Fault detection of excavator’s hydraulic system based on dynamic principal component analysis

In order to improve reliability of the excavator's hydraulic system, a fault detection approach based on dynamic principal component analysis(PCA) was proposed. Dynamic PCA is an extension of PCA, which can effectively extract the dynamic relations among process variables. With this approach, normal samples were used as training data to develop a dynamic PCA model in the first step. Secondly, the dynamic PCA model decomposed the testing data into projections to the principal component subspace(PCS) and residual subspace(RS). Thirdly, T2 statistic and Q statistic performed as indexes of fault detection in PCS and RS, respectively. Several simulated faults were introduced to validate the approach. The results show that the dynamic PCA model developed is able to detect overall faults by using T2 statistic and Q statistic. By simulation analysis, the proposed approach achieves an accuracy of 95% for 20 test sample sets, which shows that the fault detection approach can be effectively applied to the excavator's hydraulic system.

Proposal of a Component to Restrict Dust from Entering an Oil Hydraulic System through an Oil Hydraulic Cylinder

This research proposes a component to restrict dust from entering an oil hydraulic system through the rod-seal clearance of an oil hydraulic cylinder.The oil hydraulic cylinder as one of main parts of the hydraulic system,controls position of load by reciprocation.For example,on construction machines such as excavators and graders,the cylinder controls position of folk lift,crane and bucket.However,during operation,dust enters the cylinder,wears seals,causes fluid degradation and affects lubrication of valves,pumps and other parts of hydraulic system.This increases breakdown rate of cylinder and entire system.Thus,it seems necessary to reduce on intrusion of dust into the system via the hydraulic cylinder.In this research,we made an experimental apparatus to simulate intrusion of the dust into system.Results proved that the apparatus is a suitable simulator to realize the intrusion.The proposed component to restrict dust from entering cylinder was fabricated and its performance tested when inserted with various elastic rings.The component gave tremendous results when inserted with O-ring seal and a plastic nylon washer,and can be retrofitted on new and old hydraulic cylinders.It is an appropriate technology especially in developing countries where dust is still a major concern.

Components Qualification for the Safe Operation of Nuclear Power Plants

AREVA operates a world-wide unique thermal hydraulic platform to ensure high safety standards in the nuclear industries. This platform is operated as an accredited test and inspection body according to ISO 17025 and 17020 to grant a high and independently confmned quality standard. The accreditation also ensures the independency of the organization and confidentiality to the individual stakeholders, for example research centers, utilities, components suppliers, engineering companies and vendors. Especially for nuclear power plants, it is very relevant to consider that reliability depends on the integrity of its components during its life time-from design through construction, operation and maintenance. For example, a typical NPP （nuclear power plant） has 1,000 to 2,000 large valves and 7,500 to 12,500 small valves, of which about 200 to 400 are designated Safety Class 1. The qualification of these Safety Class 1 components is relevant for reactor new builds but also for installed plants. This paper explains newly established qualification tasks, the corresponding testing infrastructure, and the state of the art of testing technology. By way of example, the paper describes the program and possible sequence of qualifying NPP safety-related components.

Numerical investigations on performance improvement mechanism of a high-power vertical centrifugal pump with special emphasis on hydraulic component matching

The purpose of this paper is to investigate the performance improvement mechanism of a high power vertical centrifugal pump by using numerical calculations.Therefore,a comparative study of energy losses and internal flow characteristics in the original and optimized models was carried out with special attention to the hydraulic component matching.The optimized model(model B)was obtained by optimizing the vaned diffuser and volute based on the original model(model A),mainly the diffuser inlet diameter,diffuser inlet vane angle,volute channel inlet width and volute throat area were changed.Firstly,the comparative results on performance and energy losses of two models showed that the efficiency and head of model B was significantly increased under design and part-load conditions.It is mainly due to the dramatic reduction of energy loss PL in the diffuser and volute.Then,the comparisons of PL and flow patterns in the vaned diffuser showed that the matching optimization between the model B impeller outlet flow angle and diffuser inlet vane angle resulted in a better flow pattern in both the circumferential and axial directions of the diffuser,which leads to the PL3 reduction.The meridian velocity Vm of model B was significantly increased at diffuser inlet regions and resulted in improvements of flow patterns at diffuser middle and outlet regions as well as pressure expansion capacity.Finally,the comparisons of PL and flow characteristics in the volute showed that the turbulence loss reduction in the model B volute was due to the flow pattern improvement at diffuser outlet regions which provided better flow conditions at volute inlet regions.The matching optimization between the diffuser and volute significantly reduced the turbulence loss in volute sections 1–4 and enhanced the pressure expansion capacity in sections 8–10.

液压源回路元件选择与布置

在回路基本组合的基础上,通过添加相关液压元件和传感控制元件增加相应功能,设计出合理的液压源回路。首先进行功率分析,并根据负载要求和技术经济效益选择合适的液压源类型,选用开式或闭式控制的油液循环及功率适应方式;然后根据负载-速度特性和元件特点及其布置注意点选择液压源回路元件并进行整体布置设计,构成满足要求的液压源回路。实践表明,通过科学选择和整体设计,可以得到切实满足负载和功能要求、高能效的液压源回路。

双联液压元件新型应用与性能分析

针对现有传统液压回路在多种不同压力、不同流量工况中需要借助繁多功能控制阀来调节的功能缺陷,以及能耗大、效率低等问题,将双联液压元件应用于几种典型回路中,并对由双联液压元件组成的新型液压系统的节能特性、输出特性进行了研究分析。结果表明:双联液压元件的应用能够节省成本、简化系统、消除压力互相干扰、减少功率损失,实现了功率的匹配,达到了节能目的。

Seawater hydraulics:From the sea surface to depths of 11000 meters

Using seawater as the working medium,the seawater hydraulic system has significant advantages in the deep sea,such as eliminating contamination caused by oil leaks,no oil tanks,and the ability to automatically adapt to sea depths.As working depths increase,seawater hydraulic technology faces enormous challenges.First,the physical and chemical properties of seawater,such as density,temperature,and composition,change significantly.Second,hydraulic components are subject to an environmental pressure of up to 110 MPa,which causes serious deformation or even seizure of moving pairs and significantly affects the efficiency of hydraulic components.The friction and wear characteristics between the moving pairs also significantly change with the change in sea depth,therefore developing the matching material according to depth is necessary.Finally,the cavitation characteristic of a valve port is obviously different from that on land,so special material and structure should be used to improve the service life of the valve port.These factors severely restrict the improvement of the working depths and characteristics of seawater hydraulic components.This article focuses on the abovementioned problems and provides solutions for deep-sea seawater hydraulic technology.

液压支架立柱防冲吸能构件优化仿真及压溃实验研究

液压支架作为煤炭开采主要支护设备,经常受到冲击地压影响,防冲吸能构件起到保护液压支架作用,为获得更大的初始支反力峰值与吸能量、更小的支反力分散度,对吸能构件参数细化并通过ABAQUS有限元软件进行吸能构件的建模与压溃冲击仿真,获取吸能构件的吸能性能及屈曲变形形态,验证最优尺寸的吸能性能;对比吸能构件平均支反力的预测数据与有限元仿真数据,误差在15%以内,最优尺寸构件的平均支反力模型预测误差为−3.40%,验证吸能构件预测模型所预测数据较为准确;搭建吸能构件压溃实验台,选择5种加载速度,以准静态压溃方式对定制加工的吸能构件进行轴向加载压溃实验,实验结果表明:不同加载速度轴向压溃实验,支反力波动基本一致,最大初始支反力峰值为2253.52 kN,最大支反力标准差为206.23 kN,最小初始支反力峰值为2096.26 kN,最小支反力标准差为189.83 kN,初始支反力峰值的平均值为2149.32 kN,支反力标准差平均值为196.77 kN;不同压溃速度下的轴向压溃实验数据与吸能构件有限元仿真数据对比,初始支反力峰值、支反力标准差的相对误差分别为5.6%、11.07%;对最优尺寸吸能构件通过预测模型法、有限元仿真法、压溃实验法三种方法进行吸能性能分析,预测模型法的平均支反力为1879.7 kN,有限元仿真法的平均支反力为1945.9 kN,压溃实验法平均支反力为1919.8 kN,预测模型误差3.41%,压溃实验误差−1.3%,通过3种方法的数据验证结果,证明了吸能构件分析方法的可靠性和可行性。

海相页岩与陆相页岩体积压裂支撑剂敏感性差异机理探讨

页岩体积压裂是储层在地应力与致裂压力联合作用下形成天然裂缝与压裂裂缝相互交错的复杂缝网,现场实践表明这个复杂的缝网破裂演化过程中海相、陆相页岩储层对不同粒径的支撑剂注入具有明显的敏感性差异。通过海陆相页岩露头剖面地质调查、钻井取芯对比分析岩体结构性差异,分析海相、陆相页岩水平井水力压裂施工数据,结合位移间断边界元裂缝网络演化模拟(DFN),揭示海相与陆相页岩体积压裂支撑剂敏感性差异机理。结果表明:陆相页岩呈岩性互层结构,多种岩体结构面发育,具有高度的结构非均质性特征;在相似的工况条件下,支撑剂随高压流体注入陆相页岩储层地面采集压力波动幅度较大,支撑剂对陆相页岩敏感性强于对海相页岩敏感性;海相页岩与陆相页岩岩体结构性差异导致水力压裂过程中的起裂行为、拓展机制、缝网形态的差异化机制,天然裂隙、弱结构面越发育,相同注入条件下压裂液滤失量大缝内净压力越低,水力裂缝平均开度越小;天然裂隙与最大水平主应力夹角越大,水力裂缝沟通天然裂隙之后转向至最大水平主应力方向扩展,转向段裂缝开度越小,容易引起支撑剂聚集沉降,从而造成支撑剂敏感性强。该研究对陆相页岩储层压裂方案优化具有一定现实指导意义。

海上光伏外围防护-固定式透空堤结构型式研究进展

固定式透空堤能改善海上漂浮式光伏发电系统的深海运维环境。依据不同的消浪原理和构造将固定式透空堤分为排桩透空堤、桩基透空堤、沉箱透空堤、桩基沉箱透空堤、横板透空堤和组合透空堤6种型式,针对固定式透空堤的研究和发展进行文献综述,回顾和讨论不同结构型式研究方法、结构特点、消浪性能和实际工程应用等方面的内容,总结了当前研究存在的不足并展望了未来发展方向。

防冲击地压薄壁吸能构件的压溃吸能机理分析

当煤矿井下发生冲击地压时,矿用液压支架的冲击性失效,常常会引起巷道支护系统的破坏,进而引发巷道坍塌,造成矿难。当前通过添加吸能构件来提高支架的防冲击性能是防治巷道冲击地压的有效途径之一。而不同类型吸能构件的压溃变形模式不同,表现出的吸能特性和力学特性也不同。本文采用数值方法对不同类型、支座和壁厚的吸能构件进行了冲击压溃模拟,通过对各相关防冲吸能参数的对比分析可知:预折纹吸能构件支撑反力最大、具有良好的吸能能力,但变形过程稳定性较差;外翻式吸能构件的塑性变形能力强,有效让位行程最大,但支撑力较小,不适合单独使用;扩径式吸能构件变形过程稳定性最好,其塑性变形后的径向位移较小,节省工作空间,但支撑能力较差,适用于小型液压支架或用作其他特殊用途。

基于混合优化算法的电磁监测裂缝参数识别

压裂实时监测是水力压裂效果评价和工程参数优化的重要保障措施之一。传统电磁监测裂缝参数识别方法的准确性和精度难以保证,影响了监测效果。为了提高裂缝参数识别能力,提出了一种基于海洋捕食者密度聚类混合优化算法的电磁监测裂缝参数识别方法。利用海洋捕食者算法(MPA)进行多次寻优,以每次寻优结果作为初始数据集,然后,利用密度聚类算法(DBSCAN)进行聚类,构建中间样本数据集,最后,抽取该样本数据中值作为最终输出结果。采用Rastrigin函数进行测试,分析混合优化算法寻优能力。测试结果表明,相对粒子群优化算法(PSO),MPA算法单次寻优效果较佳。但两种算法寻优结果均具有较强随机性,其中,PSO和MPA算法50次寻优精度分别为10^(-7)~10^(2)和10^(-10)~10^(-2),而改进的混合优化算法寻优效果更稳定,寻优精度达10^(-7)。构建缝长、方位压裂模型并进行了数值模拟实验,结果表明,在噪声低于15%时,缝长和方位识别平均绝对误差分别小于1 m和1°。利用改进的算法对四川盆地某井页岩气压裂电磁监测实测数据进行分析,确定了裂缝改造的长度(缝长)与方位。实例分析结果验证了改进算法的可行性和有效性。

HFC型液压元件摩擦副摩擦学性能研究

为了研究液压元件在HFC型水-乙二醇液压液下的摩擦学性能,采用MFT-5000摩擦磨损实验机考察不同载荷和滑动频率下,3种液压元件常用材料(304钢球、ZrO2和Si3N4)和304不锈钢配副的摩擦磨损变化情况,并借助白光三维干涉仪对304钢的磨痕进行形貌分析。结果表明:在水-乙二醇液压液的润滑作用下,滑动频率对摩擦因数的影响比载荷更大,载荷对磨损体积的影响比滑动频率更大;在载荷为50 N、滑动频率为3 Hz时,ZrO2和304钢配副的摩擦因数和磨损体积均为最小,磨损机制以三体磨粒磨损为主。综合考虑,ZrO2/304钢配副在不同载荷和滑动频率下摩擦因数和磨损体积更加稳定,更加适合作为HFC型液压元件的摩擦副材料。

矿用单元式液压支架立柱“井”形防冲吸能构件特性分析

为了解决目前煤矿井下巷道支护设备和支护材料在冲击地压作用下发生损坏破坏和失效的问题,设计研发了一种新型多肋板吸能构件。首先,根据防冲支架吸能构件的作用原理,明确了吸能构件的设计要求,提出了一种多肋板型吸能构件,对吸能构件的构型和截面形状展开了结构设计,给出了多肋板型吸能构件尺寸图与三维模型图;基于简化的超折叠单元理论剖析了“井”形管的能量耗散途径,推导出了“井”形管的平均支反力预测公式;其次,采用数值模拟方法对多肋板型吸能构件吸能特性展开了仿真研究,并探究了肋板厚度和不同材料对多肋板型吸能构件的吸能性能的影响,得出了肋板厚度和材料显著影响吸能性能的结论。最后,利用MATLAB的遗传算法进行了优化,利用参数优化结果,重新设计了多肋板型吸能构件,并进行了仿真试验,将仿真试验与压溃试验的结果进行对比分析。分析表明,遗传算法迭代的多肋板型吸能构件具有较好的能量吸收参数,在平台阶段支撑反力的波动较小,能量吸收过程相对稳定,能有效达到能量吸收的效果。

数字化波浪补偿分离式液压钻机的研制

基于能源绿色、风力大等优势,海上风力发电技术近年来越来越受到重视,正由浅海向深海发展,且小型发电机逐步被大功率发电机取代。海上风力发电中风电场的选址、风机的基础设计、桩基施工、地层测试等,都离不开钻探和井内静力触探技术。为了满足海上勘察钻机的要求,研发了数字化波浪补偿分离式液压钻机,主要是在数字化、自动化、回转、波浪补偿等功能,以及模块化设计、制造工艺等方面进行了创新。通过理论参数核算、海上应用测试、深海生产施工验证,证明该钻机不仅可满足使用需求,并且比常规钻机更加方便管理、高效安全,还降低了钻探的辅助成本。

矿用自动液压锚杆钻机可靠性分配研究

针对自动液压锚杆钻机可靠性数据缺乏、结构复杂、工作环境恶劣的问题,优选了代数分配法作为其可靠性分配方法。通过结构功能分析,将钻机划分为8个组元并建立了可靠性分析模型。依据MT/T 688-1997《煤矿用锚杆钻机通用技术条件》计算了钻机故障率。运用代数分配法完成了钻机可靠性分配,研究结果表明控制系统等4个组元为薄弱环节。从提升关键部件可靠性和钻机加载试验两方面提出了钻机可靠性提升建议,对于自动液压锚杆钻机研发具有参考价值。

基于发射光谱和红外光谱技术的船用液压系统异常故障分析

文章采用发射光谱和红外光谱油液监测技术,对某船用液压系统异常故障进行分析,利用发射光谱表征添加剂元素的质量分数变化来测量液压油中混入润滑油的油量,利用红外光谱分析技术的差分模式再次进行分析,依据混入油量的多少准确定位故障部位,节约了设备的维修时间,取得了较好的效果。

面向动臂势能再生的主动式储能元件控制策略

主动式储能元件是一种针对现有液压蓄能器不足而提出的新型气-电混合型储能元件,但其存在着液压能、压缩气体能和电能间的能量耦合问题,导致其工作时抗干扰能力较差,降低了工作液压系统的节能效率。为了解决其存在抗干扰能力差的问题,针对液压挖掘机动臂液压回路的工作特点,提出了利用主动式储能元件实现动臂势能再生的系统架构,并设计了一种自抗扰控制策略及其参数优化方法,通过设计扩张状态观测器来解决干扰和参数不确定性等问题。为验证控制策略的可行性,首先介绍了主动式储能元件的结构;其次,设计了以主动式储能元件为控制对象的自抗扰控制器。建立了基于主动式储能元件的动臂势能再生系统仿真模型,并进行了试验验证。研究结果表明,蓄能器模式、普通控制模式及自抗扰控制模式的回收效率分别为42.81%、56.76%和58.60%;再利用效率分别为96.01%、97.06%和95.81%;再生效率分别为41.1%、55.1%和56.1%。仿真试验验证结果也表明,以主动式储能元件为对象提出的自抗扰控制策略有效地改善了控制性能,增强了系统压力稳定性。

页岩数字岩心重构与水力压裂数值试验

为了实现对深部页岩油储层水力裂缝扩展规律的精细研究,以吉木萨尔凹陷芦草沟组陆相页岩油储层下甜点主要油层段为研究对象,对3684.62~3705.70 m深度范围内的20组页岩样品进行扫描并构建数字岩心,开展水力压裂数值试验.试验获得了各模型的破裂压力和水力裂缝扩展路径.结果表明:破裂压力随孔隙度的增加而降低,随着脆性矿物体积分数的增加而增加,和石英体积分数呈现较明显的线性关系.水力裂缝在孔隙位置起裂,连通独立的孔隙区域并沿着贯通的孔隙区域继续扩展.在远离孔隙区域时,水力裂缝主要沿垂直于最小主应力方向延伸.水力裂缝的复杂程度均随石英体积分数和孔隙度的增加而增加,但也会受到矿物分布形态的影响.当石英体积分数或孔隙度较高且呈现大面积连通分布时,水力裂缝的扩展受到抑制,水力压裂的增渗改造效果较弱.

真三轴应力状态下海相与陆相页岩射孔压裂裂缝扩展规律对比研究

页岩油气高效开发需要对储层进行大规模压裂改造,水力裂缝垂向扩展激活纹层弱面是形成复杂压裂缝网的关键。然而,由于海相页岩与陆相页岩沉积环境、矿物成分和岩体结构存在显著差异,导致水力压裂效果差异较大,亟需对水力裂缝扩展规律进行深入探索。本文选取了龙马溪海相页岩和长7段陆相页岩,开展了力学特性试验和真三轴应力状态下水力裂缝扩展规律研究。分析了海相页岩和陆相页岩力学各向异性、注入压力曲线、压裂缝网形态与裂缝扩展过程的声发射能量。结果表明:(1)海相页岩力学强度和弹性模量明显高于陆相页岩,抗压强度相差61.4~102.2 MPa,抗拉强度差值约为1.7~2.6 MPa,弹性模量差值约为7.0~25.7 GPa,表明层理弱面对陆相页岩力学特性和破裂模式影响更为显著。(2)海相页岩破裂压力和声发射能量高于陆相页岩,水力裂缝起裂和扩展特征明显。陆相页岩注入压力曲线明显不同于海相页岩,压裂液沿层理缝滤失,造成注入压力曲线非线性增长。陆相页岩水力裂缝起裂和主破裂特征不明显,声发射能量较低。(3)海相页岩水力裂缝形态较为平直,射孔起裂后形成两条主裂缝。陆相页岩水力裂缝形态曲折,垂向扩展受到层理弱面抑制,裂缝高度较小。当压裂液黏度由60 MPa·s增大至240 MPa·s时,陆相页岩水力裂缝垂向扩展高度增大,裂缝形态更加复杂。