Distribution Performance Analysis and Experimental Research on the Port Plate Pairs of Low Speed High Torque Seawater Hydraulic Motor

The current research of seawater hydraulic motor mainly focused on piston motor and vane motor, but seldom regarded low speed high torque seawater hydraulic motor. Low speed high torque seawater hydraulic motor as a kind of energy conversion device and actuator plays an important role in seawater hydraulic transmission system. However, the physical and chemical properties of seawater, such as low viscosity, high causticity and poor lubrication, result in numerous problems. In this paper, the flow distribution characteristics of port plate pairs for the seawater hydraulic motor are investigated, and the leakage flow and power loss models of port plate pairs are established. Numerical simulations are carried out to examine the effects of water film, inlet pressure and rotating speed on the pressure distribution and leakage flow. And the friction and wear tests of port plate pairs are also carried out. Moreover, the test system of the seawater hydraulic motor is constructed and the performance of prototype with no-load or loading is conducted. The results indicate that the clearance of port plate pairs and inlet pressure have a significant effect on distribution characteristics, but the effect of rotating speed is not very obvious. The experimental results show that the minimum error rate can be maintained within 0.3% by the proposed flow model and the counter materials of 316 L against carbon-fiber-reinforced polyetheretherketone(CFRPEEK) are suitable for the port plate pairs of seawater hydraulic motor. Finally, based on the seawater hydraulic experiment platform, the volumetric efficiency of no-load and loading are obtained that the maximum can achieve 94.71% and 90.14%, respectively. This research work may improve the flow distribution performance, lubrication and the friction and wear properties, enhance energy converting efficiency of port plate pair and provide theoretical and technical support for the design of highperformance water hydraulic components.

Investigating the Relationship between Food Pairings and Plate Waste from Elementary School Lunches

Plate waste, defined as the quantity of edible food left uneaten after a meal, is a challenge for schools participating in the National School Lunch Program (NSLP). The new nutrition standards in the NSLP of United States Department of Agriculture (USDA) were implemented at the beginning of school year (SY) 2012-2013. School foodservice authorities were concerned that the new standards would result in increased plate waste and reduced participation, especially by students who paid full prices for lunch. There are many reasons for plate waste, including students’ dislike of the foods served, the composition of meals, the environment in which students are eating, the lack of time to eat, or perhaps other factors. The objective of this study was to examine the relationship between entrée/vegetable “pairings” and plate waste by elementary school students pre- and post-implementation of the new school meal standards. Plate waste was measured to determine which entrée/vegetable pairs produced the least amount of waste. Plate waste of 144 and 305 entrée/vegetable pairings was analyzed, pre- and post-implementation, respectively. Our results indicated that more nutritious meals were offered during the post-implementation period. The new school meal standards led to no significant changes in entrée plate waste, but vegetable plate waste increased by 5.6%. As such, increases in the combined entrée/vegetable plate waste were evident from 40.4% pre-implementation to 43.5% post-implementation. The top five vegetables in terms of popularity were all starchy vegetables, the majority of which were potatoes in various processed forms. The least popular vegetables were dark-green leafy vegetables, such as steamed broccoli, both pre- and post-implementation. Chicken nuggets were the most popular entrée and were wasted the least. Understanding the dynamics of food pairings and providing desirable entrée and vegetable pairings can help reduce waste from school lunches.

NEAR CRACK LINE ELASTIC-PLASTIC ANALYSIS FOR A FINITE PLATE LOADED BY TWO PAIRS OF ANTIPLANE POINT FORCES

In this paper, the improved near crack line analysis method proposed in Refs. [1] and [2] is used to investigate a center crack loaded by two pairs of antiplane point forces in a finite plate in an elastic-perfectly plastic solid. And the analytical solutions are obtained, that is elastic-plastic stress fields near the crack line and the law that the length of the plastic zone along the crack line is varied with an external loads tr,ld the bearing capacity of a finite plate with a center crack. The results of this paper are sufficiently precise near the crack line, because the assumptions of the small scale yielding theory have not been used and no other assumptions have been taken.

轴向柱塞泵配流副椭圆开口偏置类抛物线微织构多目标优化

为了提高轴向柱塞泵配流副承载性能、抗摩擦磨性能及容积效率,以某型斜盘式轴向柱塞泵配流盘为原型开展研究。首先,依据正交实验理论采用CFD方法研究椭圆开口偏置抛物线微织构(Elliptic opening offset parabola micro texture, EOOPT)形状参数对轴向柱塞泵配流副承载压强、摩擦因数的影响规律,并联合运用神经网络和遗传算法对EOOPT的形状参数进行优化设计。其次,运用响应面分析方法研究EOOPT分布参数对配流副承载压强、摩擦因数和泄漏量的影响规律,并对形状参数进行优化设计。最后对最优特征参数EOOPT织构化的柱塞泵配流副和未织构的相关性能进行对比分析,结果表明,前者的承载压强较后者提高11.23%,摩擦因数和泄漏量分别减低16.67%和2.96%。

轴向柱塞泵摩擦副理论与技术研究现状

轴向柱塞泵是液压系统中的核心动力部件,对液压控制系统有着举足轻重的意义。轴向柱塞泵中的三大摩擦副的润滑和摩擦特性影响着柱塞泵本身的性能和使用寿命。轴向柱塞泵三大摩擦副理论与技术的研究对于提升轴向柱塞泵性能和可靠性具有重要意义。梳理了轴向柱塞本三大摩擦副润滑理论和摩擦特性方面的理论与技术与提高摩擦副性能的表面改性工艺方法。

轴向柱塞泵配流副油膜温度特性

柱塞泵配流副油膜温度分布影响配流副油膜润滑、泄漏与摩擦。为了探究轴向柱塞泵配流副油膜的温度分布,搭建了配流副三点油膜厚度与多点温度测试平台。根据采集的配流副油膜三点膜厚试验数据,建立了配流副楔形油膜模型;考虑了柱塞腔、配流副油膜对缸体的静压力、配流副表面微凸体间作用力,建立了缸体轴向力平衡方程;考虑了配流副油膜的能量损失、热传导以及油液黏温特性,建立了配流副油膜热平衡模型。结果表明,配流副油膜最高温度值随着压力和斜盘倾角的增大而增大,最高温度点位置保持在高压腰型槽对称线两侧-20°~20°的区域内;最高温度理论与试验结果的相对误差小于8%。

基于圆柱型表面织构的配流盘摩擦特性研究

建立了带有圆柱型微观织构配流盘的油膜弹流润滑模型,采用有限差分法求解雷诺方程,迭代之后求得符合误差允许的离散近似解。将得到的数值解导入MATLAB中绘制出微观织构配流副油膜特性云图。通过对比不同工况下带有微观织构与不带微观织构的配流盘之间的油膜摩擦特性差异,发现织构表面的配流盘能有效提高油膜的承载力,减少配流盘与缸体之间的接触,减小摩擦系数,改善润滑条件。

轴向柱塞泵微织构配流副摩擦特性研究

在配流副表面加工微织构并研究其减摩特性。采用正交试验方法进行配流副仿真研究,得到各因素对配流副摩擦影响顺序为:转速>油膜厚度>深度>形状>直径>面积率,得出最优参数组合为:直径400μm、深度200μm的圆球形凹坑、凹坑面积率6%、油膜厚度15μm、转速1500 r/min.分析了微织构配流副的速度场、压力场、动压承载力,并对全油膜进行了仿真。搭建了轴向柱塞泵的配流副摩擦试验系统,在不同负载压力4 MPa、8 MPa、12 MPa和工作流量10 L/min、20 L/min、35 L/min下,对最佳参数的微织构配流副进行摩擦特性试验,试验结果表明,微织构配流盘的摩擦扭矩值比光滑配流盘小,与全油膜仿真结果相验证。最大差值为1.53 N·m,最大减摩率为12.47%.

轴向柱塞泵微织构配流副润滑特性研究

针对轴向柱塞泵配流副微织构表面,采用有限差分法对微织构表面进行离散化处理,利用超松弛迭代法对微织构表面流体方程进行求解,得到微织构配流副的油膜压力分布。利用MATLAB软件对微织构配流副的油膜厚度和油膜压力进行了仿真研究,分析了微织构对配流副油膜润滑特性的影响。研究结果显示:微织构能够显著改变配流副油膜的厚度和压力分布,产生动压效应。无微织构表面最高压力为0.1064 MPa,微织构配流副表面最高压力0.152 MPa,提高油膜的承载能力。

Cavitation of a Submerged Jet at the Spherical Valve Plate/Cylinder Block Interface for Axial Piston Pump

The spherical valve plate/cylinder block pair has the advantages of strong overturning resistance and large bearing area.However,the configurations of the unloading and pre-boosting triangular grooves on the spherical valve plate are different from those in the planar valve plate,resulting in special cavitation phenomenon on the spherical port plate pair.In order to study cavitation characteristics of spherical port plate pair,a dynamic CFD model of the piston pump including turbulence model,cavitation model and fluid compressibility is established.A detailed UDF compilation scheme is provided for modelling of the micron-sized spherical oil film mesh,which makes up for the lack of research on the meshing of the spherical oil film.In this paper,using CFD simulation tools,from the perspectives of pressure field,velocity field and gas volume fraction change,a detailed analysis of the transient evolution of the submerged cavitation jet in a axial piston pump with spherical valve plate is carried out.The study indicates the movement direction of the cavitation cloud cluster through the cloud image and the velocity vector direction of the observation point.The sharp decrease of velocity and gas volume fraction indicates the collapse phenomenon of bubbles on the part wall surface.These discoveries verify the special erosion effect in case of the spherical valve plate/cylinder block pair.The submerged cavitation jet generated by the unloading triangular grooves distributed on the spherical valve plate not only cause denudation of the inner wall surface of the valve plate,but also cause strong impact and denudation on the lower surface of the cylinder body.Finally,the direction of the unloading triangular groove was modified to extend the distance between it and the wall surface which can effectively alleviate the erosion effect.

ELASTIC-PLASTIC ANALYTICAL SOLUTIONS FOR AN ECCENTRIC CRACK LOADED BY TWO PAIRS OF ANTI-PLANE POINT FORCES

The improved near crack line analysis method was used to investigate an eccentric cracked plate loaded by two pairs of anti_plane point forces at the crack surface in an elastic_perfectly plastic solid. The analytical solutions of the elastic_plastic stress fields and displacements near the crack line have been found without the assumptions of the small scale yielding. The law that the length of the plastic zone along the crack line is varied with an external loads and the bearing capacity of an eccentric cracked plate are obtained.

Dynamic Characteristics of Lubrication and Wear Prediction of Slipper/Swash-Plate in Axial Piston Pumps

A novel dynamic model describing the slipper posture of the swash plate in axial piston pumps is proposed, taking into account the hydrodynamic and squeezing effects, which involves three degrees of freedom. The variation in the lubricating film thickness and the slipper tilt are accurately calculated. The influence of hydrodynamic effects and charging pressure on the slipper lubrication is discussed. The minimum film thickness, the overturning angle and the azimuth angle are obtained.Then, the trajectory of minimum thickness on the friction surface of the swash plate is predicted, the accuracy of which can be verified with the abrasion distribution of an actual swash plate. Research results can predict the durability and provide theoretical help for the design of the slipper.

LATERAL INSTABILITY OF RECTANGULAR PLATES

This paper investituites the problems of lateral buckling of rectangular plates. In the text we discuss the minimum critical load of the lateral buckling occurring on under a concentrated force, uniformly distributed load and the concentrated couples, respectively. The energy method is used in this article.

多对偶夹角开合式TENG的结构设计和发电性能分析

提出一种多对偶夹角开合式摩擦纳米发电机的结构设计,将多个极板进行圆周布置,使各极板与相邻极板均构成摩擦对偶,形成多对偶夹角开合式发电结构。利用COMSOL Multiphysics有限元仿真软件研究了该新型摩擦纳米发电机的电势分布、开路电压、电极电荷量等参数随极板极角或时间的变化规律。结果表明:1)单对极板的开路电压随两板间极角的增大而增大;2)N对“串联”极板的开路电压均值是单对极板开路电压均值的N倍;3)极板的电极电荷量随两板夹角增大而缓慢增大;4)极板的主体区域电势分布较为均匀,但在极板端部电势分布具有明显的边缘效应。

ABAQUS二次开发在多片式摩擦副仿真中的应用

针对一种多片式摩擦副结构,基于Python语言对ABAQUS软件的前处理过程进行二次开发,简化多片式摩擦副制动仿真建模过程。通过编写主控程序Frictionmodel.py,图形界面程序FrictionmodelDB.py和关联程序Frictionmodel_plugin.py,实现系统建模程序定制,对不同对数、不同尺寸的多片式摩擦结构进行快速建模,基于三维瞬态热传导理论进行航空用舱门无返回装置紧急制动工况下瞬态热应力场的有限元分析计算。结果表明,随着摩擦副数的增多,制动力增大,制动时间逐渐减少,制动温升也会降低;但接触压力分布情况也会逐渐变差,出现应力集中。通过对比分析,三对副摩擦片结构可以保持高效制动的同时,满足结构尺寸及温度要求。

基于CFD的滑靴副多场耦合特性研究

滑靴副作为斜盘式轴向柱塞泵的主要摩擦副之一,长期工作于高速、高压、高温等一些复杂极端环境中.本文建立了滑靴副中流场的基本控制方程,构建了滑靴副多物理场耦合的有限元模型,通过CFD技术对滑靴副流场进行模拟分析,并在此基础上对滑靴副流-固-热多物理场耦合进行仿真,得到不同工况下油液的压力场和速度场的变化规律以及流体的压力和温度对滑靴副的总变形量、应力的影响.结果表明,随着工作压力增大,油液在阻尼管路中压力损失增加,油腔内涡旋个数及尺寸增大.除此之外还发现滑靴副变形量和最大应力对油液温度较为敏感.本文工作为滑靴副的结构设计提供了一定的技术支持,并且对于提高滑靴副的整体性能有着重要的意义.

多弧槽球面配流副润滑特性分析与多目标优化

为改善锥形缸体球面配流副油膜润滑特性,提出一种多弧槽球面配流副结构,并采用遗传算法对多弧槽球面配流结构进行多目标优化。首先,对多弧槽球面配流副进行理论建模,采用有限容积法对油膜压力控制方程进行离散化,利用环形三对角矩阵算法(CTDMA)求解球面配流副压力分布;然后,对多弧槽球面配流副承载特性进行仿真,分析球面配流副不同弧槽结构下的油膜厚度分布及压力分布规律;最后,以缸体倾角、泄漏量和摩擦转矩为优化目标,利用多目标遗传算法优化多弧槽球面配流副的结构参数。结果表明:多弧槽结构可提升球面配流副油膜承载能力,弧槽结构最小膜厚下降3.1%~4.0%,弧槽结构最大压力显著提高,最大增幅为16.3%;同时可有效降低泄漏量、摩擦转矩,优化后综合目标性能提升10.5%,缸体倾角、泄漏量和摩擦转矩分别下降5.1%、8.1%和5.9%,有效提升了球面配流副润滑性能。

基于分形理论的柱塞泵/马达配流副润滑特性研究

为研究配流盘表面形貌对配流副润滑特性的影响,采用分形理论模拟配流盘表面形貌,建立轴向柱塞泵配流副润滑模型,使用有限差分法对模型进行求解,探讨分形参数对表面轮廓的影响,并进一步分析分形参数和配流副工况参数对油膜承载力、摩擦力、摩擦转矩和摩擦因数的影响。结果表明:分形维数越大,表面轮廓形貌复杂度越高,且粗糙表面高度随尺度系数减小而降低;随着缸体倾角和转速的增大,油膜承载力提升,但摩擦力、摩擦转矩和摩擦因数也随之升高;配流副润滑性能与分形维数呈现正相关的关系,选取较大的分形维数有利于提升配流副的润滑性能;尺度系数越小其摩擦力越小,但承载力也减小,因此需选择适中的尺度系数。

主索鞍位移滑动副结构模型试验研究

为选择更适合的主索鞍位移滑动副材料,以燕矶长江大桥为背景开展试验研究。参照该桥主索鞍位移滑动副的构造和边界条件,制作钢-不锈钢、无储脂坑的聚四氟乙烯(PTFE)板-不锈钢、有储脂坑的PTFE板-不锈钢和改性聚甲醛(POM)减摩层板-不锈钢4组滑动副材料短尺寸滑块,通过顶推试验测试4组滑块的滑动摩擦系数和结构强度,再优选2组滑动副材料制作长尺寸滑块,观察顶推试验后滑块的变形和破坏情况并进行比选。结果表明:4组短尺寸滑块在良好润滑条件下的滑动摩擦系数分别为0.083、0.017、0.013和0.018,PTFE板-不锈钢滑块在试验后均发生了塑性变形,屈服强度均低于13.59 MPa,改性POM减摩层板-不锈钢和钢-不锈钢滑块的结构强度显著大于PTFE板-不锈钢滑块;优选有储脂坑的PTFE板-不锈钢和改性POM减摩层板-不锈钢进行长尺寸滑块试验,试验后有储脂坑的PTFE板-不锈钢滑块顶推力逐次增大,变形明显,改性POM减摩层板-不锈钢滑块的表面无变形,无破坏;改性POM减摩层板-不锈钢滑块的滑动摩擦系数与PTFE板-不锈钢滑块接近,结构强度显著大于PTFE板-不锈钢滑块,为推荐的位移滑动副材料。

浮杯泵端面开槽配流副润滑特性仿真分析

配流副作为浮杯泵重要的摩擦副,良好的润滑状态对于提升柱塞泵的使用寿命和容积效率起到关键作用。在滚筒板上引入连通式阶梯槽结构,通过动静压混合润滑的支承形式改善浮杯泵配流副的润滑特性,分析配流副油膜的压力分布及动静压润滑形成原因,对比分析连通槽型、浅腔深度比和阶梯槽包角等结构参数对润滑特性的影响,发现连通式阶梯槽对配流副润滑特性起积极作用,为浮杯泵配流副结构优化提供了一定的理论支持。