阻尼孔连续型液压缓冲器研究及设计

阻尼孔离散分布式液压缓冲器缓冲力不稳定,应用受到限制。本文提出一种阻尼孔口连续变化的液压缓冲器结构,运用CFD方法确定阻尼孔流量系数,并依照理想缓冲曲线对阻尼孔口的主要参数进行设计,得到了阻尼孔口开度随缓冲位移的变化曲线。     

以水为介质阻尼孔气穴流动理论和试验研究

针对水的汽化压力高、容易发生气穴的特点,应用气穴模型理论对阻尼小孔中以水作为工作介质时的流动特性进行理论分析.在此基础上,用可视化方法对阻尼小孔中的气穴流动特性进行试验,研究阻尼孔中的气穴发生过程,分析阻尼孔内径和长径比对气穴的影响.研究结果表明阻尼孔的气穴首先在进口部位产生,并随着两端压差的增大向出口推移.大长径比的阻尼孔相对小长径比的阻尼孔而言不容易发生气穴.在相同长径比的情况下,孔径大的阻尼孔相对孔径小的阻尼孔更容易发生气穴.研究结果对阻尼小孔的选择设计具有一定的参考意义.     

近阻塞状态时液压阻尼孔流动与压力-流量特性分析

针对草捆成型液压系统中的插装阀阻尼孔阻塞问题,建立一种近阻塞状态时阻尼孔计算模型,提出阻塞裕度的概念,分析了近阻塞状态液压阻尼孔的流动及压力-流量特性.结果表明近阻塞状态时,阻塞物在入口形成"二次节流"效应,加剧了流速的变化,造成高压力梯度区的前移和低压区的扩大.阻尼孔通流能力随着压差的增大和堵塞裕度的降低而加剧.所推导的理论流量公式在阻塞裕度较小时与数值计算结果吻合良好.研究结果对阻尼孔性能退化的评估提供了参考.     

低温对风力发电机组偏航液压制动系统的影响及优化

低温环境下液压油黏度增大导致风力发电机组偏航液压制动系统性能下降,无法满足风机正常运行和安全的要求。对偏航液压制动系统受低温影响的原因及过程进行了理论分析,并对分析结果进行了仿真与试验验证。为提高偏航液压制动系统在低温环境下的响应性能,验证了短孔阻尼和制动器闭环串并联结构对提高系统制动建压和阻尼卸压速度的可行性及效果。结果表明,该方法可有效提高偏航液压制动系统在机舱低温工况下的制动能力,可为偏航液压制动系统的设计提供有益参考。     

单缸油气悬架阻尼孔压力特性建模分析

油气悬架阻尼孔的工作和结构参数对其压力特性有重要影响。根据其结构特点和工作原理,建立单缸油气悬挂试验台数学模型,采用AMESim搭建试验台单缸系统的仿真模型。对比分析初始条件阻尼孔尺寸、蓄能器充气压力、激励频率等对阻尼孔压力的影响;并对比了不同的阻尼孔直径,不同的充气压力和激励频率下油气悬架数学模型和仿真模型的结果。对数学模型和仿真模型中气体多变指数和阻尼孔流量系数进行修正,对比分析修正后阻尼孔压力和悬架的输出特性。结果表明:气体多变指数和阻尼孔流量系数均会对阻尼空压力产生较大影响;气体多变指数会随着激励频率的升高依线性规律增加;阻尼孔流量系数取值应偏大;试验结果验证了仿真模型的准确性,为进一步研究提供理论和模型参考。     

阻尼孔振荡流态下的动态特性分析

研究阻尼孔元件的动态流量特性时,由于阻尼孔动态数学模型中涉及非直接测量物理量参数的估计,利用纯数学模型难以准确描述其特性.以阻尼孔理论研究为基础,建立细长型阻尼元件的三维分析模型,通过在阻尼孔两端加载遵循正弦规律变化的动态压力载荷,采用有限元的分析方法对阻尼孔在低频微幅振荡状态下的流量特性进行分析.分析结果表明,当阻尼孔内流体处于低频微幅振荡流动状态时,其孔内瞬态流量与元件两端差压同频不同相,其瞬态流量振动幅值与元件两端差压呈比例关系,比例系数与振荡频率相关,但瞬态流量振动的相位滞后角则完全由振荡频率决定.     

涡街流量传感器压力损失系数的试验研究与计算

在天津大学电气与自动化工程学院流量实验室的气体流量试验装置上,通过改变管道内气体的压力,对涡街流量传感器的压力损失系数进行试验研究。对大量试验数据进行处理后发现,涡街流量传感器的压力损失系数会随着管道内气体压力的变化而有所变化。当管道内气体压力在0.1～1.1 Mpa的范围内变化时,压力损失系数会随着气体压力的增大而减小,变化幅度最大达到了7%。对压力损失系数随气体压力变化的规律进行分析,并给出压力损失系数随管道内气体压力变化的计算公式。     

无级变速器减压回路压力脉动关键参数识别及优化验证

针对无级变速器独立液压系统的减压回路，建立液压模型，通过引入Sobol'灵敏度分析算法，在MATLAB/AMESim软件平台上，对减压回路压力脉动衰减关键参数进行灵敏度分析。一阶灵敏度及一阶全局灵敏度的分析结果显示，先导阻尼孔、减压阀节流槽及负载流量（等效负载阻尼孔）对压力稳定性影响最大，二阶灵敏度指标显示节流槽与负载流量间的耦合作用最强。根据分析结果，对实车压力脉动现象进行关键参数响应曲面优化，并通过试验结果说明此分析方法的有效性。     

基于模拟退火算法的多孔式液压缓冲器阻尼孔优化

提出了基于模拟退火算法的阻尼孔组合优化方案,实现了多孔式液压缓冲器的优化设计。根据缓冲器缓冲过程中的受力状态和孔口流量特性，建立了多孔式缓冲器缓冲过程的动态数学模型；以阻尼孔直径、阻尼孔间距和阻尼孔数量为优化变量，基于缓冲器动态数学模型与模拟退火算法，建立了阻尼孔组合优化求解模型；根据该优化模型对阻尼孔的3个优化变量进行了组合优化，并将优化前后的数据输入到多孔式液压缓冲器的AMESim仿真模型中进行验证。仿真结果表明：同最初方案相比，组合优化后的液压缓冲器的内腔最高压力降低了12%，缓冲行程缩短了6.7%，缓冲过程更加平缓。     

不同进气角度下轴向转动孔流动特性实验研究

为了研究轴向转动孔的流动特性,在旋转试验台上对轴向进气与预旋45°进气的轴向转动孔,进行了不同压比(1.05～1.3)与不同转速(0～9000r/min)下流动特性的实验研究.研究结果表明:随着压比增加,轴向进气转动孔流量系数增加,最大增幅为12.74％;而预旋45°进气时,流量系数先增后减,最大变化幅度为21％.随着...     

不同润湿组合配流副的摩擦磨损试验研究

为调控配流副表面润湿性以提高摩擦学性能，采用低面能修饰法制备具有不同润湿性的上试样超级双相不锈钢SAF2507和下试样碳纤维增强聚醚醚酮(CFRPEEK)组成配流副，利用MMD-5A标准摩擦磨损试验机测试并分析其在蒸馏水、海水、L-HM46抗磨液压油3种润滑条件下的摩擦磨损特性。结果表明：低面能修饰使配流副上试样与下试样由亲水表面转变为疏水表面，上下试样表面虽仍保持亲油性但其油接触角明显增大；同种配流副在油、海水、水介质中摩擦因数依次减小；在水、海水、油介质下双疏水表面配流副较双亲水表面配流副摩擦因数分别减小8.2%、38.2%、24.4%；同种配流副在水、海水、油介质中磨痕深度依次减小。配流副的摩擦主要以犁沟效应和黏着磨损为主，双低表面能组合配流副能有效减小摩擦过程中的黏着磨损，从而表现出较好的摩擦学性能。     

基于遗传算法的小型化液压油源用错列翅片式换热器优化研究

紧凑、轻量化、高效节能型换热器对高端移动装备中液压油源的小型化至关重要。基于不同普朗特数流体的换热和流动阻力经验关联式设计并优化了一种矩形错列翅片式换热器。推导出相关质量、出口温度和压力损失的函数模型,通过灵敏度分析研究关键参数对目标函数的影响,从而评估各变量对换热器综合性能的贡献度。在此基础上,利用遗传算法对换热器的关键参数进行优化。同时,通过数值模拟研究优化前后换热器的流动特性和换热性能。结果表明,理论计算与数值仿真结果吻合良好。优化后换热器质量减小25.79%,换热器降温幅度提高25.24%。研究成果对液压油源的小型化和轻量化具有积极的促进作用。     

高温工质用于木材干燥除湿的试验研究

对新混合工质HTR01用于木材除湿干燥系统进行了理论循环分析和灌注式替代R22的循环性能试验研究，结果表明HTR01的制热量虽低于R22，但性能系数、压缩机排气温度和功耗等循环性能指标以及除湿能耗比均优于R22，用于木材除湿干燥可以明显提高干燥速度，干燥质量好。     

矿山井下液压设备的维护与管理

探讨井下液压设备的维护与管理。通过选择合适液压油、控制油温、保持油液清洁及减少泄漏来保持设备的正常运行。采取有效措施后能有效降低液压设备出现故障的几率。加强液压设备维护和管理,制定标准维护流程,可有效提高矿山液压设备运行的经济效益。     

Experimental investigation of the temperature fade in the cavitation zone of full journal bearings

This paper describes an experimental investigation with a rig for measuring the surface temperatures and pressures in single bore journal bearings. The test bearing was equipped with small bores, where the pressure was altered by means of a vacuum pump. The whole bearing arrangement can also be operated at different ambient pressures ranging from atmospheric down to −0.06 MPa. Oil temperatures at inlet and outlet are also measured. Experiments show a considerable drop in the temperature of oil undergoing a drop in pressure. The overall temperature level of the bearing system did not seem to affect the magnitude of the temperature drop. Experiments where the bearing system was operated at sub-ambient pressures revealed an increased temperature drop in the cavitation zone. Pressures higher than ambient were measured within the cavitation zone while the bearing was operated at sub-atmospheric pressure. The higher pressures are believed to be caused by evaporation of oil. It is therefore proposed that the temperature drop observed in the cavitation zone of journal bearings is primarily caused by evaporation of oil. However, isentropic decompression of the gases in the oil is also believed to play a role.     

螺旋扭曲膨胀管油冷却器壳程传热及压降性能试验研究

通过搭建试验测试平台测试了螺旋扭曲膨胀管油冷却器壳侧传热及压降性能,并与传统的折流板式油冷却器进行了性能对比。结果表明,螺旋扭曲膨胀管油冷却器传热和压降性能都优于传统折流板油冷却器;在相同的压降下,螺旋扭曲膨胀管油冷却器的壳程传热系数是传统折流板式油冷却器的2³倍,综合性能有明显的优越性。根据试验结果拟合出了螺旋扭曲膨胀管油冷却器壳程传热系数和压降与壳程流速的关系式,为后续螺旋扭曲膨胀管油冷却器的推广应用提供参考。     

Experiment and simulation study on cavitation flow in pressure relief valve at different hydraulic oil temperatures

Hydraulic oil is the “blood” of hydraulic system, its high temperature in low-pressure hydraulic system would promote the development of cavitation and cause severe erosion of pressure relief valve. The influence of high oil temperature on the distribution of pressure field, velocity field and vapor volume fraction are discussed experimentally and numerically. The results show that with the increasing oil temperature, the viscosity of the oil decreases, and the flow rate increases, resulting the decreasing pressure at the orifice. Higher oil temperature promotes the occurrence of cavitation in the pressure relief valve, wider low-pressure zone could be found and cavitation bubble developed more fully and towards the valve core head. When the oil temperature increases from 303 K to 353 K, the cavitation intensity rises more sharply, but the growth rate of cavitation intensity increases firstly and then decreases with the increasing input pressure. Furthermore, based on the field synergy theory, the flow resistance and energy dissipation under different oil temperatures are evaluated. Both of large viscous dissipation and effective viscosity coefficient are mainly concentrated at the orifice, which are all effected by the oil temperature, so as to the characteristics of cavitation flow. The average field synergy cosine angle and the average viscosity coefficient decreases gradually with the increasing oil temperature, while the average vapor volume fraction increases. The energy dissipation is reduced by 3.3 × 10⁷ (W m⁻³) while the hydraulic oil temperature increases from 303 K to 353 K. Appropriate hydraulic oil temperature could provide favourable working conditions for the pressure relief valve which is beneficial for extending the hydraulic system's service life.     

Simultaneous temperature measurements of bearing and seal parts of a swash plate type axial piston pump — effects of piston clearance and fluid property

Temperatures of three bearing and seal parts of a swash plate type axial piston pump were measured simultaneously using a slip ring with thermocouples’ amplifiers. The rotating cylinder block had five thermocouples, the swash-plate had four, and the valve-plate had four. Three sets of pistons with different diameters were prepared. Hydraulic mineral oil with VG22 and a water-glycol type hydraulic oil with VG32 were used as test fluids. The maximum discharge pressure was 20 MPa; the maximum rotational speed was 25 rps. The inlet oil temperature was 20–40°C. Temperatures and temperature differences between the bottom-dead-center and the top-dead-center increased concomitantly with the discharge pressure. For larger piston clearance ratios, the temperatures rose monotonically. The bearing and seal parts were markedly hotter than the discharge oil. Temperatures rose much less using the water-glycol type oil than when using the mineral oil.     

D11T推土机液压油温升高的热力学研究及技改措施

D11T推土机在矿山开采工艺采运排中起着关键的作用,其中液压系统的稳定运行是推土机正常施工作业的必要条件,然而由于冷却器设计不当,常常导致液压系统油温升高。长期高温运行会对机械设备造成不同程度的损害,从而严重影响作业进程。针对D11T推土机设备现状,通过热力学液压系统能量损失功率及液压油温升计算,提出了冷却系统技术改造的相关措施并现场实验验证。经技术改造试运行后,液压油温升得到有效控制,为设备稳定、长周期运行提供了有力保障。     

A study on the exit flow characteristics determined by the orifice configuration of multi-perforated tubes

A multi-perforated tube indicates the existence of multiple holes in various shapes on the surface of long cylinder-type or rectangular tubes, and the hole installed on the surface is called an orifice as it is relatively small in size, compared with the surface area of the tubes. In this study, flowrate distribution features and changes in discharge angle according to the blockage ratio resulting from the changes in the number of orifices and the thickness of multi-perforated tubes were investigated by means of analysis and experiment, targeting the multi-perforated tubes where rectangular orifices are installed on the both sides of square tubes. In addition, contraction coefficient and flow coefficient between orifices were analytically investigated. The more increase in blockage ratio of multi-perforated tubes, the more uniform flowrate distribution between orifices. The discharge angle becomes more and more perpendicular in the longitudinal direction of multi-perforated tubes as it gets closer to the end of orifices, exhibiting big differences at the entrance if blockage ratio is small. The more increase in the thickness of multi-perforated tubes, the more uniform flowrate distribution between orifices become as contraction coefficient increases. The flow coefficient distribution of orifices using the pressure at the entrance of the orifices of multi-perforated tubes increases in the longitudinal direction of the multi-perforated tubes, exhibiting values ranging from 0.66 to 0.68 as to BR = 0.893 ?? 0.979.