Relation between pressure variations and noise in axial type oil piston pumps

Pressure variation is one of the major sources on noise emission in the axial type oil piston pumps. Therefore, it is necessary that the pressure variation characteristics of the oil hydraulic piston pumps be clarified to reduce the pump noise. Pressure variations in a cylinder at the discharge region and the pump noise were simultaneously measured with discharge pressures and rotational speeds during the pump working. To investigate the effects of the pre-compres-sion and the V-notch in the valve plate, we used the three types of valve plates. In this research, it is clear that the pressure variation characteristics of axial type oil piston pumps is deeply related to the pre-compression and to the V-notch design in valve plate. Therefore, we could reduce the pump noise by using the appropriate pre-compression angle and the notch design that are between the suction port and the discharge port in valve plate.     

液压泵效率特性建模的神经网络方法

通过对液压泵效率特性的分析,研究液压泵效率特性的神经网络建模方法。以排量为39.57 cm3/r的柱塞液压泵作为建模对象,以少量的试验数据作为神经网络的训练样本,采用3层BP神经网络加贝叶斯正则化方法对网络进行训练,建立液压泵的流量和转矩模型,并以此为基础计算液压泵的总效率。选取不同转速和压差下的试验数据,对流量和转矩神经网络模型的泛化能力进行检验,结果表明,液压泵的总效率误差在0.2%以内。     

液压轴向柱塞泵降噪研究进展

对国内外液压轴向柱塞泵的各种降噪方法和目前的研究情况进行了综述。介绍了液压轴向柱塞泵噪声产生的主要原因及机理，对纯预压和减压式配流盘，配流盘带有节流孔，配流盘带有三角槽，配流盘带有单向阀，泵缸体带有弹性环和柱塞空心孔内安装有蓄能器这几种结构形式，从工作原理，结构特点和降噪效果上进行了分析，对液压轴向柱塞泵的降噪方法提出了建议。     

高压轴向柱塞泵滑靴副性能测试液压

为了测量35 MPa高压轴向变量柱塞泵滑靴副的油膜性能参数,需研制一套滑靴副性能测试液压系统。针对35 MPa的高压工作环境,设计出了一种高压轴向变量柱塞泵滑靴副性能测试液压系统,并建立了其AMESim仿真模型。通过仿真分析,得知该液压系统的卸压能满足工作要求,其卸荷性能良好,而且无论是卸压还是卸荷过程,液压冲击均得到有效的抑制,因而,该液压系统能够满足泵在35 MPa高压工况下平稳运行的要求,从而为提高35 MPa高压轴向变量柱塞泵滑靴副的油膜性能提供了前提保障。     

Output characteristics of a series three-port axial piston pump

Driving a hydraulic cylinder directly by a closed-loop hydraulic pump is currently a key research area in the field of electro-hydraulic control technology,and it is the most direct means to improve the energy efficiency of an electro-hydraulic control system.So far,this technology has been well applied to the pump-controlled symmetric hydraulic cylinder.However,for the differential cylinder that is widely used in hydraulic technology,satisfactory results have not yet been achieved,due to the asymmetric flow constraint.Therefore,based on the principle of the asymmetric valve controlled asymmetric cylinder in valve controlled cylinder technology,an innovative idea for an asymmetric pump controlled asymmetric cylinder is put forward to address this problem.The scheme proposes to transform the oil suction window of the existing axial piston pump into two series windows.When in use,one window is connected to the rod chamber of the hydraulic cylinder and the other is linked with a low-pressure oil tank.This allows the differential cylinders to be directly controlled by changing the displacement or rotation speed of the pumps.Compared with the loop principle of offsetting the area difference of the differential cylinder through hydraulic valve using existing technology,this method may simplify the circuits and increase the energy efficiency of the system.With the software SimulationX,a hydraulic pump simulation model is set up,which examines the movement characteristics of an individual piston and the compressibility of oil,as well as the flow distribution area as it changes with the rotation angle.The pump structure parameters,especially the size of the unloading groove of the valve plate,are determined through digital simulation.All of the components of the series arranged three distribution-window axial piston pump are designed,based on the simulation analysis of the flow pulse characteristics of the pump,and then the prototype pump is made.The basic characteristics,such as the pressure,flow and noise of the pumps under different rotation speeds,are measured on the test bench.The test results verify the correctness of the principle.The proposed research lays a theoretical foundation for the further development of a new pump-controlled cylinder system.     

Flow Ripple of Axial Piston Pump with Computational Fluid Dynamic Simulation Using Compressible Hydraulic Oil

The flow ripple, which is the source of noise in an axial piston pump, is widely studied today with the computational fluid dynamic(CFD) technology development. In the traditional CFD modeling, the fluid compressibility, which strongly influences the accuracy of the flow ripple simulation results, is often neglected. So a compressible sub-model was added with user defined function(UDF) in the CFD model to predict the flow ripple. At the same time, a test rig of flow ripple was built to study the validity of simulation. The flow ripple of pump was tested with different working parameters, including the rotation speed and the working pressure. The comparisons with experimental results show that the validity of the CFD model with compressible hydraulic oil is acceptable in analyzing the flow ripple characteristics. In this paper, the improved CFD model increases the accuracy of flow ripple rate to about one-magnitude order. Therefore, the compressible model of hydraulic oil is necessary in the flow ripple investigation of CFD simulation. The compressibility of hydraulic oil has significant effect on flow ripple, and the compression ripple takes about 88% of the total flow ripple of pump. Leakage ripple has the lowest proportion of about 4%, and geometrical ripple leakage ripple takes the remnant 8%. Besides, the influence of working parameters was investigated through the CFD simulations and experimental measurements. Comparison results show that the amplitude of flow ripple grows with the increasing of rotation speed and working pressure, and the flow ripple rate is independent of the rotation speed. However, flow ripple rate of piston pump grows with the increasing of working pressure, because the leakage ripple will increase with the pressure growing. The investigation on flow ripple of an axial piston pump using compressible hydraulic oil provides a more validity simulation model for the CFD analyzing and is beneficial to further understanding of the flow ripple characteristics in an axial piston pump.     

Fault diagnosis of axial piston pumps with multi-sensor data and convolutional neural network

Axial piston pumps have wide applications in hydraulic systems for power transmission. Their condition monitoring and fault diagnosis are essential in ensuring the safety and reliability of the entire hydraulic system. Vibration and discharge pressure signals are two common signals used for the fault diagnosis of axial piston pumps because of their sensitivity to pump health conditions. However, most of the previous fault diagnosis methods only used vibration or pressure signal, and literatures related to multi-sensor data fusion for the pump fault diagnosis are limited. This paper presents an end-to-end multi-sensor data fusion method for the fault diagnosis of axial piston pumps. The vibration and pressure signals under different pump health conditions are fused into RGB images and then recognized by a convolutional neural network. Experiments were performed on an axial piston pump to confirm the effectiveness of the proposed method. Results show that the proposed multi-sensor data fusion method greatly improves the fault diagnosis of axial piston pumps in terms of accuracy and robustness and has better diagnostic performance than other existing diagnosis methods.     

Mechanical testing of hydraulic fluids

The antiwear properties of hydraulic fluids are important because hydraulic pump and motor wear is costly. While international hydraulic fluid performance standards continue to be developed, e. g., the ISO/TC28/SC4 committee's draft ISO DIS 11158 ‘Specifications for mineral oil hydraulic fluids’, the normal hydraulic fluid performance specifications represent minimum requirements. Performance specifications for nonmineral oil hydraulic fluids are also being developed. Typically, both the user and the fluid manufacturer possess insufficient objective information about the antiwear properties of special fluids, e. g., environmentally acceptable hydraulic fluids (EAHF) or fire‐resistant hydraulic fluids (FRHF) for use in hydraulic equipment such as axial‐piston pumps, vane pumps or radial‐piston motors. Manufacturer's specifications must therefore be determined. The required lubrication properties can be determined by either laboratory pump tests or a field trial, often at the customer's expense. The lubrication properties of a hydraulic fluid should ideally be determined under conditions that are equivalent to field practice. This paper will discuss the use of the vane pump test and the FZG gear test to gauge ‘recommended’ hydraulic fluid performance; many non‐mineral hydraulic fluids, such as environmentally acceptable hydraulic fluids, fire‐resistant fluids or synthetic hydraulic fluids, cannot be used in axial‐piston systems based only on results obtained with these tests, and additional testing is always required. Proposals are made for testing of such fluids on a variable‐load test rig. These tests are done with axial‐piston pumps, or other similar displacement systems, and are intended to determine the industrial suitability of non‐mineral hydraulic fluids.     

水压轴向柱塞泵滑靴静压支承中的惯性影响

在油压轴向柱塞泵的滑靴静压支承设计中,通常忽略Navier-Stockes方程中的惯性项,这是因为它较粘性项小得多,对计算结果的影响不大.然而,在水压轴向柱塞泵的研究中,由于水的粘度比油的粘度小得多,因此,惯性项就起着较大的作用.研究了水的流动惯性对支承间隙中的压力及流速分布的影响,从而对水压静压支承设计进行修正,得出更加合理的结果.     

基于离心涡轮的液压柱塞泵自增压技术研究

液压柱塞泵由于自身吸油特性不好,入口油压低时极易造成吸油不足产生气穴,引起振动和气穴噪声,对液压系统危害很大。而且入口吸油不足还极大地限制了泵工作转速的提高和减少使用寿命。文中研究在液压柱塞泵入口腔内集成离心涡轮,实现液压柱塞泵自增压。     

基于AMESim的四配流窗口轴向柱塞马达仿真研究

参考回转机构双控马达回路原理，搭建了四配流窗口轴向柱塞马达。结合现有的两口马达结构和仿真模型，利用AMESim构建了四口柱塞马达的物理仿真模型，并搭建了简单的油液回路，包括蓄能器等构成的能量回收部分，模拟挖掘机回转机构。对模型参数进行合理的设置，分析了柱塞马达仿真模型的各项特性及负载特性。仿真结果表明，四配流窗口轴向柱塞马达运行正常，对回转能量回收有一定效果，对节能方案的创新有一定的参考。     

轴向柱塞泵主轴动平衡的设计及实验研究

对一种轴向柱塞泵主轴进行了动不平衡分析,结合其主轴的结构特点采用了两面动平衡校正方案.并在动平衡试验机上对主轴进行了动平衡实验.通过动平衡前后水压泵的噪声对比测试表明,动平衡可以大大减小泵的噪声.     

基于递归定量分析的液压泵故障识别方法

提出了一种局部投影消噪和递归定量分析相结合的轴向柱塞泵故障识别方法。以轴向柱塞泵故障振动信号为研究对象，首先用局部投影消噪方法对振动信号进行消噪；其次对消噪后的振动信号绘制递归图，进而通过递归定量分析对递归图所反映出的系统动力学信息进行特征提取，选择确定率（DET）和递归熵(ENTR)2个特征构成特征向量，构成故障特征样本；然后通过核模糊C均值聚类(KFCMC)方法对训练样本进行聚类,进而依据最小欧氏距离准则对测试样本进行故障识别；最后，将递归定量分析方法和相空间复杂网络定量特征方法进行对比。结果表明，基于递归定量分析的轴向柱塞泵故障识别方法具有更高的故障确诊率。     

双斜盘阀配流轴向柱塞式液压电机泵配流特性和变量原理的研究

提出一种有别于常规阀配流泵的"斜盘转动而缸体不动"而采用缸体和配流阀一起旋转的双斜盘阀配流轴向柱塞式液压电机泵。建立该泵配流机构的数学模型,研究各种结构参数和工作参数对配流特性的影响,尤其是配流阀芯所受离心力对配流特性的影响。以仿真模型和得出的单个柱塞腔的压力响应曲线和输出流量曲线为基础,研究该类型泵流量脉动和侧向力脉动的特点,得出随着泵的工作转速增加,流量脉动和侧向力脉动都增大,当柱塞数量足够多时,柱塞数量的奇偶性在影响流量脉动上没有明显的区别,偶数个柱塞比奇数个柱塞产生的侧向力脉动要大。提出一种新型的阀配流轴向柱塞泵的变量调节方式,并研究该变量方式的原理和调节特性。样机泵的试验结果表明该泵的工作原理可行,进而展望双斜盘阀配流轴向柱塞式液压电机泵的应用前景。     

轴向柱塞泵低气压运行特性建模与试验分析

空化是影响液压系统动态特性的重要因素,为此开展了轴向柱塞泵低压环境下的工况研究。考虑气液两相混合油液的密度、体积弹性模量和黏度的影响,限制入口油腔的最低压力,建立轴向柱塞泵的压力流量模型,计算获得轴向柱塞泵在不同工况下的流量特性,并通过试验验证。研究表明:负载增大导致更严重的空化以及泄漏,并使容积效率降低;轴向柱塞泵在达到临界流量之后,转速提升只会加剧空化,而不能提升流量;最大容积效率出现在临界流量产生之前。为轴向柱塞泵低气压性能预测提供了理论支撑。     

液压泵恒流控制的神经网络实现方法及应用研究

提出一种采用神经网络辨识负载流量原理实现液压泵恒流量调节的新方法。结合此方法,提出在种基于模糊神经网络的恒流量调节泵智能学习控制方法,并将其应用于电液比例恒流量调节轴向柱塞泵的控制,改善了该泵的控制品质。     

基于EASY5的轴向柱塞泵建模与流量特性仿真研究

以CY14-1B型斜盘式轴向柱塞泵为研究对象,分析柱塞泵结构原理与柱塞运动规律,建立柱塞泵流量数学模型。利用MSC.EASY5软件搭建柱塞泵液压虚拟样机模型,进行流量仿真计算,与液压试验台测试结果对比,验证模型的准确性。在此基础上,仿真计算不同斜盘倾角、不同内泄量情况下柱塞泵流量特性曲线,仿真模拟结果与理论分析及实际情况基本一致。结果表明:应用EASY5软件可以准确有效的实现柱塞泵建模和仿真,为进一步研究柱塞泵故障诊断提供参考,对复杂液压元件虚拟样机建模具有借鉴意义。     

轴向柱塞泵松靴故障特征信号的分析与选择

对轴向柱塞泵产生松靴故障的机理进行分析.选取振动信号和油液温升信号作为监测参量.分析研究表明,泵壳体振动信号和外泄口油液的温升信号是轴向柱塞泵松靴故障的敏感特征参量.     

考虑黏-温特性对柱塞泵空化射流的影响

黏度是液压油的基本属性之一,其值对温度变化非常敏感,而温度又是影响油液发生空化的直接因素之一,因此为研究油液的实时黏-温特性对轴向柱塞泵空化效应的影响,利用流体仿真分析软件PumpLinx建立了包括湍流模型、全空化模型等条件在内的轴向柱塞泵动态CFD模型;并在考虑配流副间隙、柱塞副间隙和滑靴副间隙基础上,通过分析对比黏度恒定和实时黏-温变化两种条件下柱塞泵温度场、速度场和气体体积分数等因素,分析了黏-温特性对轴向柱塞泵内空化效应的实时影响。结果表明:与黏度为定值相比,在实时黏-温条件下柱塞泵空化效应更加剧烈,研究过程中所建立的仿真模型为后续的优化设计提供了一定的指导。     

水压柱塞泵噪声特性的试验研究

基于阀配流式轴向水压柱塞泵的结构原理,分析了其噪声产生的主要原因,并对不同的配流阀结构型式、主轴动平衡前后、不同转速以及不同排量水压泵的噪声特性进行了对比试验研究。试验结果表明:采用平板型配流阀的水压泵噪声低于蕈阀结构的噪声;主轴动平衡后水压泵的噪声有明显降低;增大排量、降低转速可以降低泵的噪声;配流阀通径对泵的噪声影响较大。研究结果为水压泵的降噪提供了试验依据。