【作者】 杨帆；

【导师】 邓斌；

【作者基本信息】 西南交通大学 ， 机械电子工程， 2020， 博士

【摘要】 液压噪声与振动随着系统的高压化和大功率化而日益严重,亟待解决。压力脉动往往被视为液压噪声的主要来源,安装脉动衰减器抑制研究频带内的脉动波是目前减振降噪的主要途径之一。扩张室压力脉动衰减器作为一种抗性消声器,因其移动方便、相对体积小等优点而被广泛应用。基于液压系统性能的不断提升,扩张室脉动衰减器的研究也步入了一个新的阶段。因此,本文主要研究了扩张室衰减器进出口管道伸入腔室情况、腔体形状以及进出口端部位置等对脉动衰减性能的影响,并对现有扩张室脉动衰减器进行结构和性能改进,主要研究内容如下:一、论文详述了扩张室脉动衰减器频域特性建模的一维解析法(Transfer Matrix Method,TMM)。由于简单扩张室(C型)衰减器、内插管扩张室(K型)衰减器及其液压管路消声系统可划分为多种基本声学单元(等截面管道、面积突变结构、旁支管、膨胀腔),利用线性平面声波传播理论推导了这些声学单元的传递矩阵。当采用插入损失(Insertion Loss,IL)作为声学性能评价指标时,考虑到泵源阻抗和管口负载阻抗会直接影响脉动衰减器的IL,将泵源视为压力源和流量源,管口负载视为匹配和放空两类工况,把脉动压力和质量流量分别用电压和电流来代替,则管道消声系统可以通过电液类比使用等效电路加以描述,从而进行液压管道消声系统的声学分析。理论分析得到了四类IL模型,通过实验筛选出最符合实际工况的IL模型。二、声学有限元法(Finite Element Method,FEM)计算并分析了外插进出口同轴K型扩张室压力脉动衰减器圆形管道的端部修正,研究了长径比、管道壁厚与直径比对端部修正的影响。研究表明,插入圆柱腔内的管道长度过短以及过长都会使得端部修正理论失效;当直径比固定时,管道壁厚对端部修正的影响可以忽略不计;当壁厚固定时(除个别值外),端部修正会随着直径比的增加而增大。之后,继续使用FEM计算了外插进出口非同轴扩张室脉动衰减器管道的端部修正,比较了修正TMM法得出的传递损失(Transmission Loss,TL)理论值与有限元法计算结果;在平面波截止频带内,研究了内插管插入深度、偏心距以及偏转角对两类进出口偏置型扩张室脉动衰减器TL的影响。研究表明,这些结构参数会在一定程度上影响管道面积突变处高阶模态波的衰减,使得端部修正理论运用于进出口偏置型扩张室脉动衰减器TL性能预测时具有一定的局限性。三、对传统单级C型、K型扩张室脉动衰减器进行结构改进,提出了一种具有柔性衬里的C型扩张室和三类具有内插锥管、穿孔管的改进型扩张室脉动衰减器。对于柔性衬里C型扩张室脉动衰减器,利用电液类比法建立其集中参数模型,并用分布参数模型加以验证,研究了系统压力、衬里材料内部声学结构对TL的影响,结果表明:与无衬里和无空腔型聚氨酯衬里相比,C型扩张室腔室内壁敷设空腔型衬里拓宽了脉动衰减器的滤波频带;而针对三类具有内插锥管和穿孔管的扩张室脉动衰减器,利用TMM建立理论模型,并加以实验验证。研究了锥管小径、穿孔率以及孔径等结构参数对IL的影响,结果表明了在整个所关心的频带范围内,锥管和穿孔管应用于扩张室压力脉动衰减器的吸声潜力。另外,考虑到脉动衰减器安装空间的有限性,提出了应用标准遗传算法(Genetic Algorithm,GA)对两类改进型扩张室脉动衰减器进行结构优化设计,结果表明GA可做为一种快速、高效的优化工具实现给定研究频率下的滤波性能优化。在研究过程中采用了区别于TMM和FEM的新方法—格林函数法(Green’s Function Method,GM)。利用GM对矩形和正方形腔室截面的扩张室衰减器进行理论建模,其IL结果与实验测量值在整个研究频带内吻合良好,证明了该方法的可行性。通过探讨不同腔室截面形状(矩形、正方形和圆形)对衰减器滤波特性的影响,发现在截面周长一定的前提下,2000Hz频带内的圆形截面具有最优的滤波性能,正方形次之,而矩形截面性能最差;四、提出了几类两级扩张室压力脉动衰减器(阻抗复合式、两级抗性以及内插锥管两级扩张室)。针对阻抗复合式两级扩张室脉动衰减器,衬里腔室采用集中参数法建模,直通穿孔管段则采用TMM法建模,研究了系统压力、衬里内部声学结构、穿孔率以及孔径对TL的影响。研究表明,500Hz频带内任意频率下的TL受穿孔率和孔径大小的影响十分有限;针对两级抗性扩张室压力脉动衰减器,采用TMM法进行理论建模并进行实验验证。研究了穿孔率、孔径大小以及穿孔方式对其IL性能的影响。此外,通过GA对267Hz下的两级抗性扩张室吸声结构进行按需优化设计;针对两种具有内插锥管的两级扩张室脉动衰减器,建立其一维解析模型,并通过实验验证了理论模型的可靠性;基于该模型探讨了锥管小径、锥管内插长度、直通管内插长度、穿孔率以及孔径大小对2000Hz研究频率范围内的IL性能的影响,发现气体消声领域广泛采用的“微穿孔”结构不适用于压力脉动衰减器中。更多还原

【Abstract】 With the development trend of high pressure,high power and high precision,the problem of noise and vibration in hydraulic systems becomes more and more serious,which needs to be solved urgently.Pressure pulsation is often regarded as the main source of hydraulic noise,and the installation of dampers to suppress pressure pulsation within the research frequency band is one of the main approach for the reduction of hydraulic vibration and noise at present.As a kind of resistance muffler,expansion chamber hydraulic noise suppressors are widely used for their convenient movement and relatively small volume.Based on the continuous performance improvement of hydraulic systems,the research of expansion chamber pressure dampers has entered a new stage.Therefore,this thesis mainly studies the influence of extended inlet and outlet tubes,cross-section shapes of expansion chambers and locations of extended tubes on the attenuation performance,and improves the structure and performance of the existing expansion chamber dampers.Firstly,the one-dimensional(1D)transfer matrix method(TMM)for frequency characteristic analysis of expansion chamber pressure dampers is described in detail.Since simple expansion chambers,type C for short,and extended tube expansion chambers,type K for short,could be divided into several basic acoustic elements,such as constant cross-section pipes,area mutation structures,and side-branched tubes,transfer matrices of these acoustic units could be derived by the linear plane wave theory.Considering that the insertion loss(IL),which is used as the acoustic performance evaluation index,can be direcly affected by the source impedance and load impedance,hydraulic systems included type C or K pressure dampers could be simulated by the electro-hydraulic analogy.That is to say,hydraulic pump sources can be considered as pressure sources or flow sources separately,loads can be seen as matching or blow-down conditions,and the pressure pulsation and mass flow rate are replaced by the voltage and current.Four kinds of IL models are obtained by theoretical analysis,and the most suitable one could be selected by experiments.Secondly,the acoustic finite element method(FEM)is used to calculate and analyze the end correction of the circular pipes of K-type expansion chamber pressure dampers,and the influence of the length diameter ratio,the wall thickness diameter ratio on the end correction is studied.The results show that the end correction theory will fail if the extended length is too short or too long;when the diameter ratio is fixed,the influence of the wall thickness on the end correction could be neglected;when the wall thickness is fixed(except for some individual values),end corrections will increase with the increase of the diameter ratio.Then,the FEM is used to calculate the end correction of the circular pipes of a non coaxial expansion chamber and the transmission loss(TL)theoretical values obtained by the corrected 1D TMM are compared with the results of the FEM.Within the cut-off frequency band of plane waves,the effects of the insertion depth,the eccentricity and the deflection angle of the extended tubes on the TL are stuied.The results show that these structural parameters could affect the attenuation of high-order mode waves at sudden area changes to some extent,which makes the application of the end correction theory to the prediction of TL performance of non coaxial expansion chamber attenuators have some limitations.Thirdly,structural improvements for traditional single-chamber C-type and K-type expansion chamber pulsation attenuators are put forward;a C-type expansion chamber with flexible lining and three kinds of improved expansion chamber pressure dampers with inserted conical and perforated tubes are proposed.For the flexible lined C-type expansion chamber damper,the lumped parameter model is extablished by the electro-hydraulic analogy,and verified by the distributed parameter model.Then,the influence of the system pressure and the internal acoustic structure of the lining material on the TL is studied;the results show that compared with the unlined C-type expansion chamber and the cavity with unvoided polyurethane lining,the chamber with voided lining can broaden the filtering frequency band.For the three kinds of pressure dampers with inserted conical and perforated tubes,the 1D TMM is used to establish the mathematical models and verified by experiments;the effects of the structural parameters such as the slope of the conical tubes,the porosity and the hole diameters on the IL are studied.The results show that the sound absorption potential of conical and perforated tubes used in expansion chamber hydraulic noise suppressors within the whole concerned frequency band.In addition,considering that the installation space of pressure dampers is limited,this paper proposes the application of the standard genetic algorithm(GA)to optimize the structure of two kinds of expansion chamber pressure dampers with conical and perforated tubes.The results show that the GA could be used as a fast and efficient optimization tool to optimize the filtering performance at a given research frequency.A new method,the Green’s function method(GM),which is different from the 1D TMM and the three dimensional(3D)FEM,is used in the research of expansion chamber pressure dampers.The GM is used to model the dampers with rectangular and square sections;the IL results are in good agreement with the experimental data in the whole research frequency band,which proves the feasibility of the GM.Besides,the influence of three kinds of cross-section shapes,rectangle,square and circle,on the filtering characteristics is discussed.It is found that the circular section has the best performance in the range of 2000 Hz,followed by the square section,while the rectangular one is the worst.Fourthly,several types of double-chamber compound expansion chamber hydraulic attenuators,the compound impedance types,the double-chamber resistance types and the two-stage chambers with inserterd conical tubes,are proposed.For the first type,the lining chamber is modeled by the lumped parameter method,while the straight through perforated pipe section is modeled by the 1D TMM.Then,the effects of the system pressure,the internal structures of the lining,the porosity and the hole diameters on the TL are studied and the results show that the effects of the porosity and the hole diameters are minimal.For the second type,the 1D TMM is used for the theoretical modelling and verified by the experiments.The effects of the porosity,the hole diameters and the perforation patterns on the IL are studied.Besides,the GA is used to optimize the filtering performance at 267 Hz.For the last type,the 1D analytical models are established,and the reliability of the models is verified by the experiments.Based on these models,the effects of the slope of the conical tubes,the inserted length of the straight tube,the porosity and the hole diameters in the range of 2000 Hz are discussed.It is found that the microperforated structure which is widely used in the field of gas elimination is not suitable for pressure dampers.更多还原