Dynamic optimization analysis of hydraulic pipeline system based on a developed response surface method

When designing a complex pipeline with long distance and multi-supports for offshore platform,it is necessary to analyze the vibration characteristics of the complex pipeline system to ensure that there is no harmful resonance in the working conditions.Therefore,the optimal layout of support is an effective method to reduce the vibration response of hydraulic pipeline system.In this paper,a developed dynamic optimization method for the complex pipeline is proposed to investigate the vibration characteristics of complex pipeline with multi-elastic supports.In this method,the Kriging response surface model between the support position and pipeline is established.The position of the clamp in the model is parameterized and the optimal solution of performance index is obtained by genetic algorithm.The number of clamps and the interval between clamps are considered as the constraints of layout optimization,and the optimization objective is the natural frequencies of pipeline.Taking a typical offshore pipeline as example to demonstrate the effectiveness of the proposed method,the results show that the vibration performance of the hydraulic pipeline system is distinctly improved by the optimization procedure,which can provide reasonable guidance for the design of complex hydraulic pipeline system.

Vibration Performance Analysis of a Mining Vehicle with Bounce and Pitch Tuned Hydraulically Interconnected Suspension

The current investigations primarily focus on using advanced suspensions to overcome the tradeo design of ride comfort and handling performance for mining vehicles. It is generally realized by adjusting spring sti ness or damping parameters through active control methods. However, some drawbacks regarding control complexity and uncertain reliability are inevitable for these advanced suspensions. Herein, a novel passive hydraulically interconnected suspension(HIS) system is proposed to achieve an improved ride-handling compromise of mining vehicles. A lumped-mass vehicle model involved with a mechanical–hydraulic coupled system is developed by applying the free-body diagram method. The transfer matrix method is used to derive the impedance of the hydraulic system, and the impedance is integrated to form the equation of motions for a mechanical–hydraulic coupled system. The modal analysis method is employed to obtain the free vibration transmissibilities and force vibration responses under di erent road excitations. A series of frequency characteristic analyses are presented to evaluate the isolation vibration performance between the mining vehicles with the proposed HIS and the conventional suspension. The analysis results prove that the proposed HIS system can e ectively suppress the pitch motion of sprung mass to guarantee the handling performance, and favorably provide soft bounce sti ness to improve the ride comfort. The distribution of dynamic forces between the front and rear wheels is more reasonable, and the vibration decay rate of sprung mass is increased e ectively. This research proposes a new suspension design method that can achieve the enhanced cooperative control of bounce and pitch motion modes to improve the ride comfort and handling performance of mining vehicles as an e ective passive suspension system.

Frequency-domain analysis of fluid-structure interaction in aircraft hydraulic pipeline systems: numerical and experimental studies

The fluid-structure interaction(FSI)in aircraft hydraulic pipeline systems is of great concern because of the damage it causes.To accurately predict the vibration characteristic of long hydraulic pipelines with curved segments,we studied the frequency-domain modeling and solution method for FSI in these pipeline systems.Fourteen partial differential equations(PDEs)are utilized to model the pipeline FSI,considering both frequency-dependent friction and bending-flexibility modification.To address the numerical instability encountered by the traditional transfer matrix method(TMM)in solving relatively complex pipelines,an improved TMM is proposed for solving the PDEs in the frequency domain,based on the matrix-stacking strategy and matrix representation of boundary conditions.The proposed FSI model and improved solution method are validated by numerical cases and experiments.An experimental rig of a practical hydraulic system,consisting of an aircraft engine-driven pump,a Z-shaped aero-hydraulic pipeline,and a throttle valve,was constructed for testing.The magnitude ratio of acceleration to pressure is introduced to evaluate the theoretical and experimental results,which indicate that the proposed model and solution method are effective in practical applications.The methodology presented in this paper can be used as an efficient approach for the vibrational design of aircraft hydraulic pipeline systems.

Probabilistic analysis of embankment slope stability in frozen ground regions based on random finite element method

Prediction on the coupled thermal-hydraulic fields of embankment and cutting slopes is essential to the assessment on evolution of melting zone and natural permafrost table, which is usually a key factor for permafrost embankment design in frozen ground regions. The prediction may be further complicated due to the inherent uncertainties of material properties. Hence, stochastic analyses should be conducted. Firstly, Karhunen-Loeve expansion is applied to attain the random fields for hydraulic and thermal conductions. Next, the mixed-form modified Richards equation for mass transfer （i.e., mass equation） and the heat transport equation for heat transient flow in a variably saturated frozen soil are combined into one equation with temperature unknown. Furthermore, the finite element formulation for the coupled thermal-hydraulic fields is derived. Based on the random fields, the stochastic finite element analyses on stability of embankment are carried out. Numerical results show that stochastic analyses of embankment stability may provide a more rational picture for the distribution of factors of safety （FOS）, which is definitely useful for embankment design in frozen ground regions.

Fluid structure interaction for circulation valve of hydraulic shock absorber

Based on the working principle and the damping characteristic of hydraulic shock absorber, a fluid structure interaction method was presented, which was used to analyze the microcosmic and high-frequency processing mechanism of fluid structure interaction between circulation valve and liquid of hydraulic shock absorber. The fluid mesh distortion was controlled by the CEL language, and the fluid struc^tre interaction mathematical model was established. The finite element model was established by ANSYS CFX software and was analyzed by dynamic mesh technique. The local sensitive computational area was meshed by prismatic grid, which could reduce the negative volume problem during the simulation. The circulation valve and liquid of hydraulic shock absorber were simulated and analyzed under the condition of sinusoidal inlet velocity loads. Flow characteristic and dynamics characteristic were obtained. The pressure distribution and the displacement of circulation value were obtained, and the acceleration curve of circulation valve was simulated and analyzed. The conformity of the final simulation results with the experimental datum indicates that this method is accurate and reliable to analyze the dynamics characteristic between circulation valve and liquid of hydraulic shock absorber, which can provide a theoretical foundation for optimizing hydraulic shock absorber in the future.

Simulation Research on Dynamic Characteristics of Hydraulic Mount

At present,research on hydraulic mounts has mainly focused on the prediction of the dynamic stiffness and loss angle.Compared to the traditional finite element analysis method,the programming method can be used to analyze hydraulic mounts for a rapid and accurate understanding of the influence of the different mounting parameters on the dynamic stiffness and loss angle.The aims of this study were to investigate the nonlinear dynamic characteristics of a hydraulic mount,and to identify the parameters that affect the dynamic stiffness and loss angle using MATLAB software programs to obtain the influence curves of the parameters,so as to use suitable parameters as the basis for vibration analysis.A nonlinear mechanical model of a hydraulic mount was established according to the basic principles of fluid dynamics.The dynamic stiffness and loss angle of the dimensionless expression were proposed.A numerical calculation method for the dynamic performance evaluation index of the hydraulic mount was derived.A one-to-one correspondence was established between the structural parameters and peak frequency of the evaluation index.The accuracy and applicability of the mechanical model were verified by the test results.The results demonstrated the accuracy of the nonlinear mechanical model of the hydraulic mount,and the vehicle driving comfort was greatly improved by the optimization of the structural parameters.

基于加权实例推理的缓倾斜综采工作面液压支架选型研究

为实现地质构造简单的缓倾斜综采工作面液压支架智能化选型,提出了一种基于加权实例推理的液压支架选型方法。首先,建立了液压支架选型实例库;其次,采用粗糙集理论和序关系分析法进行权重构造;另外,将液压支架的条件属性分为3种类型计算相似度;最后通过匹配实例选型。以某煤矿选型方案为例,并以50组液压支架的属性数据进行验证。结果表明,该方法的准确率为88%,能够为液压支架的智能化选型提供较好的参考依据。

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。

液态金属冷却快堆子通道分析软件SACOS-LMR研发与工程应用

子通道分析方法是反应堆堆芯设计和热工水力分析的重要手段之一,对于我国提出的压水堆-快堆-聚变堆三步走核能发展战略,开发适用于液态金属冷却快堆热工安全分析的子通道分析程序具有重要意义。本文基于西安交通大学热工水力研究室自主开发的压水堆子通道程序SACOS,通过添加液态金属快堆特有的模型,如绕丝模型、盒间流模型、液态金属对流换热模型等,扩展至适用于液态金属快堆的子通道分析程序SACOS-LMR,该程序具备对液态金属快堆组件开展稳态和瞬态热工水力分析的功能。结合卡尔斯鲁厄开展的37棒钠冷瞬态实验,完成了SACOS-LMR程序的瞬态功能验证。基于验证后的SACOS-LMR程序,对欧洲铅冷快堆(ALFRED)堆芯开展了稳态工况和瞬态事故工况下的热工安全特性分析,计算结果合理,且与同类程序保持一致,表明SACOS-LMR程序可用于液态金属快堆的堆芯设计和热工水力分析研究。

不同结构参数对高速开关阀液压力的影响研究

因其具有价格低廉、抗污染性强等优点,高速开关阀已被广泛运用到各种车辆的制动系统中,其动态性能直接影响到车辆的制动效果,而阀芯所受的液压力是决定高速开关阀动态特性优劣的关键参数。针对不同参数对高速开关阀液压力的影响,以及实际工程中阀芯液压力难以测量的问题,采用计算流体动力学(CFD)对高速开关阀进行了数值模拟。首先,基于有限体积法(FVM),建立了不同开度、压差、温度、以及结构参数(阀座节流孔直径和锥角)的三维仿真模型;然后,对比不同网格数量的仿真结果,排除了网格数量对于仿真结果的影响,并详细分析了各参数对液压力的影响,得出了高速开关阀液压力与各参数之间的变化规律;最后,采用响应面分析结合遗传算法对开关阀的结构参数进行了优化。研究结果表明:随着阀芯开度的增加,节流区域发生了转变;较大的压差会导致液压力产生较大幅度的变化;相较于高温,低温对液压力有着更加显著的影响;对结构参数进行优化后,最小开度的液压力提高了49.2%,提高了阀控制稳定性,为高速开关阀线性控制设计提供了理论基础。

降雨和库水位升降条件下考虑非饱和渗透系数空间变异的边坡可靠度分析

降雨和水位升降对库岸边坡具有显著影响,传统确定性分析难以准确评估其稳定性。考虑降雨和水位升降联合作用下水力参数的空间变异性,进行非饱和土边坡可靠度分析具有重要意义。以赣江库区中的莒洲岛边坡为研究对象,以贝叶斯方法校准的多元水力参数的联合随机场为基础,建立非饱和土边坡的稳定性分析方法。根据有限的岩土力学室内试验数据,采用贝叶斯方法校准土水特征曲线的模型参数,并从VGM、VGB、VG和FX模型中选出最优模型;联合多元水力参数的随机统计特征,生成非饱和土边坡渗透系数的随机场空间分布;针对2021年5月赣江水位快速升降并伴随暴雨的工程背景,将上述方法应用于莒洲岛库岸边坡的稳定性分析。研究结果表明,暴雨与水位变化的联合作用对边坡安全系数的影响显著,确定性分析的边坡安全系数偏低,考虑非饱和渗透系数空间变异性后计算所得到的SWCC综合可靠指标不能满足规范要求,需采取额外的边坡工程加固措施以保证边坡的长期稳定性。

矿井掘进机液压系统故障分析探讨

针对煤矿井下掘进机运转过程中液压系统故障频发的状况,本文通过分析各液压系统的组成及功能,对造成液压系统故障的原因进行类型划分,即划分为机械原因和人为原因。结合维修人员素质、现场条件提出了经验判断法、系统分析法和综合判断法等进行掘进机故障分析,为掘进机液压系统维修提供了多种维修思路,提高了液压设备维修效率。

基于因子分析法和熵权法的土壤腐蚀性评价模型

为了更为准确地评价土壤对钢结构的腐蚀情况,本文采用两种多元统计方法构建土壤腐蚀性评价模型。本文首先采用因子分析法,从pH值、氧化还原电位、视电阻率、极化电流密度、质量损失5个指标中选取影响土壤对钢结构腐蚀性的两个主因子,运用熵权法对两个主因子进行权重赋值和计算得分,建立土壤腐蚀性评价模型。经多个应用实例验证其结果与该模型评价结果一致,说明该模型可推广使用。同时,该评价方法为土壤腐蚀性评价工作提供了一种具有借鉴意义的新思路。

旋启式止回阀关闭过程瞬态流固耦合特性研究

某核电厂重要厂用水系统止回阀的内部流动特性不明,缺少相应的应力应变分析,同时也较难对其进行试验研究。为此,采用动网格方法,建立了流固耦合计算模型,并进行了仿真计算,对核电厂重要厂用水系统旋启式止回阀关闭过程的流固耦合特性进行了研究。首先,针对某核电厂止回阀原型,建立了阀门及水体模型,并进行了网格无关性验证,确定了其最终的计算模型;然后,使用profile编写了阀板运动控制规则,设置了动网格模型,利用ANSYS单向流固耦合方法,设置了其交界面与约束条件,对止回阀瞬态关闭过程进行了仿真计算;最后,对关阀过程中不同开度的流场速度压力分布和结构场应力变形变化进行了分析。研究结果表明:在止回阀的关闭过程中,阀内流场最大速度在关闭初期为17.87 m/s,并逐步降低至0 m/s;止回阀的最大等效应力和最大变形量分别出现在转轴与阀体连接处以及阀板的最下部,分别为1.5474×108 Pa和4.74 mm,并随开度减小而增大。依据计算结果得到了该止回阀关闭工况的流场变化与阀门应力、变形响应特性,提高了设备运行的可靠性,可以为设备的优化设计提供参考。

基于NSMC方法的某核工程场地裂隙地下水数值模拟不确定分析

裂隙介质渗透结构表现为高度的非均质性与各项异性。为了科学有效地预测某核工程场地裂隙地下水的流动规律,揭示裂隙岩体地下水的渗流特性,笔者等采用Pilot Point调参方法与null space Monte Carlo方法(NSMC),开展了裂隙岩体渗透结构的不确定性分析研究,构建了符合实际水文地质条件的多个渗流数值模型集合。结果表明:该方法获得的各个实现地下水位模拟结果能够与实际观测数据较好吻合,可反映工程场地裂隙地下水动力特征与流动趋势;各个实现的参数化渗透结构在空间上存在一定的差异性,但整体变化趋势是保持一致的,渗透参数的不确定性表现为在实测数据分布区域相对较低,钻孔空白区域相对较高;该方法可以弥补单一、确定性模拟结果在表征裂隙介质渗透结构方面的局限性,有效地降低模型参数的不确定性与随机性。此方法对进一步提升裂隙岩体渗流模拟精度与预测能力,深化裂隙地下水迁移规律的认识具有重要的意义。

单联和双联液压管路系统流固耦合振动特性分析

飞机液压管路常用于发动机的燃油与滑油输送,由不同种类的卡箍将其固定,组成液压管路系统。根据管路形状不同,连接形式多样,常见的包括单联液压管路系统和双联液压管路系统。为避免复杂工作环境下因流固耦合振动而导致管路系统出现振动失效等问题,以典型的单联和双联液压管路系统为对象,基于管路本体的Euler-Bernoulli梁假设和黏弹性材料假设,采用牛顿法分别对管路和管路中的流体进行受力分析,再通过加减消元推导出管路系统的运动微分方程。然后,进行无量纲化处理,依据管路两端一般支承的边界条件求解出管路系统模态函数和频率方程,并通过Galerkin法将单联和双联管路系统的运动微分方程在模态空间内展开,进行振动特性的计算分析,获得内部液压油的流速、压力以及质量比对液压管路系统流固耦合振动特性的影响。

基于液压系统的风机叶片液压自调角系统

为确保冷却塔循环水系统安全可靠地运行,冷却塔风机转速以及叶片安装角度均按照最大换热量设定。但受生产工艺、环境温度等相关因素的影响,冷却塔风机的换热量在时刻变化,因此,冷却塔风机冷却能力与实际需求不匹配,造成大量能源浪费,为此,提出了一种基于液压系统的冷却塔风机叶片自调角的新型节能方法。首先,对自调角系统的工作原理进行了分析,利用Solidworks软件对自调角机构进行了结构设计,并对液压驱动系统工作原理进行了分析;然后,借助风力机气动载荷的计算方法,得到了液压系统提供的驱动力随安装角度变化的曲线;最后,利用AMESim仿真软件探究了多种液压回路自调角的工作特性,分析了调速阀内部元件节流阀开度对液压回路稳定性的影响。研究结果表明:自调角装置可以实现风机在不停机的工况下调节叶片的安装角度;采用PID调速阀液压回路可提高系统工作的精度和稳定性;当调速阀内部节流口的开度K=0.08时,可有效减少振荡时间,减小振荡峰值。

考虑非饱和渗透系数随机场统计特征的库岸老滑坡稳定性分析

库岸边坡如果在历史上发生过滑坡灾害,计算所得的安全系数将略高于临界状态值1.0,仅以安全系数评价库岸老滑坡的稳定性,将导致预测结果与边坡稳定状态不相符合。提出以土水特征曲线和非饱和渗透系数为核心的水力参数联合随机(场)统计特征为基础,建立库岸边坡稳定性的可靠度分析方法。首先根据有限的室内土水特征关系试验数据,采用贝叶斯理论校准土水特征曲线VGM、VGB、VG和FX模型参数的随机统计特征,并得到模型备选组合的概率。其次根据饱和渗透系数的随机场统计特征,联合土水特征曲线的随机统计特征,生成库岸边坡非饱和渗透系数的随机场空间分布。最后分析仅考虑土水特征曲线随机统计特征的库岸边坡稳定性失效概率,以及综合考虑非饱和渗透系数随机场统计特征的可靠指标。针对三峡库区石榴树包老滑坡在2020年强降雨和长江水位快速升降的工程背景,开展考虑渗流作用的非饱和土边坡稳定性可靠度分析。研究结果表明,虽然边坡稳定性的安全系数较低,但是可靠指标满足规范不小于2.70的要求,无需采取额外的边坡工程加固措施,建议继续开展边坡的长期健康监测。

基于变环量设计的混流泵叶轮多工况优化

由于外部运行条件频繁变化,混流泵常于非设计工况运行,导致其运行效率偏低。针对混流泵开展多工况优化以扩大其高效区范围具有重要意义。采用环量法,以轮毂及轮缘处流线方向环量的偏导数(载荷)、叶轮出口处翼展方向环量控制参数以及叶片尾缘倾角为设计参数,以设计点扬程为约束条件,以0.8、1.2倍设计点处效率为优化目标,结合实验设计、近似模型和优化算法对一导叶式混流泵叶轮进行变环量优化与分析。研究结果表明:变环量设计在混流泵叶轮的多工况优化中是有效的;轮毂处流线方向前加载,轮缘处流线方向后加载,叶轮出口处环量从轮毂到轮缘递增分布均有利于混流泵性能的提升;优化后混流泵模型在0.8、1.0、1.2倍设计流量处泵段效率分别为81.11%、88.38%和80.56%,在设计流量处扬程为12.33 m,相比于原始模型,效率分别提升0.63、3.18、6.72个百分点,而扬程变化小于2%。因此,所提出的基于变环量设计的混流泵叶轮多工况优化方法是有效的,可以为同类型叶轮机械的设计优化提供参考。

主挖力臂配比对主挖区界定及挖掘性能评价的影响研究

主挖区的挖掘性能是分析评价挖掘机性能的关键指标,其范围界定直接影响评价结果,而作业力臂又与作业范围和挖掘力性能密不可分。以某22 t反铲液压挖掘机为例,引入力臂系数的概念并基于力臂曲线和各机构传动比曲线,选取不同主挖力臂系数并以不同挖掘方式所引起的力臂变化为依据建立了主挖力臂配比方案。基于工作域图谱分析法和极限挖掘力模型,分别求解其理论挖掘力和限制因素来分析不同主挖区的挖掘性能。研究结果表明:对于作业范围,铲斗力臂主要影响其挖高和卸高,斗杆力臂主要影响其挖径,动臂力臂主要影响挖深和挖高。对于挖掘性能,增大某作业缸力臂会使得挖掘力增大,而相应的作业缸充分发挥比会减小;相反,增大某非作业缸力臂对挖掘力影响较小,但其作业缸充分发挥比会增大;斗杆力臂主要影响其平均挖掘力,而铲斗力臂主要影响其最大挖掘力。基于此,将对于斗杆挖掘以0.6∶0.8∶0.6的力臂系数配比、对于铲斗和复合挖掘以0.6∶0.8∶0.8的力臂系数配比方案所形成的主挖区作为各自挖掘方式的最佳挖掘性能主挖区。该研究提出了以主挖力臂系数的配比方式定义主挖区的方法,揭示了不同主挖力臂配比对挖掘性能的影响规律,为挖掘性能分析和工装优化提供了评判指标和参考方向。