular section giving the highest extrusion pressure followed by circular with square section die opening, giving the least extrusion pressure for any given die reduction at any given die land lengths. The proper choice of die land length is imperative if excessive pressure buildup at the emergent section is to be avoided so as to maintain good quality and metallurgical structure of the extrudates. This paper was recommended for publication in revised form by Associate Editor Youngseog Lee Ajiboye, Joseph S. received his B.Eng, M.Eng, and PhD degrees in Mechanical Engineering from the University of Ilorin, Nigeria, in 1988, 1995 and 2006 res-pectively. Dr. Ajiboye is a lecturer in the Department of Mechanical Engineering, Uni-versity of Lagos, Nigeria. He is currently a Contract Research Scientist at KAIST Valufacture Institute of Mechanical Engineering, School of Mechanical, Aerospace & Systems Engineering, Korea Advanced Institute of Science and Technology, Daejeon 305 - 701, Korea. Dr. Ajiboye’s research interests include ECAE/P, determination of frictional effects in metal forming operations, upper bound and finite element in plasticity.     

降低液压系统压力脉动方法

通过对液压系统中产生压力脉动的机理分析,介绍被动滤波和主动滤波两种降低压力脉动的方法。通过对比,提出主动滤波是降低压力脉动的一种行之有效的方法。     

射流管三级电液伺服阀建模与动态特性仿真研究

叙述了射流管式三级电液伺服阀的结构及其工作原理,针对其结构建立了数学模型,并加入PD校正环节,导入MATLAB软件进行仿真,获得其阶跃响应曲线和开环伯德图。通过时域和频域分析表明,加入PD校正环节,使得系统局部相位超前,增加了系统的幅值裕度和相位裕度,因此其可大幅缩短三级阀的调整时间并增强其稳定性,同时反馈杆刚度和功率级滑阀阀芯面积对三级阀的动态响应有很大影响。通过有限元分析了圆形截面和矩形截面的反馈杆刚度,结果表明,在等面积时,由于矩形截面惯性矩大于圆形截面惯性矩,在相同的力作用下,矩形截面的反馈杆的位移较小,因此其反馈杆刚度较大,可提高先导级阀的动态反馈性能,从而更有利于三级阀的动态响应。     

Diffractive attenuators of laser radiation: Fabrication and optical characteristics

This paper reports on theoretical and experimental studies of a new class of zero-order diffractive elements — diffractive light attenuators with variable transmission. Results of tests of circular diffractive attenuators for wavelengths of 532 and 1064 nm with amplitude and phase transmission functions are presented. Methods of fabrication of the attenuators are discussed, and the characteristics of prototype modles are considered. It is shown that phase attenuators in the form of embossed circular diffractive gratings with a period of 2 to 6 µm and a variable duty cycle are not selective to polarization and allow controlling the radiation power of pulsed (including femtosecond) and continuous lasers over a wide range (> 100 times).